On March 15, 2024, a space-based observatory detected bursts of low-energy x-rays from deep in the ancient universe, varying in brightness for more than 17 minutes before disappearing. About an hour later, ground-based telescopes picked up visible light from the same source, tracing it back to when the universe was only around a billion years old.
The Einstein's newly launched investigation has detected a distant explosion that has the potential to increase what we know about the universe's earliest years. Using the wide-field X-ray telescope, the spacecraft detected so-called soft, or low-energy, X-rays, which lasted an unusually long time. These events are known as fast x-ray transients (FXRT), and the newly spotted burst is designated EP240315A.
After monitoring the burst at radio wavelengths over a period of three months, the team of astronomers behind the discovery confirmed that the energy output was consistent with a gamma-ray burst dating back to when the universe was Only 10 percent of the current age. So given an estimated age of the universe of 13.8 billion years, the explosion occurred when the universe was approximately 1.38 billion years old.
“These results show that a large part of FXRTs can be related to [gamma-ray bursts] And sensitive x-ray monitors, such as the Einstein probe can detect them in the distant universe, “Roberto Ricci, a researcher at the University of Rome tor Vergata, Italy, and one of the authors behind the new Paper The discovery was detailed, told a statement. “Combining the power of X-rays and radio observations gives us a new way to explore ancient explosions even when their gamma rays have not been detected.”
EP240315A marks the first time that soft x-rays have been detected from an ancient eruption that lasted for a long duration. Follow-up observations using the Gemini-North telescope in Hawaii and the Very Large Telescope in Chile that measured visible light from the same location confirmed that the burst originated around 12.5 billion light-years away.
Gamma-ray bursts are brief flashes of high-energy light and are the most powerful explosions in the universe, usually triggered by the collapse of a massive star or the merger of neutron stars. Those explosions are also known to emit significant amounts of x-rays. The recently discovered soft X-rays have been traced back to GRB 240315C, a gamma-ray burst first detected by the Burst Alert Telescope (BAT) on NASA's Neil Gehrels Swift Observatory, with additional data provided by the Konus Instrument aboard the NASA's Wind Spacecraft.
Although gamma-ray bursts are associated with X-rays, the newly discovered fast x-ray transient is an anomaly. X-rays usually precede gamma rays by a few tens of seconds, but EP240315A was detected more than six minutes (372 seconds) before GRB 240315C. “Such a long delay has never been observed before,” Hui Sun, a team member from the Einstein Probe Science Center at the National Astronomical Observatories, Chinese Academy of Sciences, and co-author of the new study, said in a statement.
The mystery behind the long duration of time between x-rays and gamma-ray bursts, in addition to the long duration of the X-rays themselves, has led to the question of whether gamma-ray bursts explode the way the belief of scientists.
The Einstein Probe, an X-ray telescope operated by the Chinese Academy of Sciences, and built in collaboration with the European Space Agency and the Max Planck Institute for Extraterrestrial Physics, launched on January 9, 2024. The wide-field X-ray that Telescope takes in X-ray light in square tubes in a grid, which means it can observe 3,600 square degrees (just under one-tenth of the celestial sphere) in a single shot.
“As soon as we opened the eyes of the Einstein probe to the sky, it found interesting new phenomena,” Erik Kuulkers, ESA's Einstein project scientist, said in a statement. “That's great and should mean many more interesting discoveries to come.”
