HD 219828

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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
BD+17° 4896, GSC 01716-01182, HIP 115100, SAO 108536
Database references

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[edit]

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.

The HD 219828 planetary system
(in order from star)
Mass Semimajor axis
Orbital period
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[edit]


  1. ^ Valencia; Oconnell, R; Sasselov, D (2006). "Internal structure of massive terrestrial planets". Icarus. 181 (2): 545–554. arXiv:astro-ph/0511150Freely accessible. Bibcode:2006Icar..181..545V. doi:10.1016/j.icarus.2005.11.021. 
  2. ^ 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/0702459Freely accessible. Bibcode:2007A&A...467..721M. doi:10.1051/0004-6361:20066845. 
  3. ^ 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:1605.06942Freely accessible [astro-ph]. Bibcode:2016A&A...592A..13S. doi:10.1051/0004-6361/201628374. 

External links[edit]

Coordinates: Sky map 23h 18m 46.7353s, +18° 38′ 44.590″