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Leo II (dwarf galaxy)
Encyclopedia
Leo II is an dwarf spheroidal galaxy
about 690,000 light-year
s away in the constellation
Leo
. As of October 2008 it is one of 24 known satellite galaxies of the Milky Way
.
As of 2007 Leo II is thought to have a core radius of 178 ± 13 pc and a tidal radius of 632 ± 32 pc.
It was discovered in 1950 by Robert G. Harrington
and Albert George Wilson
, from the Mount Wilson
and Palomar Observatories
in California.
optical-infrared telescope
in Mauna Kea, Hawaii. Over 2 nights, 90 minutes of exposures were taken and 82,252 star
s were detected down to a visible magnitude
of 26. They found that Leo II consists of largely of metal-poor
older star
s, a sign that it has survived the galactic cannibalism under which massive galaxies (e.g., the Milky Way
) consume smaller galaxies to attain their extensive size.
Observation at ESO
estimates Leo II's mass to be (2.7 ± 0.5)×107 M⊙
.
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...
about 690,000 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...
. As of October 2008 it is one of 24 known satellite galaxies 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...
.
As of 2007 Leo II is thought to have a core radius of 178 ± 13 pc and a tidal radius of 632 ± 32 pc.
It was discovered in 1950 by Robert G. Harrington
Robert G. Harrington
Robert G. Harrington was an American astronomer who worked at Palomar Observatory. He should not be confused with Robert Sutton Harrington, who was also an astronomer, but was born later and worked at the US Naval Observatory....
and Albert George Wilson
Albert George Wilson
Albert George Wilson is an American astronomer.He was born in Houston, Texas. He received his Ph.D. in mathematics from Caltech in 1947; his thesis title was Axially Symmetric Thermal Stresses in a Semi-Infinite Solid....
, from the Mount Wilson
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
and Palomar Observatories
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
in California.
Recent Findings
In 2007 a team of 15 scientists observed Leo II through the 8.2 meter SubaruSubaru (telescope)
Subaru Telescope is the 8.2 metre flagship telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades...
optical-infrared telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
in Mauna Kea, Hawaii. Over 2 nights, 90 minutes of exposures were taken and 82,252 star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s were detected down to a visible magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 26. They found that Leo II consists of largely of metal-poor
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
older star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s, a sign that it has survived the galactic cannibalism under which massive galaxies (e.g., 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...
) consume smaller galaxies to attain their extensive size.
Observation at ESO
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
estimates Leo II's mass to be (2.7 ± 0.5)×107 M⊙
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
.
See also
- Dwarf GalaxyDwarf galaxyA dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
- Local GroupLocal GroupThe Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
, a description of the group of galaxies that includes the Milky Way