Segue 2

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Segue 2 Dwarf Galaxy[1]
Observation data (J2000 epoch)
ConstellationAries
Right ascension02h 19m 16s[1]
Declination+20° 10′ 31″[1]
Distance114 kly (35 kpc)[2]
Apparent magnitude (V)15.2 ± 0.2[2]
Characteristics
TypedSph[2]
Mass5.5×105[2] M
Mass/Light ratio650[2] M/L
Apparent size (V)6.8+0.4
−0.4
[2]
Other designations
Segue 2[2]
See also: Galaxy, List of galaxies

Segue 2 is a dwarf spheroidal galaxy situated in the constellation Aries and discovered in 2009 in the data obtained by Sloan Digital Sky Survey.[2] The galaxy is located at the distance of about 35 kpc (35,000 parsecs (110,000 ly)) from the Sun and moves towards the Sun with the speed of 40 km/s.[2] It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 34 pc.[2]

The name is due to the fact that it was found by the SEGUE program, the Sloan Extension for Galactic Understanding and Exploration.

Segue 2 is one of the smallest and faintest satellites[note 1] of the Milky Way[4]—its integrated luminosity is about 800 times that of the Sun (absolute visible magnitude of about −2.5), which is much lower than the luminosity of the majority of globular clusters.[2] However, the mass of the galaxy—about 550,000 solar masses—is substantial, corresponding to the mass to light ratio of about 650.[2]

The stellar population of Segue 2 consists mainly of old stars formed more than 12 billion years ago.[2] The metallicity of these old stars is also very low at [Fe/H] < −2, which means that they contain at least 100 times less heavy elements than the Sun.[2] The stars of Segue 2 were probably among the first stars to form in the Universe. Currently, there is no star formation in Segue 2.[2]

Segue 2 is located near the edge of Sagittarius Stream and at the same distance. It may once have been a satellite of Sagittarius Dwarf Elliptical Galaxy or its star cluster.[2]

In June 2013 The Astrophysical Journal reported that Segue 2 was bound together with dark matter.[5][6][7]

Circa 1,000 stars are supposed to exist within the galaxy.[8]

Notes[edit]

  1. Only Segue 1 and Willman 1 are fainter.[3]


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References[edit]

  1. 1.0 1.1 1.2 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 Belokurov, V.Expression error: Unrecognized word "etal". (2009). "Segue 2: A Prototype of the Population of Satellites of Satellites". Mon. Not. R. Astron. Soc. 397 (4): 1748–1755. arXiv:0903.0818. Bibcode 2009MNRAS.397.1748B. doi:10.1111/j.1365-2966.2009.15106.x.
  3. Martin, Nicolas F.; de Jong, Jelte T. A.; Rix, Hans-Walter (2008). "A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites". The Astrophysical Journal 684 (2): 1075–1092. arXiv:0805.2945. Bibcode 2008ApJ...684.1075M. doi:10.1086/590336.
  4. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  5. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  6. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  7. UCI Scientists Size Up Universe’s Most Lightweight Dwarf Galaxy with Keck Observatory Steve Steve, W. M. Keck Observatory updated June 7, 2013
  8. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
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As a reminder, article comments are only for discussions on how to improve the article. Please direct other comments to a user's talk page. Please be formal and do not use excessive uppercase. Please be advised you may receive an automatic block if you break the article comments policy. For information regarding what is acceptable/not acceptable in article comments, please message Icons-flag-ru.png Joey (talk), Natalia (talk), Icons-flag-fr.png ynoss (talk), or Icons-flag-ca.png Daniel (older account/talk).


Preceded by
Willman 1
Least massive galaxy known
2013 — 
150,000MSun
Succeeded by
incumbent