Leo V is a dwarf spheroidal galaxy situated in the Leo

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 origins of the e ...

and discovered in 2007 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 a distance of about 180 kpc from the Sun and moves away from the Sun with the velocity of about 173 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately spherical shape with the

half-light radius Galaxy effective radius or half-light radius (R_e) is the radius at which half of the total light of a galaxy is emitted. This assumes the galaxy has either intrinsic circular symmetry, spherical symmetry or is at least circularly symmetric as vie ...

of about 130 pc. Leo V is one of the smallest and faintest satellites of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

—its integrated luminosity is about 10,000 times that of the Sun (absolute visible magnitude of about ), which is much lower than the luminosity of a typical globular cluster. However, its mass is about 330 thousand

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es, which means that Leo's V

mass to light ratio In astrophysics and physical cosmology the mass-to-light ratio, normally designated with the Greek letter upsilon, , is the quotient between the total mass of a spatial volume (typically on the scales of a galaxy or a cluster) and its luminosity ...

is around 75. A relatively high mass to light ratio implies that Leo V is dominated by

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

. The stellar population of Leo V consists mainly of old stars formed more than 12 billion years ago. The metallicity of these stars is also very low at , which means that they contain 100 times less heavy elements than the Sun. The galaxy is located only 3 degrees away from another Milky Way satellite, Leo IV. The latter is also closer to the Sun by 20 kpc. These two galaxies may be physically associated with each other. There is evidence that they are connected by a star bridge.

Notes

References

{{Milky Way Dwarf spheroidal galaxies 4713563 Leo (constellation) Local Group Milky Way Subgroup ?