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
- ↑ Valencia; Oconnell, R; Sasselov, D (2006). "Internal structure of massive terrestrial planets". Icarus. 181 (2): 545–554. arXiv:astro-ph/0511150. Bibcode:2006Icar..181..545V. doi:10.1016/j.icarus.2005.11.021.
- ↑ Melo, C.; Santos, N. C.; Gieren, W.; Pietrzynski, G.; Ruiz, M. T.; Sousa, S. G.; Bouchy, F.; Lovis, C.; Mayor, M.; Pepe, F.; Queloz, D.; da Silva, R.; Udry, S. (2007). "A new Neptune-mass planet orbiting HD 219828". Astronomy and Astrophysics. 467 (2): 721–727. arXiv:astro-ph/0702459. Bibcode:2007A&A...467..721M. doi:10.1051/0004-6361:20066845.
- ↑ N. C. Santos; A. Santerne; J. P. Faria; J. Rey; A. C. M. Correia; J. Laskar; S. Udry; V. Adibekyan; F. Bouchy; E. Delgado-Mena; C. Melo; X. Dumusque; G. Hébrard; C. Lovis; M. Mayor; M. Montalto; A. Mortier; F. Pepe; P. Figueira; J. Sahlmann; D. Ségransan; S. G. Sousa (2016). "An extreme planetary system around HD219828. One long-period super Jupiter to a hot-neptune host star". arXiv:1605.06942 [astro-ph].
External links
- "HD 219828". The Extrasolar Planets Encyclopaedia.
Coordinates: 23h 18m 46.7353s, +18° 38′ 44.590″