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A gamma-ray burst recounts the formation of stars in the young universe
:: 13 January, 2009
Phenomena among the most violent of the universe, gamma-ray bursts may be used as cosmological probes. Thanks to them, a team of astrophysicists has to study the conditions for star formation in galaxies is 10 billion years.
GRB 080607 is a long gamma-ray burst (GRB for Gamma Ray Burst) detected on 7 June 2008 by the Swift satellite instruments. Very soon a battery of instruments on the ground took over, including the Katzman Automatic Imaging Telescope of the Lick Observatory and the Keck I telescope in Hawaii where the Low Resolution Imaging Spectrograph (LRIS) began spectroscopic analysis 15 minutes after Detection burst. These observations have provided an assessment of the redshift of GRB 080607 and thus its distance. It is known as gamma-ray burst that occurred in a galaxy about 3 billion years after the birth of the observable universe.
Gamma-ray bursts are the most violent explosions in the Universe. Currently, we think it is either hypernovae resulting from the explosion of very massive stars caused by the formation of a black hole in their heart (for long bursts) or the collision of two stars Compact, mainly neutron stars (short bursts). Very bright, these phenomena are visible at cosmological distances, and thus to draw conclusions on the overall structure of the universe and observe what was happening during its first billion years. After a burst of gamma rays, powerful but brief, a transitional light emission persists for a longer time. It is the afterglow, visible in the optical domain.
Molecular analysis of nursery
Jason X. Prochaska is a professor of astronomy and astrophysics at the University of California at Santa Cruz. With his colleagues, he has published an article in Astrophysical Journal Letters showing how it was possible for the first time, thanks to GRB 080607, detect molecules in the nurseries of stars within the galaxy host this burst. We knew already realize this kind of analysis of the composition atoms using the GRB galaxies in a time too remote, ie there are 10 billion years. But here, there are molecules of CO, carbon monoxide and molecular hydrogen (H2).
It was also found that GRB 080607 was the brightest gamma-ray burst GRB 080319B after. It is the presence of a large amount of dust in the molecular cloud where the explosion occurred has stolen some observers amateurs land that gamma-ray burst. Taking into account this factor of extinction in the spectrum of GRB, researchers have shown that the formation of stars in the galaxy at that time should be quite similar to that seen in the Milky Way. In particular, the abundances of elements other than hydrogen and helium, ie the metallicity in the jargon and astrophysicists are quite similar to the Sun.
However, the spectrum also shows many absorption lines - almost half of them - not yet resemble anything known. According to Prochaska, it may be that they do not match any radiative process Atomic and Molecular observed in the laboratory or in a galaxy so far, making it the most fascinating spectrum he has seen in his life. These astronomers are currently seeking to obtain more accurate images of the galaxy where the gamma-ray burst has occurred and to log their comments on the region where stars are formed with the global properties of the galaxy.
Tags: gamma-ray bursts , long gamma-ray burst ,
