 Size comparison of Kepler-9c (left) with Jupiter (right) | |
| Discovery[1][2] | |
|---|---|
| Discovered by | Kepler Mission team |
| Discovery site | Kepler space telescope |
| Discovery date | 26 August 2010 |
| Transit | |
| Designations | |
| KOI-377.02[3] | |
| Orbital characteristics | |
| 0.225 ± 0.001 AU (33,660,000 ± 150,000 km) | |
| Eccentricity | 0 |
| 38.91d | |
| Inclination | 88.12 |
| Star | Kepler-9[4] |
| Physical characteristics | |
| 0.823 ± 0.067RJ | |
| Mass | 0.171 ± 0.013MJ |
| Temperature | 536K |
Kepler-9c is one of the first seven extrasolar planets,exoplanets, discovered by NASA'sKepler Mission, and one of at least two planets orbiting the starKepler-9. Kepler-9c andKepler-9b were the first exoplanets confirmed to betransiting their star.[5][1] The planet's discovery was announced by theKepler Mission team on August 26, 2010 after its initial discovery by Kepler. At the time, it was one of 700 planetary candidates noted by Kepler.
Observations of the planet have suggested that it is a hydrogen–helium gas giant that is slightly smaller thanSaturn, and that it orbits nearby its star at .225AU. Kepler-9c and b are notable in that the planets share a pattern oforbital resonance, in which the orbit of each planet stabilizes the orbit of the other. During the time it was observed by the spacecraft, the planet's orbit, which lasts on average approximately 38 days, shortened by 39 minutes everyorbital period because of this effect. Its orbit, over time, oscillates slightly above and below a 2:1 ratio with planetb.
As with most exoplanets, the name "Kepler-9c" denotes that it is the second planet discovered in the orbit of the starKepler-9. Kepler-9 itself was named after theKepler Mission, aNASA project oriented towards discovering planets that aretransiting their home stars.[6]
The planet was one of 700 planetary candidates considered by Kepler in its first 43 days of operation. It was highlighted as a part of one of five star systems that seemed to hold multiple transiting planets. Kepler-9c andKepler-9b were confirmed as the first planets discovered to transit the same star.[2]
Initial estimates concerning Kepler-9c's mass were refined by follow-up observations made by the Keck 1 Telescope at theW.M. Keck Observatory atMauna Kea,Hawaii. Keck was able to confirm that Kepler-9c and Kepler-9b were planets that were slightly smaller than planetSaturn.[2]
Kepler-9c is a gas giant that is smaller and slightly less massive than planetSaturn. It is approximately 0.171MJ, or 17% the mass of planetJupiter. It also has a radius of 0.823RJ, which makes it slightly smaller (1.5%) than Saturn. The planet is, on average, situated 0.225AU from the star.[7]
It is probable that the planet is composed ofhydrogen andhelium. The planet orbits on the same plane asKepler-9b, a second and larger gas giant located in theKepler-9 system. While observing the planet, the Kepler team noticed that Kepler-9b and c orbited in a 1:2 ratio, where Kepler-9b orbits its star every 19 days and Kepler-9c orbits every 38 days. The gravitational pull that each planet has on the other, known asorbital resonance, keeps the planets in a stable orbit. This phenomenon is the first of its kind seen outside the Solar System. Every time Kepler-9c completed an orbit during the observation period, its orbital period decreased by about 39 minutes. At some point, however, this trend will reverse and its orbit will increase. The lengths of its orbit will oscillate slightly above and below the 2:1 ratio.[8]
Kepler-9c makes an appearance in Carol & the End of the World where it is on the collision course towards Earth, and humanity embraces for the end times that will occur in the less than a year or so.
Media related toKepler-9 c at Wikimedia Commons
