HD 219828
HD 219828 is an 8th magnitude star approximately 239 light years away in the constellation of Pegasus. It is a yellow subgiant, meaning that hydrogen fusion has ceased in its core.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 18m 46.7342s[1] |
| Declination | 18° 38′ 44.6152″[1] |
| Apparent magnitude (V) | 8.04 |
| Characteristics | |
| Spectral type | G0IV |
| Astrometry | |
| Proper motion (μ) | RA: −5.075±0.139[1] mas/yr Dec.: 6.037±0.067[1] mas/yr |
| Parallax (π) | 13.6489 ± 0.0660[1] mas |
| Distance | 239 ± 1 ly (73.3 ± 0.4 pc) |
| Details | |
| Other designations | |
| Database references | |
| SIMBAD | data |
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,[3] 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.[4] 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.[5] 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
- HD 159868
- List of extrasolar planets
References
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- "HD 219828". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-12-19.
- Valencia; Oconnell, R; Sasselov, D (2006). "Internal structure of massive terrestrial planets". Icarus (Submitted manuscript). 181 (2): 545–554. arXiv:astro-ph/0511150. Bibcode:2006Icar..181..545V. doi:10.1016/j.icarus.2005.11.021.
- Melo, C.; et al. (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". Astronomy & Astrophysics. 592: A13. arXiv:1605.06942. Bibcode:2016A&A...592A..13S. doi:10.1051/0004-6361/201628374.