Burst of gamma rays from 10 billion light years away offers glimpse into the early universe
A short gamma ray burst known to astronomers as SGRB181123B is the second most-distant well-established SGRB ever seen, and the most distant to ever known to display an optical afterglow. Examination of this object could reveal data about the behavior of the densest stars in the Universe at a time when our Universe was still in its adolescence.
Short gamma ray burst are incredibly short-lived events (sometimes lasting for a matter of hours before fading), occurring far from Earth. These characteristics combine to make these events notoriously difficult to detect and study.
The discovery of such an event nearly two years ago led to a hasty coalition of telescopes aimed at the enigmatic object.
“We certainly did not expect to discover a distant SGRB, as they are extremely rare and very faint. We perform ‘forensics’ with telescopes to understand its local environment, because what its home galaxy looks like can tell us a lot about the underlying physics of these systems,” said Dr. Wen-fai Fong, assistant professor in the Department of Physics and Astronomy at Northwestern University.
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It was two years ago on Thanksgiving…
On Thanksgiving night in 2018, astronomers found a feast of data from the Neil Gehrels Swift Observatory, revealing a previously-unseen SGRB. The team managing observations for the space-borne observatory contacted astronomers at one of the word’s greatest ground-based telescopes, Gemini North on Mauna Kea in Hawaii.
“It was unreal. I was in New York with my family and had finished having a big Thanksgiving dinner. Just as I had gone to sleep, the alert went off and woke me up. While somewhat of a nuisance, you literally never know when you’ll land a big discovery like this! I immediately triggered the Gemini observations and notified Kerry. Thankfully, she happened to be observing at Keck that night and was able to rearrange her original observing plan and repoint the telescope towards the SGRB,” Wen-fai recalls.
The international Gemini Observatory (a program of NSF’s NOIRLab), quickly confirmed the finding, utilizing their 8.1 meter telescope on Mauna Kea. Astronomers there also dated the event to the “teenage” years of the Universe, less than four billion years after the Big Bang.
“We took advantage of the unique rapid-response capabilities and exquisite sensitivity of Gemini North and its GMOS imager to obtain deep observations of the burst mere hours after its discovery. The Gemini images were very sharp, and allowed us to pinpoint the location to a specific galaxy,” said Kerry Paterson of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) at Northwestern University.
These observations were reinforced by data recorded at the W.M. Keck Observatory in Hawaii and Multi-Mirror Telescope (MMT) at Fred Lawrence Whipple Observatory on Mount Hopkins in Arizona.
This was a triumph for this international collaboration of astronomers, quickly networking several observatories, to observe this short-lived event.