Leo II (or Leo B) 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 to systems that are comp ...
about 690,000
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away in the
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 ...
Leo. It is one of 24 known
satellite galaxies
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound ...
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 ...
.
[
]
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 George Harrington
Robert George Harrington (December 3, 1904 – June 15, 1987) 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 U ...
and
Albert George Wilson
Albert George Wilson (July 28, 1918 – August 27, 2012) was an American astronomer and a discoverer of minor planets.
He was born in Houston, Texas. He received his Ph.D. in mathematics from Caltech in 1947; his thesis title was ''Axially ...
, from the
Mount Wilson and
Palomar Observatories in California.
Recent Findings
In 2007 a team of 15 scientists observed Leo II through the 8.2 meter
Subaru
( or ; ) is the automaker, automobile manufacturing division of Japanese transportation conglomerate (company), conglomerate Subaru Corporation (formerly known as Fuji Heavy Industries), the Automotive industry#By manufacturer, twenty-first ...
optical-infrared
telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...
in Mauna Kea, Hawaii. Over 2 nights, 90 minutes of exposures were taken and 82,252
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s were detected down to a visible
magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...
of 26. They found that Leo II consists largely of
metal-poor
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
older
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s, a sign that it has survived the galactic cannibalism under which massive galaxies (e.g., 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 ...
) consume smaller galaxies to attain their extensive size.
[
]
Observation at
ESO
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based ast ...
estimates Leo II's mass to be (2.7 ± 0.5)×10
7 M⊙.
[
]
See also
*
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is ...
*
Local Group
The Local Group is the galaxy group that includes the Milky Way.
It has a total diameter of roughly , and a total mass of the order of .
It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
, a description of the group of galaxies that includes 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 ...
.
References
*
External links
*
Dwarf elliptical galaxies
Peculiar galaxies
Local Group
Milky Way Subgroup
Leo (constellation)
34176
?
{{Elliptical-galaxy-stub