Cassiopeia Dwarf
Encyclopedia
The Cassiopeia Dwarf is a dwarf spheroidal galaxy
about 2.58 Mly
away in the constellation
Cassiopeia
. The Cassiopeia Dwarf is part of the Local group of galaxies and a satellite galaxy
of the Andromeda Galaxy
(M31).
The Cassiopeia Dwarf was found in 1998, together with the Pegasus Dwarf
, by a team of astronomers (Karachentsev and Karachentseva) in Russia
and the Ukraine
. The Cassiopeia Dwarf and the Pegasus Dwarf are farther from M31 than its other known companion galaxies, yet still appear bound to it by gravity. Neither galaxy contains any young, massive star
s or shows traces of recent star formation. Instead, both seem dominated by very old stars, with ages of up to 10 billion years.
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 2.58 Mly
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
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....
Cassiopeia
Cassiopeia (constellation)
Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopea was one of the 48 constellations listed by the 2nd century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today...
. The Cassiopeia Dwarf is part of the Local group of galaxies and a satellite galaxy
Satellite galaxy
A satellite galaxy orbits a larger galaxy due to gravitational attraction. Although a galaxy is made of a large number of objects which are not connected to each other, it has a center of mass, which represents a weighted average of the positions of each component object...
of the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
(M31).
The Cassiopeia Dwarf was found in 1998, together with the Pegasus Dwarf
Pegasus Dwarf Spheroidal Galaxy
The Pegasus Dwarf Spheroidal is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus...
, by a team of astronomers (Karachentsev and Karachentseva) in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
and the Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
. The Cassiopeia Dwarf and the Pegasus Dwarf are farther from M31 than its other known companion galaxies, yet still appear bound to it by gravity. Neither galaxy contains any young, massive 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 or shows traces of recent star formation. Instead, both seem dominated by very old stars, with ages of up to 10 billion years.