HD 140283

HD 140283

HD 140283
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Libra[1]
Right ascension 15h 43m 3.10s[1]
Declination −10° 56′ 00.6″[1]
Apparent magnitude (V) 7.223[1]
Astrometry
Radial velocity (Rv)−169 km/s
Proper motion (μ) RA: −1114.93 mas/yr
Dec.: −304.36 mas/yr
Parallax (π)17.15[2] ± 0.14 mas
Distance190.1 ± 1.5 ly
(58.30 ± 0.48[2] pc)
DetailsSIMBAD
Radius1.4 R☉
Luminosity3.83 L☉
Temperature5777 ± 55[2] K
Metallicity [Fe/H]−2.40 ± 0.10[2] dex
Rotational velocity (v sin i)≤ 3.9[3] km/s
Age14.46 ± 0.8 (minimum 13.66)[2] Gyr
Database references
SIMBADdata

HD 140283, informally nicknamed Methuselah star,[4] is a metal-poor subgiant star about 190 light years away from the Earth in the constellation Libra.[1][2] Its apparent magnitude is 7.223.[1] The star has been known to astronomers for over a century as a high-velocity star, and an early spectroscopic analysis by Chamberlain and Aller found it to have a substantially lower metal content than the Sun.[5] Modern spectroscopic analyses find an iron content about a factor of 250 lower than that of the Sun. It is one of the closest Population II stars to us.

Age and significance

Because HD 140283 is neither on the main sequence nor a red giant, its position in the Hertzsprung-Russell diagram can be interpreted with theoretical models of stellar evolution to infer the stellar age. For field stars (as opposed to stars in clusters) it is rare to know a star's luminosity, surface temperature and composition precisely enough to get a well-constrained value for the stellar age; because of their relative scarcity, this is even rarer for a Population II star like HD 140283. One recent study[6][7] used the Fine Guidance Sensors of NASA's Hubble Space Telescope to measure a precise parallax (and therefore distance and luminosity) for the star,[2] and employ this information to estimate an age for the star of 14.46 ± 0.8 billion years.[2] Due to the uncertainty in the value, this age for the star may not conflict with the age of the Universe determined by the Planck satellite, 13.799 ± 0.021.[2][8] Once dubbed the "Methuselah Star" by the popular press due to its age, the star must have formed soon after the Big Bang[2] and is one of the oldest stars known.[9] Accurate determinations of the ages of metal-poor stars, such as HD 140283 and those in globular clusters, set a lower limit for the possible age of the Universe independent of cosmological theory or observations.[10]

Studies of the star also help astronomers understand the Universe's early history. Very low but non-zero metallicities of stars like HD 140283 indicate the star was born in the second generation of stellar creation; their heavy-element content is believed to have come from truly zero-metal stars (Population III stars), none of which have yet been identified.[11] The first stars are thought to have been born a few hundred million years after the Big Bang, and they died in supernova explosions after only a few million years.[11] A second generation of stars, the generation in which HD 140283 is theorized to have been born, could not have coalesced until gas, heated from the supernova explosions of the earlier stars, cooled down.[11] The age of HD 140283 indicates that the time it took for the gases to cool was likely only a few tens of millions of years.[11]

The relative proportions of the heavy elements in metal-poor stars like HD 140283 also inform us about the nucleosynthetic yield and therefore the internal state of the now-extinct Population III stars. Like HD 122563, CS22892-0052, and CD -38 245, HD 140283 has an excesses of oxygen and the alpha elements relative to iron:[2] while the proportions of these elements is much lower in HD 140283 than in the Sun, they are not as low as is the case for iron. The implication is that the first population of stars generated the alpha elements preferentially to other groups of elements, including the iron peak and s-process. Unlike those other metal-poor stars, HD 140283 has a detectable amount of lithium,[12] a consequence of HD 140283 having not yet evolved into a red giant and thus has not yet undergone the first dredge-up.

References

  1. 1 2 3 4 5 6 "HD 140283". Sky-map.org. Retrieved February 23, 2013.
  2. 1 2 3 4 5 6 7 8 9 10 11 H. E. Bond; E. P. Nelan; D. A. VandenBerg; G. H. Schaefer; D. Harmer (2013). "HD 140283: A Star in the Solar Neighborhood that Formed Shortly After the Big Bang". The Astrophysical Journal Letters 765 (1): L12. arXiv:1302.3180. Bibcode:2013ApJ...765L..12B. doi:10.1088/2041-8205/765/1/L12.
  3. ↑ A. J. Gallagher; et al. (2010). "The barium isotopic mixture for the metal-poor subgiant star HD 140283". Astronomy and Astrophysics 523: A24. arXiv:1008.3541. Bibcode:2010A&A...523A..24G. doi:10.1051/0004-6361/201014970.
  4. ↑ "Hubble Finds 'Birth Certificate' of Oldest Known Star". Science Daily. March 7, 2013. Retrieved August 11, 2013.
  5. ↑ J. W. Chamberlain; L. H. Aller (1951). "The Atmospheres of A-Type Subdwarfs and 95 Leonis". Astrophysical Journal 114: 52. Bibcode:1951ApJ...114...52C. doi:10.1086/145451.
  6. ↑ "Our neighbor star almost as old as universe". RT.com. January 13, 2013. Retrieved 2013-02-23.
  7. ↑ "Hubble finds birth certificate of oldest known star". Phys.Org. March 7, 2013. Retrieved 2013-03-07.
  8. ↑ Planck Collaboration (2015). "Planck 2015 results. XIII. Cosmological parameters (See Table 4 on page 31 of pfd).". arXiv:1502.01589. Bibcode:2015arXiv150201589P.
  9. ↑ L. Smith (January 14, 2013). "The oldest star in the universe: Astronomers find HD 140283 is at least 13.2 billion dates old". Daily Mail. Retrieved February 23, 2013.
  10. ↑ D. Majaess (February 23, 2013). "Nearby Ancient Star is Almost as Old as the Universe". Universe Today. Retrieved February 23, 2013.
  11. 1 2 3 4 R. Cowen (January 10, 2013). "Nearby star is almost as old as the Universe". Nature News. doi:10.1038/nature.2013.12196. Retrieved February 23, 2013.
  12. ↑ F. Spite; M. Spite (1982). "Abundance of lithium in unevolved halo stars and old disk stars - Interpretation and consequences". Astronomy & Astrophysics 115 (2): 357–366. Bibcode:1982A&A...115..357S.
This article is issued from Wikipedia - version of the Wednesday, April 20, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.