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

. The galaxy was discovered in 1999 by various authors on the

Second Palomar Observatory Sky Survey The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observator ...

(POSS II) films.

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

General information

See also

Notes

References

External links