![]() Normally that emission decreases over time,” said Alessio Mei, a doctoral candidate at the Gran Sasso Science Institute in L’Aquila, Italy, who led a group that studied the data. “This is the first time we’ve seen such an excess of high-energy gamma rays in the afterglow of a merger event. (Visible light’s energy measures between about 2 and 3 electron volts, for comparison.) These gamma rays reached energies of up to 1 billion electron volts. Fermi detected high-energy gamma rays starting 1.5 hours post-burst and lasting more than 2 hours. The light following the burst, called the afterglow emission, also exhibited unusual features. Perhaps some distant long bursts could also produce kilonovae, but we haven’t been able to see them. The event was also relatively nearby, by gamma-ray burst standards, which may have allowed telescopes to catch the kilonova’s fainter light. Some have suggested the burst’s oddities could be explained by the merger of a neutron star with another massive object, like a black hole. ![]() Many research groups have delved into the observations collected by Swift, Fermi, the Hubble Space Telescope, and others. Their observations have provided the earliest look yet at the first stages of a kilonova.Ĭredit: NASA, ESA, Rastinejad et al. “The kilonova we observed is the proof that connects mergers to these long-duration events, forcing us to rethink how black holes are formed.”įermi and Swift detected the burst simultaneously, and Swift was able to rapidly identify its location in the constellation Boötes, enabling other facilities to quickly respond with follow-up observations. ![]() “Many years ago, Neil Gehrels, an astrophysicist and Swift’s namesake, suggested that neutron star mergers could produce some long bursts,” said Eleonora Troja, an astrophysicist at the University of Rome who led another team that studied the burst. This decay results in the production of heavy elements like gold and platinum. Heat generated by the radioactive decay of elements in the neutron-rich debris likely creates the kilonova’s visible and infrared light. Scientists hypothesize that jets of high-speed particles, launched by the merger, produce the initial gamma-ray flare before they collide with the wreckage. They also generate gravitational waves, or ripples in space-time – although none were detected from this event.Įventually the neutron stars collide and merge, creating a cloud of hot debris emitting light across multiple wavelengths. As the stars circle ever closer, they strip neutron-rich material from each other. Credit: NASA’s Goddard Space Flight CenterĪ classic short gamma-ray burst begins with two orbiting neutron stars, the crushed remnants of massive stars that exploded as supernovae. Download high-resolution video and images from NASA’s Scientific Visualization Studio. Watch to learn how an event called GRB 211211A rocked scientists’s understanding of gamma-ray bursts – the most powerful explosions in the cosmos. This discovery has deep implications for how the universe’s heavy elements came to be.” “The high-energy burst lasted about a minute, and our follow-up observations led to the identification of a kilonova. “This burst, named GRB 211211A, was paradigm-shifting as it is the first long-duration gamma-ray burst traced to a neutron star merger origin,” said Jillian Rastinejad, a graduate student at Northwestern University in Evanston, Illinois, who led one team that studied the burst. Scientists sometimes observe short bursts with a following flare of visible and infrared light called a kilonova. Short bursts emit gamma rays for less than two seconds and are caused by mergers of dense objects like neutron stars. Long bursts emit gamma rays for two seconds or more and originate from the formation of dense objects like black holes in the centers of massive collapsing stars. The event has rattled scientists’ understanding of gamma-ray bursts (GRBs), the most powerful events in the universe.įor the last few decades, astronomers have generally divided GRBs into two categories. 11, 2021, NASA’s Neil Gehrels Swift Observatory and Fermi Gamma-ray Space Telescope detected a blast of high-energy light from the outskirts of a galaxy around 1 billion light-years away.
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