Epoch 2000 Equinox 2000
|Right ascension||23h 18m 46.7353s|
|Declination||+18° 38′ 44.590″|
|Apparent magnitude (V)||+8.04|
In 2007, a Neptune-mass planet was found orbiting the star by Melo. According to the author, assuming an Earth-like rocky composition, 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. 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. The planet c is also a potential target for GAIA astrometry or atmospheric characterization using direct imaging or high-resolution spectroscopy.
(in order from star)
|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||—||—|
- Valencia; Oconnell, R; Sasselov, D (2006). "Internal structure of massive terrestrial planets". Icarus. 181 (2): 545–554. Bibcode:2006Icar..181..545V. arXiv: . 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. Bibcode:2007A&A...467..721M. arXiv: . 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: [astro-ph].
- "HD 219828". The Extrasolar Planets Encyclopaedia.
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