Kepler-9d
| Exoplanet | List of exoplanets | |
|---|---|---|
| Parent star | ||
| Star | Kepler-9 (KOI-377) | |
| Constellation | Lyra | |
| Right ascension | (α) | 19h 2m 17.76s |
| Declination | (δ) | +38° 24′ 3.2″ |
| Apparent magnitude | (mV) | 13.9 |
| Mass | (m) | 1.07 M☉ |
| Radius | (r) | 1.02 R☉ |
| Temperature | (T) | 5777 (± 61) K |
| Metallicity | [Fe/H] | 0.12 (± 0.04) |
| Age | ~1 Gyr | |
| Physical characteristics | ||
| Mass | (m) | unknownM⊕ |
| Radius | (r) | 1.64R⊕ |
| Density | (ρ) | unknowng cm−3 |
| Temperature | (T) | 2026 |
| Orbital elements | ||
| Semi-major axis | (a) | 0.02730AU |
| Eccentricity | (e) | 0 |
| Orbital period | (P) | 1.592851d |
| Inclination | (i) | unknown° |
| Discovery information | ||
| Discovery date | 1 January 2011 | |
| Discoverer(s) | ||
| Discovery method | Transit (Kepler Mission) | |
| Discovery status | Announced via publication | |
Kepler-9d, formerly known as KOI-377.03, is a planet in orbit around the sunlike star Kepler-9. Initially discovered by Kepler spacecraft, a terrestrial planet-searching satellite built and operated by NASA, Kepler-9d is most likely a Super-Earth, with an estimated radius approximately 60% larger than that of Earth's, although its exact mass cannot be determined. Kepler-9d orbits Kepler-9 every 1.56 days at a distance of .0273 AU from its star, an extremely close distance. Although Kepler-9d is the closest planet to its star in its system, it is named Kepler-9d instead of Kepler-9b because two gas giants, Kepler-9b and Kepler-9c, were confirmed first. The original studies into the system first suggested that Kepler-9d might be a planet, but a follow-up investigation made by the Kepler team later confirmed that it was; the confirmation of Kepler-9d as a planet was made public with the team's paper, which was published in the Astrophysical Journal on January 1, 2011 . The team used telescopes at the W.M. Keck Observatory in Hawaii to follow up on the Kepler space telescope's initial discovery.
Kepler-9d's name comes from it being the third planet discovered in the orbit of Kepler-9. Kepler-9 was named for the Kepler spacecraft, a NASA satellite that aims to discover terrestrial planets in transit around, or crossing in front of, their host stars as seen from Earth. This transit causes a regular interval in which the star briefly and slightly dims as the planet crosses it.
Flagged initially as a transit event by the satellite, Kepler-9d was given the designation KOI 377.03. It was recognized as a potential planet after a study into the system confirmed Kepler-9b and Kepler-9c, but follow-up studies had to be completed to verify that it was indeed a planet, and that the apparent transit event was not due to a background eclipsing binary star in the aperture of Kepler's photometer. Kepler's team exhaustively disproved that the small transit event could have been anything but a planet, and their results were published in the Astrophysical Journal on January 1, 2011. Follow-up observations were conducted by the High Resolution Echelle Spectrometer at the W.M. Keck Observatory in Hawaii, as well as the WIYN Observatory in Arizona and the Palomar Observatory in California.
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