Eta Pegasi

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Eta Pegasi
Location of η Pegasi (circled) near the center
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 22h 43m 00.13743s[1]
Declination +30° 13′ 16.4822″[1]
Apparent magnitude (V) +2.95[2]
Characteristics
Spectral type G2 II + F0 V[3]
U−B color index +0.57[2]
B−V color index +0.86[2]
Distance
196 ± 8 ly
(60 ± 3 pc)
Absolute magnitude (MV)–1.18[6]
Semi-amplitude
(K1)
(primary)		14.37 km/s
Details
η Peg A
Gyr
HR 8650, SAO 90734[10]
Database references
SIMBADdata

Eta Pegasi or η Pegasi, formally named Matar /ˈmeɪtɑːr/,[11][12] is a binary star in the constellation of Pegasus. The apparent visual magnitude of this star is +2.95,[2] making it the fifth-brightest member of Pegasus. Based upon parallax measurements, the distance to this star is about 214 light-years (66 parsecs) from the Sun.[1]

Nomenclature

η Pegasi (Latinised to Eta Pegasi) is the star's Bayer designation.

It bore the traditional name Matar, derived from the Arabic سعد المطر Saʽd al Maṭar, meaning lucky star of rain.[13] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN approved the name Matar for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[12]

In Chinese, 離宮 (Lì Gōng), meaning Resting Palace, refers to an asterism consisting η Pegasi, λ Pegasi, μ Pegasi, ο Pegasi, τ Pegasi and ν Pegasi.[15] Consequently, η Pegasi itself is known as 離宮四 (Lì Gōng sì), "the Fourth Star of Resting Palace".[16]

Namesake

Crater class cargo ship named after the star.[citation needed
]

Properties

The Eta Pegasi system consists of a pair of stars in a binary orbit with a

projected rotational velocity of 1.7 km s−1 with an estimated rotation period of 818 days.[6]

The secondary component is an

F-type main sequence star with a classification of F0 V.[3] The secondary star is 3.56 magnitudes fainter that the primary star at 700 nm.[17] There are also 2 class G stars further away that may or may not be physically related to the main pair.[citation needed
]

References

  1. ^
    S2CID 18759600
    .
  2. ^
    Bibcode:1966CoLPL...4...99J
    .
  3. ^
    doi:10.1086/313152
  4. Bibcode:1953GCRV..C......0W
    .
  5. doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR
    .
  6. ^
    Bibcode:2000A&A...361..614P
  7. ^
    doi:10.1088/0004-6256/135/1/209
  8. ^
    S2CID 119427037
    .
  9. ^
    doi:10.1086/117702
  10. ^ "eta Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-03.
  11. ISBN 978-1-931559-44-7
    .
  12. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016.
  13. Bibcode:1944PA.....52....8D
  14. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  15. ISBN 978-986-7332-25-7
    .
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. S2CID 118803592
    .
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