HD 10180

HD 10180, also designated 2MASS J01375356-6030414, is a Sun-like star in the southern constellation Hydrus that is notable for its large planetary system. Since its discovery, at least six exoplanets have been observed orbiting it, and some studies have proposed up to nine potential planets, which would make it potentially the largest of all known planetary systems, including the Solar System.[8][5]

HD 10180

View of the sky around the star HD 10180 (center)
Credit: ESO
Observation data
Epoch J2000      Equinox J2000
Constellation Hydrus
Right ascension 01h 37m 53.57724s[1]
Declination −60° 30′ 41.4821″[1]
Apparent magnitude (V) 7.33[2]
Characteristics
Evolutionary stage Main sequence
Spectral type G1V[3]
Astrometry
Radial velocity (Rv)35.44±0.12[1] km/s
Proper motion (μ) RA: −14.303±0.017 mas/yr[1]
Dec.: 8.058±0.016 mas/yr[1]
Parallax (π)25.6611 ± 0.0146 mas[1]
Distance127.10 ± 0.07 ly
(38.97 ± 0.02 pc)
Details
Mass1.062 ± 0.017[4] M☉
Radius1.20 ± 0.318[4] R☉
Luminosity1.49 ± 0.02[5] L☉
Surface gravity (log g)4.39[6] cgs
Temperature5,911[6] K
Metallicity [Fe/H]0.08[6] dex
Rotation24 ± 3 days[5]
Rotational velocity (v sin i)< 3[5] km/s
Age7.3[7] Gyr
Other designations
2MASS J01375356-6030414, CD–61°285, HD 10180, HIP 7599, SAO 248411[2]
Database references
SIMBADdata

Characteristics

Based upon parallax measurements, it is located at a distance of 127 light-years (39 parsecs) from Earth.[9] The apparent visual magnitude of this star is 7.33, which is too faint to be viewed with the naked eye although it can be readily observed with a small telescope.[10] 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.[11] 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.[5]

A survey in 2015 ruled out the existence of any stellar companions at projected distances from 13 to 324 astronomical units.[12]

Planetary system
The HD 10180 planetary system[8][13][14]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) ≥1.3±0.8 M🜨 0.0222±0.0011 1.17766+0.00021
−0.00022		 0.05+0.49
−0.05		 — —
c ≥13.2±0.4 M🜨 0.06412±0.00101 5.75969±0.00028 0.073±0.031 >0.2841° —
i (unconfirmed) ≥1.9+1.6
−1.8 M🜨		 0.0904+0.0043
−0.0047		 9.655+0.022
−0.072		 0.05+0.23
−0.05		 — —
d ≥12.0±0.7 M🜨 0.12859±0.00202 16.3570±0.0038 0.131±0.052 >0.2005° —
e ≥25.6±1.0 M🜨 0.2699±0.0043 49.748±0.025 0.051±0.033 >0.2366° —
j (unconfirmed) ≥5.1+3.1
−3.2 M🜨		 0.330+0.017
−0.016		 67.55+0.68
−0.88		 0.07+0.12
−0.07		 — —
f ≥19.4±1.2[15] M🜨 0.4929±0.0078 122.744±0.232 0.119±0.054 >0.3028° —
g ≥23.3±4.4 M🜨 1.427±0.028 615[15] 0.15±0.10[15] >0.3663° —
h ≥46.3±3.4[15] M🜨 3.381±0.121 2500[15] 0.095±0.086 >0.5496° —

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, and possibly as many as seven.[5][16] 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.

On April 5, 2012, astronomer Mikko Tuomi of the University of Hertfordshire submitted a paper to Astronomy and Astrophysics approved for publishing on 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).[8]

Subsequent studies since 2014 have found that a six-planet model is the best fit to the data.[13][15][17] 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.

In 2017, an orbital simulation showed that the formation of dynamically stable families of comets in the HD 10180 system is unlikely. The identified reason for the instability of cometary orbits was the location of the most massive planet HD 10180 h in the outermost orbit.[18]

Orbital arrangement
Orbits of the HD 10180 planetary system, using the orbital configuration from an eight-body (the star and seven planets) Newtonian model taking into account tidal dissipation[note 2]

The system contains six planets with minimum masses from 12 to 46 times Earth's (ranging in mass from roughly Uranus to sub-Saturn) at orbital radii of 0.06, 0.13, 0.27, 0.49, 1.43 and 3.38 AU. In the Solar System this set of orbits would fit within the main asteroid belt.

There are no planets known to be in mean-motion resonances, although the system has a number of near resonances[5] including 3c:2i:1d and 3e:2j:1f. 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).[5] A 2020 study set upper limits on the masses of the confirmed planets based on non-detections in Gaia astrometry: planet c is <8.626 MJ, planet d is <10.37 MJ, planet e is <20.44 MJ, planet f is <14.03 MJ, planet g is <10.62 MJ, and planet h is <22.63 MJ.[14] While some of these upper limits are in the mass range of brown dwarfs, it is likely that the true masses are significantly smaller.

Planets
Artist's impression of HD 10180 d. Also depicted are planets b and c in transit.

HD 10180 b is a possible Earth-sized planet (minimum mass 1.3 times Earth's) located at 0.02 AU. Its orbital radius was originally estimated to have a near-circular orbit at a distance of 0.02225 ± 0.00035 AU (closer than Mercury, about one-seventh the distance and correspondingly hotter), taking 1.1 days to complete a full orbit.[19] The estimated parameters of planet b were revised in 2012 with a slightly smaller orbital radius and a more eccentric orbit.[8] The false detection probability was initially 1.4%;[5] its probability was improved by Mikko Tuomi in 2012, but it was not confirmed by subsequent studies, such as Kane in 2014.[13]

HD 10180 c, with a minimum mass comparable to that of Uranus, is a hot Neptune. Dynamical simulations suggest that if the mass gradient was any more than a factor of two, the system would not be stable. Its orbital period and eccentricity were originally estimated at 5.75979 ± 0.00062 and 0.045 ± 0.026 respectively; however, these were revised in 2012 in favour of a more eccentric orbit. The false detection probability is less than 0.1%.[5]

HD 10180 i is a possible but unconfirmed hot super-Earth claimed by Mikko Tuomi in 2012.[8] Subsequent studies have not confirmed it.

HD 10180 d is a hot Neptune. Its mass was initially estimated at >11.75 ± 0.65 Earth masses (smaller than Uranus) and on a slightly eccentric orbit; however, this was re-estimated with a larger mass and less eccentric orbit in 2012.

HD 10180 e is thought to be a hot Neptune with about twice the mass of Neptune. Its estimated orbital distance and eccentricity were downscaled in 2012. The false detection probability is less than 0.1%.[5]

HD 10180 j is a possible but unconfirmed hot super-Earth or gas dwarf claimed by Mikko Tuomi in 2012.[8] Subsequent studies have not confirmed it.

HD 10180 f is a hot Neptune and similar in mass to HD 10180 e. At an orbital distance of 0.49 AU and eccentricity of 0.12, its orbit is analogous to that of Mercury with a similar black-body-temperature range, though with its high mass, any greenhouse effect caused by an atmosphere would give it searing Venus-like or greater temperatures. Its estimated orbital distance and eccentricity were downscaled slightly in 2012. The false detection probability is less than 0.1%.[5]

HD 10180 g is a giant planet with a mass larger than Neptune's. It has a significantly eccentric orbit[13] at 1.4 AU and either crosses the system's predicted habitable zone or lies within it[13][20] though it does not fit current models for planetary habitability due to its large mass (at least 23 times Earth). If it is a gas giant, it is likely of Sudarsky Class II. There is a possibility that a natural satellite with sufficient atmospheric pressure could have liquid water on its surface. Its estimated orbital distance and eccentricity were downscaled in 2012 but remains in the habitable zone. The false detection probability is less than 0.1%.[5]

HD 10180 h is the largest and outermost known planet in the system. Originally, it was thought to be a Saturn-sized giant planet with a minimum mass 65 times that of Earth, though this minimum mass has since been revised downward to 46 Earth masses.[15] Orbiting at 3.4 AU, a distance comparable to the distance of the outer part of the asteroid belt from the Sun and as such it is likely a Sudarsky Class I planet. The spurious detection probability is 0.6%.[5]

See also
  • Kepler-90, a star with eight known planets (the first known to have an equal number of planets as the Solar System).
  • TRAPPIST-1, a star with seven known planets.

Notes
  1. For [Fe/H] equal to 0.08, the proportion is given by:
    100.08 = 1.20
    or 120%.
  2. The parameters are taken from the Newtonian fit taking into account tidal dissipation given in table 6 of Lovis et al. (2010). A purely Keplerian solution with slightly different parameters is given in table 3 of the same paper.

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. "HD 10180 -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-08-24.
  3. Nordström, B.; et al. (May 2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418 (3): 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID 11027621.
  4. Takeda, Genya; Ford, Eric B.; Sills, Alison; Rasio, Frederic A.; Fischer, Debra A.; Valenti, Jeff A. (2007). "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog". The Astrophysical Journal Supplement Series. 168 (2): 297. arXiv:astro-ph/0607235. Bibcode:2007ApJS..168..297T. doi:10.1086/509763. S2CID 18775378.
  5. Lovis, C; et al. (August 8, 2010). "The HARPS search for southern extra-solar planets XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems". Astronomy & Astrophysics. 528: A112. arXiv:1011.4994. Bibcode:2011A&A...528A.112L. doi:10.1051/0004-6361/201015577. S2CID 73558341.
  6. Sousa, S. G.; et al. (August 2007). "Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes". Astronomy and Astrophysics. 487 (1): 373–381. arXiv:0805.4826. Bibcode:2008A&A...487..373S. doi:10.1051/0004-6361:200809698. S2CID 18173201.
  7. Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics Supplement Series. 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511. Note: see VizieR catalogue V/130.
  8. Tuomi, Mikko (6 April 2012). "Evidence for 9 planets in the 10180 system". Astronomy & Astrophysics. 543: A52. arXiv:1204.1254. Bibcode:2012A&A...543A..52T. doi:10.1051/0004-6361/201118518. S2CID 15876919.
  9. Gill, Victoria (August 24, 2010). "Rich exoplanet system discovered". BBC News. BBC. Retrieved August 24, 2010.
  10. Sherrod, P. Clay; Koed, Thomas L. (2003). A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations. Astronomy Series. Courier Dover Publications. p. 9. ISBN 978-0-486-42820-8.
  11. "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on March 18, 2012. Retrieved 2012-01-16.
  12. Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3): 3127–3136. Bibcode:2015MNRAS.450.3127M. doi:10.1093/mnras/stv771.
  13. Kane, Stephen R.; Gelino, Dawn M. (2014). "On the Inclination and Habitability of the Hd 10180 System". The Astrophysical Journal. 792 (2): 111. arXiv:1408.4150. Bibcode:2014ApJ...792..111K. doi:10.1088/0004-637X/792/2/111. S2CID 42857278.
  14. Kiefer, F.; et al. (2021). "Determining the true mass of radial-velocity exoplanets with Gaia". Astronomy & Astrophysics. 645: A7. arXiv:2009.14164. doi:10.1051/0004-6361/202039168.VizieR-table 9
  15. Cretignier, M.; Dumusque, X.; Hara, N. C.; Pepe, F. (2021). "YARARA: Significant improvement in RV precision through post-processing of spectral time series". Astronomy and Astrophysics. 653: A43. arXiv:2106.07301. Bibcode:2021A&A...653A..43C. doi:10.1051/0004-6361/202140986. S2CID 235422291.
  16. "Richest Planetary System Discovered: Up to seven planets orbiting a Sun-like star" (Press release). European Southern Observatory. August 24, 2010. Retrieved 2010-08-24.
  17. Hara, Nathan C.; Unger, Nicolas; Delisle, Jean-Baptiste; Díaz, Rodrigo F.; Ségransan, Damien (2022). "Detecting exoplanets with the false inclusion probability". Astronomy & Astrophysics. 663: A14. arXiv:2105.06995. doi:10.1051/0004-6361/202140543. S2CID 234679625.
  18. Loibnegger, Birgit; Dvorak, Rudolf; Cuntz, Manfred (2017). "Case Studies of Exocomets in the System of HD 10180". The Astronomical Journal. 153 (5): 203. arXiv:1712.02386. Bibcode:2017AJ....153..203L. doi:10.3847/1538-3881/aa67ef. S2CID 119295263.
  19. Chang, Kenneth. "Kepler Telescope Detects Possible Earth-Size Planet", The New York Times, August 26, 2010. Accessed August 26, 2010.
  20. "Solar System 2.0 (beta) - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 2013-06-09. Retrieved 2012-04-13.
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