Exoplanet Explained

An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not then recognized as such. The first confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. According to statistics from the NASA Exoplanet Archive, [1] The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.[2]

There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone.[3] In several cases, multiple planets have been observed around a star.[4] About 1 in 5 Sun-like stars[5] have an "Earth-sized"[6] planet in the habitable zone.[7] [8] [9] Assuming there are 200 billion stars in the Milky Way,[10] it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if planets orbiting the numerous red dwarfs are included.[11]

The least massive exoplanet known is Draugr (also known as PSR B1257+12 A or PSR B1257+12 b), which is about twice the mass of the Moon. The most massive exoplanet listed on the NASA Exoplanet Archive is HR 2562 b,[12] [13] [14] about 30 times the mass of Jupiter. However, according to some definitions of a planet (based on the nuclear fusion of deuterium), it is too massive to be a planet and might be a brown dwarf instead. Known orbital times for exoplanets vary from less than an hour (for those closest to their star) to thousands of years. Some exoplanets are so far away from the star that it is difficult to tell whether they are gravitationally bound to it.

Almost all planets detected so far are within the Milky Way. However, there is evidence that extragalactic planets, exoplanets located in other galaxies, may exist.[15] [16] The nearest exoplanets are located 4.2 light-years (1.3 parsecs) from Earth and orbit Proxima Centauri, the closest star to the Sun.[17]

The discovery of exoplanets has intensified interest in the search for extraterrestrial life. There is special interest in planets that orbit in a star's habitable zone (sometimes called "goldilocks zone"), where it is possible for liquid water, a prerequisite for life as we know it, to exist on the surface. However, the study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life.[18]

Rogue planets are those that do not orbit any star. Such objects are considered a separate category of planets, especially if they are gas giants, often counted as sub-brown dwarfs.[19] The rogue planets in the Milky Way possibly number in the billions or more.[20] [21]

Definition

IAU

The official definition of the term planet used by the International Astronomical Union (IAU) only covers the Solar System and thus does not apply to exoplanets.[22] [23] The IAU Working Group on Extrasolar Planets issued a position statement containing a working definition of "planet" in 2001 and which was modified in 2003.[24] An exoplanet was defined by the following criteria:

This working definition was amended by the IAU's Commission F2: Exoplanets and the Solar System in August 2018.[25] [26] The official working definition of an exoplanet is now as follows:

Alternatives

The IAU's working definition is not always used. One alternate suggestion is that planets should be distinguished from brown dwarfs on the basis of their formation. It is widely thought that giant planets form through core accretion, which may sometimes produce planets with masses above the deuterium fusion threshold;[27] [28] [29] massive planets of that sort may have already been observed.[30] Brown dwarfs form like stars from the direct gravitational collapse of clouds of gas, and this formation mechanism also produces objects that are below the limit and can be as low as .[31] Objects in this mass range that orbit their stars with wide separations of hundreds or thousands of AU and have large star/object mass ratios likely formed as brown dwarfs; their atmospheres would likely have a composition more similar to their host star than accretion-formed planets, which would contain increased abundances of heavier elements. Most directly imaged planets as of April 2014 are massive and have wide orbits so probably represent the low-mass end of a brown dwarf formation.[32] One study suggests that objects above formed through gravitational instability and should not be thought of as planets.[33]

Also, the 13-Jupiter-mass cutoff does not have a precise physical significance. Deuterium fusion can occur in some objects with a mass below that cutoff. The amount of deuterium fused depends to some extent on the composition of the object.[34] As of 2011, the Extrasolar Planets Encyclopaedia included objects up to 25 Jupiter masses, saying, "The fact that there is no special feature around in the observed mass spectrum reinforces the choice to forget this mass limit".[35] As of 2016, this limit was increased to 60 Jupiter masses[36] based on a study of mass–density relationships.[37] The Exoplanet Data Explorer includes objects up to 24 Jupiter masses with the advisory: "The 13 Jupiter-mass distinction by the IAU Working Group is physically unmotivated for planets with rocky cores, and observationally problematic due to the sin i ambiguity."[38] The NASA Exoplanet Archive includes objects with a mass (or minimum mass) equal to or less than 30 Jupiter masses.[39] Another criterion for separating planets and brown dwarfs, rather than deuterium fusion, formation process or location, is whether the core pressure is dominated by Coulomb pressure or electron degeneracy pressure with the dividing line at around 5 Jupiter masses.[40] [41]

Nomenclature

See main article: Exoplanet naming convention. The convention for naming exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union (IAU). For exoplanets orbiting a single star, the IAU designation is formed by taking the designated or proper name of its parent star, and adding a lower case letter.[42] Letters are given in order of each planet's discovery around the parent star, so that the first planet discovered in a system is designated "b" (the parent star is considered "a") and later planets are given subsequent letters. If several planets in the same system are discovered at the same time, the closest one to the star gets the next letter, followed by the other planets in order of orbital size. A provisional IAU-sanctioned standard exists to accommodate the designation of circumbinary planets. A limited number of exoplanets have IAU-sanctioned proper names. Other naming systems exist.

History of detection

For centuries scientists, philosophers, and science fiction writers suspected that extrasolar planets existed, but there was no way of knowing whether they were real in fact, how common they were, or how similar they might be to the planets of the Solar System. Various detection claims made in the nineteenth century were rejected by astronomers.

The first evidence of a possible exoplanet, orbiting Van Maanen 2, was noted in 1917, but was not recognized as such. The astronomer Walter Sydney Adams, who later became director of the Mount Wilson Observatory, produced a spectrum of the star using Mount Wilson's 60-inch telescope. He interpreted the spectrum to be of an F-type main-sequence star, but it is now thought that such a spectrum could be caused by the residue of a nearby exoplanet that had been pulverized by the gravity of the star, the resulting dust then falling onto the star.[43]

The first suspected scientific detection of an exoplanet occurred in 1988. Shortly afterwards, the first confirmation of detection came in 1992 from the Arecibo Observatory, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. In February 2018, researchers using the Chandra X-ray Observatory, combined with a planet detection technique called microlensing, found evidence of planets in a distant galaxy, stating, "Some of these exoplanets are as (relatively) small as the moon, while others are as massive as Jupiter. Unlike Earth, most of the exoplanets are not tightly bound to stars, so they're actually wandering through space or loosely orbiting between stars. We can estimate that the number of planets in this [faraway] galaxy is more than a trillion."[44]

On 21 March 2022, the 5000th exoplanet beyond the Solar System was confirmed.[45]

On 11 January 2023, NASA scientists reported the detection of LHS 475 b, an Earth-like exoplanet – and the first exoplanet discovered by the James Webb Space Telescope.[46]

Early speculations

In the sixteenth century, the Italian philosopher Giordano Bruno, an early supporter of the Copernican theory that Earth and other planets orbit the Sun (heliocentrism), put forward the view that fixed stars are similar to the Sun and are likewise accompanied by planets.

In the eighteenth century, the same possibility was mentioned by Isaac Newton in the "General Scholium" that concludes his Principia. Making a comparison to the Sun's planets, he wrote "And if the fixed stars are the centres of similar systems, they will all be constructed according to a similar design and subject to the dominion of One."[47]

In 1952, more than 40 years before the first hot Jupiter was discovered, Otto Struve wrote that there is no compelling reason that planets could not be much closer to their parent star than is the case in the Solar System, and proposed that Doppler spectroscopy and the transit method could detect super-Jupiters in short orbits.[48]

Discredited claims

Claims of exoplanet detections have been made since the nineteenth century. Some of the earliest involve the binary star 70 Ophiuchi. In 1855, William Stephen Jacob at the East India Company's Madras Observatory reported that orbital anomalies made it "highly probable" that there was a "planetary body" in this system.[49] In the 1890s, Thomas J. J. See of the University of Chicago and the United States Naval Observatory stated that the orbital anomalies proved the existence of a dark body in the 70 Ophiuchi system with a 36-year period around one of the stars.[50] However, Forest Ray Moulton published a paper proving that a three-body system with those orbital parameters would be highly unstable.[51]

During the 1950s and 1960s, Peter van de Kamp of Swarthmore College made another prominent series of detection claims, this time for planets orbiting Barnard's Star.[52] Astronomers now generally regard all early reports of detection as erroneous.[53]

In 1991, Andrew Lyne, M. Bailes and S. L. Shemar claimed to have discovered a pulsar planet in orbit around PSR 1829-10, using pulsar timing variations.[54] The claim briefly received intense attention, but Lyne and his team soon retracted it.[55]

Confirmed discoveries

See main article: Discoveries of exoplanets.

See also: List of exoplanet firsts.

As of, a total of confirmed exoplanets are listed in the NASA Exoplanet Archive, including a few that were confirmations of controversial claims from the late 1980s. The first published discovery to receive subsequent confirmation was made in 1988 by the Canadian astronomers Bruce Campbell, G. A. H. Walker, and Stephenson Yang of the University of Victoria and the University of British Columbia.[56] Although they were cautious about claiming a planetary detection, their radial-velocity observations suggested that a planet orbits the star Gamma Cephei. Partly because the observations were at the very limits of instrumental capabilities at the time, astronomers remained skeptical for several years about this and other similar observations. It was thought some of the apparent planets might instead have been brown dwarfs, objects intermediate in mass between planets and stars. In 1990, additional observations were published that supported the existence of the planet orbiting Gamma Cephei,[57] but subsequent work in 1992 again raised serious doubts.[58] Finally, in 2003, improved techniques allowed the planet's existence to be confirmed.[59]

On 9 January 1992, radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of two planets orbiting the pulsar PSR 1257+12.[60] This discovery was confirmed, and is generally considered to be the first definitive detection of exoplanets. Follow-up observations solidified these results, and confirmation of a third planet in 1994 revived the topic in the popular press.[61] These pulsar planets are thought to have formed from the unusual remnants of the supernova that produced the pulsar, in a second round of planet formation, or else to be the remaining rocky cores of gas giants that somehow survived the supernova and then decayed into their current orbits. As pulsars are aggressive stars, it was considered unlikely at the time that a planet may be able to be formed in their orbit.[62]

In the early 1990s, a group of astronomers led by Donald Backer, who were studying what they thought was a binary pulsar (PSR B1620−26 b), determined that a third object was needed to explain the observed Doppler shifts. Within a few years, the gravitational effects of the planet on the orbit of the pulsar and white dwarf had been measured, giving an estimate of the mass of the third object that was too small for it to be a star. The conclusion that the third object was a planet was announced by Stephen Thorsett and his collaborators in 1993.[63]

On 6 October 1995, Michel Mayor and Didier Queloz of the University of Geneva announced the first definitive detection of an exoplanet orbiting a main-sequence star, nearby G-type star 51 Pegasi.[64] [65] This discovery, made at the Observatoire de Haute-Provence, ushered in the modern era of exoplanetary discovery, and was recognized by a share of the 2019 Nobel Prize in Physics. Technological advances, most notably in high-resolution spectroscopy, led to the rapid detection of many new exoplanets: astronomers could detect exoplanets indirectly by measuring their gravitational influence on the motion of their host stars. More extrasolar planets were later detected by observing the variation in a star's apparent luminosity as an orbiting planet transited in front of it.

Initially, the most known exoplanets were massive planets that orbited very close to their parent stars. Astronomers were surprised by these "hot Jupiters", because theories of planetary formation had indicated that giant planets should only form at large distances from stars. But eventually more planets of other sorts were found, and it is now clear that hot Jupiters make up the minority of exoplanets.[66] In 1999, Upsilon Andromedae became the first main-sequence star known to have multiple planets.[67] Kepler-16 contains the first discovered planet that orbits a binary main-sequence star system.[68]

On 26 February 2014, NASA announced the discovery of 715 newly verified exoplanets around 305 stars by the Kepler Space Telescope. These exoplanets were checked using a statistical technique called "verification by multiplicity".[69] [70] [71] Before these results, most confirmed planets were gas giants comparable in size to Jupiter or larger because they were more easily detected, but the Kepler planets are mostly between the size of Neptune and the size of Earth.

On 23 July 2015, NASA announced Kepler-452b, a near-Earth-size planet orbiting the habitable zone of a G2-type star.[72]

On 6 September 2018, NASA discovered an exoplanet about 145 light years away from Earth in the constellation Virgo.[73] This exoplanet, Wolf 503b, is twice the size of Earth and was discovered orbiting a type of star known as an "Orange Dwarf". Wolf 503b completes one orbit in as few as six days because it is very close to the star. Wolf 503b is the only exoplanet that large that can be found near the so-called small planet radius gap. The gap, sometimes called the Fulton gap,[73] [74] is the observation that it is unusual to find exoplanets with sizes between 1.5 and 2 times the radius of the Earth.[75]

In January 2020, scientists announced the discovery of TOI 700 d, the first Earth-sized planet in the habitable zone detected by TESS.[76]

Candidate discoveries

As of January 2020, NASA's Kepler and TESS missions had identified 4374 planetary candidates yet to be confirmed,[77] several of them being nearly Earth-sized and located in the habitable zone, some around Sun-like stars.[78] [79] [80]

In September 2020, astronomers reported evidence, for the first time, of an extragalactic planet, M51-ULS-1b, detected by eclipsing a bright X-ray source (XRS), in the Whirlpool Galaxy (M51a).[81] [82]

Also in September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an Earth-mass rogue planet unbounded by any star, and free floating in the Milky Way galaxy.[83] [84]

Detection methods

See main article: Methods of detecting exoplanets.

Direct imaging

Planets are extremely faint compared to their parent stars. For example, a Sun-like star is about a billion times brighter than the reflected light from any exoplanet orbiting it. It is difficult to detect such a faint light source, and furthermore, the parent star causes a glare that tends to wash it out. It is necessary to block the light from the parent star to reduce the glare while leaving the light from the planet detectable; doing so is a major technical challenge which requires extreme optothermal stability.[85] All exoplanets that have been directly imaged are both large (more massive than Jupiter) and widely separated from their parent stars.

Specially designed direct-imaging instruments such as Gemini Planet Imager, VLT-SPHERE, and SCExAO will image dozens of gas giants, but the vast majority of known extrasolar planets have only been detected through indirect methods.

Indirect methods

  • Transit method

If a planet crosses (or transits) in front of its parent star's disk, then the observed brightness of the star drops by a small amount. The amount by which the star dims depends on its size and on the size of the planet, among other factors. Because the transit method requires that the planet's orbit intersect a line-of-sight between the host star and Earth, the probability that an exoplanet in a randomly oriented orbit will be observed to transit the star is somewhat small. The Kepler telescope used this method.

  • Radial velocity or Doppler method

As a planet orbits a star, the star also moves in its own small orbit around the system's center of mass. Variations in the star's radial velocity—that is, the speed with which it moves towards or away from Earth—can be detected from displacements in the star's spectral lines due to the Doppler effect. Extremely small radial-velocity variations can be observed, of 1 m/s or even somewhat less.[86]

  • Transit timing variation (TTV)

When multiple planets are present, each one slightly perturbs the others' orbits. Small variations in the times of transit for one planet can thus indicate the presence of another planet, which itself may or may not transit. For example, variations in the transits of the planet Kepler-19b suggest the existence of a second planet in the system, the non-transiting Kepler-19c.[87] [88]

  • Transit duration variation (TDV)

When a planet orbits multiple stars or if the planet has moons, its transit time can significantly vary per transit. Although no new planets or moons have been discovered with this method, it is used to successfully confirm many transiting circumbinary planets.[89]

  • Gravitational microlensing

Microlensing occurs when the gravitational field of a star acts like a lens, magnifying the light of a distant background star. Planets orbiting the lensing star can cause detectable anomalies in magnification as it varies over time. Unlike most other methods which have a detection bias towards planets with small (or for resolved imaging, large) orbits, the microlensing method is most sensitive to detecting planets around 1–10 AU away from Sun-like stars.

  • Astrometry

Astrometry consists of precisely measuring a star's position in the sky and observing the changes in that position over time. The motion of a star due to the gravitational influence of a planet may be observable. Because the motion is so small, however, this method was not very productive until the 2020s. It has produced only a few confirmed discoveries,[90] [91] though it has been successfully used to investigate the properties of planets found in other ways.

  • Pulsar timing

A pulsar (the small, ultradense remnant of a star that has exploded as a supernova) emits radio waves extremely regularly as it rotates. If planets orbit the pulsar, they will cause slight anomalies in the timing of its observed radio pulses. The first confirmed discovery of an extrasolar planet was made using this method. But as of 2011, it has not been very productive; five planets have been detected in this way, around three different pulsars.

  • Variable star timing (pulsation frequency)

Like pulsars, there are some other types of stars which exhibit periodic activity. Deviations from periodicity can sometimes be caused by a planet orbiting it. As of 2013, a few planets have been discovered with this method.[92]

  • Reflection/emission modulations

When a planet orbits very close to a star, it catches a considerable amount of starlight. As the planet orbits the star, the amount of light changes due to planets having phases from Earth's viewpoint or planets glowing more from one side than the other due to temperature differences.[93]

  • Relativistic beaming

Relativistic beaming measures the observed flux from the star due to its motion. The brightness of the star changes as the planet moves closer or further away from its host star.[94]

  • Ellipsoidal variations

Massive planets close to their host stars can slightly deform the shape of the star. This causes the brightness of the star to slightly deviate depending on how it is rotated relative to Earth.[95]

  • Polarimetry

With the polarimetry method, a polarized light reflected off the planet is separated from unpolarized light emitted from the star. No new planets have been discovered with this method, although a few already discovered planets have been detected with this method.[96] [97]

  • Circumstellar disks

Disks of space dust surround many stars, thought to originate from collisions among asteroids and comets. The dust can be detected because it absorbs starlight and re-emits it as infrared radiation. Features on the disks may suggest the presence of planets, though this is not considered a definitive detection method.

Formation and evolution

See also: Accretion (astrophysics), Nebular hypothesis and Planetary migration.

Planets may form within a few to tens (or more) of millions of years of their star forming.[98] [99] [100] [101] [102] The planets of the Solar System can only be observed in their current state, but observations of different planetary systems of varying ages allows us to observe planets at different stages of evolution. Available observations range from young proto-planetary disks where planets are still forming[103] to planetary systems of over 10 Gyr old.[104] When planets form in a gaseous protoplanetary disk,[105] they accrete hydrogen/helium envelopes.[106] [107] These envelopes cool and contract over time and, depending on the mass of the planet, some or all of the hydrogen/helium is eventually lost to space. This means that even terrestrial planets may start off with large radii if they form early enough.[108] [109] [110] An example is Kepler-51b which has only about twice the mass of Earth but is almost the size of Saturn, which is a hundred times the mass of Earth. Kepler-51b is quite young at a few hundred million years old.[111]

Planet-hosting stars

See main article: Planet-hosting star. There is at least one planet on average per star.About 1 in 5 Sun-like stars have an "Earth-sized" planet in the habitable zone.[112]

Most known exoplanets orbit stars roughly similar to the Sun, i.e. main-sequence stars of spectral categories F, G, or K. Lower-mass stars (red dwarfs, of spectral category M) are less likely to have planets massive enough to be detected by the radial-velocity method.[113] [114] Despite this, several tens of planets around red dwarfs have been discovered by the Kepler telescope, which uses the transit method to detect smaller planets.

Using data from Kepler, a correlation has been found between the metallicity of a star and the probability that the star hosts a giant planet, similar to the size of Jupiter. Stars with higher metallicity are more likely to have planets, especially giant planets, than stars with lower metallicity.[115]

Some planets orbit one member of a binary star system,[116] and several circumbinary planets have been discovered which orbit both members of a binary star. A few planets in triple star systems are known[117] and one in the quadruple system Kepler-64.

Orbital and physical parameters

See main article: Exoplanet orbital and physical parameters.

General features

Color and brightness

See also: Sudarsky's gas giant classification. In 2013, the color of an exoplanet was determined for the first time. The best-fit albedo measurements of HD 189733b suggest that it is deep dark blue.[118] [119] Later that same year, the colors of several other exoplanets were determined, including GJ 504 b which visually has a magenta color,[120] and Kappa Andromedae b, which if seen up close would appear reddish in color.[121] Helium planets are expected to be white or grey in appearance.[122]

The apparent brightness (apparent magnitude) of a planet depends on how far away the observer is, how reflective the planet is (albedo), and how much light the planet receives from its star, which depends on how far the planet is from the star and how bright the star is. So, a planet with a low albedo that is close to its star can appear brighter than a planet with a high albedo that is far from the star.[123]

The darkest known planet in terms of geometric albedo is TrES-2b, a hot Jupiter that reflects less than 1% of the light from its star, making it less reflective than coal or black acrylic paint. Hot Jupiters are expected to be quite dark due to sodium and potassium in their atmospheres, but it is not known why TrES-2b is so dark—it could be due to an unknown chemical compound.[124] [125] [126]

For gas giants, geometric albedo generally decreases with increasing metallicity or atmospheric temperature unless there are clouds to modify this effect. Increased cloud-column depth increases the albedo at optical wavelengths, but decreases it at some infrared wavelengths. Optical albedo increases with age, because older planets have higher cloud-column depths. Optical albedo decreases with increasing mass, because higher-mass giant planets have higher surface gravities, which produces lower cloud-column depths. Also, elliptical orbits can cause major fluctuations in atmospheric composition, which can have a significant effect.[127]

There is more thermal emission than reflection at some near-infrared wavelengths for massive and/or young gas giants. So, although optical brightness is fully phase-dependent, this is not always the case in the near infrared.

Temperatures of gas giants reduce over time and with distance from their stars. Lowering the temperature increases optical albedo even without clouds. At a sufficiently low temperature, water clouds form, which further increase optical albedo. At even lower temperatures, ammonia clouds form, resulting in the highest albedos at most optical and near-infrared wavelengths.

Magnetic field

In 2014, a magnetic field around HD 209458 b was inferred from the way hydrogen was evaporating from the planet. It is the first (indirect) detection of a magnetic field on an exoplanet. The magnetic field is estimated to be about one-tenth as strong as Jupiter's.[128] [129]

The magnetic fields of exoplanets may be detectable by their auroral radio emissions with sensitive enough radio telescopes such as LOFAR.[130] [131] The radio emissions could enable determination of the rotation rate of the interior of an exoplanet, and may yield a more accurate way to measure exoplanet rotation than by examining the motion of clouds.[132]

Earth's magnetic field results from its flowing liquid metallic core, but on massive super-Earths with high pressure, different compounds may form which do not match those created under terrestrial conditions. Compounds may form with greater viscosities and high melting temperatures, which could prevent the interiors from separating into different layers and so result in undifferentiated coreless mantles. Forms of magnesium oxide such as MgSi3O12 could be a liquid metal at the pressures and temperatures found in super-Earths and could generate a magnetic field in the mantles of super-Earths.[133] [134]

Hot Jupiters have been observed to have a larger radius than expected. This could be caused by the interaction between the stellar wind and the planet's magnetosphere creating an electric current through the planet that heats it up (Joule heating) causing it to expand. The more magnetically active a star is, the greater the stellar wind and the larger the electric current leading to more heating and expansion of the planet. This theory matches the observation that stellar activity is correlated with inflated planetary radii.[135]

In August 2018, scientists announced the transformation of gaseous deuterium into a liquid metallic hydrogen form. This may help researchers better understand giant gas planets, such as Jupiter, Saturn and related exoplanets, since such planets are thought to contain a lot of liquid metallic hydrogen, which may be responsible for their observed powerful magnetic fields.[136] [137]

Although scientists previously announced that the magnetic fields of close-in exoplanets may cause increased stellar flares and starspots on their host stars, in 2019 this claim was demonstrated to be false in the HD 189733 system. The failure to detect "star-planet interactions" in the well-studied HD 189733 system calls other related claims of the effect into question.[138]

In 2019, the strength of the surface magnetic fields of 4 hot Jupiters were estimated and ranged between 20 and 120 gauss compared to Jupiter's surface magnetic field of 4.3 gauss.[139] [140]

Plate tectonics

In 2007, two independent teams of researchers came to opposing conclusions about the likelihood of plate tectonics on larger super-Earths[141] [142] with one team saying that plate tectonics would be episodic or stagnant[143] and the other team saying that plate tectonics is very likely on super-Earths even if the planet is dry.[144]

If super-Earths have more than 80 times as much water as Earth, then they become ocean planets with all land completely submerged. However, if there is less water than this limit, then the deep water cycle will move enough water between the oceans and mantle to allow continents to exist.[145] [146]

Volcanism

Large surface temperature variations on 55 Cancri e have been attributed to possible volcanic activity releasing large clouds of dust which blanket the planet and block thermal emissions.[147] [148]

Rings

The star 1SWASP J140747.93-394542.6 was occulted by an object that is circled by a ring system much larger than Saturn's rings. However, the mass of the object is not known; it could be a brown dwarf or low-mass star instead of a planet.[149] [150]

The brightness of optical images of Fomalhaut b could be due to starlight reflecting off a circumplanetary ring system with a radius between 20 and 40 times that of Jupiter's radius, about the size of the orbits of the Galilean moons.[151]

The rings of the Solar System's gas giants are aligned with their planet's equator. However, for exoplanets that orbit close to their star, tidal forces from the star would lead to the outermost rings of a planet being aligned with the planet's orbital plane around the star. A planet's innermost rings would still be aligned with the planet's equator so that if the planet has a tilted rotational axis, then the different alignments between the inner and outer rings would create a warped ring system.[152]

Moons

See main article: Exomoon. In December 2013 a candidate exomoon of the rogue planet or red dwarf MOA-2011-BLG-262L was announced.[153] On 3 October 2018, evidence suggesting a large exomoon orbiting Kepler-1625b was reported.[154]

Atmospheres

Atmospheres have been detected around several exoplanets. The first to be observed was HD 209458 b in 2001.[155]

As of February 2014, more than fifty transiting and five directly imaged exoplanet atmospheres have been observed,[156] resulting in detection of molecular spectral features; observation of day–night temperature gradients; and constraints on vertical atmospheric structure.[157] Also, an atmosphere has been detected on the non-transiting hot Jupiter Tau Boötis b.[158] [159]

In May 2017, glints of light from Earth, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in the atmosphere.[160] [161] The technology used to determine this may be useful in studying the atmospheres of distant worlds, including those of exoplanets.

Comet-like tails

KIC 12557548 b is a small rocky planet, very close to its star, that is evaporating and leaving a trailing tail of cloud and dust like a comet.[162] The dust could be ash erupting from volcanos and escaping due to the small planet's low surface-gravity, or it could be from metals that are vaporized by the high temperatures of being so close to the star with the metal vapor then condensing into dust.[163]

In June 2015, scientists reported that the atmosphere of GJ 436 b was evaporating, resulting in a giant cloud around the planet and, due to radiation from the host star, a long trailing tail 9order=flipNaNorder=flip long.[164]

Insolation pattern

Tidally locked planets in a 1:1 spin-orbit resonance would have their star always shining directly overhead on one spot, which would be hot with the opposite hemisphere receiving no light and being freezing cold. Such a planet could resemble an eyeball, with the hotspot being the pupil.[165] Planets with an eccentric orbit could be locked in other resonances. 3:2 and 5:2 resonances would result in a double-eyeball pattern with hotspots in both eastern and western hemispheres.[166] Planets with both an eccentric orbit and a tilted axis of rotation would have more complicated insolation patterns.[167]

Surface

Surface composition

Surface features can be distinguished from atmospheric features by comparing emission and reflection spectroscopy with transmission spectroscopy. Mid-infrared spectroscopy of exoplanets may detect rocky surfaces, and near-infrared may identify magma oceans or high-temperature lavas, hydrated silicate surfaces and water ice, giving an unambiguous method to distinguish between rocky and gaseous exoplanets.[168]

Surface temperature

Measuring the intensity of the light it receives from its parent star can estimate the temperature of an exoplanet. For example, the planet OGLE-2005-BLG-390Lb is estimated to have a surface temperature of roughly −220 °C (50 K). However, such estimates may be substantially in error because they depend on the planet's usually unknown albedo, and because factors such as the greenhouse effect may introduce unknown complications. A few planets have had their temperature measured by observing the variation in infrared radiation as the planet moves around in its orbit and is eclipsed by its parent star. For example, the planet HD 189733b has been estimated to have an average temperature of 1,205 K (932 °C) on its dayside and 973 K (700 °C) on its nightside.[169]

Habitability

See also: Astrobiology, Circumstellar habitable zone and Planetary habitability. As more planets are discovered, the field of exoplanetology continues to grow into a deeper study of extrasolar worlds, and will ultimately tackle the prospect of life on planets beyond the Solar System.[170] At cosmic distances, life can only be detected if it is developed at a planetary scale and strongly modified the planetary environment, in such a way that the modifications cannot be explained by classical physico-chemical processes (out of equilibrium processes).[170] For example, molecular oxygen in the atmosphere of Earth is a result of photosynthesis by living plants and many kinds of microorganisms, so it can be used as an indication of life on exoplanets, although small amounts of oxygen could also be produced by non-biological means.[171] Furthermore, a potentially habitable planet must orbit a stable star at a distance within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces.[172] [173]

Habitable zone

See main article: Habitable zone. The habitable zone around a star is the region where the temperature is just right to allow liquid water to exist on the surface of a planet; that is, not too close to the star for the water to evaporate and not too far away from the star for the water to freeze. The heat produced by stars varies depending on the size and age of the star, so that the habitable zone can be at different distances for different stars. Also, the atmospheric conditions on the planet influence the planet's ability to retain heat so that the location of the habitable zone is also specific to each type of planet: desert planets (also known as dry planets), with very little water, will have less water vapor in the atmosphere than Earth and so have a reduced greenhouse effect, meaning that a desert planet could maintain oases of water closer to its star than Earth is to the Sun. The lack of water also means there is less ice to reflect heat into space, so the outer edge of desert-planet habitable zones is further out.[174] [175] Rocky planets with a thick hydrogen atmosphere could maintain surface water much further out than the Earth–Sun distance.[176] Planets with larger mass have wider habitable zones because gravity reduces the water cloud column depth which reduces the greenhouse effect of water vapor, thus moving the inner edge of the habitable zone closer to the star.[177]

Planetary rotation rate is one of the major factors determining the circulation of the atmosphere and hence the pattern of clouds: slowly rotating planets create thick clouds that reflect more and so can be habitable much closer to their star. Earth with its current atmosphere would be habitable in Venus's orbit, if it had Venus's slow rotation. If Venus lost its water ocean due to a runaway greenhouse effect, it is likely to have had a higher rotation rate in the past. Alternatively, Venus never had an ocean because water vapor was lost to space during its formation [178] and could have had its slow rotation throughout its history.[179]

Tidally locked planets (a.k.a. "eyeball" planets[180]) can be habitable closer to their star than previously thought due to the effect of clouds: at high stellar flux, strong convection produces thick water clouds near the substellar point that greatly increase the planetary albedo and reduce surface temperatures.[181]

Planets in the habitable zones of stars with low metallicity are more habitable for complex life on land than high metallicity stars because the stellar spectrum of high metallicity stars is less likely to cause the formation of ozone thus enabling more ultraviolet rays to reach the planet's surface.[182] [183]

Habitable zones have usually been defined in terms of surface temperature, however over half of Earth's biomass is from subsurface microbes,[184] and the temperature increases with depth, so the subsurface can be conducive for microbial life when the surface is frozen and if this is considered, the habitable zone extends much further from the star,[185] even rogue planets could have liquid water at sufficient depths underground.[186] In an earlier era of the universe the temperature of the cosmic microwave background would have allowed any rocky planets that existed to have liquid water on their surface regardless of their distance from a star.[187] Jupiter-like planets might not be habitable, but they could have habitable moons.[188]

Ice ages and snowball states

See also: Ice age and Snowball Earth. The outer edge of the habitable zone is where planets are completely frozen, but planets well inside the habitable zone can periodically become frozen. If orbital fluctuations or other causes produce cooling, then this creates more ice, but ice reflects sunlight causing even more cooling, creating a feedback loop until the planet is completely or nearly completely frozen. When the surface is frozen, this stops carbon dioxide weathering, resulting in a build-up of carbon dioxide in the atmosphere from volcanic emissions. This creates a greenhouse effect which thaws the planet again. Planets with a large axial tilt[189] are less likely to enter snowball states and can retain liquid water further from their star. Large fluctuations of axial tilt can have even more of a warming effect than a fixed large tilt.[190] [191] Paradoxically, planets orbiting cooler stars, such as red dwarfs, are less likely to enter snowball states because the infrared radiation emitted by cooler stars is mostly at wavelengths that are absorbed by ice which heats it up.[192] [193]

Tidal heating

If a planet has an eccentric orbit, then tidal heating can provide another source of energy besides stellar radiation. This means that eccentric planets in the radiative habitable zone can be too hot for liquid water. Tides also circularize orbits over time, so there could be planets in the habitable zone with circular orbits that have no water because they used to have eccentric orbits.[194] Eccentric planets further out than the habitable zone would still have frozen surfaces, but the tidal heating could create a subsurface ocean similar to Europa's.[195] In some planetary systems, such as in the Upsilon Andromedae system, the eccentricity of orbits is maintained or even periodically varied by perturbations from other planets in the system. Tidal heating can cause outgassing from the mantle, contributing to the formation and replenishment of an atmosphere.[196]

Potentially habitable planets

See also: List of potentially habitable exoplanets and List of nearest terrestrial exoplanet candidates.

A review in 2015 identified exoplanets Kepler-62f, Kepler-186f and Kepler-442b as the best candidates for being potentially habitable.[197] These are at a distance of 1200, 490 and 1,120 light-years away, respectively. Of these, Kepler-186f is in similar size to Earth with its 1.2-Earth-radius measure, and it is located towards the outer edge of the habitable zone around its red dwarf star.

When looking at the nearest terrestrial exoplanet candidates, Proxima Centauri b is about 4.2 light-years away. Its equilibrium temperature is estimated to be -39C.[198]

Earth-size planets

See also: Earth analog.

  • In November 2013, it was estimated that 22±8% of Sun-like[5] stars in the Milky Way galaxy may have an Earth-sized[6] planet in the habitable[7] zone. Assuming 200 billion stars in the Milky Way,[10] that would be 11 billion potentially habitable Earths, rising to 40 billion if red dwarfs are included.[11]
  • Kepler-186f, a 1.2-Earth-radius planet in the habitable zone of a red dwarf, was reported in April 2014.
  • Proxima Centauri b, a planet in the habitable zone of Proxima Centauri, the nearest known star to the solar system with an estimated minimum mass of 1.27 times the mass of the Earth.
  • In February 2013, researchers speculated that up to 6% of small red dwarfs may have Earth-size planets. This suggests that the closest one to the Solar System could be 13 light-years away. The estimated distance increases to 21 light-years when a 95% confidence interval is used.[199] In March 2013, a revised estimate gave an occurrence rate of 50% for Earth-size planets in the habitable zone of red dwarfs.[200]
  • At 1.63 times Earth's radius Kepler-452b is the first discovered near-Earth-size planet in the "habitable zone" around a G2-type Sun-like star (July 2015).[201]

Planetary system

See main article: Planetary system. Exoplanets are often members of planetary systems of multiple planets around a star. The planets interact with each other gravitationally and sometimes form resonant systems where the orbital periods of the planets are in integer ratios. The Kepler-223 system contains four planets in an 8:6:4:3 orbital resonance.[202]

Some hot Jupiters orbit their stars in the opposite direction to their stars' rotation.[203] One proposed explanation is that hot Jupiters tend to form in dense clusters, where perturbations are more common and gravitational capture of planets by neighboring stars is possible.[204]

Search projects

  • CoRoT – Space telescope that found the first transiting rocky planet.[205]
  • Kepler – Mission to look for large numbers of exoplanets using the transit method.
  • TESS – To search for new exoplanets; rotating so by the end of its two-year mission it will have observed stars from all over the sky. It is expected to find at least 3,000 new exoplanets.
  • HARPS – High-precision echelle planet-finding spectrograph installed on the ESO's 3.6m telescope at La Silla Observatory in Chile.
  • ESPRESSO – A rocky planet-finding, and stable spectroscopic observing, spectrograph mounted on ESO's 4 by 8.2m VLT telescope, sited on the levelled summit of Cerro Paranal in the Atacama Desert of northern Chile.
  • ANDES – The ArmazoNes High Dispersion Echelle Spectrograph, a planet finding and planet characterisation spectrograph, is expected to be fitted onto ESO's ELT 39.3m telescope. ANDES was formally known as HIRES, which itself was created after a merger of the consortia behind the earlier CODEX (optical high-resolution) and SIMPLE (near-infrared high-resolution) spectrograph concepts.

See also

Further reading

  • Book: Boss, Alan . 2009 . The Crowded Universe: The Search for Living Planets . Basic Books . 2009cusl.book.....B. none. (Hardback); (Paperback).
  • Book: Dorminey, Bruce . 2001 . Distant Wanderers . Springer-Verlag . Distant Wanderers (book). none. (Hardback); (Paperback).
  • Book: Jayawardhana, Ray . 2011 . Strange New Worlds: The Search for Alien Planets and Life beyond Our Solar System . Princeton, NJ . Princeton University Press. none. (Hardcover).
  • Book: Perryman, Michael . 2011 . The Exoplanet Handbook . Cambridge University Press . 978-0-521-76559-6. none.
  • Book: Seager . Sara . 2011 . Exoplanets . University of Arizona Press. none. .
  • Book: Villard . Ray . Cook . Lynette R. . 2005 . Infinite Worlds: An Illustrated Voyage to Planets Beyond Our Sun . University of California Press . Infinite Worlds: An Illustrated Voyage to Planets Beyond Our Sun. none. .
  • Book: Yaqoob, Tahir . 2011 . Exoplanets and Alien Solar Systems . New Earth Labs (Education and Outreach). none. (Paperback).
  • Book: van Dishoeck . Ewine F. . 835 . Bergin . Edwin A. . Lis . Dariusz C. . Lunine . Jonathan I. . Protostars and Planets VI . 2014 . 10.2458/azu_uapress_9780816531240-ch036 . Water: From Clouds to Planets . 978-0-8165-3124-0 . 1401.8103 . 2014prpl.conf..835V . 55875067. none.

External links

Notes and References

  1. News: Brennan . Pat . Cosmic Milestone: NASA Confirms 5,000 Exoplanets . 21 March 2022 . . 2 April 2022.
  2. News: O'Callaghan . Jonthan . JWST Heralds a New Dawn for Exoplanet Science – The James Webb Space Telescope is opening an exciting new chapter in the study of exoplanets and the search for life beyond Earth . 23 January 2023 . . 23 January 2023 .
  3. F. J. Ballesteros. A. Fernandez-Soto. V. J. Martinez. Title: Diving into Exoplanets: Are Water Seas the Most Common?. 2019. 10.1089/ast.2017.1720. 30789285. Astrobiology. 19. 5. 642–654. 10261/213115. 73498809. free.
  4. Cassan . A. . Kubas . D. . Beaulieu . J. -P. . Dominik . M. . Horne . K. . Greenhill . J. . Wambsganss . J. . Menzies . J. . Williams . A. . Jørgensen . 10.1038/nature10684 . U. G. . Udalski . A. . Bennett . D. P. . Albrow . M. D. . Batista . V. . Brillant . S. . Caldwell . J. A. R. . Cole . A. . Coutures . C. . Cook . K. H. . Dieters . S. . Prester . D. D. . Donatowicz . J. . Fouqué . P. . Hill . K. . Kains . N. . Kane . S. . Marquette . J. -B. . Martin . R. . Pollard . K. R. . Sahu . K. C.. One or more bound planets per Milky Way star from microlensing observations . Nature . 481 . 7380 . 167–169 . 11 January 2012. 22237108. 2012Natur.481..167C. 1202.0903 . 2614136 .
  5. For the purpose of this 1 in 5 statistic, "Sun-like" means G-type star. Data for Sun-like stars was not available so this statistic is an extrapolation from data about K-type stars.
  6. For the purpose of this 1 in 5 statistic, Earth-sized means 1–2 Earth radii.
  7. For the purpose of this 1 in 5 statistic, "habitable zone" means the region with 0.25 to 4 times Earth's stellar flux (corresponding to 0.5–2 AU for the Sun).
  8. Web site: Sanders . R.. 4 November 2013. Astronomers answer key question: How common are habitable planets?. newscenter.berkeley.edu.
  9. Petigura . E. A.. Howard . A. W.. Marcy . G. W.. 2013. Prevalence of Earth-size planets orbiting Sun-like stars. Proceedings of the National Academy of Sciences. 110. 48. 19273–19278. 1311.6806. 2013PNAS..11019273P. 10.1073/pnas.1319909110. 24191033. 3845182. free.
  10. About 1/4 of stars are GK Sun-like stars. The number of stars in the galaxy is not accurately known, but assuming 200 billion stars in total, the Milky Way would have about 50 billion Sun-like (GK) stars, of which about 1 in 5 (22%) or 11 billion would have Earth-sized planets in the habitable zone. Including red dwarfs would increase this to 40 billion.
  11. News: Khan . Amina . Milky Way may host billions of Earth-size planets . 4 November 2013 . . 5 November 2013.
  12. Web site: HR 2562 b . . 15 February 2018 .
  13. Konopacky, Quinn M. . Rameau, Julien . Duchêne, Gaspard . Filippazzo, Joseph C. . Giorla Godfrey, Paige A. . Marois, Christian . Nielsen, Eric L. . Discovery of a Substellar Companion to the Nearby Debris Disk Host HR 2562 . 2016ApJ...829L...4K . 20 September 2016 . 1608.06660 . The Astrophysical Journal Letters . 10.3847/2041-8205/829/1/L4 . 829 . 1 . 10. 10150/621980 . 44216698 . free .
  14. Maire . A. . Rodet . L. . Lazzoni . C. . Boccaletti . A. . Brandner . W. . Galicher . R. . Cantalloube . F. . Mesa . D. . Klahr . H. . Beust . H. . Chauvin . G. . Desidera . S. . Janson . M. . Keppler . M. . Olofsson . J. . Augereau . J. . Daemgen . S. . Henning . T. . Thébault . P. . Bonnefoy . M. . Feldt . M. . Gratton . R. . Lagrange . A. . Langlois . M. . Meyer . M. R. . Vigan . A. . D’Orazi . V. . Hagelberg . J. . Le Coroller . H. . Ligi . R. . Rouan . D. . Samland . M. . Schmidt . T. . Udry . S. . Zurlo . A. . Abe . L. . Carle . M. . Delboulbé . A. . Feautrier . P. . Magnard . Y. . Maurel . D. . Moulin . T. . Pavlov . A. . Perret . D. . Petit . C. . Ramos . J. R. . Rigal . F. . Roux . A. . Weber . L. . 2018 . VLT/SPHERE astrometric confirmation and orbital analysis of the brown dwarf companion HR 2562 B . Astronomy & Astrophysics . 615 . A177. 10.1051/0004-6361/201732476. 1804.04584 . 2018A&A...615A.177M . free.
  15. Web site: Zachos . Elaine . More Than a Trillion Planets Could Exist Beyond Our Galaxy – A new study gives the first evidence that exoplanets exist beyond the Milky Way. . https://web.archive.org/web/20210428194238/https://www.nationalgeographic.com/science/article/exoplanets-discovery-milky-way-galaxy-spd. dead. 28 April 2021. 5 February 2018 . . 5 February 2018 .
  16. Web site: Mandelbaum . Ryan F. . Scientists Find Evidence of Thousands of Planets in Distant Galaxy . 5 February 2018 . . 5 February 2018 .
  17. 2016Natur.536..437A. A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature. 536. 7617. 437–440. Anglada-Escudé. Guillem. Amado. Pedro J.. Barnes. John. Berdiñas. Zaira M.. Butler. R. Paul. Coleman. Gavin A. L.. de la Cueva. Ignacio. Dreizler. Stefan. Endl. Michael. Giesers. Benjamin. Jeffers. Sandra V.. Jenkins. James S.. Jones. Hugh R. A.. Kiraga. Marcin. Kürster. Martin. López-González. María J.. Marvin. Christopher J.. Morales. Nicolás. Morin. Julien. Nelson. Richard P.. Ortiz. José L.. Ofir. Aviv. Paardekooper. Sijme-Jan. Reiners. Ansgar. Rodríguez. Eloy. Rodríguez-López. Cristina. Sarmiento. Luis F.. Strachan. John P.. Tsapras. Yiannis. Tuomi. Mikko. Mathias. Zechmeister. 3. 2016. 1609.03449. 10.1038/nature19106. 27558064. 4451513.
  18. News: Overbye . Dennis . Dennis Overbye . As Ranks of Goldilocks Planets Grow, Astronomers Consider What's Next . https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2015/01/07/science/space/as-ranks-of-goldilocks-planets-grow-astronomers-consider-whats-next.html . 2022-01-01 . limited . 6 January 2015 . The New York Times.
  19. C. . Beichman. Christopher R. . Gelino. J. Davy. Kirkpatrick. Michael C. . Cushing. Sally . Dodson-Robinson. Mark S.. Marley. Caroline V. . Morley. E. L. . Wright. 2014. WISE Y Dwarfs As Probes of the Brown Dwarf-Exoplanet Connection. The Astrophysical Journal. 783 . 2 . 68. 1401.1194 . 2014ApJ...783...68B. 10.1088/0004-637X/783/2/68. 119302072.
  20. Web site: 2014-03-13. A Guide to Lonely Planets in the Galaxy. https://web.archive.org/web/20210518220530/https://www.nationalgeographic.com/science/article/a-guide-to-lonely-planets-in-the-galaxy. dead. 18 May 2021. 2022-01-17. National Geographic . Drake . Nadia . Nadia Drake . en.
  21. Strigari . L. E.. Barnabè . M.. Marshall . P. J.. Blandford. R. D.. Nomads of the Galaxy. 2012. 423 . 2 . 1856–1865. Monthly Notices of the Royal Astronomical Society. 1201.2687. 2012MNRAS.423.1856S. 10.1111/j.1365-2966.2012.21009.x. free . 119185094. estimates 700 objects >10−6 solar masses (roughly the mass of Mars) per main-sequence star between 0.08 and 1 Solar mass, of which there are billions in the Milky Way.
  22. Web site: IAU 2006 General Assembly: Result of the IAU Resolution votes. 2006. 25 April 2010.
  23. Web site: Brit, R. R.. 2006. Why Planets Will Never Be Defined. Space.com. 13 February 2008.
  24. Web site: 28 February 2003. Working Group on Extrasolar Planets: Definition of a "Planet". IAU position statement. 23 November 2014.
  25. Web site: Official Working Definition of an Exoplanet. IAU position statement. 29 November 2020.
  26. Lecavelier des Etangs . A. . Lissauer . Jack J. . June 2022 . The IAU working definition of an exoplanet . New Astronomy Reviews . en . 94 . 101641 . 10.1016/j.newar.2022.101641. 2203.09520 . 2022NewAR..9401641L . 247065421 .
  27. 0710.5667 . Giant Planet Formation by Core Accretion . Extreme Solar Systems . 398 . 235 . 2008ASPC..398..235M . Mordasini. C. . Alibert . Yann . Benz . Willy . Naef . Dominique . 2008 .
  28. 0802.1810 . Structure and evolution of super-Earth to super-Jupiter exoplanets. I. Heavy element enrichment in the interior . Baraffe . I. . 2008 . Astronomy and Astrophysics . 482 . 1 . 315–332 . 10.1051/0004-6361:20079321 . 2008A&A...482..315B . Chabrier . G. . Barman . T. . 16746688 .
  29. Deuterium Burning in Massive Giant Planets and Low-mass Brown Dwarfs Formed by Core-nucleated Accretion . The Astrophysical Journal . 2013 . 770 . 2 . 120 . 10.1088/0004-637X/770/2/120 . 1305.0980 . 2013ApJ...770..120B . Bodenheimer . Peter . D'Angelo . Gennaro . Lissauer . Jack J. . Fortney . Jonathan J. . Saumon . Didier . 118553341 .
  30. 10.1051/0004-6361/200912427 . The SOPHIE northern extrasolar planets. I. A companion close to the planet/brown-dwarf transition around HD16760 . Bouchy . François . Hébrard . Guillaume . Udry . Stéphane . Delfosse . Xavier . Boisse . Isabelle . Desort . Morgan . Bonfils . Xavier . Eggenberger . Anne . Ehrenreich . David . Forveille . Thierry . Le Coroller . Hervé . Lagrange . Anne-Marie . Lovis . Christophe . Moutou . Claire . Pepe . Francesco . Perrier . Christian . Pont . Frédéric . Queloz . Didier . Santos . Nuno C. . Ségransan . Damien . Vidal-Madjar . Alfred . 2009 . Astronomy and Astrophysics . 505 . 2 . 853–858 . 2009A&A...505..853B . free .
  31. 2003IAUS..211..529B. Nomenclature: Brown Dwarfs, Gas Giant Planets, and ?. Kumar. Shiv S.. 211. 2003. 532. Brown Dwarfs .
  32. 10.1088/0004-637X/794/2/159. A Statistical Analysis of Seeds and Other High-Contrast Exoplanet Surveys: Massive Planets or Low-Mass Brown Dwarfs?. The Astrophysical Journal. 794. 2. 159. 2014. Brandt . T. D. . McElwain . M. W. . Turner . E. L. . Mede . K. . Spiegel . D. S. . Kuzuhara . M. . Schlieder . J. E. . Wisniewski . J. P. . Abe . L.. Biller . B.. Brandner . W.. Carson . J.. Currie . T.. Egner . S.. Feldt . M.. Golota . T.. Goto . M.. Grady . C. A.. Guyon . O.. Hashimoto . J.. Hayano . Y.. Hayashi . M.. Hayashi . S.. Henning . T.. Hodapp . K. W.. Inutsuka . S.. Ishii . M.. Iye . M.. Janson . M.. Kandori . R.. etal. 2014ApJ...794..159B. 1404.5335 . 119304898.
  33. Schlaufman. Kevin C.. 2018-01-22. Evidence of an Upper Bound on the Masses of Planets and its Implications for Giant Planet Formation. The Astrophysical Journal. 853. 1. 37. 10.3847/1538-4357/aa961c. 1801.06185. 2018ApJ...853...37S. 55995400. 1538-4357 . free .
  34. 10.1088/0004-637X/727/1/57. The Deuterium-Burning Mass Limit for Brown Dwarfs and Giant Planets. The Astrophysical Journal. 727. 1. 57. 2011. Spiegel . D. S. . Burrows . Adam . Milsom . J. A. . 2011ApJ...727...57S. 1008.5150 . 118513110.
  35. Schneider . J. . Dedieu . C. . Le Sidaner . P. . Savalle . R. . Zolotukhin . I. . Defining and cataloging exoplanets: The exoplanet.eu database. 2011. 532. 79. . 1106.0586. 10.1051/0004-6361/201116713. A79 . 2011A&A...532A..79S. 55994657 .
  36. Book: Schneider, Jean. Exoplanets versus brown dwarfs: the CoRoT view and the future. III.8 Exoplanets versus brown dwarfs: The CoRoT view and the future. 2016. 157. 10.1051/978-2-7598-1876-1.c038. 1604.00917. 978-2-7598-1876-1. 118434022.
  37. 1506.05097. Hatzes Heike Rauer. Artie P.. A Definition for Giant Planets Based on the Mass-Density Relationship. 2015. 10.1088/2041-8205/810/2/L25. 810. 2. The Astrophysical Journal. L25. 2015ApJ...810L..25H . 119111221.
  38. 1012.5676 . The Exoplanet Orbit Database. 2010. 2011PASP..123..412W . 10.1086/659427. 123. 902. Publications of the Astronomical Society of the Pacific. 412–422. Wright. J. T.. Fakhouri. O.. Marcy. G. W.. Han. E.. Feng. Y.. Johnson. John Asher. Howard. A. W.. Fischer. D. A.. Valenti . J. A.. Anderson. J.. Piskunov. N.. 51769219.
  39. Web site: Exoplanet Criteria for Inclusion in the Exoplanet Archive. 2022-01-17. exoplanetarchive.ipac.caltech.edu.
  40. 10.1146/annurev.earth.34.031405.125058 . Annu. Rev. Earth Planet. Sci. . 34 . Planetesimals To Brown Dwarfs: What is a Planet? . 193–216 . 2006 . astro-ph/0608417 . 2006AREPS..34..193B. Basri . Gibor . Brown . Michael E. . 119338327 . Submitted manuscript .
  41. 2003IAUS..211..529B. Nomenclature: Brown Dwarfs, Gas Giant Planets, and ?. Liebert. James. 211. 2003. 533. Brown Dwarfs .
  42. Web site: International Astronomical Union IAU. www.iau.org. 29 January 2017.
  43. Web site: Landau . Elizabeth . Overlooked Treasure: The First Evidence of Exoplanets . 1 November 2017 . . 1 November 2017 .
  44. Zachos . Elaina . More Than a Trillion Planets Could Exist Beyond Our Galaxy – A new study gives the first evidence that exoplanets exist beyond the Milky Way. . https://web.archive.org/web/20210428194238/https://www.nationalgeographic.com/science/article/exoplanets-discovery-milky-way-galaxy-spd . dead . 28 April 2021 . . 5 February 2018 . 31 July 2022.
  45. Web site: Cosmic Milestone: NASA Confirms 5,000 Exoplanets. March 21, 2022. NASA. April 5, 2022.
  46. News: Chow . Denise . James Webb Telescope finds its first exoplanet – The planet is almost the same size as Earth, according to a research team led by astronomers at the Johns Hopkins University Applied Physics Laboratory.. 11 January 2023 . . 12 January 2023 .
  47. Book: Newton, Isaac. I. Bernard Cohen . Anne Whitman. The Principia: A New Translation and Guide. University of California Press. 1999. 1713. 940. 978-0-520-08816-0.
  48. Proposal for a project of high-precision stellar radial velocity work. Struve. Otto . The Observatory. 72. 199–200 . 1952. 1952Obs....72..199S .
  49. Jacob, W. S.. 1855. On Certain Anomalies presented by the Binary Star 70 Ophiuchi. Monthly Notices of the Royal Astronomical Society. 15 . 9. 228–230. 1855MNRAS..15..228J . 10.1093/mnras/15.9.228. free.
  50. See . T. J. J. . Thomas Jefferson Jackson See . 1896 . Researches on the orbit of 70 Ophiuchi, and on a periodic perturbation in the motion of the system arising from the action of an unseen body . The Astronomical Journal . 16 . 17–23 . 10.1086/102368 . 1896AJ.....16...17S.
  51. Sherrill, T. J.. 1999. Journal for the History of Astronomy. A Career of Controversy: The Anomaly of T. J. J. See. 30 . 98 . 25–50. 1999JHA....30...25S . 10.1177/002182869903000102. 117727302.
  52. van de Kamp, P. . 1969. Alternate dynamical analysis of Barnard's star. Astronomical Journal. 74 . 757–759. 10.1086/110852. 1969AJ.....74..757V.
  53. Book: Boss, Alan. The Crowded Universe: The Search for Living Planets. Basic Books. 2009. 31–32. 978-0-465-00936-7.
  54. Bailes . M. . Lyne . A. G. . Andrew Lyne. Shemar . S. L. . 10.1038/352311a0 . 1991Natur.352..311B. A planet orbiting the neutron star PSR1829–10 . Nature . 352 . 6333 . 311–313 . 1991 . 4339517 .
  55. 10.1038/355213b0. No planet orbiting PS R1829–10. Nature. 355. 6357. 213. 1992. Lyne . A. G.. Bailes . M. . 1992Natur.355..213L. 40526307. free.
  56. Campbell . B. . Walker . G. A. H. . Yang . S. . A search for substellar companions to solar-type stars . 10.1086/166608 . The Astrophysical Journal . 331 . 902 . 1988 . 1988ApJ...331..902C. free .
  57. Lawton . A. T.. Wright . P.. 1989. A planetary system for Gamma Cephei?. Journal of the British Interplanetary Society. 42. 335–336. 1989JBIS...42..335L.
  58. Walker . G. A. H. 1992. Gamma Cephei – Rotation or planetary companion?. Astrophysical Journal Letters. 396. 2. L91–L94. 10.1086/186524. 1992ApJ...396L..91W. Bohlender . D. A.. Walker . A. R.. Irwin . A. W.. Yang . S. L. S.. Larson . A.. free.
  59. Hatzes . A. P.. Cochran . William D.. A Planetary Companion to Gamma Cephei A. Astrophysical Journal. 2003. 599. 2. 1383–1394. 10.1086/379281. 2003ApJ...599.1383H. astro-ph/0305110. Endl. Michael. McArthur. Barbara. Paulson. Diane B.. Walker. Gordon A. H.. Campbell. Bruce. Yang. Stephenson. 11506537.
  60. Wolszczan . A. . 1992Natur.355..145W. Frail . D. A. . 10.1038/355145a0 . A planetary system around the millisecond pulsar PSR1257 + 12 . Nature . 355 . 6356 . 145–147 . 1992 . 4260368 .
  61. News: Scientists Uncover Evidence of New Planets Orbiting Star . . Robert . Holtz . 22 April 1994 . 20 April 2012 . 17 May 2013 . https://web.archive.org/web/20130517225034/http://tech.mit.edu/V114/N22/psr.22w.html . dead .
  62. Book: Rodriguez Baquero, Oscar Augusto. 2017. La presencia humana más allá del sistema solar. Human presence beyond the solar system. Spanish. 29. RBA. 978-84-473-9090-8.
  63. Web site: Oldest Known Planet Identified . . 2006-05-07.
  64. 10.1038/378355a0. A Jupiter-mass companion to a solar-type star. Nature. 378. 6555. 355–359. 1995. Mayor . M. . Queloz . D. . 1995Natur.378..355M. 4339201.
  65. Gibney. Elizabeth. In search of sister earths. Nature. 18 December 2013. 504. 7480. 357–365. 10.1038/504357a. 24352276. 2013Natur.504..357. . free.
  66. Wenz . John . Lessons from scorching hot weirdo-planets . Knowable Magazine . Annual Reviews . 10 October 2019 . 10.1146/knowable-101019-2. free . 4 April 2022 . en.
  67. 10.1038/19409. 1999. Lissauer . J. J. . Three planets for Upsilon Andromedae. Nature. 398. 6729. 659. 1999Natur.398..659L. 204992574. free.
  68. 10.1126/science.1210923. 21921192. Kepler-16: A Transiting Circumbinary Planet. Science. 333. 6049. 1602–1606. 2011. Doyle . L. R.. Carter . J. A.. Fabrycky . D. C.. Slawson . R. W.. Howell . S. B.. Winn . J. N.. Orosz . J. A.. Prša . A.. Welsh . W. F.. Quinn . S. N.. Latham . D.. Torres . G.. Buchhave . L. A.. Marcy . G. W.. Fortney . J. J.. Shporer . A.. Ford . E. B.. Lissauer . J. J.. Ragozzine . D.. Rucker . M.. Batalha . N.. Jenkins . J. M.. Borucki . W. J.. Koch . D.. Middour . C. K.. Hall . J. R.. McCauliff . S.. Fanelli . M. N.. Quintana . E. V.. Holman . M. J.. etal. 2011Sci...333.1602D. 1109.3432 . 206536332.
  69. Web site: Johnson . Michele . Harrington . J.D. . NASA's Kepler Mission Announces a Planet Bonanza, 715 New Worlds . 26 February 2014 . . 26 February 2014 . 26 February 2014 . https://web.archive.org/web/20140226202703/http://www.nasa.gov/ames/kepler/nasas-kepler-mission-announces-a-planet-bonanza/ . dead .
  70. Web site: Wall. Mike. Population of Known Alien Planets Nearly Doubles as NASA Discovers 715 New Worlds. 26 February 2014. 27 February 2014. space.com.
  71. News: Kepler telescope bags huge haul of planets. 27 February 2014. 26 February 2014. Jonathan Amos . BBC News.
  72. Web site: Johnson . Michelle . Chou . Felicia . NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth . 23 July 2015 . NASA.
  73. News: NASA . Discovery alert! Oddball planet could surrender its secrets . 28 November 2018 . Exoplanet Exploration: Planets Beyond our Solar System.
  74. Fulton . Benjamin J. . Petigura . Erik A. . Howard . Andrew W. . Isaacson . Howard . Marcy . Geoffrey W. . Cargile . Phillip A. . Hebb . Leslie . Weiss . Lauren M. . Johnson . John Asher . Morton . Timothy D. . Sinukoff . Evan . Crossfield . Ian J. M. . Hirsch . Lea A. . 2017-09-01 . The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets* . The Astronomical Journal . 154 . 3 . 109 . 10.3847/1538-3881/aa80eb . free . 1703.10375 . 2017AJ....154..109F . 0004-6256.
  75. Web site: Radius Gap . 2024-04-03 . sites.astro.caltech.edu.
  76. Web site: [VIDEO] TOI 700d : une planète de la taille de la Terre découverte dans une "zone habitable"]. midilibre.fr. fr. 2020-04-17.
  77. Web site: Exoplanet and Candidate Statistics. NASA Exoplanet Archive, California Institute of Technology. 2020-01-17.
  78. Web site: Kepler . https://web.archive.org/web/20131105082102/http://www.nasa.gov/mission_pages/kepler/main/index.html . 5 November 2013 . NASA . nasa.gov . Jerry Colen . 4 November 2013 . 4 November 2013.
  79. Web site: Harrington . J. D. . Johnson . M. . 4 November 2013 . NASA Kepler Results Usher in a New Era of Astronomy .
  80. Web site: NASA's Exoplanet Archive KOI table. NASA. 28 February 2014. https://archive.today/20140226203336/http://exoplanetarchive.ipac.caltech.edu/cgi-bin/ExoTables/nph-exotbls?dataset=cumulative. 26 February 2014. dead.
  81. News: Crane . Leah . Astronomers may have found the first planet in another galaxy . 23 September 2020 . . 25 September 2020 .
  82. Di Stafano, R. . et al. . M51-ULS-1b: The First Candidate for a Planet in an External Galaxy . 18 September 2020 . astro-ph.HE . 2009.08987 .
  83. News: Gough . Evan . A Rogue Earth-Mass Planet Has Been Discovered Freely Floating in the Milky Way Without a Star . 1 October 2020 . . 2 October 2020 .
  84. Mroz, Przemek. et al.. A terrestrial-mass rogue planet candidate detected in the shortest-timescale microlensing event . The Astrophysical Journal. 29 September 2020 . 903. 1. L11. 10.3847/2041-8213/abbfad. 2009.12377 . 2020ApJ...903L..11M. 221971000 . free .
  85. Book: Perryman, Michael. The Exoplanet Handbook. limited. Cambridge University Press. 2011. 149. 978-0-521-76559-6.
  86. 10.1051/0004-6361/201117055. The HARPS search for Earth-like planets in the habitable zone. Astronomy & Astrophysics. 534. A58. 2011. Pepe . F.. Lovis . C.. Ségransan . D.. Benz . W.. Bouchy . F.. Dumusque . X.. Mayor . M.. Queloz . D.. Santos . N. C.. Udry . S.. 2011A&A...534A..58P. 1108.3447 . 15088852.
  87. http://www.scientificcomputing.com/news-DS-Planet-Hunting-Finding-Earth-like-Planets-071910.aspx Planet Hunting: Finding Earth-like Planets
  88. 10.1088/0004-637X/743/2/200. 1109.1561. 2011ApJ...743..200B. The Kepler-19 System: A Transiting 2.2 R⊕ Planet and a Second Planet Detected Via Transit Timing Variations. The Astrophysical Journal. 743. 2. 200. 2011. Ballard . S. . Fabrycky . D. . Fressin . F. . Charbonneau . D. . Desert . J. M. . Torres . G. . Marcy . G. . Burke . C. J. . Isaacson . H. . Henze . C. . Steffen . J. H. . Ciardi . D. R. . Howell . S. B. . Cochran . W. D. . Endl . M. . Bryson . S. T. . Rowe . J. F. . Holman . M. J. . Lissauer . J. J. . Jenkins . J. M. . Still . M. . Ford . E. B. . Christiansen . J. L. . Middour . C. K. . Haas . M. R. . Li . J. . Hall . J. R. . McCauliff . S. . Batalha . N. M. . Koch . D. G. . 42698813. etal.
  89. Pál . A. . Kocsis . B. . Periastron Precession Measurements in Transiting Extrasolar Planetary Systems at the Level of General Relativity . 2008 . 10.1111/j.1365-2966.2008.13512.x . Monthly Notices of the Royal Astronomical Society . 389 . 1 . 191–198 . free . 0806.0629. 2008MNRAS.389..191P . 15282437 .
  90. 2208.14553 . Curiel . Salvador . Ortiz-León . Gisela N. . Mioduszewski . Amy J. . Sanchez-Bermudez . Joel . September 2022 . 3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion . . 164 . 3 . 93 . 10.3847/1538-3881/ac7c66 . 2022AJ....164...93C. 251953478 . free .
  91. Sozzetti . A. . Pinamonti . M. . etal . September 2023 . The GAPS Programme at TNG. XLVII. A conundrum resolved: HIP 66074b/Gaia-3b characterised as a massive giant planet on a quasi-face-on and extremely elongated orbit . . 677 . L15 . 10.1051/0004-6361/202347329 . free . 2023A&A...677L..15S. 2108/347124 . free .
  92. 10.1038/nature06143. 17851517. 2007Natur.449..189S . A giant planet orbiting the 'extreme horizontal branch' star V 391 Pegasi. Nature. 449. 7159. 189–191. 2007. Silvotti . R.. Schuh . S.. Janulis . R.. Solheim . J. -E. . Bernabei . S.. Østensen . R.. Oswalt . T. D.. Bruni . I.. Gualandi . R.. Bonanno . A.. Vauclair . G.. Reed . M.. Chen . C. -W. . Leibowitz . E.. Paparo . M.. Baran . A.. Charpinet . S.. Dolez . N.. Kawaler . S.. Kurtz . D.. Moskalik . P.. Riddle . R.. Zola . S.. 4342338.
  93. Jenkins. J.M.. Laurance R. Doyle. 20 September 2003. Detecting reflected light from close-in giant planets using space-based photometers. Astrophysical Journal. 1. 595. 429–445. 10.1086/377165. 2003ApJ...595..429J. astro-ph/0305473 . 17773111.
  94. astro-ph/0303212 . 2003ApJ...588L.117L . 10.1086/375551 . Periodic Flux Variability of Stars due to the Reflex Doppler Effect Induced by Planetary Companions . 2003 . Loeb . A. . Gaudi . B. S. . The Astrophysical Journal Letters . 588 . 2 . L117. 10066891 .
  95. Web site: Atkinson. Nancy. 2013-05-13. Using the Theory of Relativity and BEER to Find Exoplanets. 2023-02-12. Universe Today. en-US.
  96. 10.1017/S1743921306009252. Search and investigation of extra-solar planets with polarimetry. Proceedings of the International Astronomical Union. 1. 165. 2006. Schmid . H. M.. Beuzit . J. -L. . Feldt . M.. Gisler . D.. Gratton . R.. Henning . T. . Joos . F.. Kasper . M.. Lenzen . R.. Mouillet . D.. Moutou . C.. Quirrenbach . A.. Stam . D. M.. Thalmann . C.. Tinbergen . J.. Verinaud . C.. Waters . R.. Wolstencroft . R.. 2006dies.conf..165S. free.
  97. 10.1086/527320. First Detection of Polarized Scattered Light from an Exoplanetary Atmosphere. The Astrophysical Journal. 673. 1. L83. 2008. Berdyugina . S. V.. Berdyugin . A. V.. Fluri . D. M.. Piirola . V. . 2008ApJ...673L..83B. 0712.0193 . 14366978.
  98. Book: 0906.5011. 2009AIPC.1158....3M . 10.1063/1.3215910 . Initial Conditions of Planet Formation: Lifetimes of Primordial Disks . AIP Conference Proceedings . 1158 . 3 . 2009 . Mamajek . Eric E. . Usuda . Tomonori . Tamura . Motohide . Ishii . Miki . Exoplanets and Disks: Their Formation and Diversity . 16660243 . Exoplanets and Disks: Their Formation and Diversity: Proceedings of the International Conference
  99. 10.1086/380390. astro-ph/0310191. On the Formation Timescale and Core Masses of Gas Giant Planets. The Astrophysical Journal. 598. 1. L55–L58. 2003. Rice . W. K. M.. Armitage . P. J. . 2003ApJ...598L..55R. 14250767.
  100. 10.1038/nature00995. A short timescale for terrestrial planet formation from Hf–W chronometry of meteorites. Nature. 418. 6901. 949–952. 2002. Yin . Q. . Jacobsen . S. B.. Yamashita . K.. Blichert-Toft . J.. Télouk . P.. Albarède . F.. 2002Natur.418..949Y . 12198540. 4391342.
  101. Book: D'Angelo, G.. Durisen, R. H. . Lissauer, J. J.. Giant Planet Formation . 2010exop.book..319D. Exoplanets . University of Arizona Press, Tucson, AZ. S. Seager. . 319–346. 2011. http://www.uapress.arizona.edu/Books/bid2263.htm. 1006.5486 .
  102. Book: D'Angelo, G.. Lissauer, J. J.. Formation of Giant Planets . 2018haex.bookE.140D. Handbook of Exoplanets . Springer International Publishing AG, part of Springer Nature. Deeg H., Belmonte J. . 2319–2343. 2018. 1806.05649. 10.1007/978-3-319-55333-7_140. 978-3-319-55332-0. 116913980.
  103. Calvet. Nuria. Nuria Calvet. D'Alessio. Paola. Hartmann. Lee. Wilner. David. Walsh. Andrew. Sitko. Michael. Evidence for a developing gap in a 10 Myr old protoplanetary disk. The Astrophysical Journal. 2001. 568. 2. 1008–1016. 10.1086/339061. 2002ApJ...568.1008C. astro-ph/0201425. 8706944.
  104. Fridlund. Malcolm. Gaidos. Eric. Barragán. Oscar. Persson. Carina. Gandolfi. Davide. Cabrera. Juan. Hirano. Teruyuki. Kuzuhara. Masayuki. Csizmadia. Sz. Nowak. Grzegorz. Endl. Michael. Grziwa. Sascha. Korth. Judith. Pfaff. Jeremias. Bitsch. Bertram. Johansen. Anders. Mustill. Alexander. Davies. Melvyn. Deeg. Hans. Palle. Enric. Cochran. William. Eigmüller. Philipp. Erikson. Anders. Guenther. Eike. Hatzes. Artie. Kiilerich. Amanda. Kudo. Tomoyuki. MacQueen. Philipp. Narita. Norio. Nespral. David. Pätzold. Martin. Prieto-Arranz. Jorge. Rauer. Heike. van Eylen. Vincent. EPIC210894022b −A short period super-Earth transiting a metal poor, evolved old star. Astronomy & Astrophysics. 604. A16. 28 April 2017. 1704.08284. 10.1051/0004-6361/201730822. 39412906.
  105. D'Angelo. G.. Bodenheimer, P. . In Situ and Ex Situ Formation Models of Kepler 11 Planets. The Astrophysical Journal. 2016. 828. 1. id. 33 (32 pp.). 10.3847/0004-637X/828/1/33. 1606.08088 . 2016ApJ...828...33D . 119203398 . free .
  106. D'Angelo. G.. Bodenheimer, P. . Three-Dimensional Radiation-Hydrodynamics Calculations of the Envelopes of Young Planets Embedded in Protoplanetary Disks. The Astrophysical Journal. 2013. 778. 1. 77 (29 pp.). 10.1088/0004-637X/778/1/77. 1310.2211 . 2013ApJ...778...77D . 118522228.
  107. D'Angelo. G.. Weidenschilling, S. J. . Lissauer, J. J. . Bodenheimer, P. . Growth of Jupiter: Enhancement of core accretion by a voluminous low-mass envelope. Icarus. 2014. 241. 298–312. 1405.7305. 10.1016/j.icarus.2014.06.029. 2014Icar..241..298D. 118572605.
  108. 10.1093/mnras/stu085 . 1401.2765 . Origin and loss of nebula-captured hydrogen envelopes from 'sub'- to 'super-Earths' in the habitable zone of Sun-like stars . Monthly Notices of the Royal Astronomical Society . 439 . 4 . 3225–3238 . 2014 . Lammer . H. . Stokl . A. . Erkaev . N. V. . Dorfi . E. A. . Odert . P. . Gudel . M. . Kulikov . Y. N. . Kislyakova . K. G. . Leitzinger . M. . free . 2014MNRAS.439.3225L. 118620603.
  109. 1001.0917 . Johnson . R. E. . Thermally-Diven Atmospheric Escape . The Astrophysical Journal . 716 . 2 . 1573–1578 . 2010 . 10.1088/0004-637X/716/2/1573 . 2010ApJ...716.1573J . 36285464.
  110. 1006.0021. 2010Icar..210..539Z . 10.1016/j.icarus.2010.07.013 . 210 . 2 . Atmospheric mass loss by stellar wind from planets around main sequence M stars . Icarus . 539–544 . 2010 . Zendejas . J. . Segura . A. . Raga . A.C. . 119243879.
  111. 10.1088/0004-637X/783/1/53. Very Low Density Planets Around Kepler-51 Revealed with Transit Timing Variations and an Anomaly Similar to a Planet-Planet Eclipse Event . The Astrophysical Journal . 783 . 1 . 53 . 2014 . Masuda . K. . 2014ApJ...783...53M . 1401.2885 . 119106865.
  112. Petigura . E. A.. Howard . A. W.. Marcy . G. W.. 2013. Prevalence of Earth-size planets orbiting Sun-like stars. Proceedings of the National Academy of Sciences. 110. 48. 19273–19278. 1311.6806. 2013PNAS..11019273P. 10.1073/pnas.1319909110 . 24191033 . 3845182. free.
  113. 2008. The Keck Planet Search: Detectability and the Minimum Mass and Orbital Period Distribution of Extrasolar Planets. Publications of the Astronomical Society of the Pacific. 120. 867. 531–554. 0803.3357. 10.1086/588487. 2008PASP..120..531C. Geoffrey Marcy. Steven S. Vogt. Debra Fischer . Cumming. Andrew. Butler. R. Paul. Marcy. Geoffrey W.. Vogt. Steven S.. Wright. Jason T.. Fischer. Debra A.. 10979195.
  114. 10.1051/0004-6361:200500193 . The HARPS search for southern extra-solar planets VI: A Neptune-mass planet around the nearby M dwarf Gl 581 . Astronomy and Astrophysics . 443 . 3 . L15–L18 . 2005 . Bonfils . Xavier . Forveille . Thierry . Delfosse . Xavier . Udry . Stéphane . Mayor . Michel . Perrier . Christian . Bouchy . François . Pepe . Francesco . Queloz . Didier . Bertaux . Jean-Loup . 2005A&A...443L..15B . astro-ph/0509211 . 59569803 .
  115. 10.1088/0004-6256/149/1/14. Revealing a Universal Planet–Metallicity Correlation for Planets of Different Solar-Type Stars. The Astronomical Journal. 149. 1. 14. 2014. Wang . J. . Fischer . D. A. . 2015AJ....149...14W. 1310.7830 . 118415186.
  116. Web site: Science work. 2022-01-17. www.univie.ac.at.
  117. Web site: STAR-DATA. 2022-01-17. www.univie.ac.at.
  118. Web site: Garner. Rob. 2016-10-31. NASA Hubble Finds a True Blue Planet. 2022-01-17. NASA.
  119. 10.1088/2041-8205/772/2/L16. 1307.3239. The Deep Blue Color of HD189733b: Albedo Measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at Visible Wavelengths. The Astrophysical Journal. 772. 2. L16. 2013. Evans . T. M. . Pont . F. D. R. . Sing . D. K. . Aigrain . S.. Suzanne Aigrain . Barstow . J. K. . Désert . J. M. . Gibson . N. . Heng . K. . Knutson . H. A. . Lecavelier Des Etangs . A. . 2013ApJ...772L..16E. 38344760.
  120. 1307.2886. Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504. The Astrophysical Journal. 774. 11. 11. 2013. etal. 10.1088/0004-637X/774/1/11. 2013ApJ...774...11K . Kuzuhara. M.. Tamura. M.. Kudo. T.. Janson. M.. Kandori. R.. Brandt. T. D.. Thalmann. C.. Spiegel. D.. Biller. B.. Carson. J.. Hori. Y.. Suzuki. R. . Burrows . Adam . Henning. T.. Turner. E. L.. McElwain. M. W.. Moro-Martín. A.. Suenaga. T.. Takahashi. Y. H.. Kwon. J.. Lucas. P.. Abe. L.. Brandner. W.. Egner. S.. Feldt. M.. Fujiwara. H.. Goto. M.. Grady. C. A.. Guyon. O.. Hashimoto. J.. 53343537.
  121. Direct Imaging Discovery of a 'Super-Jupiter' Around the late B-Type Star Kappa And. 15 November 2012. 1211.3744. Carson. Thalmann. Janson. Kozakis. Bonnefoy. Biller. Schlieder. Currie. McElwain. 2013ApJ...763L..32C . 10.1088/2041-8205/763/2/L32. 763. 2. The Astrophysical Journal. L32. 119253577.
  122. News: Helium-Shrouded Planets May Be Common in Our Galaxy . SpaceDaily . 16 June 2015 . 3 August 2015.
  123. http://phl.upr.edu/library/notes/theapparentbrightnessandsizeofexoplanetsandtheirstars The Apparent Brightness and Size of Exoplanets and their Stars
  124. Web site: Coal-Black Alien Planet Is Darkest Ever Seen . 11 August 2011 . Space.com . 12 August 2011.
  125. 1108.2297 . 2011MNRAS.417L..88K . 10.1111/j.1745-3933.2011.01127.x . 417 . 1 . Detection of visible light from the darkest world . Monthly Notices of the Royal Astronomical Society: Letters . L88–L92 . 2011 . Kipping . David M. . Spiegel . David S. . free . 119287494.
  126. 10.1088/0004-637X/761/1/53 . 1210.4592 . Photometrically derived masses and radii of the planet and star in the TrES-2 system . The Astrophysical Journal . 761 . 1 . 53 . 2012 . Barclay . T. . Huber . D. . Rowe . J. F. . Fortney . J. J. . Morley . C. V. . Quintana . E. V. . Fabrycky . D. C. . Barentsen . G. . Bloemen . S. . Christiansen . J. L. . Demory . B. O. . Fulton . B. J. . Jenkins . J. M. . Mullally . F. . Ragozzine . D. . Seader . S. E. . Shporer . A. . Tenenbaum . P. . Thompson . S. E. . 2012ApJ...761...53B . 18216065.
  127. 1412.6097 . Burrows . Adam . Scientific Return of Coronagraphic Exoplanet Imaging and Spectroscopy Using WFIRST . astro-ph.EP . 2014 .
  128. Web site: Charles Q. Choi. 2014-11-20. Unlocking the Secrets of an Alien World's Magnetic Field. 2022-01-17. Space.com. en.
  129. 10.1126/science.1257829. 25414310 . Magnetic moment and plasma environment of HD 209458b as determined from Ly observations . Science . 346 . 6212 . 981–984 . 2014 . Kislyakova . K. G.. Holmstrom . M. . Lammer . H. . Odert . P. . Khodachenko . M. L. . 2014Sci...346..981K . 1411.6875 . 206560188.
  130. 10.1111/j.1365-2966.2011.18528.x. 1102.2737. Magnetosphere-ionosphere coupling at Jupiter-like exoplanets with internal plasma sources: Implications for detectability of auroral radio emissions. Monthly Notices of the Royal Astronomical Society. 414. 3. 2125–2138. 2011. Nichols . J. D.. free . 2011MNRAS.414.2125N. 56567587.
  131. Web site: 2011-04-18. Radio Telescopes Could Help Find Exoplanets. 2022-01-17. Redorbit. en-US.
  132. Web site: Radio Detection of Extrasolar Planets: Present and Future Prospects. NRL, NASA/GSFC, NRAO, Observatoìre de Paris. 15 October 2008. 30 October 2008. https://web.archive.org/web/20081030022342/http://www.ece.vt.edu/swe/lwa/memo/lwa0013.pdf. dead.
  133. Kean. Sam. Forbidden plants, forbidden chemistry. Distillations. 2016. 2. 2. 5. 22 March 2018. 23 March 2018. https://web.archive.org/web/20180323154914/https://www.sciencehistory.org/distillations/magazine/forbidden-planet-forbidden-chemistry. dead.
  134. Web site: Charles Q. Choi. 2012-11-22. Super-Earths Get Magnetic 'Shield' from Liquid Metal. 2022-01-17. Space.com. en.
  135. 10.1088/2041-8205/765/2/L25. Stellar Magnetic Fields As a Heating Source for Extrasolar Giant Planets. The Astrophysical Journal. 765. 2. L25. 2013. Buzasi . D.. 1302.1466 . 2013ApJ...765L..25B . 118978422.
  136. News: Chang . Kenneth . Settling Arguments About Hydrogen With 168 Giant Lasers – Scientists at Lawrence Livermore National Laboratory said they were "converging on the truth" in an experiment to understand hydrogen in its liquid metallic state. . https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2018/08/16/science/metallic-hydrogen-lasers.html . 2022-01-01 . limited . 16 August 2018 . The New York Times . 18 August 2018.
  137. Staff . Under pressure, hydrogen offers a reflection of giant planet interiors – Hydrogen is the most-abundant element in the universe and the simplest, but that simplicity is deceptive . 16 August 2018 . . 18 August 2018.
  138. Route. Matthew. The Rise of ROME. I. A Multiwavelength Analysis of the Star-Planet Interaction in the HD 189733 System. The Astrophysical Journal. 10 February 2019. 872. 1. 79. 10.3847/1538-4357/aafc25. 1901.02048. 2019ApJ...872...79R. 119350145 . free .
  139. Web site: Passant Rabie. 2019-07-29. Magnetic Fields of 'Hot Jupiter' Exoplanets Are Much Stronger Than We Thought. 2022-01-17. Space.com. en.
  140. Cauley. P. Wilson. Shkolnik. Evgenya L.. Llama. Joe. Lanza. Antonino F.. Dec 2019. Magnetic field strengths of hot Jupiters from signals of star-planet interactions. Nature Astronomy. 3. 12. 1128–1134. 10.1038/s41550-019-0840-x. 1907.09068. 2019NatAs...3.1128C. 198147426. 2397-3366.
  141. 10.1016/j.epsl.2009.07.015 . Convection scaling and subduction on Earth and super-Earths . 2009 . Valencia . Diana . O'Connell . Richard J.. Earth and Planetary Science Letters . 286 . 3–4 . 492–502 . 2009E&PSL.286..492V.
  142. 10.1016/j.epsl.2011.07.029. Plate tectonics on super-Earths: Equally or more likely than on Earth. 2011 . Van Heck . H.J. . Tackley . P.J. . Earth and Planetary Science Letters . 310 . 3–4 . 252–261 . 2011E&PSL.310..252V.
  143. 10.1029/2007GL030598 . Geological consequences of super-sized Earths. 2007 . O'Neill . C. . Lenardic . A. . 41617531. Geophysical Research Letters . 34. 19. L19204 . 2007GeoRL..3419204O. free .
  144. Diana . Valencia . Richard J.. O'Connell . Dimitar D . Sasselov . November 2007 . Inevitability of Plate Tectonics on Super-Earths. Astrophysical Journal Letters . 670 . 1 . L45–L48 . 10.1086/524012 . 0710.0699. 2007ApJ...670L..45V. 9432267.
  145. Web site: Super Earths Likely To Have Both Oceans and Continents – Astrobiology. 2022-01-17. astrobiology.com. 7 January 2014 .
  146. 10.1088/0004-637X/781/1/27 . Water Cycling Between Ocean and Mantle: Super-Earths Need Not Be Waterworlds . The Astrophysical Journal . 781. 1 . 27 . 2014 . Cowan . N. B. . Abbot . D. S. . 2014ApJ...781...27C . 1401.0720 . 56272100.
  147. Astronomers May Have Found Volcanoes 40 Light-Years From Earth . https://web.archive.org/web/20150509051828/http://news.nationalgeographic.com/2015/05/150506-volcano-planet-space-cancri-astronomy/ . dead . 9 May 2015 . Michael D. Lemonick . 6 May 2015 . 8 November 2015 . National Geographic.
  148. 1505.00269 . 2016MNRAS.455.2018D . 10.1093/mnras/stv2239 . 455 . 2 . Variability in the super-Earth 55 Cnc e . Monthly Notices of the Royal Astronomical Society . 2018–2027 . 2015 . Demory . Brice-Olivier . Gillon . Michael . Madhusudhan . Nikku . Queloz . Didier . free . 53662519.
  149. Web site: Scientists Discover a Saturn-like Ring System Eclipsing a Sun-like Star. 2022-01-17. www.spacedaily.com.
  150. 10.1088/0004-6256/143/3/72. Planetary Construction Zones in Occultation: Discovery of an Extrasolar Ring System Transiting a Young Sun-Like Star and Future Prospects for Detecting Eclipses by Circumsecondary and Circumplanetary Disks. The Astronomical Journal. 143. 3. 72. 2012. Mamajek . E. E. . Quillen . A. C. . Pecaut . M. J. . Moolekamp . F. . Scott . E. L. . Kenworthy . M. A. . Cameron . A. C. . Parley . N. R. . 2012AJ....143...72M. 1108.4070 . 55818711.
  151. 10.1126/science.1166609. Optical Images of an Exosolar Planet 25 Light-Years from Earth. Science. 322. 5906. 1345–1348. 2008. Kalas . P.. Graham . J. R.. Chiang . E.. Fitzgerald . M. P.. Clampin . M.. Kite . E. S.. Stapelfeldt . K.. Marois . C.. Krist . J. . 0811.1994 . 19008414. 2008Sci...322.1345K. 10054103.
  152. 1104.3863. 2011ApJ...734..117S . 10.1088/0004-637X/734/2/117 . 734 . 2 . Warm Saturns: On the Nature of Rings around Extrasolar Planets That Reside inside the Ice Line . The Astrophysical Journal . 117. 2011 . Schlichting . Hilke E. . Chang . Philip . 42698264.
  153. 10.1088/0004-637X/785/2/155. 1312.3951. MOA-2011-BLG-262Lb: A sub-Earth-mass moon orbiting a gas giant or a high-velocity planetary system in the galactic bulge. The Astrophysical Journal. 785. 2. 155. 2014. Bennett . D. P.. Batista . V.. Bond . I. A.. Bennett . C. S.. Suzuki . D.. Beaulieu . J. -P. . Udalski . A.. Donatowicz . J.. Bozza . V.. Abe . F.. Botzler . C. S.. Freeman . M.. Fukunaga . D.. Fukui . A.. Itow . Y.. Koshimoto . N.. Ling . C. H.. Masuda . K.. Matsubara . Y.. Muraki . Y.. Namba . S.. Ohnishi . K.. Rattenbury . N. J.. Saito . T. . Sullivan . D. J.. Sumi . T.. Sweatman . W. L.. Tristram . P. J.. Tsurumi . N.. Wada . K.. etal. 2014ApJ...785..155B. 118327512.
  154. Teachey. Alex. Kipping. David M.. 1 October 2018. Evidence for a large exomoon orbiting Kepler-1625b. Science Advances. en. 4. 10. eaav1784. 10.1126/sciadv.aav1784. 30306135. 6170104. 2375-2548. 2018SciA....4.1784T. 1810.02362.
  155. Charbonneau. David. etal. 2002. Detection of an Extrasolar Planet Atmosphere. The Astrophysical Journal. 568. 1. 377–384. astro-ph/0111544. 2002ApJ...568..377C. 10.1086/338770. 14487268.
  156. Book: Madhusudhan. Nikku. 739. Knutson. Heather. Fortney. Jonathan. Barman. Travis. Protostars and Planets VI. 2014. 10.2458/azu_uapress_9780816531240-ch032. Exoplanetary Atmospheres. 978-0-8165-3124-0. 1402.1169 . 2014prpl.conf..739M . 118337613.
  157. 1005.4037 . Seager . S. . Deming . D. . Exoplanet Atmospheres . 2010. 10.1146/annurev-astro-081309-130837 . 2010ARA&A..48..631S . 48 . Annual Review of Astronomy and Astrophysics . 631–672. 119269678 .
  158. Weighing the Non-transiting Hot Jupiter τ Boo b . Rodler . F. . Lopez-Morales . M. . Ribas . I. . The Astrophysical Journal Letters . 753 . 1 . L25 . L25. July 2012 . 1206.6197 . 2012ApJ...753L..25R . 10.1088/2041-8205/753/1/L25 . 119177983 .
  159. 10.1038/nature11161. 22739313. The signature of orbital motion from the dayside of the planet τ Boötis b. Nature. 486. 7404. 502–504. 2012. Brogi . M. . Snellen . I. A. G. . De Kok . R. J. . Albrecht . S. . Birkby . J. . De Mooij . E. J. W. . 1206.6109 . 2012Natur.486..502B . 4368217.
  160. News: St. Fleur . Nicholas . Spotting Mysterious Twinkles on Earth From a Million Miles Away . https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2017/05/19/science/dscovr-satellite-ice-glints-earth-atmosphere.html . 2022-01-01 . limited . 19 May 2017 . The New York Times . 20 May 2017.
  161. Marshak . Alexander . Várnai . Tamás . Kostinski . Alexander . Terrestrial glint seen from deep space: oriented ice crystals detected from the Lagrangian point. 15 May 2017 . . 10.1002/2017GL073248 . 44 . 10 . 5197–5202. 2017GeoRL..44.5197M . 109930589 . 11603/13118 . free .
  162. Web site: University. Leiden. Evaporating exoplanet stirs up dust. 2022-01-17. phys.org. en.
  163. Web site: 2012-05-18. New-found exoplanet is evaporating away. 2022-01-17. TGDaily. en-US.
  164. News: Bhanoo . Sindya N. . A Planet with a Tail Nine Million Miles Long . 25 June 2015 . . 25 June 2015.
  165. Web site: Raymond. Sean. 2015-02-20. Forget "Earth-Like"—We'll First Find Aliens on Eyeball Planets. 2022-01-17. Nautilus. 23 June 2017. https://web.archive.org/web/20170623082602/http://nautil.us/blog/forget-earth_likewell-first-find-aliens-on-eyeball-planets. dead.
  166. 10.1016/j.icarus.2014.12.017. 2015Icar..250..395D . 250 . Insolation patterns on eccentric exoplanets . Icarus . 395–399. 2015 . Dobrovolskis . Anthony R..
  167. 10.1016/j.icarus.2013.06.026. 2013Icar..226..760D . 226 . 1 . Insolation on exoplanets with eccentricity and obliquity. Icarus . 760–776. 2013 . Dobrovolskis . Anthony R..
  168. 1204.1544. 2012ApJ...752....7H . 10.1088/0004-637X/752/1/7 . 752. 1 . Theoretical Spectra of Terrestrial Exoplanet Surfaces. The Astrophysical Journal. 7. 2012 . Hu . Renyu . Ehlmann . Bethany L. . Seager . Sara . 15219541 .
  169. 10.1038/nature05782 . A map of the day–night contrast of the extrasolar planet HD 189733b . 0705.0993 . 17495920 . 2007Natur.447..183K . Nature . 447 . 7141 . 183–186 . 2007 . Knutson . H. A. . Charbonneau . D. . Allen . L. E. . Lori Allen (astronomer) . Fortney . J. J. . Agol . E. . Cowan . N. B. . Showman . A. P. . Cooper . C. S. . Megeath . S. T. . 4402268.
  170. Planetary Environments and Origins of Life: How to reinvent the study of Origins of Life on the Earth and Life in the . BIO Web of Conferences 2 . 2014. Ollivier . Marc . Maurel . Marie-Christine . 10.1051/bioconf/20140200001. 2 . 00001. free .
  171. News: Oxygen Is Not Definitive Evidence of Life on Extrasolar Planets . NAOJ. Astrobiology Web . 10 September 2015 . 11 September 2015.
  172. A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around kepler m-dwarfs . Kopparapu, Ravi Kumar . The Astrophysical Journal Letters . 2013 . 767 . 1 . 10.1088/2041-8205/767/1/L8 . 1303.2649 . L8. 2013ApJ...767L...8K . 119103101.
  173. Cruz . Maria . Coontz . Robert . Exoplanets – Introduction to Special Issue . . 340 . 565. 10.1126/science.340.6132.565 . 23641107 . 6132 . 2013 . free.
  174. Web site: Choi . Charles Q. . 1 September 2011 . Astrobiology Magazine . Alien Life More Likely on 'Dune' Planets. https://web.archive.org/web/20131202223111/http://www.astrobio.net/exclusive/4188/alien-life-more-likely-on-%25E2%2580%2598dune%25E2%2580%2599-planets . 2 December 2013 .
  175. Abe . Y. . Abe-Ouchi . A. . Sleep . N. H. . Zahnle . K. J. . Habitable Zone Limits for Dry Planets . 10.1089/ast.2010.0545 . Astrobiology . 11 . 5 . 443–460 . 2011 . 21707386. 2011AsBio..11..443A .
  176. 10.1126/science.1232226. 23641111 . Exoplanet Habitability. Science. 340. 6132. 577–581. 2013. Seager . S.. 2013Sci...340..577S. 10.1.1.402.2983 . 206546351 .
  177. 1404.5292. 2014ApJ...787L..29K . 10.1088/2041-8205/787/2/L29 . 787. 2 . Habitable Zones around Main-sequence Stars: Dependence on Planetary Mass. The Astrophysical Journal. L29. 2014 . Kopparapu . Ravi Kumar . Ramirez . Ramses M. . Schottelkotte . James . Kasting . James F. . Domagal-Goldman . Shawn . Eymet . Vincent . 118588898 .
  178. 10.1038/nature12163. 23719462. Emergence of two types of terrestrial planet on solidification of magma ocean. Nature. 497. 7451. 607–610. 2013. Hamano . K. . Abe . Y. . Genda . H. . 2013Natur.497..607H. 4416458.
  179. 10.1088/2041-8205/787/1/L2 . 1404.4992 . Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate . The Astrophysical Journal . 787 . 1 . L2 . 2014 . Yang . J. . Boué . G. L. . Fabrycky . D. C. . Abbot . D. S. . 2014ApJ...787L...2Y . 56145598 . 2016-07-28 . https://web.archive.org/web/20160412161026/http://home.uchicago.edu/~junyang28/Papers/Yang-et-al-Rotation_Rate.pdf . 2016-04-12 . dead .
  180. Web site: Real-life Sci-Fi World #2: the Hot Eyeball planet. planetplanet. 2014-10-07.
  181. 1307.0515. 2013ApJ...771L..45Y . 10.1088/2041-8205/771/2/L45 . 771. 2 . The Astrophysical Journal. L45. 2013 . Yang . Jun . Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets . Cowan . Nicolas B. . Abbot . Dorian S. . 14119086 .
  182. News: Starr . Michelle . Scientists Think They've Narrowed Down The Star Systems Most Likely to Host Life . 19 April 2023 . . 19 April 2023 .
  183. Shapiro, Anna V. . et al. . Metal-rich stars are less suitable for the evolution of life on their planets . 18 April 2023 . . 14 . 1893 . 1893 . 10.1038/s41467-023-37195-4 . 37072387 . 10113254 . 2023NatCo..14.1893S .
  184. 10.1016/j.palaeo.2004.10.018. Expanding frontiers in deep subsurface microbiology. Palaeogeography, Palaeoclimatology, Palaeoecology. 219. 1–2. 131–155. 2005. Amend . J. P. . Teske . A. . 2005PPP...219..131A.
  185. News: 2014-01-07. Further away planets 'can support life' say researchers. en-GB. BBC News. 2023-02-12.
  186. 10.1088/2041-8205/735/2/L27. 1102.1108. The Steppenwolf: A Proposal for a Habitable Planet in Interstellar Space. The Astrophysical Journal. 735. 2. L27. 2011. Abbot . D. S.. Switzer . E. R.. 2011ApJ...735L..27A. 73631942.
  187. 10.1017/S1473550414000196. The habitable epoch of the early Universe. International Journal of Astrobiology. 13. 4. 337–339. 2014. Loeb . A. . 1312.0613 . 2014IJAsB..13..337L . 10.1.1.748.4820. 2777386.
  188. Web site: Andy . Ridgway . 29 July 2015 . Home, sweet exomoon: The new frontier in the search for ET. 2023-02-12. New Scientist. en-US.
  189. 1401.5323. 2015P&SS..105...43L. Habitability of Earth-like planets with high obliquity and eccentric orbits: Results from a general circulation model . Planetary and Space Science. Linsenmeier . Manuel . Pascale . Salvatore . Lucarini . Valerio . 2014 . 10.1016/j.pss.2014.11.003 . 105 . 43–59. 119202437.
  190. Web site: Kelley . Peter . 15 April 2014 . Astronomers: 'Tilt-a-worlds' could harbor life. 2023-02-12. UW News. en.
  191. 10.1089/ast.2013.1129. 24611714. Effects of Extreme Obliquity Variations on the Habitability of Exoplanets. Astrobiology. 14. 4. 277–291. 2014. Armstrong . J. C. . Barnes . R.. Domagal-Goldman . S.. Breiner . J.. Quinn . T. R. . Meadows . V. S. . 2014AsBio..14..277A. 1404.3686 . 3995117.
  192. Web site: Kelley . Peter . 18 July 2013 . A warmer planetary haven around cool stars, as ice warms rather than cools. 2023-02-12. UW News. en.
  193. 10.1088/2041-8205/785/1/L9. Spectrum-Driven Planetary Deglaciation Due to Increases in Stellar Luminosity. The Astrophysical Journal. 785. 1. L9. 2014. Shields . A. L. . Bitz . C. M. . Cecilia Bitz. Meadows . V. S. . Joshi . M. M. . Robinson . T. D. . 1403.3695 . 2014ApJ...785L...9S . 118544889.
  194. 10.1089/ast.2012.0851. 23537135. Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating. Astrobiology. 13. 3. 225–250. 2013. Barnes . R. . Mullins . K. . Goldblatt . C. . Meadows . V. S. . Kasting . J. F. . Heller . R. . 2013AsBio..13..225B. 1203.5104 . 3612283.
  195. 10.1089/ast.2013.1088. 24380533. Superhabitable Worlds. Astrobiology. 14. 1. 50–66. 2014. Heller . R. . Armstrong . J. . 2014AsBio..14...50H. 1401.2392 . 1824897.
  196. 10.1111/j.1365-2966.2008.13868.x. Tidal heating of terrestrial extrasolar planets and implications for their habitability. Monthly Notices of the Royal Astronomical Society. 391. 1. 237–245. 2008. Jackson . B. . Barnes . R. . Greenberg . R. . free. 2008MNRAS.391..237J. 0808.2770 . 19930771.
  197. Web site: A Review of the Best Habitable Planet Candidates . Paul Gilster, Andrew LePage. 2015-01-30. Centauri Dreams, Tau Zero Foundation. 2015-07-24.
  198. Book: The Mystery of the Seven Spheres: How Homo sapiens will Conquer Space. Giovanni F. Bignami. Springer. 2015. 978-3-319-17004-6 . 110.
  199. News: Closest 'Alien Earth' May Be 13 Light-Years Away . Space.com . 6 February 2013 . TechMediaNetwork . 7 February 2013 . Howell, Elizabeth.
  200. Kopparapu . Ravi Kumar . A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around Kepler M-dwarfs . . March 2013 . 1303.2649 . 2013ApJ...767L...8K. 767. 1 . L8. 10.1088/2041-8205/767/1/L8. 119103101 .
  201. Web site: NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth. 2015-07-23. 2015-07-23 .
  202. Web site: Emspak. Jesse. Kepler Finds Bizarre Systems. International Business Times. March 2, 2011. International Business Times Inc.. March 2, 2011.
  203. Web site: NAM2010 at the University of Glasgow. 2010-04-15. 2011-07-16. https://web.archive.org/web/20110716051715/http://www.astro.gla.ac.uk/nam2010/pr10.php. dead.
  204. Web site: Trading spaces: How swapping stars create hot Jupiters . Paul M. Sutter . Universe Today . December 9, 2022 .
  205. Moutou . Claire . Deleuil . Magali . Guillot . Tristan . Baglin . Annie . Bordé . Pascal . Bouchy . Francois . Cabrera . Juan . Csizmadia . Szilárd . Deeg . Hans J. . 2013-11-01 . CoRoT: Harvest of the exoplanet program . Icarus . 226 . 2 . 1625–1634 . 10.1016/j.icarus.2013.03.022 . 0019-1035. 1306.0578 . 2013Icar..226.1625M .

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Exoplanet".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.