NGC 4147 is the ''

New General Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and ...

'' identifier for a globular cluster of stars in the northern

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 ...

of Coma Berenices. It was discovered by English astronomer William Herschel on March 14, 1784, who described it as "very bright, pretty large, gradually brighter in the middle". With an apparent visual magnitude of 10.7, it is located around 60,000

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 from the Sun at a relatively high

galactic latitude The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way Galaxy, and the fundamental plane parallel to an ap ...

of 77.2°. This is a relatively small globular cluster, ranking 112th in luminosity among the Milky Way globular cluster population. It is considered an

Oosterhoff type I A globular cluster is a spheroidal conglomeration of stars. wikt:globular, 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 mil ...

cluster (OoI), despite having a relatively low

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 ...

. Indeed, it has the lowest metallicity of any OoI cluster known. There are 19

RR Lyrae variable RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and ...

star candidates and as many as 23 blue stragglers. A high proportion of the latter are concentrated near the dense core of the cluster, which is consistent with the idea that blue stragglers form through stellar mergers. The cluster lies some from the Galactic Center, and is relatively isolated from other globular clusters in the galaxy. The position of this cluster makes it a candidate for association with the Sagittarius tidal stream, and thus it may have been captured by the Milky Way after separation from the

Sagittarius Dwarf Spheroidal 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 ...

. A contour map of the cluster appears to show S-shaped tidal arms stretching to the north and south for several tidal radii. Such features are predicted for globular clusters that follow elliptical orbits and are near their apogalacticon.

References

External links

* {{DEFAULTSORT:NGC 4147 Globular clusters Coma Berenices 17840314 4147