HIP 11915

HIP 11915 is a G-type main-sequence star located about 190 light-years from Earth in the constellation Cetus.[2] It is best known for its characteristics, which are very similar to those of the Sun, including the mass, radius, temperature, metallicity and age, which means that it is almost a solar twin, being just 500 million years younger than the Sun and with a lower metallicity.[lower-alpha 1] It is also known for its planetary companion, HIP 11915 b, which has a mass and orbital distance very similar to that of Jupiter, but probably with a slightly higher orbital eccentricity.

HIP 11915
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus
Right ascension 02h 33m 49.026s[1]
Declination –19° 36′ 42.500″[1]
Apparent magnitude (V) 8.58[2]
Characteristics
Evolutionary stage Main sequence
Spectral type G5V[2]
Astrometry
Radial velocity (Rv)+14.1 ± 0.5[1] km/s
Parallax (π)18.63 ± 0.29[1] mas
Distance175 ± 3 ly
(53.7 ± 0.8 pc)
Absolute magnitude (MV)4.83[3]
Details
Mass1.0046[2] M☉
Radius~1.01 R☉
Luminosity1+0.13
−0.12[4] L☉
Surface gravity (log g)4.46[5] cgs
Temperature5760 ± 4[2] K
Metallicity [Fe/H]−0.059[5] dex
Rotational velocity (v sin i)0.99[5] km/s
Age4.16 ± 0.65[5] Gyr
Other designations
HD 16008, HIP 11915, SAO 148468, BD-20°481[1]
Database references
SIMBADdata

This star is entry number 11915 in the Hipparcos Catalogue. The star is located at 02:33:49.02495 right ascension, −19° 36' 42.5032" dec.[1][8] Too faint to be seen with the unaided eye, the star can be spotted with good binoculars.[8]

Stellar characteristics

HIP 11915 is a G-type main sequence star that is approximately the same mass of and likely 101% the radius of the Sun. It has a temperature of 5760 K and is 4.16 billion years old,[2][5] nearly 500 million years younger than the Sun, which is about 4.6 billion years old[9] and has a temperature of 5778 K.[10]

The star is slightly poor in metals, with a metallicity ([Fe/H]) of about −0.059, or about 87% of the amount of iron and other heavier metals found in the Sun.[5] Given the similar properties of the Sun, HIP 11915's luminosity is likely close to the same as the Sun (give or take about 10% in uncertainty).

Planetary system
The HIP 11915 planetary system[2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 0.99 ± 0.06 MJ 4.8 ± .01 3830.0 ± 150 0.1 ± 0.07 — —

The system contains a gas giant, HIP 11915 b, with a mass and orbit very similar to that of Jupiter, located at approximately the same distance from its star. The discovery of HIP 11915 b is significant, because it is the first, and to date only, distant planetary system found that may be somewhat like the Solar System.[11] The radial velocity data also indicates that there is no large gas giant in this system with an orbital period of less than 1000 days. This means that there could be one or more terrestrial planets in the inner parts of the system, and the possibility of a habitable Earth-like planet.

This new discovery was made at the La Silla Observatory in Chile, using the High Accuracy Radial Velocity Planet Searcher instrument mounted on the European Southern Observatory's 3.6-meter telescope.[12][13]

According to Jorge Meléndez, who led the University of São Paulo, Brazil team that discovered HIP 11915 b, "the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy".[14]

Comparison to the Sun

This chart compares the properties of the Sun to HIP 11915.

Identifier J2000 Coordinates Distance
(ly)		 Stellar
Class		 Mass
(M☉)		 Radius
(R☉)		 Temperature
(K)		 Metallicity
(dex)		 Age
(Gyr)		 Notes
Right ascension Declination
Sun — — 0.00 G2V 1 1 5,778 +0.00 4.6 [7]
HIP 11915 [15] 02h 33m 49.02s −19° 36′ 42.5″ 190 G5V 1.00 1.01 5,760 −0.059 4.1 [16]

Footnotes
  1. An exact solar twin would be a G2V star with a 5778 K temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation.[6][7]

References
  1. "HD 16008". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 29 March 2018.
  2. "Planet HIP 11915". Retrieved 17 July 2015.
  3. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  4. Sousa, S. G.; et al. (2011). "Spectroscopic stellar parameters for 582 FGK stars in the HARPS volume-limited sample. Revising the metallicity-planet correlation". Astronomy and Astrophysics. 533: A141. arXiv:1108.5279. Bibcode:2011A&A...533A.141S. doi:10.1051/0004-6361/201117699. S2CID 119273370.Vizier catalog entry
  5. Dos Santos, Leonardo A.; et al. (2016). "The Solar Twin Planet Search: IV. The Sun as a typical rotator and evidence for a new rotational braking law for Sun-like stars". Astronomy & Astrophysics. 592: A156. arXiv:1606.06214. Bibcode:2016A&A...592A.156D. doi:10.1051/0004-6361/201628558. S2CID 53533614.
  6. "Solar Variability and Terrestrial Climate - NASA Science". Retrieved 8 January 2013.
  7. Williams, D.R. (2004). "Sun Fact Sheet". NASA. Retrieved 2009-06-23.
  8. "The star HIP 11915 in the constellation of Cetus". European Southern Observatory. 15 July 2015. Retrieved 17 July 2015.
  9. Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  10. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  11. "Jupiter's twin spotted". business standard. IANS. July 16, 2015. Retrieved 16 July 2015.
  12. "HIP 11915b: Jupiter Twin Found Orbiting Sun-Like Star". Sci-News.com. Jul 15, 2015. Retrieved 16 July 2015.
  13. Bora, Kukil (16 July 2015). "Jupiter Look-Alike Discovered Orbiting Sun-Like Star; Could There Be An Earth Twin?". ib times. Retrieved 16 July 2015.
  14. "Jupiter Twin Discovered Around Solar Twin". European Southern Observatory. Retrieved 16 July 2015.
  15. HIP 11915 at SIMBAD - Ids - Bibliography - Image.
  16. M. Bedell; J. Meléndez; J. L. Bean; I. Ramírez; M. Asplund; A. Alves-Brito; L. Casagrande; S. Dreizler; T. Monroe; L. Spina; M. Tucci Maia (June 26, 2015). "The Solar Twin Planet Search II. A Jupiter twin around a solar twin" (PDF). Astronomy & Astrophysics. 581: A34. arXiv:1507.03998. Bibcode:2015A&A...581A..34B. doi:10.1051/0004-6361/201525748. S2CID 56004595. Retrieved 17 July 2015.

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