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HD 219828

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] Moreover 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).

The HD 219828 system
(in order from star)
Mass Semimajor axis
Orbital period
b >0.066 MJ 0.052 3.8335 ± 0.0013 0
c (unconfirmed) ≥0.7 MJ ≈0.68 ≥181 ≥0.3

See also

* HD 159868
* List of extrasolar planets


1. ^ Valencia et al.; Oconnell, R; Sasselov, D (2006). "Internal structure of massive terrestrial planets". Icarus 181 (2): 545–554. doi:10.1016/j.icarus.2005.11.021. Bibcode: 2006Icar..181..545V. http://arxiv.org/abs/astro-ph/0511150.
2. ^ Melo et al.; Santos, N. C.; Gieren, W.; Pietrzynski, G.; Ruiz, M. T.; Sousa, S. G.; Bouchy, F.; Lovis, C. et al. (2007). "A new Neptune-mass planet orbiting HD 219828". Astronomy and Astrophysics 467 (2): 721–727. doi:10.1051/0004-6361:20066845. Bibcode: 2007A&A...467..721M. http://arxiv.org/abs/astro-ph/0702459.

External links

* "HD 219828". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=HD+219828.

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