A team of scientists from the Noirlab found that some gamma bursts (Gamma ray bursts – Grb) did not originate in the intergalactic space, as previously assumed. According to a study just published in Monthly Notices of the Royal Astronomical Society the Grbs come from galaxies that are remarkably distant – and therefore faint – far away 10 billion light years from us.
This finding suggests that gamma ray bursts, which form during collisions of neutron starsmay have been more common in the past than expected.
This research required the combined power of some of the largest telescopes on Earth and in space, including the Gemini North in Hawaii and the Gemini Southin Chile. The other observatories involved are the Nasa-Esa space telescope Hubblethe Lowell Discovery Telescope in Arizona, the Great Telescope in the Canary Islands, the Very Large Telescope of the ex and theKeck Observatory in Hawaii.
The researchers started the work by examining the data concerning 120 gamma ray burst captured by two instruments aboard the observatory Swift of NASA. Further studies on the afterglow – carried out at the Lowell Observatory – have pinpointed the location of the Grbs more accurately. Afterglow studies have shown that 43 Grb they were not associated with any known galaxies and appeared in the relatively empty space between galaxies.
Astronomers have proposed two possible explanations for the phenomenon. According to the first, the progenitor neutron stars formed as a binary pair within a distant galaxy and subsequently moved together in intergalactic space, only to merge billions of years later. According to the other theory, however, neutron stars would have merged several billion light-years away in their home galaxies, and would now appear extremely faint due to their great distance from Earth.
“We considered that this second scenario was the most plausible – said Brendan O’Connor, first author of the study – we collected detailed images of the positions of the Grb and we discovered galaxies otherwise invisible 8-10 billion light years from Earth”.
To make these detections, the astronomers used a variety of optical and infrared instruments mounted on the Gemini telescopes. This result could help the scientific community to better understand thechemical evolution of the Universe. The merger of neutron stars triggers a cascading series of nuclear reactions necessary to produce heavy metals, such as gold, platinum and thorium. Shifting the cosmic time scale back to neutron star mergers means that the young Universe was much richer in heavy elements than had previously been hypothesized.
“This mapping dedicated to the galaxies that host the Grb – concludes Martin Still, head of the Gemini program at the National Science Foundation – has provided a convincing answer to the long-standing mystery of the nature of neutron star environments”.
Photo credit: NoirLab / Nsf / Aura / J. da Silva / Spaceengine
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