Lacaille 8760

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Lacaille 8760
Microscopium Bode.jpg
Red circle.svg
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]
Distance 12.947 ± 0.002  ly
(3.9696 ± 0.0006  pc)
Absolute magnitude  (MV)8.69 [4]
Details
Mass 0.60 [4]   M☉
Radius 0.51 [8]   R☉
Luminosity (bolometric)0.072 [9]   L☉
Luminosity (visual, LV)0.029  L☉
Surface gravity (log g)4.78 [8]   cgs
Temperature 3,800 [10]   K
Metallicity [Fe/H]−0.01±0.04 [11]   dex
Rotation 40±12 d [12]
Rotational velocity (v sin i)3.3 [6]  km/s
Age 4.8±2.9 [13]   Gyr
Other designations
AX Microscopii, AX Mic, CD−39°14192, GJ  825, HD  202560, HIP  105090, LHS  66 [5]
Database references
SIMBAD data
Exoplanet Archive data
ARICNS data
Microscopium constellation map.svg
Red pog.png
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) AXMicLightCurve.png
An ultraviolet band light curve for a flare on AX Microscopii, adapted from Byrne (1981)

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.

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References

  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. 1 2 3 4 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. 1 2 3 4 "The One Hundred Nearest Star Systems", RECONS, Georgia State University , retrieved 2015-06-25.
  5. 1 2 3 4 "V* AX Mic -- Flare Star", SIMBAD, Centre de Données astronomiques de Strasbourg , retrieved 2011-02-18.
  6. 1 2 3 4 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. 1 2 3 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. 1 2 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. 1 2 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.
  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. 1 2 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. 1 2 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. 1 2 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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