HD 117939

HD 117939 is a Sun-like star 98 light years (30.23 parsecs) from the Sun. HD 117939 is a G-type star and a near solar twin, It is much older than the sun at 6.1 billion years, compared to the sun at 4.6 billion years old.[2] HD 117939 is found in the constellation of Centaurus. HD 117939 has an apparent magnitude of 7.291.

HD 117939
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 13h 34m 32.64965s[1]
Declination −38° 54′ 25.9713″[1]
Apparent magnitude (V) 7.27[2]
Characteristics
Spectral type G4V[2]
Astrometry
Proper motion (μ) RA: 446.17[1] mas/yr
Dec.: -394.11[1] mas/yr
Parallax (π)33.27 ± 0.61[1] mas
Distance98 ± 2 ly
(30.1 ± 0.6 pc)
Details
Temperature5,730[2] K
Metallicity [Fe/H]-0.29[2] dex
Age6.1[2] Gyr
Other designations
CD−38° 8635, GJ 9450, HD 117939, HIP 66238, SAO 204606
Database references
SIMBADdata
Morgan-Keenan spectral classification of stars. The sun is a G-class (G2V) star and is more massive than 95% of all stars. Only 7.6% are G-class stars

To date no exact solar twin (precisely matching all important properties of the Sun) has been found, however, there are some stars that come very close to being identical to the Sun, and as such are considered solar twins by the majority of the public. An exact solar twin would be a G2V star with a 5,778K temperature, would be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation.[3] G2V stars with an age of 4.6 billion years are at their most stable state. Proper metallicity and size are also very important to low luminosity variation. [4][5]

Sun comparison

Chart compares the sun to HD 117939.

Identifier J2000 Coordinates Distance
(ly)		 Stellar
Class		 Temperature
(K)		 Metallicity
(dex)		 Age
(Gyr)		 Notes
Right ascension Declination
Sun — — 0.00 G2V 5,778 +0.00 4.6 [6]
HD 117939 13h 34m 32.6s –38° 54′ 26″ 98 G4V 5,730 -0.29 6.1


See also
  • List of nearest stars

References
  1. van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. "HD 117939". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-26.
  3. NASA, Science News, Solar Variability and Terrestrial Climate, Jan. 8, 2013
  4. University of Nebraska-Lincoln astronomy education group, Stellar Luminosity Calculator
  5. National Center for Atmospheric Research, The Effects of Solar Variability on Earth's Climate, 2012 Report
  6. Williams, D.R. (2004). "Sun Fact Sheet". NASA. Retrieved 2009-06-23.
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