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View of the sky around the star HD 10180 Credit: ESO |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Hydrus |
| Right ascension | 01h 37m 53.57672s[1] |
| Declination | −60° 30′ 41.4954″[1] |
| Apparent magnitude (V) | 7.33[2] |
| Characteristics | |
| Spectral type | G1V[3] |
| Astrometry | |
| Radial velocity (Rv) | +35.2[3] km/s |
| Proper motion (μ) | RA: -14.60[1] mas/yr Dec.: 6.51[1] mas/yr |
| Parallax (π) | 25.63 ± 0.38[1] mas |
| Distance | 127 ± 2 ly (39 ± 0.6 pc) |
| Details | |
| Mass | 1.062 ± 0.017[4] M☉ |
| Radius | 1.20 ± 0.318[4] R☉ |
| Surface gravity (log g) | 4.39[5] |
| Luminosity | 1.49 ± 0.02[6] L☉ |
| Temperature | 5,911[5] K |
| Metallicity [Fe/H] | 0.08[5] dex |
| Rotation | 24 ± 3 days[6] |
| Rotational velocity (v sin i) | < 3[6] km/s |
| Age | 7.3[7] Gyr |
| Other designations | |
HD 10180 is a Sun-like star in the southern constellation Hydrus. It has at least five planets, and possibly as many as seven. Based upon parallax measurements, is about 127 light-years away from the Earth.[8] The apparent magnitude of this star is 7.33, which is too faint to be viewed with the unaided eye. At a declination of −60°, this star can not be observed north of the tropics.
The stellar classification of this star is G1V, which indicates it is a G-type main sequence star that is generating energy at its core through the thermonuclear fusion of hydrogen. The effective temperature of the chromosphere is 5,911 K, giving the star a yellow hue like the Sun. The mass of this star is estimated as 6% greater than the Sun's mass, while it has a 120% of the Sun's radius and 149% of the Sun's luminosity. HD 10180 has a 20% higher proportion of elements other than hydrogen/helium compared to the Sun.[note 1] It is an inactive star with no significant magnetic activity. The estimated period of rotation is about 24 days.[6]
In 2010, a research team led by Christophe Lovis of the University of Geneva announced that the star has at least five planets, and possibly as many as seven.[9][6] The planets were detected using the HARPS spectrograph, in conjunction with the ESO's 3.6 m telescope at La Silla Observatory in Chile, using Doppler spectroscopy.
The system contains five planets with minimum masses from 12 to 25 times Earth's (comparable to the mass of the ice giant planets Uranus and Neptune in our Solar System) at orbital radii of 0.06, 0.13, 0.27, 0.49 and 1.42 AU. The false detection probabilities for these five planets are all much less than 0.1%.[6] In addition, there is a possible Earth-sized planet located at 0.02 AU (minimum mass 1.4 times Earth's; spurious detection probability 1.4%), and a possible Saturn-sized giant planet at 3.4 AU (minimum mass 65 times Earth's; spurious detection probability 0.6%). This represents the largest number of planets detected in an extrasolar planetary system (the previous record holder, the 55 Cancri system, has five).[6]
HD 10180's five Neptune-sized planets have orbital radii ranging from one sixth that of Mercury to just short of that of Mars. The innermost planet, while Earth-like in diameter, has an orbital radius about one-seventeenth that of Mercury, and would be correspondingly hotter.[10] The outermost planet revolves at a distance from HD 10180 comparable to the distance of the outer part of the asteroid belt from our Sun.
The planetary system contains no planets in mean motion resonances, although it has a number of near resonances.[6] The approximate ratios of periods of adjacent orbits are (proceeding outward): 1:5, 1:3, 1:3, 2:5, 1:5, 3:11.
Since the inclination of the planets' orbits is unknown, only minimum planetary masses can presently be obtained. Dynamical simulations suggest that the system cannot be stable if the true masses of the planets exceed the minimum masses by a factor of greater than three (corresponding to an inclination of less than 20°, where 90° is edge-on).[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b (unconfirmed) | >1.35 ± 0.23 M⊕ | 0.02225 ± 0.00035 | 1.17768 ± 0.00010 | 0.0000 ± 0.0025 |
| c | >13.10 ± 0.54 M⊕ | 0.0641 ± 0.0010 | 5.75979 ± 0.00062 | 0.045 ± 0.026 |
| d | >11.75 ± 0.65 M⊕ | 0.1286 ± 0.0020 | 16.3579 ± 0.0038 | 0.088 ± 0.041 |
| e | >25.1 ± 1.2 M⊕ | 0.2699 ± 0.0042 | 49.745 ± 0.022 | 0.026 ± 0.036 |
| f | >23.9 ± 1.4 M⊕ | 0.4929 ± 0.0078 | 122.76 ± 0.17 | 0.135 ± 0.046 |
| g | >21.4 ± 3.4 M⊕ | 1.422 ± 0.026 | 601.2 ± 8.1 | 0.19 ± 0.14 |
| h | >64.4 ± 4.6 M⊕ | 3.40 ± 0.11 | 2222 ± 91 | 0.080 ± 0.070 |