Stellar family in crowded and violent neighbourhood is surprisingly normal

June 5th, 2009 - 12:21 pm ICT by ANI  

Munich, June 5 (ANI): Astronomers have found that a stellar family near a supermassive black hole at the heart of the Milky Way, is surprisingly normal.

Using ESO’s Very Large Telescope, astronomers have obtained one of the sharpest views ever of the Arches Cluster - an extraordinary dense cluster of young stars near the supermassive black hole.

Despite the extreme conditions, astronomers were surprised to find that the same proportions of low- and high-mass young stars in the cluster as are found in more tranquil locations in our Milky Way.

The massive Arches Cluster is a rather peculiar star cluster. It is located 25 000 light-years away towards the constellation of Sagittarius (the Archer), and contains about a thousand young, massive stars, less than 2.5 million years old.

It is an ideal laboratory to study how massive stars are born in extreme conditions as it is close to the centre of our Milky Way, where it experiences huge opposing forces from the stars, gas and the supermassive black hole that reside there.

The Arches Cluster is ten times heavier than typical young star clusters scattered throughout our Milky Way and is enriched with chemical elements heavier than helium.

Using the NACO adaptive optics instrument on ESO’s Very Large Telescope, located in Chile, astronomers scrutinized the cluster in detail.

The new study confirms the Arches Cluster to be the densest cluster of massive young stars known.

It is about three light-years across with more than a thousand stars packed into each cubic light-year, an extreme density a million times greater than in the Sun’s neighbourhood.

Astronomers studying clusters of stars have found that higher mass stars are rarer than their less massive brethren, and their relative numbers are the same everywhere, following a universal law.

For many years, the Arches Cluster seemed to be a striking exception.

“With the extreme conditions in the Arches Cluster, one might indeed imagine that stars won’t form in the same way as in our quiet solar neighbourhood,” said Pablo Espinoza, the lead author of the paper reporting the new results.

“However, our new observations showed that the masses of stars in this cluster actually do follow the same universal law,” he added.

The total mass of the cluster seems to be about 30 000 times that of the Sun, much more than was previously thought.

“That we can see so much more is due to the exquisite NACO images,” said co-author Jorge Melnick. (ANI)

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