Kepler-9
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 2m 17.76s |
| Declination | +38° 24′ 3.2″ |
| Apparent magnitude (V) | 13.9 [1] |
| Astrometry | |
| Distance | 650[2] pc |
| Characteristics | |
| Spectral type | G2V |
| Details | |
| Mass | 1.07[2] M☉ |
| Radius | 1.02[2] R☉ |
| Surface gravity (log g) | 4.49 ± 0.09[2] cgs |
| Temperature | 5777 ± 61[2] K |
| Metallicity | [Fe/H] = +0.12 ± 0.04[2] |
| Age | ~1[2] Gyr |
| Other designations | |
Kepler-9 is a sunlike star in the constellation Lyra. It is situated in the Kepler Mission's field of view. Kepler-9 has three confirmed extrasolar planets, all discovered by Kepler using the transit method. The discovery was announced on August 26, 2010. It was the first multiplanet system to be discovered using such a method. Two of Kepler-9's planets are engaged in orbital resonance.
Nomenclature and history
Kepler-9 was named for the Kepler Mission, a project headed by NASA that was designed to search for Earth-like planets.[3] Unlike stars such as Aldebaran or Sirius, Kepler-9 does not have a colloquial name.
In June 2010, some 43 days after Kepler came online, its operating scientists submitted a list of over 700 exoplanet candidates for review. Of those, five were originally suspected to have more than one planet. Kepler-9 was one of the multiplanetary systems; it was identified as such when scientists noticed significant variations in the time intervals at which Kepler-9 was transited.[4] Kepler-9 holds the first multiplanetary system discovered using the transit method.[5] The discovery of the planets was announced on August 26, 2010.[6]
Star and planetary system
There are three confirmed planets, all of which orbit a sunlike G-type star. The outer two planets, Kepler-9b (the inner one) and Kepler-9c (the outer one), are low density gas giants that are respectively 25% and 17% the mass of Jupiter and around 80% the radius of Jupiter. Both planets have a density less than that of water, similar to Saturn. The innermost planet, Kepler-9d, is a super-Earth with a mass that is 7.0 times that of Earth. It orbits the star every 1.592851 days and has a radius that is 1.60 times that of Earth's radius.[2] It is estimated that there is a 0.59% chance that the discoveries are false.[2]
From Kepler-9d (closest to star) to Kepler-9b (second from star), the ratio of their orbits is 1:12. However, the ratio of the orbits of the two outer planets is 1:2, a relationship known as a mean motion resonance. Kepler-9b and Kepler-9c are the first transiting planets detected in such an orbital configuration.[7] The resonance causes the orbital speeds of each planet to change, and thus causes the transit times of the two planets to vary. The period of Kepler-9b is presently increasing by 4 minutes per orbit, while that of Kepler-9c is decreasing by 39 minutes per orbit. These orbital changes allowed the masses of the planets (a parameter not normally obtainable via the transit method) to be estimated using a dynamical model. The mass estimates were further refined using radial velocity measurements obtained with the HIRES instrument of the Keck 1 telescope.[7][8]
Kepler-9b and 9c are thought to have formed beyond the "frost line". They are then thought to have migrated inward due to interactions with the remains of the protoplanetary disk. They would have been captured into orbital resonance during this migration.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| d | 7.0 M🜨 | 0.0273 | 1.592851 | 0 | — | 1.60 R🜨 |
| b | 0.252 ± 0.013 MJ | 0.140 ± 0.001 | 19.24 | 0 | — | 0.842 ± 0.069 RJ |
| c | 0.171 ± 0.013 MJ | 0.225 ± 0.001 | 38.91 | 0 | — | 0.823 ± 0.067 RJ |
See also
References
- ^ "Notes for star Kepler-9". Extrasolar Planets Encyclopaedia. 2010. Retrieved 6 February 2011.
- ^ a b c d e f g h i Guillermo Torres, François Fressin, Natalie M. Batalha, William J. Borucki, Timothy M. Brown, Stephen T. Bryson, Lars A. Buchhave, David Charbonneau, David R. Ciardi, Edward W. Dunham, Daniel C. Fabrycky, Eric B. Ford, Thomas N. Gautier III, Ronald L. Gilliland, Matthew J. Holman, Steve B. Howell, Howard Isaacson, Jon M. Jenkins, David G. Koch, David W. Latham, Jack J. Lissauer, Geoffrey W. Marcy, David G. Monet, Andrej Prsa, Darin Ragozzine, Jason F. Rowe, Dimitar D. Sasselov (2010). "Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for KOI-377, and strong evidence for a super-Earth-size planet in a multiple system". arXiv:1008.4393 [astro-ph.EP].
{{cite arXiv}}: Unknown parameter|version=ignored (help)CS1 maint: multiple names: authors list (link) - ^ "Kepler: About the Mission". Kepler Mission. NASA. 2011. Retrieved 13 January 2011.
- ^ "NASA's Kepler Mission Discovers Two Planets Transiting Same Star". NASA Jet Propulsion Laboratory. NASA. 26 August 2010. Retrieved 13 January 2011.
- ^ Nancy Atkinson (26 August 2010). "Kepler Discovers Multi-Planet System". Universe Today. Retrieved 13 January 2011.
- ^ a b "NASA's Kepler Mission Discovers Two Planets Transiting the Same Star". NASA. 2010-08-26. Retrieved 2010-08-26.
- ^ a b c Matthew J. Holman, Daniel C. Fabrycky, Darin Ragozzine, Eric B. Ford, Jason H. Steffen, William F. Welsh, Jack J. Lissauer, David W. Latham, Geoffrey W. Marcy, Lucianne M. Walkowicz, Natalie M. Batalha, Jon M. Jenkins, Jason F. Rowe, William D. Cochran, Francois Fressin, Guillermo Torres, Lars A. Buchhave, Dimitar D. Sasselov, William J. Borucki, David G. Koch, Gibor Basri, Timothy M. Brown, Douglas A. Caldwell, David Charbonneau, Edward W. Dunham, Thomas N. Gautier III, John C. Geary, Ronald L. Gilliland, Michael R. Haas, Steve B. Howell, David R. Ciardi, Michael Endl, Debra Fischer, Gabor Furész, Joel D. Hartman, Howard Isaacson, John A. Johnson, Phillip J. MacQueen, Althea V. Moorhead, Robert C. Morehead, Jerome A. Orosz (2010). "Kepler-9: A System of Multiple Planets Transiting a Sun-Like Star, Confirmed by Timing Variations". Science. Forthcoming: 51. doi:10.1126/science.1195778.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Alexander, Amir (2010-08-27). "From the Ground and from Space, New Planetary Systems Unveiled". Planetary Society web site. The Planetary Society. Retrieved 2010-08-27.
{{cite web}}: External link in|work=
- Astronomy Now, "Kepler finds first double planet transiting system", Keith Cooper, 26 August 2010 (accessed 7 September 2010)