Satellite galaxies of the Milky Way explained
The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.[1]
There are 61 small galaxies confirmed to be within 420abbr=offNaNabbr=off of the Milky Way, but not all of them are necessarily in orbit, and some may themselves be in orbit of other satellite galaxies. The only ones visible to the naked eye are the Large and Small Magellanic Clouds, which have been observed since prehistory. Measurements with the Hubble Space Telescope in 2006 suggest the Magellanic Clouds may be moving too fast to be orbiting the Milky Way.[2] Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of 2.6kpc[3] or roughly a twentieth that of the Milky Way.
Characteristics
Satellite galaxies that orbit from 1000abbr=onNaNabbr=on of the edge of the disc of the Milky Way Galaxy to the edge of the dark matter halo of the Milky Way at from the center of the galaxy, are generally depleted in hydrogen gas compared to those that orbit more distantly. This is because of their interactions with the dense hot gas halo of the Milky Way that strip cold gas from the satellites. Satellites beyond that region still retain copious quantities of gas.[4] [5]
List
The Milky Way's satellite galaxies include the following:[6] [7]
| Name | Diameter (kpc) | Distance
(kpc) | Absolute visual magnitude | Type | data-sort-type=number | Discovered |
|---|
| 4 | 48.5 | -18.1 | SBm | prehistoric |
| 2.9 | 130 | -8.5 | Irr? | 2018 |
| 2.6 | 20 | -13.5 | E | 1994 |
| 2.2 | 117.5 | -8.2 | dSph | 2016 [8] |
| 2 | 61 | -16.8 | Irr | prehistoric |
| 1.1 | 220 | -8.6 | dSph | 2006 |
| 1.5 | 8 | -14.4 | Irr | 2003 |
| 1.0 | 46 | -5.75 | dSph? | 2009 |
| 0.8 | 90 | -11.1 | dE3 | 1937 |
| 0.7 | 80 | -8.8 | dE0 | 1954 |
| 0.7 | 135 | -6.6 | dSph | 2006 |
| 0.7 | 210 | -9.8 | dE0 | 1950 |
| 0.6 | 140 | -13.4 | dE2 | 1938 |
| Eridanus II[9] | 0.55 | 366 | -7.1 | dSph | 2015 |
| 0.5 | 90 | -9.3 | dE3 | 1990 |
| 0.5 | 100 | -9.1 | dE3 | 1977 |
| 0.5 | 250 | -12.0 | dE3 | 1950 |
| 0.4 | 60 | -8.8 | dE4 | 1954 |
| 0.34 | 420 | -8.0 | dSph/dIrr | 2006 |
| Aquarius II | 0.32 | 108 | -4.2 | dSph | 2016 [10] |
| 0.30 | 60 | -6.3 | dSph | 2006 |
| 0.30 | 155 | -4.9 | dSph | 2006 |
| 0.30 | 160 | -5.8 | dSph | 2006 |
| Tucana IV | 0.25 | 48 | -3.5 | dSph | 2015 |
| Columba I | 0.21 | 182 | -4.5 | dSph | 2015 |
| 0.20 | 30 | -4.25 | dG D | 2006 |
| Grus II | 0.19 | 53 | -3.9 | dSph | 2015 [11] |
| Cetus III | 0.18 | 251 | -2.4 | dSph? | 2017 [12] |
| 0.14 | 42 | -4.1 | dSph | 2006 |
| Hydra II | 0.14 | 128 | -4.8 | dSph | 2015 [13] |
| Reticulum III | 0.13 | 92 | -3.3 | dSph | 2015 |
| 0.12 | 180 | -5.0 | dSph | 2010 |
| Pegasus III | 0.11 | 215 | -3.4 | dSph | 2015 [14] [15] |
| Hydrus I | 0.10 | 28 | -4.7 | dSph | 2018 [16] |
| 0.10 | 42 | -2.7 | dSph | 2007 |
| Tucana III | 0.09 | 25 | -2.4 | dSph | 2015 |
| 0.09 | 91 | -0.3 | dSph? | 2016 |
| Horologium II | 0.09 | 78 | -2.6 | dSph | 2015 [17] |
| Sagittarius II | 0.08 | 67 | -5.2 | dSph | 2015 |
| 0.08 | 180 | -5.2 | dSph | 2007 |
| 0.07 | 30 | -1.8 | dSph | 2015 |
| 0.07 | 35 | -2.5 | dSph | 2007 |
| 0.06 | 23 | -1.5 | dSph | 2007 |
| Draco II | 0.04 | 20 | -2.9 | dSph | 2015 [18] |
| Tucana V | 0.03 | 55 | -1.6 | dSph | 2015 |
| Cetus II | 0.03 | 30 | 0.0 | dSph? | 2015 |
| 0.064 | 30 | -3.6 | dSph | 2015 [19] [20] |
| Tucana II | 0.33 | 70 | -3.9 | dSph | 2015 |
| 1.5 | 80 | -13 | dSph? | 2009 |
| DES 1 | 0.02 | 82 | -3.05 | GC | 2016 [21] |
| Eridanus III | 0.028 | 90 | -2.4 | dSph? | 2015 |
| Horologium I | 0.06 | 100 | -3.5 | dSph? | 2015 |
| 0.074 | 100 | -3.5 | GC | 2015 |
| Phoenix II | 0.0521 | 100 | -3.7 | dSph? | 2015 |
| 0.64 | 100 | -5.5 | dG D | 2005 |
| Pictoris I | 0.058 | 115 | -3.7 | dSph? | 2015 |
| Grus I | 0.12 | 120 | -3.4 | dSph | 2015 |
| Pegasus IV | 0.082 | 90 | -4.25 | dSph | 2022 [22] |
| Carina II | 0.182 | 36 | -4.5 | dSph | 2018 [23] |
| Carina III | 0.06 | 28 | -2.4 | GC? | 2018 |
| Boötes IV | 0.28 | 209 | -4.53 | dSph | 2019 [24] |
| Centaurus I | 0.076 | 116 | -5.55 | dSph | 2020 [25] |
| Pictor II | 0.046 | 46 | -3.2 | dSph | 2016 [26] |
| 0.02 | 38 | -2.53 | dSph | 2018 [27] |
| Ursa Major III | 0.003 | 10 | +2.2 | dSph | 2023 |
| Sextans II | - | - | - | - | 2024[28] |
| Virgo III | - | - | - | - | 2024 | |
Map with clickable regions
Image:Satellite_Galaxies.svg|frame|center|Milky Way's satellite galaxies (clickable map)
rect 289 219 352 251 Milky Wayrect 319 252 380 281 Sagittarius Dwarf Elliptical Galaxyrect 187 81 229 113 Sextans Dwarfrect 168 273 249 318 Large Magellanic Cloudrect 229 326 288 368 Small Magellanic Cloudrect 297 376 352 407 Sculptor Dwarfrect 183 446 234 476 Fornax Dwarfrect 107 297 150 332 Carina Dwarfrect 296 107 339 144 Bootes Dwarfrect 336 180 408 196 Ursa Major IIrect 357 40 423 59 Ursa Major Irect 370 110 428 142 Ursa Minor Dwarfrect 430 119 470 154 Draco Dwarf
desc bottom-left
Streams
See also: List of stellar streams. The Sagittarius Dwarf Spheroidal Galaxy is currently in the process of being consumed by the Milky Way and is expected to pass through it within the next 100 million years. The Sagittarius Stream is a stream of stars in polar orbit around the Milky Way leeched from the Sagittarius Dwarf. The Virgo Stellar Stream is a stream of stars that is believed to have once been an orbiting dwarf galaxy that has been completely distended by the Milky Way's gravity.
See also
Further reading
- The Dearth of Neutral Hydrogen in Galactic Dwarf Spheroidal Galaxies . K. Spekkens . N. Urbancic . B. S. Mason . B. Willman . J. E. Aguirre . 30 September 2014 . 1410.0028 . 2014ApJ...795L...5S . 10.1088/2041-8205/795/1/L5 . The Astrophysical Journal Letters . 795 . 1 . 13 October 2014 . L5. 35113298 .
Notes and References
- An Eclectic View of our Milky Way Galaxy . David G. Turner . 15 August 2013 . September 2013 . Canadian Journal of Physics . 92 . 9 . 959–963 . 10.1139/cjp-2013-0429 . 2014CaJPh..92..959T . 1310.0014 . 118390693 .
- Web site: Press release: Magellanic Clouds May Be Just Passing Through. Harvard University. January 9, 2007.
- Karachentsev . I. D. . Karachentseva . V. E. . Hutchmeier . W. K. . Makarov . D. I. . A Catalog of Neighboring Galaxies . . 2004 . 127 . 4 . 2031–2068 . 2004AJ....127.2031K . 10.1086/382905 . free .
- News: Milky Way Ransacks Nearby Dwarf Galaxies. SpaceDaily . 17 October 2014 .
- News: Milky Way ransacks nearby dwarf galaxies. ScienceDaily . 15 October 2014 .
- Web site: Milky Way satellite galaxies . Sjölander, Nils . https://web.archive.org/web/20140219170336/http://www.astro.uu.se/~ns/mwsat.html . 2014-02-19 .
- The Astrophysical Journal Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 . A. Drlica-Wagner . 2020 . The Astrophysical Journal. 893 . 1 . 47 . 10.3847/1538-4357/ab7eb9 . 10150/642363 . 208857848 . free . free .
- The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater . Torrealba, G. . Koposov, S.E. . Belokurov, V. . Irwin, M. . Monthly Notices of the Royal Astronomical Society . 10.1093/mnras/stw733 . 13 April 2016 . 2016MNRAS.459.2370T . 459 . 3 . 2370–2378 . free . 1601.07178.
- Deep imaging of Eridanus II and its lone star cluster . The Astrophysical Journal . 824 . 1 . L-14 . D. . Crnojević . D.J. . Sand . D. . Zaritsky. Kristine Spekkens . K. . Spekkens . B. . Willman . J.R. . Hargis . 1604.08590 . 2016ApJ...824L..14C . 10.3847/2041-8205/824/1/L14 . 2016. 2202492 . free .
- At the survey limits: Discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data . G. . Torrealba . S.E. . Koposov . V. . Belokurov . M. . Irwin . M. . Collins . M. . Spencer . R. . Ibata . M. . Matteo . A. . Bonaca . P. . Jethwa . 1605.05338 . 10.1093/mnras/stw2051 . 463 . 1 . Monthly Notices of the Royal Astronomical Society . 712–722 . 2016MNRAS.463..712T . 2016. free .
- Eight ultra-faint galaxy candidates discovered in Year Two of the Dark Energy Survey . Drlica-Wagner, A. . etal . The Astrophysical Journal . 813 . 2 . 109 . 10.1088/0004-637X/813/2/109 . 4 November 2015 . 1508.03622 . 2015ApJ...813..109D. 55909299 .
- Homma . Daisuke . Chiba . Masashi . Okamoto . Sakurako . Komiyama . Yutaka . Tanaka . Masayuki . Tanaka . Mikito . Ishigaki . Miho N. . Hayashi . Kohei . Arimoto . Nobuo . 2017-04-19 . Searches for New Milky Way Satellites from the First Two Years of Data of the Subaru/Hyper Suprime-Cam Survey: Discovery of Cetus III . Publications of the Astronomical Society of Japan . 70 . S18 . 1704.05977 . 10.1093/pasj/psx050. 2018PASJ...70S..18H .
- Hydra II: A faint and compact Milky Way dwarf galaxy found in the survey of the Magellanic stellar history . Nicolas F. . Martin . Survey of the Magellanic Stellar History . The Astrophysical Journal Letters . 23 April 2015 . 804 . 1 . L5 . 10.1088/2041-8205/804/1/L5. 1503.06216 . 2015ApJ...804L...5M . 7814048 .
- A hero's dark horse: Discovery of an ultra-faint Milky Way satellite in Pegasus . Dongwon . Kim . Helmut . Jerjen . Dougal . Mackey . Gary S. . Da Costa . Antonino P. . Milone . The Astrophysical Journal Letters . 12 May 2015 . 804 . 2 . L-44 . 10.1088/2041-8205/804/2/L44 . 1503.08268 . 2015ApJ...804L..44K. 119302178 .
- Portrait of a dark horse: Photometric properties and kinematics of the ultra-faint Milky Way satellite Pegasus III . Dongwon . Kim . Helmut . Jerjen . Marla . Geha. Marla Geha . Anirudh . Chiti . Antonino P. . Milone . Dougal . Mackey . Gary . da Costa . Anna . Frebel . Blair . Conn . 1608.04934 . 10.3847/0004-637X/833/1/16 . 833 . 1 . The Astrophysical Journal . 16. 2016ApJ...833...16K . 2016 . 73677994 . free .
- Koposov . Sergey E. . Walker . Matthew G. . Belokurov . Vasily . Casey . Andrew R. . Geringer-Sameth . Alex . Mackey . Dougal . Da Costa . Gary . Erkal . Denis . Jethwa . Prashin . 2018-10-01 . Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge* . Monthly Notices of the Royal Astronomical Society . en . 479 . 4 . 5343–5361 . 10.1093/mnras/sty1772 . free . 0035-8711. 1804.06430. 2018MNRAS.479.5343K .
- Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellation . 28 July 2015 . Kim, Dongwon . Jerjen, Helmut . amp . The Astrophysical Journal Letters . 808 . 2 . L-39 . 10.1088/2041-8205/808/2/L39 . 1505.04948 . 2015ApJ...808L..39K . 117190468 .
- Sagittarius II, Draco II and Laevens 3: Three new Milky Way satellites discovered in the PAN-STARRS 1 3π survey . Laevens . B.P.M . Martin . N.F. . Bernard . E.J. . Schlafly . E.F. . Sesar . B. . The Astrophysical Journal . 1 November 2015 . 813 . 1 . 44 . 10.1088/0004-637X/813/1/44 . 1507.07564 . 2015ApJ...813...44L. 54042426 .
- Beasts of the Southern Wild. Discovery of a large number of ultra faint satellites in the vicinity of the Magellanic Clouds . Koposov, Sergey E. . Belokurov, Vasily . Torrealba, Gabriel . Evans, N. Wyn . 10 March 2015 . 1503.02079 . The Astrophysical Journal . 2015ApJ...805..130K . 10.1088/0004-637X/805/2/130 . 805 . 2 . 130. 118267222 .
- Eight New Milky Way companions discovered in first-year Dark Energy Survey data . DES Collaboration . 10 March 2015 . 1503.02584 . The Astrophysical Journal . 2015ApJ...807...50B . 10.1088/0004-637X/807/1/50 . 807 . 1 . 50. 12011753 .
- Digging deeper into Southern skies: A compact Milky Way companion discovered in first-year Dark Energy Survey data . Luque, E. . etal . Monthly Notices of the Royal Astronomical Society . 458 . 1 . 603–612 . 10.1093/mnras/stw302 . 9 February 2016 . free . 1508.02381 . 2016MNRAS.458..603L.
- 2203.11788 . 10.3847/1538-4357/aca1c3 . Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus . 2023 . Cerny . W. . Simon . J. D. . Li . T. S. . Drlica-Wagner . A. . Pace . A. B. . Martínez-Vázquez . C. E. . Riley . A. H. . Mutlu-Pakdil . B. . Mau . S. . Ferguson . P. S. . Erkal . D. . Munoz . R. R. . Bom . C. R. . Carlin . J. L. . Carollo . D. . Choi . Y. . Ji . A. P. . Manwadkar . V. . Martínez-Delgado . D. . Miller . A. E. . Noël . N. E. D. . Sakowska . J. D. . Sand . D. J. . Stringfellow . G. S. . Tollerud . E. J. . Vivas . A. K. . Carballo-Bello . J. A. . Hernandez-Lang . D. . James . D. J. . Nidever . D. L. . The Astrophysical Journal . 942 . 2 . 111 . 2023ApJ...942..111C . 247597301 . 1 . free .
- Torrealba . G. . Belokurov . V. . Koposov . S. E. . Bechtol . K. . Drlica-Wagner . A. . Olsen . K. A. G. . Vivas . A. K. . Yanny . B. . Jethwa . P. . 2018-01-22 . Discovery of two neighbouring satellites in the Carina constellation with MagLiteS . Monthly Notices of the Royal Astronomical Society . 475 . 4 . 5085–5097 . 10.1093/mnras/sty170 . free . 1801.07279 . dmy-all.
- Boötes. IV. A new Milky Way satellite discovered in the Subaru Hyper Suprime-Cam Survey and implications for the missing satellite problem . Homma . 2019 . Publications of the Astronomical Society of Japan . 71 . 5 . 10.1093/pasj/psz076 . 1906.07332 . 2019PASJ...71...94H .
- Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey . Mau . 2020 . The Astrophysical Journal . 890 . 2 . 136 . 10.3847/1538-4357/ab6c67 . 1912.03301 . 2020ApJ...890..136M . 208857609 . free .
- Drlica-Wagner . An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey . 2016 . The Astrophysical Journal . 833 . 1 . L5 . 10.3847/2041-8205/833/1/L5 . 1609.02148 . 2016ApJ...833L...5D . 1885/153579 . 56071154 . free .
- A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters . Muñoz . 2018 . The Astrophysical Journal . 860 . 1 . 66 . 10.3847/1538-4357/aac16b . 1806.06891 . 2018ApJ...860...66M . 118978019 . free .
- Web site: Robert Lea . 2024-07-02 . Scientists finally found 2 of the Milky Way's missing satellite galaxies. What could this mean for astronomy? . 2024-07-04 . Space.com . en.
