HD 219828
| Observation data Epoch 2000 Equinox 2000 |
|
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 18m 46.7353s |
| Declination | +18° 38′ 44.590″ |
| Apparent magnitude (V) | +8.04 |
| Distance | 264.5 ly (81.1 pc) |
| Spectral type | G0IV |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 219828 is an 8th magnitude star approximately 265 light years away in the constellation of Pegasus. It is a yellow subgiant, meaning that hydrogen fusion has ceased in its core.
Planetary system
In 2007, a Neptune-mass planet was found orbiting the star by Melo. According to the author, assuming an Earth-like rocky composition,[1] the planet could yield a radius 2.2 times that of Earth. This could be furtherly proved if transit were observed, though, as authors state, it is a difficult task.[2] At this point, it was suggested that a best fit orbital solution hints the presence of an additional planetary companion (so far unconfirmed) with 70% of Jupiter's mass, likely orbital separation of 0.68 Astronomical units and eccentric orbit (e=0.3). However, in 2016, further analysis or radial velocity data confirmed the presence of an outer planet larger and more eccentric than was originally believed. With high eccentricity and a high mass ratio between the two planets, the system is quite unique.[3] The planet c is also a potential target for GAIA astrometry or atmospheric characterization using direct imaging or high-resolution spectroscopy.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >21.0 ± 1.4 M⊕ | 0.045 | 3.834887 ± 0.000096 | 0.059 ± 0.036 | — | — |
| c | >15.1 ± 0.85 MJ | 5.96 | 4791 ± 75 | 0.8115 ± 0.0032 | — | — |
See also
References
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Coordinates: 
23h 18m 46.7353s, +18° 38′ 44.590″
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