Scientists have discovered what they were very young galaxies in the universe


25/04/2011

Astronomers using the orbiting space telescope GALEX (Galaxy Evolution Explorer), closer to understanding why the most massive stellar explosions occur in very young galaxies.

"It’s like a Sumo wrestler in a small car" Smart Car "," - said Don Neill, a member of the NASA team at the California Institute of Technology in Pasadena, who is lead author of a new study published in the journal Astrophysical Journal.

"The most powerful explosions of massive stars occur in galaxies with extremely low weight. New information indicates that massive stars in small galaxies remain so until its explosion, while in larger galaxies, they gradually decrease with aging and its during its explosion is not so great, "- said Neil.

Over the past few years, astronomers have found an unexpectedly large number of bright stellar explosions in so-called dwarf galaxies (1000 times smaller than the Milky Way). The explosions of stars, called supernovae, occur when massive stars (whose weight is a hundred times the mass of our sun) ends its existence.

Astronomers use ultraviolet information obtained by GALEX, to a more detailed study dwarf galaxies. As the newly emerging stars emit ultraviolet light in large quantities, this orbiting telescope that scans the sky in ultraviolet light, has become the ideal device for measuring the speed of star formation in galaxies.

The results showed that small galaxies as expected, did not have a large mass and velocity of star formation in them is high. In other words, small galaxies produce large star in a small amount.

"Even in these small galaxies in which explosions occur, the big guys are rare," - said co-author Michael Rich, who is a member of the research team.

In addition, this study enabled us to explain the reason for the more frequent explosions of massive stars in small galaxies, compared to the massive stars in larger galaxies such as the Milky Way. The reason is that small galaxies have fewer heavy atoms such as carbon or oxygen, than their larger counterparts. These small galaxies are younger and therefore have not been able to enrich the space of heavy atoms.

As explained by Neil and his co-authors, the lack of heavy atoms in the atmosphere of massive stars can lose less by the aging of the matter. In fact, the massive stars in small galaxies in old age is thicker than the massive stars in large galaxies. And the bigger the star, the bigger the explosion will happen when it becomes a supernova.

"These stars are like heavyweight champions, beat all records" - said Neil.

Rich added, "These dwarf galaxies are of particular interest to astronomers because they are very similar to those galaxies that were in our young universe shortly after the Big Bang. GALEX - is a powerful tool that allows us to know what were the galaxies when the Universe was quite young. "

Original: Physorg


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