Arches Cluster

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Observation data (2000. epoch)
Arches Cluster
False color IR image of the Arches Cluster
Constellation	Sagittarius
Right ascension	17^h 45^m 50.5^s
Declination	-28° 49′ 28″
Distance	25000 lty (8500 pc)
Notable features	Optically obscured
See also: Open cluster, List of open clusters

The Arches Cluster is the densest known star cluster in the Milky Way, and is located about 100 light years away from the center of our galaxy, in the constellation Sagittarius. Due to extremely heavy optical extinction by dust in this region, the cluster is obscured in the visual bands, and is observed in the X-ray, infrared, and radio bands. The radius of the cluster is approximately one light year. It contains 150 or more young, very hot stars that are many times larger and more massive than our Sun. Such stars live for only a few million years before exhausting their hydrogen fuel, due to their extreme luminosity. The cluster also contains hot gas, produced in shocks by collisions among the massive, high-velocity stellar winds flowing outwards from the stars.

This star cluster and the Quintuplet cluster, another massive young cluster in the region, are estimated to be two to four million years old. The most massive of their stars are expected to become supernovas, forming neutron stars or black holes, or else be torn apart by tidal forces from the black hole known to lie at the Galactic center.^{[citation needed]}

[edit] Research

Recent work by Donald Figer, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, suggests that 150 solar masses is the upper limit of stars in the current era of the universe.^[1] He used the Hubble Space Telescope to observe about a thousand stars in the Arches cluster and found no stars over that limit despite a statistical expectation that there should be several.