Pisces II (dwarf galaxy)
|Pisces II Dwarf Galaxy|
|Observation data (J2000 epoch)|
|Right ascension||22h 58m 31s|
|Declination||+05° 57′ 09″|
|Distance||585 kly (180 kpc)|
|Apparent dimensions (V)||2.2+0.2
|Apparent magnitude (V)||16.3|
Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.
Pisces II is one of the smallest and faintest satellites of the Milky Way—its integrated luminosity is about 10,000 times that of the Sun (absolute magnitude of about −5), which corresponds to the luminosity of an average globular cluster. The stellar population of Pisces II consists mainly of moderately old stars formed 10–12 billion years ago. The metallicity of these old stars is low at −2.3 < [Fe/H] < −1.7, which means that the percentage of their mass that consists of "heavy metals"[A] is no more than 1/ of the corresponding percentage in the Sun.
- In astronomy and physical cosmology, unlike other physical sciences, "heavy metals" refers to all elements except hydrogen and helium.
- Belokurov, V.; Walker, M. G.; Evans, N. W.; Gilmore, G.; Irwin, M. J.; Just, D.; Koposov, S.; Mateo, M.; Olszewski, E.; Watkins, L.; Wyrzykowski, L. (2010). "Big Fish, Little Fish: Two New Ultra-Faint Satellites of the Milky Way". The Astrophysical Journal 712: L103. arXiv:1002.0504. Bibcode:2010ApJ...712L.103B. doi:10.1088/2041-8205/712/1/L103.