A diagram of the planetary system of Kepler-56
| |
| Discovery | |
|---|---|
| Discovered by | Daniel Huber et al.[1] |
| Discovery date | 16 October 2013 |
| Transit method | |
| Orbital characteristics | |
| 0.1028 ± 0.0037 AU (15,380,000 ± 550,000 km)[1] | |
| 10.5016+0.0011 −0.0010[1] d | |
| Star | Kepler-56 |
| Physical characteristics | |
| 6.51+0.29 −0.28[1] R🜨 | |
| Mass | 22.1+3.9 −3.6[1] ME |
Mean density | 0.442+0.080 −0.072 g cm−3 |
Kepler-56b (KOI-1241.02)[2] is a hot Neptune[1]—a class of exoplanets—located roughly 3,060 light-years (940 parsecs) away. It is somewhat larger than Neptune[3] and orbits its parent star Kepler-56 and was discovered in 2013 by the Kepler Space Telescope.
Kepler-56b is about 0.1028 AU (9.56 million mi; 15.38 million km) away from its host star[1] (about one-tenth of the distance between Earth to the Sun), making it even closer to its parent star than Mercury (0.39 AU [36 million mi; 58 million km]) and Venus (0.72 AU [67 million mi; 110 million km]). It takes 10.5 days for Kepler-56b to complete a full orbit around its star.[1] Further research shows that Kepler-56b's orbit is about 45° misaligned to the host star's equator. Later radial velocity measurements have revealed evidence of a gravitational perturbation from Kepler-56d.
Both Kepler-56b and Kepler-56c will be devoured by their parent star in about 130 and 155 million years.[4] Even further research shows that it will have its atmosphere boiled away by intense heat from the star, and it will be stretched by the strengthening stellar tides.[4] The measured mass of Kepler-56b is about 30% larger than Neptune's mass, but its radius is roughly 70% larger than Neptune's. Therefore, Kepler-56b should have a hydrogen/helium envelope containing a significant fraction of its total mass.[5][6] Like Kepler-11b and Kepler-11c, the envelope's light elements are susceptible to photo-evaporation caused by radiation from the central star. For example, it has been calculated that Kepler-11c lost over 50% of its hydrogen/helium envelope after formation.[7] However, the larger mass of Kepler-56b, compared to that of Kepler-11c, reduces the efficiency of mass loss.[7] Nonetheless, the planet may have been significantly more massive in the past and may keep losing mass in the future.
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