Ancient Cosmic Blast Puzzles Scientists: Soft X-rays Fluctuate for Over 17 Minutes
In an extraordinary cosmic event, a space-based observatory has detected unusual bursts of low-energy X-rays from deep in the ancient universe. The phenomenon lasted for an astonishing 17 minutes, casting a spotlight on our understanding of the earliest years of the cosmos.
The freshly launched Einstein Probe, equipped with its wide-field X-ray telescope, made the intriguing find. This spacecraft is already making waves by spotting distant explosions that could rewrite our knowledge of the universe’s formative years. The event, designated EP240315a, was classified as a fast X-ray transient (FXRT), but it didn’t behave like any FXRT we’ve seen before.
After meticulous monitoring at radio wavelengths for three months, astronomers confirmed that the energy output was akin to a gamma-ray burst dating back to when the universe was a mere 10 percent of its current age. That makes it approximately 1.38 billion years old, when our universe was in its infancy.
"The results show that a substantial fraction of FXRTs might be associated with gamma-ray bursts," stated Roberto Ricci, a researcher at the University of Rome Tor Vergata. He is one of the authors behind the paper detailing the discovery. "Combining the power of X-ray and radio observations gives us a new way to explore these ancient explosions, even without detecting their gamma rays."
EP240315a is unprecedented, marking the first time soft X-rays were detected from an ancient explosion lasting so long. Follow-up observations using the Gemini-North telescope in Hawaii and the Very Large Telescope in Chile pinpointed the source to around 12.5 billion light-years away.
Gamma-ray bursts, the universe’s most powerful explosions, are typically brief flashes of high-energy light, triggered by the collapse of massive stars or the merger of neutron stars. But this particular FXRT was an anomaly. While X-rays usually precede gamma rays by a few tens of seconds, EP240315a was seen more than six minutes before the gamma-ray burst, a delay never observed before.
The mystery behind this long duration, both of the X-rays and the gap between them and the gamma-ray burst, is driving astronomers to question our current understanding of how these cosmic phenomena explode.
The Einstein Probe, launched on January 9, 2024, is managed by the Chinese Academy of Sciences in collaboration with the European Space Agency and the Max Planck Institute for Extraterrestrial Physics. Its Wide-field X-ray Telescope can observe a vast area of the sky at once, snapping up X-ray light in square tubes arranged in a grid.
"We’ve only just begun looking with Einstein Probe, and it’s already finding fascinating new phenomena," commented Erik Kuulkers, ESA’s Einstein Probe project scientist. "There’s a lot more to come, I’m sure."
As we continue to explore the cosmos, discoveries like EP240315a remind us that the universe is full of surprises, ready to challenge our understanding and fuel our curiosity.
