Palomar 12 is a

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

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 ...

Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half fi ...

, and is a member of the Palomar Globular Clusters group. First discovered on the

National Geographic Society – Palomar Observatory Sky Survey The National Geographic Society – Palomar Observatory Sky Survey (NGS-POSS, or just POSS, also POSS I) was a major astronomical survey, that took almost 2,000 photographic plates of the night sky. It was conducted at Palomar Observatory, Californ ...

plates 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

Fritz Zwicky Fritz Zwicky (; ; February 14, 1898 – February 8, 1974) was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and ...

, it was initially catalogued as a globular cluster; however, Zwicky came to believe it was actually a nearby dwarf galaxy in the

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 ...

. It is a relatively young cluster, being about 30% younger than most of the globular clusters in 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 ...

. It is metal-rich with a

metallicity 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 ...

of . It has an average luminosity distribution of . Based on

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

studies, this cluster was first suspected in 2000 to have been captured from the

Sagittarius Dwarf Elliptical Galaxy The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy (Sgr dE or Sag DEG), is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters in ...

(''SagDEG'') about 1.7 Ga ago. It is now generally believed to have originated in that galaxy and is associated with the

Sagittarius Stream In astronomy, the Sagittarius Stream is a long, complex structure made of stars that wrap around the Milky Way galaxy in an orbit that nearly crosses the galactic poles. It consists of Tidal stripping, tidally stripped stars from the Sagittarius Dw ...

. It is estimated to be 6.5 Gyr old.

References

External links

Simbad reference data

* * {{DEFAULTSORT:Palomar 12 Globular clusters Sagittarius Dwarf Spheroidal Galaxy Capricornus ?

• In typography, a bullet or bullet point, , is a typographical symbol or glyph used to introduce items in a list. For example: *Point 1 *Point 2 *Point 3 The bullet symbol may take any of a variety of shapes, such as circular, square, diamo ...

Local Group

See also

References

External links