Title: Unveiling the Universe's Mystery: A Blast of X-Rays Detected by Einstein Probe
On March 15, 2024, a space-based observatory identified an intriguing occurrence: bursts of low-energy X-rays hailing from the ancient cosmos, persisting for an uncommon 17-minute span before gradually intensifying. Redirecting our gaze toward Earth, ground-based telescopes captured visible light from the same origin a mere hour later. This celestial phenomenon, residing in the primordial universe, was just over one billion years old.
The Einstein Probe, fresh off the launch pad, is already shining a light on ancient explosions capable of redefining our comprehension of the universe's primeval epochs. Its wide-field X-ray telescope identified so-called soft, or low-energy, X-rays from the spacecraft's namesake discovery, EP240315a.
Spanning over a trio of months, subsequent radio wave monitoring corroborated the transient's energy output, aligning with an estimated gamma-ray burst from when the universe was simply 10% of its current age. This temporal occurrence equated to an approximately 1.38-billion-year-old universe.
"These findings imply that a substantial portion of fast X-ray transients may be associated with gamma-ray bursts. Sensitive X-ray monitors such as Einstein Probe can accurately pinpoint them within the distant cosmos," noted Roberto Ricci, a researcher at the University of Rome Tor Vergata, italy, and one of EP240315a's authors. "Fusing the power of X-ray and radio observations grants us a novel avenue to explore these ancient explosions, even without detecting their gamma rays."
The EP240315a anomaly marks the first instance of detecting soft X-rays from a historical explosion enduring such an extended duration. Feedback from the Gemini-North telescope in Hawaii and the Very Large Telescope in Chile confirmed that the visible light trace back to around 12.5 billion light-years away, making it the farthest-reaching assigned explosion thus far.
Gamma-ray bursts represent the universe's most powerful explosions, typically triggered by the demise of colossal stars or the fusion of neutron stars. Moreover, these bursts are renowned for emitting noticeable bolts of X-rays. The newly discovered soft X-rays were linked to GRB 240315C, a gamma-ray burst initially detected by the Burst Alert Telescope (BAT) on NASA's Neil Gehrels Swift Observatory, drawing upon additional data from the Konus instrument aboard NASA's Wind spacecraft.
Although gamma-ray bursts are inextricably linked to X-rays, the EP240315a discovery is noteworthy in its irregularities. The X-rays usually appear prior to the gamma rays by a mere few seconds, yet EP240315a was found more than six minutes (at approximately 372 seconds) before GRB 240315C. "This lengthy delay has never been observed before in gamma-ray bursts," Hui Sun, a researcher from the Einstein Probe Science Center at the National Astronomical Observatories, Chinese Academy of Sciences, and co-author of the paper detailing the EP240315a revelation, declared.
The underlying enigma surrounding the extended time between the X-rays and gamma-ray burst, coupled with the protracted life span of the X-rays themselves, merit ongoing investigation. These puzzle pieces raise serious questions about whether gamma-ray bursts unfold as scientists presumed.
The Einstein Probe, an X-ray telescope overseen by the Chinese Academy of Sciences, was jointly developed with contributions from the European Space Agency and the Max Planck Institute for Extraterrestrial Physics, entering the cosmic arena on January 9, 2024. Its Wide-field X-ray Telescope captures X-ray light within rectangular tubes structured in a grid, enabling observation of nearly 10% of the celestial sphere in a single sweep.
"As soon as Einstein Probe stared at the cosmos, it discovered intriguing phenomena," Erik Kuulkers, the Einstein Probe project scientist for the European Space Agency, expressed. "This is a promising indication of many more exciting discoveries yet to come."
The discovery of soft X-rays from EP240315a has opened up new possibilities in the field of astronomy, as scientists can now explore historical explosions using a combination of X-ray and radio observations, even without detecting their gamma rays. This technology-driven approach could significantly advance our understanding of the universe's earliest epochs and challenge existing theories about gamma-ray bursts.
As we delve deeper into the mysteries of space, the future of astronomy could be shaped by advances in technology and collaboration between international science communities, leading to groundbreaking discoveries that push the boundaries of our current knowledge. This includes the development of powerful space-based observatories like the Einstein Probe, which rely on cutting-edge science to unravel the secrets of the universe, from its distant past to its enigmatic present.
