In a groundbreaking discovery, China’s Einstein Probe (EP) astronomical satellite has detected soft X-ray signals from an explosion in the early universe, marking the first time in human history such a feat has been achieved. The findings were published in the journal Nature Astronomy on Thursday.
On March 15, 2024, the Wide-field X-ray Telescope aboard the EP satellite observed a faint pulse signal from a burst event in the soft X-ray band. This burst, named EP240315a, showed rapid fluctuations in brightness and lasted over 17 minutes before slowly fading away.
Unlocking Secrets of the Early Universe
Telescopes from around the world later confirmed that this burst originated from the distant early universe. At the time of this explosion, the universe was only 10 percent of its current age, and the signal took 12.5 billion years to reach Earth.
“This is just the beginning,” said Yuan Weimin, principal investigator of the EP mission and a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences (CAS). “The discovery showcases the remarkable potential of the Einstein Probe in detecting cosmic explosions from the early universe.”
International Collaboration Enhances Findings
The identification of EP240315a led to an international collaboration between the EP team and Dr. Roberto Ricci from the University of Rome Tor Vergata in Italy. Dr. Ricci initiated long-term radio band monitoring of this gamma-ray burst (GRB). Utilizing the Australia Telescope Compact Array, his three-month radio observations confirmed that EP240315a’s energy output aligns with the characteristics of a GRB.
GRBs are among the most powerful explosive phenomena known in the universe, typically resulting from the explosion of massive stars. Further analysis revealed that EP240315a is associated with a GRB designated as GRB240315C.
“These results show that a substantial fraction of fast X-ray transients may be associated with GRBs,” said Dr. Ricci. “Sensitive X-ray monitors like the Einstein Probe can pinpoint them in the distant universe. By combining the power of X-ray and radio observations, we have a new way to explore these ancient explosions even without detecting their gamma rays.”
A Cosmic Mystery Unveiled
However, mysteries remain. Unusually, in the case of EP240315a, the X-rays arrived more than six minutes before the gamma rays, whereas typically X-rays appear just tens of seconds earlier.
“Such a long delay has never been observed before,” said Sun Hui, an associate researcher at the National Astronomical Observatories of CAS and one of the study’s co-first authors.
Gao He, a co-corresponding author from Beijing Normal University, noted that this discovery offers a fresh perspective and could lead to a re-evaluation of existing GRB models.
Exploring the Universe with Soft X-Rays
Scientists classify X-rays based on their energy levels: soft X-rays have lower energy, while hard X-rays have higher energy. The detection of soft X-ray signals from such an ancient explosion opens a new window for researching the early cosmos.
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China's astronomical satellite detected explosion from early universe
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