Kepler-91b explained
| Kepler-91b |
| Discovered: | 2013 |
| Discovery Method: | Transit (Kepler Mission) |
| Apsis: | astron |
| Semimajor: | AU |
| Period: | d |
| Density: | 0.44g/cm3 |
| Albedo: | 0.39 [1] |
Kepler-91b is a giant planet orbiting Kepler-91, a star slightly more massive than the Sun. Kepler-91 has left the main sequence and is now a red giant branch star.
Discovery and further confirmation
Kepler-91b was detected by analyzing the data of Kepler spacecraft where a transit-like signal was found. Initially thought to be a false positive due to light curve variations by a self-luminous object, it was later revealed that due to low density of Kepler-91's shape is distorted to slightly ellipsoidal shape due to gravitational effects of the planet. Ellipsoidal light variations caused by Kepler-91b constitute more than the third of light variations compared to transit depth. Ellipsoidal light variations also allowed to determine the planet's mass. It was also found that Kepler-91b reflects some of the starlight from its star.[2]
Further analysis managed to question the planetary nature of the object, suspecting that it is a self-luminous object.[3] However, the planetary nature was eventually confirmed again through both the radial velocity technique[4] and re-analysis of the light curve modulations.[5]
Characteristics
Kepler-91b is about 14% less massive than Jupiter while being more than 35% larger, making it less than half of the density of water. Kepler-91b orbits around the host star in about 6.25 days. Despite being one of the least edge-on orbits relative to Earth with inclination being about 68.5 degrees, transit was detected due to low semi-major axis to host star radius ratio.
Kepler-91b is expected to be engulfed by the parent star within about 55 million years.[2] [1]
Possible trojan companion
The possibility of a trojan planet to Kepler-91b was suggested due to the presence of a small dim in the phase-folded light curve at phase 0.68. This was subsequently studied but the conclusion was that the transit-signal was a false-positive.[6]
External links
Notes and References
- 1407.2245. Esteves. Lisa J.. Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry. The Astrophysical Journal. 804. 2. 150. De Mooij. Ernst J. W.. Jayawardhana. Ray. 2014. 10.1088/0004-637X/804/2/150. 2015ApJ...804..150E. 117798959.
- 1312.3943. Lillo-Box. J.. Kepler-91b: A planet at the end of its life. Planet and giant host star properties via light-curve variations. Astronomy & Astrophysics. 562. A109. Barrado. D.. Moya. A.. Montesinos. B.. Montalbán. J.. Bayo. A.. Barbieri. M.. Régulo. C.. Mancini. L.. Bouy. H.. Henning. T.. 2013. 10.1051/0004-6361/201322001. 2014A&A...562A.109L. 118486056.
- Sliski. David H.. Kipping. David M.. 2014. A High False Positive Rate for Kepler Planetary Candidates of Giant Stars using Asterodensity Profiling. The Astrophysical Journal. 788. 2. 148. 1401.1207. 2014ApJ...788..148S. 10.1088/0004-637X/788/2/148. 118665291.
- Lillo-Box. J.. Barrado. D.. Henning. Th.. Mancini. L.. Ciceri. S.. Figueira. P.. Santos. N. C.. Aceituno. J.. Sánchez. S.. August 2014. Radial velocity confirmation of Kepler-91 b. Astronomy & Astrophysics. en. 568. L1. 10.1051/0004-6361/201424587. 0004-6361. 1408.1528. 118424631.
- Barclay. Thomas. Endl. Michael. Huber. Daniel. Foreman-Mackey. Daniel. Cochran. William D.. MacQueen. Phillip J.. Rowe. Jason F.. Quintana. Elisa V.. 2015. Radial Velocity Observations and Light Curve Noise Modeling Confirm that Kepler-91b is a Giant Planet Orbiting a Giant Star. The Astrophysical Journal. en. 800. 1. 46. 10.1088/0004-637X/800/1/46. 0004-637X. 1408.3149. 2015ApJ...800...46B. 118528237.
- 1511.01068. Placek. Ben. Characterization of Kepler-91b and the Investigation of a Potential Trojan Companion Using EXONEST. The Astrophysical Journal. 814. 2. 147. Knuth. Kevin H.. Angerhausen. Daniel. Jenkins. Jon M.. 2015. 10.1088/0004-637X/814/2/147. 2015ApJ...814..147P. 118366565.
