HD 10180 is a G-type main-sequence star located around 127 light years from Earth in the constellation of Hydrus. The star has a planetary system of seven planets, and it possibly has as many as nine, which makes it one of the largest of all known planetary systems. If the two unconfirmed planets are confirmed, it would be the largest of any known planetary system, including the Solar System. Other stars that have a large number of known planets are Kepler-90, TRAPPIST-1, Kepler-11 and 55 Cancri.
Characteristics[]
The star is located at about a distance of 127 light years. The apparent visual magnitude of this star is 7.33, which means it is too faint to be viewed with the naked eye although it can be observed with a small telescope. At a declination of −60°, this star cannot be seen at latitudes north of the tropics.
HD 10180 is a G1V-type star, and thus generates energy at its core through the thermonuclear fusion of hydrogen. The mass of this star is estimated as 6% greater than the Sun's mass, it has a radius of 120% that of the Sun, and is radiating 149% of the Sun's luminosity. The effective temperature of the star's chromosphere is 5,911 K, giving it a yellow-hued glow like the Sun. HD 10180 has a 20% higher abundance of elements other than hydrogen/helium compared to the Sun.[note 1] With an estimated age of 7.3 billion years, it is a stable star with no significant magnetic activity. The estimated period of rotation is about 24 days.
Planetary system[]
On August 24, 2010, a research team led by Christophe Lovis of the University of Geneva announced that the star has at least five planets, potentially as many as seven. These planets were detected using the HARPS spectograph, in conjunction with the ESO's 3.6 m telescope at the La Silla Observatory in Chile, using Doppler spectroscopy.
On April 5, 2012, astronomer Mikko Tuomi of the University of Hertfordshire submitted a paper to Astronomy and Astrophysics approved for publishing on the April 6, 2012 that proposed a nine planet model for the system. Re-analysing the data using Bayesian probability analysis, previously known planets' parameters were revised and further evidence was found for the innermost planet (b) as well as evidence of two additional planets (i and j).
The system is not known to be a transiting planetary system and as such planets are unlikely to be detected or verified by the transit method.
| Planet | Mass | Semimajor axis | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >1.3 Earth mass | 0.02222 AU | 1.17766 days | 0.0005 | N/A | N/A |
| c | >13.0 Earth mass | 0.0641 AU | 5.759 days | 0.07 | N/A | N/A |
| i (unconfirmed) | >1.9 Earth mass | 0.0904 AU | 9.655 days | 0.05 | N/A | N/A |
| d | >11.9 Earth mass | 0.1284 AU | 16.354 days | 0.011 | N/A | N/A |
| e | >25.0 Earth mass | 0.270 AU | 49.75 days | 0.001 | N/A | N/A |
| j (unconfirmed) | >5.1 Earth mass | 0.330 AU | 67.55 days | 0.13 | N/A | N/A |
| f | >23.9 Earth mass | 0.4929 AU | 122.88 days | 0.13 | N/A | N/A |
| g | >21.4 Earth mass | 1.415 AU | 596 days | 0.03 | N/A | N/A |
| h | >65.8 Earth mass | 3.49 AU | 2300 days | 0.18 | N/A | N/A |