Boötes III (dwarf galaxy)
Encyclopedia
Bootes III is an overdensity in the Milky Way's halo
, which may be a disrupted dwarf spheroidal galaxy
. It is situated in the Bootes constellation and was discovered in 2009 in the data obtained by Sloan Digital Sky Survey
. The galaxy is located at the distance of about 46 kpc from the Sun and moves away the Sun with the speed of about 200 km/s. It has an elongated shape (axis ratio of 2:1) with the radius of about 0.5 kpc. The large size and an irregular shape may indicate that Bootes III in a transitional phase between a gravitationally bound galaxy and completely unbound system.
Boots III is one of the smallest and faintest satellites of the Milky Way
—its integrated luminosity is about 18,000 times that of the Sun (absolute visible magnitude of about −5.8), which is much lower than the luminosity of many globular cluster
s. The mass of Bootes III is difficult to estimate because the galaxy is in process of being disrupted. In this case the velocity dispersion of its stars is not related to its mass.
The stellar population of Bootes III consists mainly of moderately old stars formed more than 12 billion years ago. The metallicity of these old stars is low at , which means that they contain 120 times less heavy elements than the Sun. Bootes III may the source of stars of the Styx stream in the galactic halo, which was discovered together with this galaxy.
Galactic halo
The term galactic halo is used to denote an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:* the galactic spheroid...
, which may be a disrupted dwarf spheroidal galaxy
Dwarf spheroidal galaxy
Dwarf spheroidal galaxy is a term in astronomy applied to low luminosity galaxies that are companions to the Milky Way and to the similar systems that are companions to the Andromeda Galaxy M31...
. It is situated in the Bootes constellation and was discovered in 2009 in the data obtained by Sloan Digital Sky Survey
Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-filter 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 was named after the Alfred P...
. The galaxy is located at the distance of about 46 kpc from the Sun and moves away the Sun with the speed of about 200 km/s. It has an elongated shape (axis ratio of 2:1) with the radius of about 0.5 kpc. The large size and an irregular shape may indicate that Bootes III in a transitional phase between a gravitationally bound galaxy and completely unbound system.
Boots III is one of the smallest and faintest satellites of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
—its integrated luminosity is about 18,000 times that of the Sun (absolute visible magnitude of about −5.8), which is much lower than the luminosity of many globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
s. The mass of Bootes III is difficult to estimate because the galaxy is in process of being disrupted. In this case the velocity dispersion of its stars is not related to its mass.
The stellar population of Bootes III consists mainly of moderately old stars formed more than 12 billion years ago. The metallicity of these old stars is low at , which means that they contain 120 times less heavy elements than the Sun. Bootes III may the source of stars of the Styx stream in the galactic halo, which was discovered together with this galaxy.