Lacaille 8760

Short description: Star in the constellation Microscopium

Coordinates:  21h 17m 15.269s, −38° 52′ 02.51″

Lacaille 8760

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
Equinox J2000.0]] (ICRS)
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[3] mas/yr
Dec.: −1,145.396[3] mas/yr
Parallax (π)| 251.9124 ± 0.0352[7] mas
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

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 France 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

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. ↑ 3.0 3.1 3.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
4. ↑ 4.0 4.1 4.2 4.3 "The One Hundred Nearest Star Systems", RECONS (Georgia State University), http://www.astro.gsu.edu/RECONS/TOP100.posted.htm, retrieved 2015-06-25.
5. ↑ 5.0 5.1 5.2 5.3 "V* AX Mic -- Flare Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=AX+Mic, retrieved 2011-02-18.
6. ↑ 6.0 6.1 6.2 6.3 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, doi:10.1051/0004-6361:20065602, Bibcode: 2006A&A...460..695T. See the online data.
7. ↑ Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
8. ↑ 8.0 8.1 8.2 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, doi:10.1086/509763, Bibcode: 2007ApJS..168..297T, http://exoplanets.org/SPOCS_evol.html, retrieved 2011-08-26.
9. ↑ 9.0 9.1 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. doi:10.1088/0004-637X/801/2/143. Bibcode: 2015ApJ...801..143M. Vizier catalog entry
10. ↑ 10.0 10.1 Gautier, Thomas N., III et al. (September 2007), "Far-Infrared Properties of M Dwarfs", The Astrophysical Journal 667 (1): 527–536, doi:10.1086/520667, Bibcode: 2007ApJ...667..527G.
11. ↑ Lindgren, Sara; Heiter, Ulrike (2017). "Metallicity determination of M dwarfs. Expanded parameter range in metallicity and effective temperature". Astronomy and Astrophysics 604: A97. doi:10.1051/0004-6361/201730715. Bibcode: 2017A&A...604A..97L. https://www.aanda.org/articles/aa/full_html/2017/08/aa30715-17/aa30715-17.html.
12. ↑ 12.0 12.1 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. ↑ 13.0 13.1 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, doi:10.1051/0004-6361/201935733, A50, Bibcode: 2019A&A...630A..50B.
14. ↑ Croswell, Ken (July 2003), "The Brightest Red Dwarf", Sky & Telescope: 32, http://www.kencroswell.com/thebrightestreddwarf.html, retrieved 2011-02-18.
15. ↑ Francis Baily. A Catalogue of 9766 Stars (1847), Page 219
16. ↑ 16.0 16.1 Byrne, P. B. (April 1981), "Gliese 825 - A new flare star", Monthly Notices of the Royal Astronomical Society 195 (2): 143–147, doi:10.1093/mnras/195.2.143, Bibcode: 1981MNRAS.195..143B.
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, doi:10.1088/0004-637X/743/2/141, Bibcode: 2011ApJ...743..141C.
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", Astronomy and Astrophysics 379 (2): 634–659, doi:10.1051/0004-6361:20011330, Bibcode: 2001A&A...379..634G, http://www.aanda.org/articles/aa/pdf/2001/44/aah2819.pdf.
20. ↑ Despain, K. H. (December 1981), "Low-mass evolution - Zero-age main sequence to asymptotic giant branch", Astrophysical Journal, Part 1 251: 639–653, doi:10.1086/159510, Bibcode: 1981ApJ...251..639D.

## External links

* SolStation article

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← Celestial objects within 10–15 light-years →

| Primary member type|

Celestial objects by systems. Secondary members are listed in small print.

| Subgiant stars|

| F-type|

* Procyon (α CMi) (11.41+0.04−0.03 ly)
* white dwarf B

|

| Main-sequence
stars|

| G-type|

* τ Cet (11.905±0.007 ly)
* 5? planets: b
* c
* d
* e
* f

|

K-type|

* ε Eri (10.475±0.003 ly)
* 1 (2?) planets: b
* c?
* 61 Cyg (11.409±0.022 ly)
* K-type main-sequence star B
* ε Ind (11.815±0.012 ly)
* 2 T-type brown dwarfs: Ba
* Bb
* 1? planets

M-type
(red dwarfs)|

* Ross 248 (10.298±0.023 ly)
* Lac 9352 (10.685+0.025−0.024 ly)
* Ross 128 (10.94±0.06 ly)
* EZ Aqr (11.08±0.13 ly)
* 2 red dwarfs: B
* C
* Σ 2398 (11.40±0.07 ly)
* red dwarf B
* Gmb 34 (11.70±0.03 ly)
* red dwarf B
* planet Ab
* DX Cnc (11.83±0.13 ly)
* Gliese 1061 (12.04±0.06 ly)
* YZ Cet (12.20±0.14 ly)
* Luyten's Star (12.20±0.04 ly)
* SCR 1845-6357 (12.57±0.05 ly)
* T-type brown dwarf B
* Teegarden's star (12.58±0.05 ly)
* Kapteyn's Star (12.78±0.04 ly)
* 1 (2?) planets: b
* c
* Lac 8760 (12.87±0.04 ly)
* Kruger 60 (13.18±0.08 ly)
* red dwarf B
* Ross 614 (13.36±0.04 ly)
* red dwarf B
* Wolf 1061 (14.0±0.1 ly)
* 3 planets: b
* c
* d
* Wolf 424 (14.05+0.27−0.26 ly)
* red dwarf B
* GJ 1 (14.15±0.06 ly)
* TZ Ari (14.584±0.07 ly)
* LHS 292 (14.89±0.01 ly)
* GJ 687 (14.77±0.06 ly)
* planet b
* GJ 674 (14.81+0.10−0.09 ly)
* planet b
* G 208-44 (14.81±0.07 ly)
* 2 red dwarfs: B
* G 208-45

| Degenerate
stars|

| White dwarfs|

* van Maanen 2 (14.03+0.12−0.11 ly)

|

| Brown dwarfs|

| M-type|

* DEN 1048−3956 (13.15±0.03 ly)
* 2M1540 (17.344±0.009 ly)

|

T-type|

* WISE 1506+7027 (11.1+2.3−1.3 ly)
* UGPS J0722-0540 (13.43±0.13 ly)

Y-type|

* WISE 0350−5658 (12.1+5.2−1.3 ly)

Italic are systems without known trigonometric parallax.

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Constellation of Microscopium

* List of stars in Microscopium
* Microscopium in Chinese astronomy

Stars|

| Bayer|

* α
* β
* γ
* δ
* ε
* ζ
* η
* θ1
* θ2
* ι
* ν

|

Flamsteed|

* 2 PsA
* 3 PsA

Variable|

* R
* S
* T
* U
* V
* ZZ
* AT
* AU
* AV
* AW
* BI
* BO
* BY
* DD

HR|

* 7817
* 7832
* 7853
* 7856
* 7893
* 7909
* 7915
* 7933
* 7935
* 7970
* 7971
* 7987
* 7991
* 8031
* 8046
* 8050
* 8100
* 8104
* 8108
* 8117
* 8124
* 8142
* 8200
* 8202

HD|

* 195902
* 196748
* 197900
* 201242
* 202628

Other|

* Lacaille 8760 (AX)
* 2MASS J20360829−3607115
* PSR J2124−3358
* WASP-7

| Exoplanets|

* WASP-7b

|

Galaxies|

| NGC|

* 6925
* 7012
* 7057
* 7060

|

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