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Lacaille 8760

Coordinates: Sky map 21h 17m 15.269s, −38° 52′ 02.51″
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Lacaille 8760
Lacaille 8760 is located in the constellation Microscopium.
Lacaille 8760 is located in the constellation Microscopium.
Image of Lacaille 8760 (circled) in Bode's Uranographia (1801).[1] In the corresponding catalog this star is listed as № 36 in constellation Microscopium.[2]

Observation data
Epoch J2000      Equinox J2000
Constellation Microscopium
Right ascension 21h 17m 15.269s[3]
Declination −38° 52′ 02.51″[3]
Apparent magnitude (V) 6.67[4]
Characteristics
Spectral type M0Ve[5][6]
U−B color index +1.165[5]
B−V color index +1.395[5]
Variable type Flare star
Astrometry
Radial velocity (Rv)+20.7[6] km/s
Proper motion (μ) RA: −3,258.553 mas/yr[3]
Dec.: −1,145.396 mas/yr[3]
Parallax (π)251.9124 ± 0.0352 mas[7]
Distance12.947 ± 0.002 ly
(3.9696 ± 0.0006 pc)
Absolute magnitude (MV)8.69[4]
Details
Mass0.60[4] M☉
Radius0.51[8] R☉
Luminosity (bolometric)0.072[9] L☉
Luminosity (visual, LV)0.029 L☉
Surface gravity (log g)4.78[8] cgs
Temperature3,800[10] K
Metallicity [Fe/H]−0.01±0.04[11] dex
Rotation40±12 d[12]
Rotational velocity (v sin i)3.3[6] km/s
Age4.8±2.9[13] Gyr
Other designations
AX Microscopii, AX Mic, CD−39°14192, GJ 825, HD 202560, HIP 105090, LHS 66[5]
Database references
SIMBADdata
Exoplanet Archivedata
ARICNSdata
Lacaille 8760 is located in the constellation Microscopium.
Lacaille 8760 is located in the constellation Microscopium.
Lacaille 8760
Location of Lacaille 8760 in the constellation Microscopium

Lacaille 8760 (AX Microscopii) is a red dwarf star in the constellation Microscopium. It is one of the nearest stars to the Sun at about 12.9 light-years' distance, and the brightest M-class main-sequence star in Earth's night sky, although it is generally too faint to be seen without a telescope. At an apparent magnitude of +6.7, it may only be visible to the unaided eye under exceptionally good viewing conditions, under dark skies.

This star 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.[14] Number 8760 was assigned to this star in the 1847 edition of Lacaille's catalogue of 9,766 stars by Francis Baily.[15]

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,[16] and it was given the variable star designation AX Microscopii, or AX Mic. As a flare star it is relatively quiescent.

An ultraviolet band light curve for a flare on AX Microscopii, adapted from Byrne (1981)[16]

Lacaille 8760 is one of the largest and brightest red dwarfs known, with about 60%[4] the mass and 51%[8] the radius of the Sun. It is about five[13] billion years old and is spinning at a projected rotational velocity of 3.3 km/s,[6] giving it a rotation period of roughly 40 days.[12] The star is radiating 7.2%[9] of the luminosity of the Sun from its photosphere at an effective temperature of 3,800 K.[10]

Despite efforts by astronomers, as of 2011 no planets had been detected in orbit around this star.[17]

Lacaille 8760 orbits around the galaxy with a relatively high ellipticity of 0.23.[18] Its closest approach to the Sun occurred about 20,000 years ago when it came within 12 light-years (3.7 parsecs).[19] Due to its low mass (60% of the Sun), it has an expected lifespan of about 75 billion (7.5 × 1010) years,[20] seven times longer than the Sun's.

References

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  1. ^ e-rara.ch. Johann Elert Bode. Uranographia star atlas (1801), Tabula XVI
  2. ^ Johann Elert Bode. Allgemeine Beschreibung und Nachweisung der Gestirne (1801), Page 67
  3. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  4. ^ a b c d "The One Hundred Nearest Star Systems", RECONS, Georgia State University, retrieved 2015-06-25.
  5. ^ a b c d "V* AX Mic -- Flare Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-02-18.
  6. ^ a b c d 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, S2CID 16080025. See the online data.
  7. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  8. ^ 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, S2CID 18775378, retrieved 2011-08-26.
  9. ^ a b Moro-Martín, A.; et al. (March 2015). "Does the Presence of Planets Affect the Frequency and Properties of Extrasolar Kuiper Belts? Results from the Herschel Debris and Dunes Surveys". The Astrophysical Journal. 801 (2): 28. arXiv:1501.03813. Bibcode:2015ApJ...801..143M. doi:10.1088/0004-637X/801/2/143. S2CID 55170390.Vizier catalog entry
  10. ^ a b 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, S2CID 15732144.{{citation}}: CS1 maint: multiple names: authors list (link)
  11. ^ Lindgren, Sara; Heiter, Ulrike (2017). "Metallicity determination of M dwarfs. Expanded parameter range in metallicity and effective temperature". Astronomy and Astrophysics. 604: A97. arXiv:1705.08785. Bibcode:2017A&A...604A..97L. doi:10.1051/0004-6361/201730715. S2CID 119216828.
  12. ^ a b 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.
  13. ^ a b Boehle, A.; et al. (October 2019), "Combining high-contrast imaging and radial velocities to constrain the planetary architectures of nearby stars", Astronomy & Astrophysics, 630: 17, arXiv:1907.04334, Bibcode:2019A&A...630A..50B, doi:10.1051/0004-6361/201935733, S2CID 195874049, A50.
  14. ^ Croswell, Ken (July 2003), "The Brightest Red Dwarf", Sky & Telescope: 32, retrieved 2011-02-18.
  15. ^ Francis Baily. A Catalogue of 9766 Stars (1847), Page 219
  16. ^ a b Byrne, P. B. (April 1981), "Gliese 825 - A new flare star", Monthly Notices of the Royal Astronomical Society, 195 (2): 143–147, Bibcode:1981MNRAS.195..143B, doi:10.1093/mnras/195.2.143.
  17. ^ 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, S2CID 119270911.
  18. ^ Allen, C.; Herrera, M. A. (April 1998), "The Galactic Orbits of Nearby UV Ceti Stars", Revista Mexicana de Astronomía y Astrofísica, 34: 37–46, Bibcode:1998RMxAA..34...37A.
  19. ^ García-Sánchez, J.; et al. (2001), "Stellar encounters with the solar system" (PDF), Astronomy and Astrophysics, 379 (2): 634–659, Bibcode:2001A&A...379..634G, doi:10.1051/0004-6361:20011330.
  20. ^ 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.
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