Lacaille 8760

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Lacaille 8760
Observation data
Epoch J2000      Equinox J2000
Constellation Microscopium
Right ascension 21h 17m 15.2697s[1]
Declination −38° 52′ 02.502″[1]
Apparent magnitude (V) 6.67[2]
Characteristics
Spectral type M0Ve[3][4]
U−B color index +1.165[3]
B−V color index +1.395[3]
Variable type Flare star
Astrometry
Radial velocity (Rv) +20.7[4] km/s
Proper motion (μ) RA: -3258.79[1] mas/yr
Dec.: -1146.51[1] mas/yr
Parallax (π) 253.36 ± 1.13[1] mas
Distance 12.87 ± 0.06 ly
(3.95 ± 0.02 pc)
Absolute magnitude (MV) 8.69[2]
Details
Mass 0.60[2] M
Radius 0.51[5] R
Surface gravity (log g) 4.78[5] cgs
Temperature 3,800[6] K
Rotation 40 ± 12 days[7]
Rotational velocity (v sin i) 3.3[4] km/s
Age < 0.40[5] Gyr
Other designations
AX Microscopii, AX Mic, GJ 825, HD 202560, LHS 66, CD-39°14192, GCTP 5117, HIP 105090.[3]
Database references
SIMBAD data
Exoplanet Archive data
ARICNS data

Lacaille 8760 (AX Microscopii) is a red dwarf in the constellation Microscopium, the microscope. Although it is slightly too faint to be seen without a telescope, it is one of the nearest stars to the Sun at about 12.9 light years distance. It was originally listed in a 1763 catalog that was published posthumously by the French Abbé Nicolas Louis de Lacaille. He observed it in the southern sky while working from an observatory at the Cape of Good Hope.[8]

In the past Lacaille 8760 has been classified anywhere from spectral class K7 down to M2. In 1979 the Irish astronomer Patrick Byrne discovered that it is a flare star,[9] and it was given the variable star designation AX Microscopii. As a flare star it is relatively quiet, only erupting on average less than once per day.

Lacaille 8760 orbits around the galaxy with a relatively high ellipticity of 0.23.[10] Its closest approach to the Sun occurred about 20,000 years ago when it came within 12 ly (3.7 pc).[11] Due to its low mass (60% of the Sun), it has an expected lifespan of about 7.5 × 1010 years,[12] seven times longer than the Sun's.

Despite efforts by astronomers, as of 2011 no planets have been detected in orbit around this star.[13]

Although Lacaille 8760 is the brightest red dwarf visible in the night sky,[14] it is still too dim to be viewed by the average naked eye. It is also one of the largest and brightest red dwarf known, with about 60% the mass and 51% the radius of the Sun.

See also[edit]

References[edit]

  1. ^ a b c d e Perryman, M. A. C. et al. (July 1997), The HIPPARCOS Catalogue, Astronomy and Astrophysics 323: L49–L52, Bibcode:1997A&A...323L..49P. 
  2. ^ a b c The One Hundred Nearest Star Systems, RECONS (Georgia State University), retrieved 2011-02-18. 
  3. ^ a b c d V* AX Mic -- Flare Star, SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2011-02-18. 
  4. ^ a b c Torres, C. A. O. et al. (December 2006), Search for associations containing young stars (SACY). I. Sample and searching method, Astronomy and Astrophysics 460 (3): 695–708, arXiv:astro-ph/0609258, Bibcode:2006A&A...460..695T, doi:10.1051/0004-6361:20065602.  See the online data.
  5. ^ a b c Takeda, Genya et al. (February 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): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763, retrieved 2011-08-26. 
  6. ^ Gautier, Thomas N., III et al. (September 2007), Far-Infrared Properties of M Dwarfs, The Astrophysical Journal 667 (1): 527–536, arXiv:0707.0464, Bibcode:2007ApJ...667..527G, doi:10.1086/520667. 
  7. ^ Byrne, P. B.; Doyle, J. G. (January 1989), Activity in late-type dwarfs. III - Chromospheric and transition region line fluxes for two dM stars, Astronomy and Astrophysics 208 (1–2): 159–165, Bibcode:1989A&A...208..159B. 
  8. ^ Croswell, Ken (July 2003), The Brightest Red Dwarf, Sky & Telescope: 32, retrieved 2011-02-18. 
  9. ^ Byrne, P. B. (April 1981), Gliese 825 - A new flare star, Monthly Notices of the Royal Astronomical Society 195: 143–147, Bibcode:1981MNRAS.195..143B. 
  10. ^ Allen, C.; Herrera, M. A. (April 1998), The Galactic Orbits of Nearby UV Ceti Stars, Revista Mexicana de Astronomia y Astrofisica 34: 37–46, Bibcode:1998RMxAA..34...37A. 
  11. ^ García-Sánchez, J. et al. (2001), Stellar encounters with the solar system, Astronomy and Astrophysics 379: 634–659, Bibcode:2001A&A...379..634G, doi:10.1051/0004-6361:20011330. 
  12. ^ Despain, K. H. (December 1981), Low-mass evolution - Zero-age main sequence to asymptotic giant branch, Astrophysical Journal, Part 1 251: 639–653, Bibcode:1981ApJ...251..639D, doi:10.1086/159510. 
  13. ^ Carson, J. C. et al. (December 2011), Low-mass evolution - Zero-age main sequence to asymptotic giant branch, The Astrophysical Journal 743 (2): 141, arXiv:1110.2191, Bibcode:2011ApJ...743..141C, doi:10.1088/0004-637X/743/2/141. 
  14. ^ Odert, P. et al. (2008), Habitability of M-type Stars - a Catalogue of Nearby M Dwarfs, Central European Astrophysical Bulletin 32: 149–156, Bibcode:2008CEAB...32..149O. 

External links[edit]