Image of Lacaille 8760 (circled) inBode'sUranographia (1801).[1] In the corresponding catalog this star is listed as№ 36 in constellation Microscopium.[2]
Location of Lacaille 8760 in the constellationMicroscopium
Lacaille 8760 (AX Microscopii) is ared dwarf star in theconstellationMicroscopium. It is one of thenearest stars to the Sun at about 12.9light-years' distance, and the brightestM-classmain-sequence star in Earth's night sky, although it is generally too faint to be seen without atelescope. At anapparent 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 theFrench AbbéNicolas-Louis de Lacaille. He observed it in the southern sky while working from an observatory at theCape of Good Hope.[12] Number8760 was assigned to this star in the 1847 edition of Lacaille's catalogue of 9,766 stars byFrancis Baily.[13]
In the past, Lacaille 8760 has been classified anywhere from spectral classK7 down toM2. In 1979, theIrish astronomer Patrick Byrne discovered that it is aflare star,[14] and it was given thevariable star designation AX Microscopii, or AX Mic. As a flare star it is relatively quiescent.
Lacaille 8760 is one of the largest and brightest red dwarfs known, with about 60%[4] the mass and 51%[7] the radius of the Sun. It is about five[11] billion years old and is spinning at aprojected rotational velocity of 3.3 km/s.[6] The star is radiating 7.2%[8] of the luminosity of the Sun from itsphotosphere at aneffective temperature of 3,800 K.[9]
Despite efforts by astronomers, as of 2011 no planets had been detected in orbit around this star.[15]
Lacaille 8760 orbits around the galaxy with a relatively highellipticity of 0.23.[16] Its closest approach to the Sun occurred about 20,000 years ago when it came within 12 light-years (3.7parsecs).[17] Due to its low mass (60% of the Sun), it has an expected lifespan of about 75 billion (7.5 × 1010) years,[18] seven times longer than the Sun's.
^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.
^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.
