A surprising look at ingredients of galaxies
Washington: Astronomers have identified a pair of young galaxies with surprising chemical ingredients in the early Universe following a Gamma-ray burst - brightest explosions in space.
The NASA Fermi Gamma-ray Space Telescope first spotted the burst, called GRB 090323.
Very soon afterwards it was picked up by the X-ray detector on NASA’s Swift satellite and with the GROND system at the MPG/ESO 2.2-metre telescope in Chile (eso1049) and then studied in great detail using ESO’s Very Large Telescope (VLT) just one day after it exploded.
The VLT observations showed that the brilliant light from the gamma-ray burst had passed through its own host galaxy and another galaxy nearby.
These galaxies are being seen as they were about 12 billion years ago. Such distant galaxies are very rarely caught in the glare of a gamma-ray burst.
“When we studied the light from this gamma-ray burst we didn’t know what we might find. It was a surprise that the cool gas in these two galaxies in the early Universe proved to have such an unexpected chemical make-up,” said Sandra Savaglio (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the study.
“These galaxies have more heavy elements than have ever been seen in a galaxy so early in the evolution of the Universe. We didn’t expect the Universe to be so mature, so chemically evolved, so early on,” she stated.
By carefully analysing the telltale fingerprints from different chemical elements the team was able to work out the composition of the cool gas in these very distant galaxies, and in particular how rich they were in heavy elements.
It is expected that galaxies in the young Universe will be found to contain smaller amounts of heavier elements than galaxies at the present day, such as the Milky Way.
But the new observations, surprisingly, revealed that some galaxies were already very rich in heavy elements less than two billion years after the Big Bang.