Pisces II (Psc II) is a

dwarf spheroidal galaxy A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are c ...

situated in the

Pisces Pisces may refer to: *Pisces (astrology), an astrological sign Astronomy *Pisces (constellation), a constellation ** Pisces Overdensity, an overdensity of stars in the Milky Way's halo that is situated in the Pisces constellation ** Pisces II, a ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

and discovered in 2010 in the data obtained by the

Sloan Digital Sky Survey The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 a ...

. The galaxy is located at the distance of about 180 kpc (kilo

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s) from the Sun. It is classified as a

(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 The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

—its integrated

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

is about 10,000 times that of the Sun ( absolute magnitude of about −5), which corresponds to the luminosity of an average

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

. The stellar population of Pisces II consists mainly of moderately old stars formed 10–12 billion years ago. The

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

of these old stars is low at , which means that the percentage of their mass that consists of "heavy metals" is no more than of the corresponding percentage in the Sun. In 2016, follow-up work on Pegasus III highlighted that both it and Pisces II lie relatively close to each other (within approximately 43 kpc) and share similar radial velocities in the Galactic standard of rest frame (note: this is not the same as the LSR). This suggests that these two satellite galaxies may actually be associated with one another, and there is also a possibility that there was an even closer passage about 1 billion years ago. However, further

spectroscopic Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

measurements are required to confirm their association.

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