Gamma Microscopii

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Gamma Microscopii
Diagram showing star positions and boundaries of the Microscopium constellation and its surroundings
Location of γ Microscopii (circled)
Observation data
ICRS
)
Constellation
Microscopium
Right ascension 21h 01m 17.46047s[1]
Declination −32° 15′ 27.9574″[1]
Apparent magnitude (V) 4.680[2]
Characteristics
Spectral type G6 III[3]
U−B color index +0.575[2]
B−V color index +0.882[2]
R−I color index +0.32[4]
Distance
223 ± 8 ly
(68 ± 2 pc)
Absolute magnitude (MV)0.49[7]
Details
Myr
HIP 103738, HR 8039, SAO 212636, WDS 21013-3215A.[11][12]
Database references
SIMBADdata

Gamma Microscopii (γ Microscopii, γ Mic) is the brightest

viewed from city skies. The distance to this star has been determined using parallax measurements made with the Gaia telescope, which place it at 223 ± 8 light-years (68.4 ± 2.5 parsecs
).

Based upon a

G-type giant star. It is a core helium fusing star that is classified as a member of the red clump evolutionary branch, although the metallicity of this star—meaning the abundance of elements other than hydrogen and helium—is anomalously low for a member of this group.[10] The effective temperature of the star's outer envelope is 5,050 K,[9] giving it the yellow-hued glow typical of G-type stars.[13]

In the

Ursa Major Moving Group of stars that share a similar location and a common trajectory through space.[7] Backwards extrapolation of the motion of γ Microscopii has shown that approximately 3.8 million years ago, it was only around 6 light-years from the Sun.[14] It would then have had an apparent magnitude of −3 and have been brighter than Sirius is now.[8] Shortly before that, around 3.9 million years ago, it likely passed within 1.14 to 3.45 light-years of the Sun, possibly massive enough and close enough to disturb the Oort cloud.[15] The same authors looked at Proper Motion Data collected with Gaia DR2 and didn't confirm the close encounter based on that dataset. Additional information is needed to identify the root cause for the mismatch between Hipparcos and Gaia datasets in that case.[16]

Gamma Microscopii has a

gravitationally bound to γ Microscopii, but is merely a line of sight companion.[8][17]

The Bayer designation γ Microscopii was not assigned by Bayer himself. It was given the Flamsteed designation of 1 Piscis Austrini before Lacaille created the constellation of Microscopium in 1756.[18]

References

  1. ^
    S2CID 18759600
  2. ^
    doi:10.1093/mnras/172.3.667
  3. ^
    S2CID 55727428, archived from the original
    (PDF) on 2017-09-22, retrieved 2018-11-04
  4. CDS ID V/50
    . Accessed on line November 20, 2008.
  5. Bibcode:1953GCRV..C......0W
    .
  6. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR
    .
  7. ^
    doi:10.1086/368241
  8. ^ a b c d e f g Gamma Mic, Stars, Jim Kaler. Accessed on line March 19, 2015.
  9. ^
    doi:10.1086/191527
  10. ^
    Bibcode:2002AcA....52..159K
  11. ^ * gam Mic -- Star in double system, database entry, SIMBAD. Accessed on line November 20, 2008.
  12. ^ a b Entry 21013-3215, The Washington Double Star Catalog Archived 2009-01-31 at the Wayback Machine, United States Naval Observatory. Accessed on line November 20, 2008.
  13. Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original
    on 2012-03-18, retrieved 2012-01-16
  14. doi:10.1051/0004-6361:20011330
  15. S2CID 59039482
    . A35.
  16. S2CID 56269929
    .
  17. S2CID 14878976
    .
  18. S2CID 118445625
    .
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