"We are in awe and are very fortunate to be able to study it"
Figure 1 Observations of GRB221009A by the Gemini South Telescope in Chile
(Image source: Gemini Observatory/NOIRLab/NSF/AURA//B. O'Connor (UMD/GWU)
& J. Rastinejad & W. Fong (西北大学))
On October 9, 2022, a bright light swept over our planet and even temporarily "blinded" several satellite probes, all eyes focused on the super-intense gamma-ray burst that lit up the sky. Gamma rays are the most energetic type of explosion known in the universe other than the Big Bang, and their appearance is often a sign of the birth of a black hole.
In just a few hours, tens of thousands of telescopes around the world pointed to the source of the explosion and recorded this moment that will go down in history. Nicknamed "BOAT" (brightest of all time) and officially known as "GRB221009A", scientists hope to shed light on physics in a terrible black hole. Brandon O'Connor of Maryland and George Washington University said, "This is a once-in-a-century, or even once-in-a-millennium event, and we are amazed at its appearance and are glad we had the opportunity to study it." ”
In fact, gamma rays are not unusual, with a beam passing over the Earth almost every day, and appearing more frequently in the universe. The neutron star is created in the explosion of a massive stellar supernova, and the skeleton of the star gradually burns out of energy, and the gamma rays caused by the collapse shine for only a fraction of a second. Gamma rays, caused by black holes, can last for several minutes, and they are created from supernova explosions, devouring large amounts of material from the parent star and not being ejected in the form of huge jets.
The observed gamma-ray bursts were particularly prominent than before, producing photons that bombarded the detector for up to 10 minutes and carried much higher energy than usual observations. At 18 teraelectron volts, the GRB221009A has twice as much photon energy as the Large Hadron Collider, the most powerful particle generator on Earth. The aftermath of the explosion produced by the interaction of gamma rays with cosmic dust was also unusual, and although the gamma ray source was blocked by the thick bands of the Milky Way, it shone brighter than previously seen, and the explosion ionized the Earth's atmosphere, interfering with long-wave radio communications.
Figure 2 Gamma-ray burst of GRB221009A observed by the Gemini South Telescope in Chile
(Image source: Gemini Observatory/NOIRLab/NSF/AURA//B. O'Connor (UMD/GWU)
& J. Rastinejad & W. Fong (西北大学))
Brandon O'Connor said that on October 14, 2022, five days after the gamma ray was launched, we traced about 30% of the source of the gamma ray from the dusty Sagittarius Galaxy, also known as the Arrow Galaxy, with the help of the Gemini South Telescope in Chile. Another surprise was that the gamma-ray burst was closer to Earth than ever before.
Northwestern University student Jillian Rastinejad, who participated in the measurement, said the ray was produced by the collapse of massive stars, which are short-lived. They follow the history of star formation in the universe, so the more intense the star formation, the more these bursts, about half the age of the universe. However, this gamma-ray burst occurred later and closer to us.
Astronomers speculate that GRB221009A originated 2.4 billion light-years away from Earth, and that closer ray bursts have been observed before, but this time the high energy is outstanding. "It's because it's dazzling enough that we have plenty of time to dig into more detail," Brandon O'Connor noted, "and with at least 50 telescopes currently observing in full wavelength, we're able to make the most of science and technology."
In fact, the ray burst lasted only a few minutes, but the aftermath could last for weeks. Scientists are also looking for supernovae-induced explosions, which eject material more slowly. Brandon O'Connor said that our current understanding is that massive stars collapse inward to form black holes, and the remains of the stars are constantly sucked in, ejected from the black hole with the formation of jets, and orbit at nearly the speed of light, forming gamma-ray bursts. At the same time, a portion of the wreckage bounced outwards and moved at a slower speed, creating a supernova explosion.
Figure 3 Cosmic dust ring ignited by the strongest gamma-ray burst
(Image source: NASA/Swift/A. Beardmore (University of Leicester, UK))
The original gamma-ray burst interacts with surrounding matter to form aftermaths, which span the electromagnetic spectrum and are best observed in the X-ray and radio wave regions, and scientists are still working on observing the aftermath of the rays, which were first captured by NASA's gamma-ray tracking satellite Swift, forming colored rings around the source a few hours after the explosion, Rastinejad said.
Telescopes can now see the first signs of a supernova explosion in GRB221009A places, and Rastinejad noted that the explosion will be fully unfolding in front of us in the coming weeks, but we may not be able to see the entire supernova explosion die due to the limited location of the explosion source. It gradually moves behind the Sun, so it lasts until the end of November this year, and we will not be able to observe it again until February next year.
She noted that in 2023, NASA's James Webb and the Hubble Space Telescope will join the effort, contributing their superior optical and infrared detection capabilities, respectively. Exploring the energy produced by explosions is a landmark event, as is the chemistry involved, and we still don't know how some of the heavy elements in the universe are produced, and studying supernovae can help us solve the puzzle.
Figure 4 Newborn black holes form powerful jets of gamma-ray rays
(图片来源:NASA/ESA/M. Grain Knife)
In the 60s of the 20th century, gamma rays were discovered by accident by a military satellite used by the United States to spy on Soviet nuclear tests, and gamma rays remained a mystery for decades, until the 90s, when scientists first realized that gamma rays hidden in various corners of the universe could be related to the collapse of stars.
Much of the current understanding of gamma-ray rays is still based on theoretical calculations and simulations, and scientists believe that this gamma-ray burst will be a good correction to previous theories. Scientists will take advantage of this once-in-a-lifetime opportunity, and a large number of articles will be published in the coming months.
Although explosions of similar energy have been a boon for scientific research, scientists do not want such big explosions to occur near Earth, preferably not in our galaxy. Scientists believe that gamma rays coming to Earth from thousands of light-years away would destroy the ozone layer, triggering changes in the atmosphere and eventually creating an ice age. In fact, a similar gamma-ray burst caused one of the five major extinction events on Earth – the Ordovician mass extinction about 440 million years ago.
"Fortunately, the gamma-ray burst from this jet is very narrow, only a few degrees wide," says Brandon O'Connor, "and if it happens to happen in our galaxy and is pointing at us, it would be dangerous, but fortunately the probability of such a phenomenon is very low."
补充解释：① NOIRLab：National Optical-Infrared Astronomy Research Laboratory
National Laboratory for Optical Infrared Astronomy
② NSF：National Science Foundation 美国国家科学基金会
③ AURA：Association of Universities for Research in Astronomy
Joint Organization of University Astronomical Research
(4) Tether electron volts, also known as megaelectron volts, 10^12 ev
(5) LHC: Large Hadron Collider
⑥ Swift：Swift Gamma-ray Burst Explorer 雨燕γ射线暴探测器
BY: Tereza Pultarova
FY: gxm
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