The Pegasus Dwarf Spheroidal (also known as ''Andromeda VI'' or ''Peg dSph'' for short) 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 as systems that are c ...
about
2.7 million light-year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
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 first constellati ...
Pegasus
Pegasus (; ) is a winged horse in Greek mythology, usually depicted as a white stallion. He was sired by Poseidon, in his role as horse-god, and foaled by the Gorgon Medusa. Pegasus was the brother of Chrysaor, both born from Medusa's blood w ...
. The Pegasus Dwarf is a member of the
Local Group
The Local Group is the galaxy group that includes the Milky Way, where Earth is located. 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 a
satellite galaxy
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and Luminosity, luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents ...
of the
Andromeda Galaxy
The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a Galaxy#Isophotal diameter, D25 isop ...
(M31).
General information
The Pegasus Dwarf Spheroidal is a galaxy with mainly metal-poor stellar populations. Its
metallicity
In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...
is
e/H≃ −1.3.
It is located at the
right ascension
Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...
23h51m46.30s and
declination
In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...
+24d34m57.0s in the
equatorial coordinate system
The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of astronomical object, celestial objects. It may be implemented in spherical coordinate system, spherical or Cartesian coordinate system, rect ...
(
epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided b ...
J2000.0), and in a distance of 820 ± 20
kpc from
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
and a distance of 294 ± 8
kpc from the
Andromeda Galaxy
The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a Galaxy#Isophotal diameter, D25 isop ...
.
The galaxy was discovered in 1999
by various authors on the
Second Palomar Observatory Sky Survey (POSS II) films.
See also
*
List of Andromeda's satellite galaxies
The Andromeda Galaxy (M31) has satellite galaxies just like the Milky Way. Orbiting M31 are at least 35 dwarf galaxies: the brightest and largest is M110, which can be seen with a basic telescope. The second-brightest and closest one to M31 is ...
*
Pegasus Dwarf Irregular Galaxy (Peg DIG)
*
Pegasus galaxy, the
Stargate Atlantis
''Stargate Atlantis'' (usually stylized in all caps and often abbreviated ''SGA'') is an Adventure film, adventure and military science fiction television series and part of MGM's Stargate, ''Stargate'' franchise. The show was created by Brad W ...
fictional location (probably the Pegasus Dwarf Irregular Galaxy).
Notes
- For an angular distance θ between ''C'' and
''G'', their mutual linear distance ''R'' is given by:
''R''2 = ''D'' + ''D'' - 2 × ''D''''g'' × ''D''''c'' × cos(θ)
References
External links
NASA/IPAC Extragalactic Database: ''Pegasus Dwarf Spheroidal''
{{Andromeda galaxy
Dwarf spheroidal galaxies
2807158
Local Group
Low surface brightness galaxies
Andromeda Subgroup
Pegasus (constellation)
Astronomical objects discovered in 1999