Mystery of missing stars in Universe may finally be solved

Friday, November 19, 2010

WASHINGTON - Star births in the Universe occur round the clock and according to calculations, we should be able to see a lot more stars than we currently do - so where have all the stars gone?

Dr. Pflamm-Altenburg and Professor Dr. Pavel Kroupa at the University of Bonn worked with Dr. Carsten Weidner from St. Andrews University and could have solved the long-standing puzzle.

The mismatch happens because of the manner in which astronomers calculate the birth rate.

“For the local Universe - i.e., the Milky Way as our home and the adjacent galaxies - it is relatively simple. Here we are able to count the young stars one by one, using huge telescopes,” said Kroupa.

But this method works only for galaxies in our immediate vicinity. Many galaxies are so distant that even the best telescope simply overlooks their small stars. Occasionally, there is an especially large whopper among the newbie’s in the sky, which leaves its traces in the light of even the farthest galaxies. The number of large whoppers then determines the strength of this trace.

In our immediate vicinity, these large whoppers occur with a fixed probability. There are always about 300 lightweights to one “big star baby.”

But the Bonn scientists found the ratio to be skewed. Their hypothesis is that at times when the galactic nurseries are booming, they generate a considerably higher number of stellar heavies than normal.

The reason for this, according to this theory, is so-called stellar crowding. For stars are not single children; they are born in groups, as so-called star clusters. At birth, these clusters are always of a similar size - no matter whether they contain 100 star embryos - or 100,000.

Consequently, at times of a high birth rate, space can be at a premium in star clusters. Astronomers call such galaxies that are particularly rich in mass “ultra-compact dwarf galaxies,” or UCD’s for short. In these, things are so tight that some of the young stars fuse during formation. Thus, more stars rich in mass than normal emerge.

The “small to large” ratio is then only about 50 to 1.

“In other words, we used to estimate the number of newly formed small stars by far too high,” explained Weidner. (ANI)

Filed under: Science and Technology

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