HD 17156
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 02h 49m 44.49s |
| Declination | +71° 45′ 11.64″ |
| Apparent magnitude (V) | 8.17 |
| Absolute magnitude (V) | 3.70 |
| Distance | 255.19 ly (78.24 pc) |
| Spectral type | G0IV |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 17156 is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. The Sun to star distance is 255.19 ly or 78.24 pc.
The mass of the star is 20% more massive and 47% larger than our Sun. Based on its absolute magnitude of 3.70 and spectral type of G0, the star is thought to be hotter than the Sun. Based on the chromospheric observations, it was found that the age is 5.7 ± 1.3 billion years.[1] The total lifetime of a 1.2 sol mass star should be 1.2 -2.5 × 1010, which is under 6.4 billion years; this star is in the last stage on the main sequence, and its nearby planets will soon be engulfed.
Based on spectral observations, the star was found to be metal-rich, 74% more metals than Sol. As of 2008, it is thought that two extrasolar planets orbit the star, but only one has been confirmed.
Planetary system
It is the first star in Cassiopeia around which an orbiting planet was discovered (in 2007). In February 2008, a second planet (HD 17156 c) was proposed, with a 5:1 mean motion resonance to the inner planet HD 17156 b.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 3.111 MJ | 0.1594 | 21.21725 | 0.6717 | — | — |
| c (unconfirmed) | 0.063 MJ | 0.481 | 111.314 | 0.136 | — | — |
References
- ^ Fischer; et al. (2007). "Five Intermediate-Period Planets from the N2K Sample" (abstract). The Astrophysical Journal. 669 (2): 1336–1344. doi:10.1086/521869.
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See also
External links
- "Notes for star HD 17156". The Extrasolar Planets Encyclopaedia. Retrieved 2008-06-30.
- Extrasolar Planet Interactions by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona