According to a group of astronomers led by Prof Jean Turner of the University of California, Los Angeles, more than a million infant stars are forming in a massive star cluster in NGC 5253.
This Hubble Space Telescope image shows the local dwarf galaxy NGC 5253; superimposed is the gas (fuzzy red to yellow) as seen by the Submillimeter Array; the bright white area is Cloud D. Image credit: J. L. Turner et al.
NGC 5253 is one of the nearest of the known blue compact dwarf galaxies. It is located 11 million light-years away the constellation Centaurus.
The galaxy is considered part of the Centaurus A/Messier 83 group of galaxies, which includes the famous radio galaxy Centaurus A and the spiral galaxy Messier 83.
Previous studies have suggested the possibility that its peculiar nature could result from a close encounter with its closer neighbor, Messier 83.
The newly-discovered star cluster, named Cloud D, is buried within a supernebula in NGC 5253.
It contains more than 7,000 massive O-type stars – the most luminous of all known stars – and has one billion times the luminosity of our Sun, but is invisible in ordinary light, hidden by its own hot gases.
The amount of dust surrounding the stars in the cluster is extraordinary – around 15,000 solar masses.
“The cluster is about 3 million years old, which in astronomical terms, is remarkably young. It is likely to live for more than a billion years,” said Prof Turner, the lead author of the paper published in the journal Nature.
“NGC 5253 has approximately nine times as much dark matter as visible matter — a much higher rate than the inner parts of the Milky Way. In coming years, the cloud could be destroyed by stars that become supernovae, which would spin all of the gas and elements created by the stars into interstellar space.”
Prof Turner added: “our Milky Way Galaxy has not formed gigantic star clusters for billions of years. It is still forming new stars, but not in nearly such large numbers. Some astronomers had believed that such giant star clusters could form only in the early Universe.”
“How much of a gas cloud gets turned into stars varies in different parts of the Universe. In the Milky Way, the rate for gas clouds the size of Cloud D is less than 5%. In Cloud D, the rate is at least ten times higher, and perhaps much more.”
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J. L. Turner et al. 2015. Highly efficient star formation in NGC 5253 possibly from stream-fed accretion. Nature 519, 331–333; doi: 10.1038/nature14218
