Segue 2

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Galaxy
Segue 2
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AladinLite
Constellation Aries
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 02 h 19 m 16 s
declination 20 ° 10 ′ 31 ″
Appearance
Morphological type dSph  
Brightness  (visual) 15.2 mag
Angular expansion Half light radius:
3 ′, 4 ± 0 ′, 2
Physical data
Affiliation Local group  
Radial velocity −40 km / s  
distance 114,000 ly /
35,000 pc
Absolute brightness −2.5 mag
Dimensions 550,000 M ☉
history
discovery Belokurov et al.
Discovery date 2007
Catalog names
Segue 2

Segue 2 is a spheroidal dwarf galaxy (dSph) in the constellation of Aries . She was discovered in the year 2007 the data for analysis survey of the Sloan Digital Sky Survey . The galaxy lies at a distance of about 35 k pc from the solar system and has a heliocentric radial velocity of −40 km / s . It has an approximately round shape and a very small half-light radius of only 34 pc for dwarf galaxies .

properties

Segue 2 is one of the smallest and faintest satellites (only Segue 1 and Willman 1 are fainter) of the Milky Way . The integral luminosity is only 800 L ☉ with an absolute brightness of M V = −2.5 mag, which is significantly less than that of the majority of globular clusters . Nevertheless, the mass of the galaxy is around 550,000 M ☉, which leads to a mass-luminosity ratio of 650.

The stellar population of Segue 2 consists mainly of older stars that more than 12  billion originated years. This makes them one of the very first stars to have formed in the universe . At the moment, no relevant star formation can be determined in Segue 2 .

With a value of [Fe / H] <−2 the metallicity is correspondingly low, i. that is, compared to our sun, it has less than a hundredth of heavy elements .

Segue 2 is located near the edge of the Sagittarius Current and also about the same distance from the solar system. It may once have been a satellite of the Sagittarius dwarf galaxy or one of its globular clusters.

Individual evidence

  1. ↑ SIMBAD Astronomical Database . In: Results for Segue 2 . Retrieved February 13, 2010.
  2. ↑ a b c d e f g h i j k l m n V. Belokurov, Walker, MG; Evans, NW et al. : Segue 2: A Prototype of the Population of Satellites of Satellites . In: Mon. Not. R. Astron. Soc. . 397, No. 4, 2009, pp. 1748-1755. arxiv : 0903.0818 . bibcode : 2009MNRAS.397.1748B . doi : 10.1111 / j.1365-2966.2009.15106.x .
  3. ^ Nicolas F. Martin, de Jong, Jelte TA; Rix, Hans-Walter: A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites . In: The Astrophysical Journal . 684, No. 2, 2008, pp. 1075-1092. arxiv : 0805.2945 . bibcode : 2008ApJ ... 684.1075M . doi : 10.1086 / 590336 .