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Lacaille 8760

Coordinates:Sky map21h17m15.269s,−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) inBode'sUranographia(1801).[1]In the corresponding catalog this star is listed as№ 36in constellation Microscopium.[2]

Observation data
EpochJ2000EquinoxJ2000
Constellation Microscopium
Right ascension 21h17m15.269s[3]
Declination −38° 52′ 02.51″[3]
Apparent magnitude(V) 6.67[4]
Characteristics
Spectral type M0Ve[5][6]
U−Bcolor index +1.165[5]
B−Vcolor index +1.395[5]
Variable type Flare star
Astrometry
Radial velocity(Rv)+20.7[6]km/s
Proper motion(μ)RA:−3,258.553mas/yr[3]
Dec.:−1,145.396mas/yr[3]
Parallax(π)251.9124 ± 0.0352mas[7]
Distance12.947 ± 0.002ly
(3.9696 ± 0.0006pc)
Absolute magnitude(MV)8.69[4]
Details
Mass0.60[4]M☉
Radius0.51[8]R☉
Luminosity (bolometric)0.072[9]L☉
Luminosity (visual, LV)0.029L☉
Surface gravity(logg)4.78[8]cgs
Temperature3,800[10]K
Metallicity[Fe/H]−0.01±0.04[11]dex
Rotation40±12 d[12]
Rotational velocity(vsini)3.3[6]km/s
Age4.8±2.9[13]Gyr
Other designations
AX Microscopii, AX Mic,CD−39°14192,GJ825,HD202560,HIP105090,LHS66[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 constellationMicroscopium

Lacaille 8760(AX Microscopii) is ared dwarfstar in theconstellationMicroscopium.It is one of thenearest starsto the Sun at about 12.9light-years' distance, and the brightestM-classmain-sequencestar in Earth's night sky, although it is generally too faint to be seen without atelescope.At anapparent magnitudeof +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 theFrenchAbbéNicolas-Louis de Lacaille.He observed it in the southern sky while working from an observatory at theCape of Good Hope.[14]Number8760was assigned to this star in the 1847 edition of Lacaille's catalogue of 9,766 stars byFrancis Baily.[15]

In the past, Lacaille 8760 has been classified anywhere from spectral classK7down toM2.In 1979, theIrishastronomer Patrick Byrne discovered that it is aflare star,[16]and it was given thevariable star designationAX Microscopii, or AX Mic. As a flare star it is relatively quiescent.

Anultraviolet bandlight curvefor 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 aprojected rotational velocityof 3.3 km/s,[6]giving it arotation periodof roughly 40 days.[12]The star is radiating 7.2%[9]of the luminosity of the Sun from itsphotosphereat aneffective temperatureof 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 highellipticityof 0.23.[18]Its closest approach to the Sun occurred about 20,000 years ago when it came within 12 light-years (3.7parsecs).[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.Uranographiastar atlas (1801),Tabula XVI
  2. ^Johann Elert Bode.Allgemeine Beschreibung und Nachweisung der Gestirne(1801),Page 67
  3. ^abcBrown, A. G. A.;et al. (Gaia collaboration) (August 2018)."GaiaData 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 sourceatVizieR.
  4. ^abcd"The One Hundred Nearest Star Systems",RECONS,Georgia State University,retrieved2015-06-25.
  5. ^abcd"V* AX Mic -- Flare Star",SIMBAD,Centre de Données astronomiques de Strasbourg,retrieved2011-02-18.
  6. ^abcdTorres, 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,S2CID16080025.See the online data.
  7. ^Brown, A. G. A.;et al. (Gaia collaboration) (2021)."GaiaEarly 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.S2CID227254300.(Erratum:doi:10.1051/0004-6361/202039657e).Gaia EDR3 record for this sourceatVizieR.
  8. ^abcTakeda, 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,S2CID18775378,retrieved2011-08-26.
  9. ^abMoro-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.S2CID55170390.Vizier catalog entry
  10. ^abGautier, 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,S2CID15732144.{{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.S2CID119216828.
  12. ^abByrne, 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. ^abBoehle, 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,S2CID195874049,A50.
  14. ^Croswell, Ken (July 2003),"The Brightest Red Dwarf",Sky & Telescope:32,retrieved2011-02-18.
  15. ^Francis Baily.A Catalogue of 9766 Stars(1847),Page 219
  16. ^abByrne, 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,S2CID119270911.
  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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