Astronomers are at a crossroads with a cosmic explosion detected by the Einstein Probe spacecraft in April of last year. Designated EP240408A, this highly energetic event initially puzzled researchers, who thought it might be either a gamma-ray burst from a neutron star collision or the end of a massive star’s life.
However, the explosion did not align with typical expectations of these phenomena. EP240408A’s peculiar characteristics might hint at an entirely new cosmic process. This intriguing possibility led an international team of astronomers to conduct follow-up studies with an array of telescopes, both on the ground and in space.
The team utilized sophisticated data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and Neutron star Interior Composition Explorer (NICER). The high luminosity and rapid duration of EP240408A challenge conventional explanations, suggesting the involvement of a brand-new cosmic event.
“EP240408A matches aspects of different cosmic phenomena, but it doesn’t fully fit with any traditional model,” observed Brendan O’Connor, a researcher from Carnegie Mellon University. “The data points to something unprecedented!”
The Elusive Jetted TDE
Tidal disruption events (TDEs) occur when a star ventures too close to a supermassive black hole at the center of a galaxy. The immense gravity of these black holes, equivalent to millions or billions of suns, warps the star through a process known as spaghettification. The stellar material, now in a plasma state, creates an accretion disk around the black hole, feeding it over time.
(Image credit: Robert Lea (created with Canva))
Researchers propose that jetted TDEs, which account for only about 1% of TDEs, occur when the rotation axis of the black hole is misaligned with the orbital plane of the star. Over weeks or years, the magnetic forces of the black hole align the material, causing jets to form and directing them away from the star-destroying event, setting jetted TDEs apart from other events.
Previous Research: A Closer Look
Earlier studies, published in The Astrophysical Journal Letters in October 2023, explored the unique aspects of jetted TDEs. The misalignment theory caught the attention of the EP240408A research team, providing insights into the still-unknown mechanics of these rare explosions.
Understanding the magnetic properties and the eventual alignment of stellar material offers potential breakthroughs in classifying TDEs. This process is believed to take weeks to years, during which vigorous jets are produced, differentiating jetted TDEs from ordinary star-consuming events.
Gamma-Ray Bursts: A Familiar Mystery
Gamma-ray bursts (GRBs) have captivated astronomers since their discovery in 1967. These bursts are powerful cosmic explosions, producing stunning amounts of energy—up to a quintillion times greater than the sun’s radiation output.
(Image credit: Robert Lea (created by Canva))
GRBs can emerge from various cosmic phenomena, such as the colliding and merging of neutron stars or the death of a massive star resulting in the birth of a stellar-mass black hole. However, the characteristics of EP240408A indicated it to be something distinct, perhaps hinting at a jetted TDE.
NICER’s Critical Role
The success of pinpointing EP240408A’s nature hinges significantly on the capabilities of the Neutron star Interior Composition Explorer (NICER). NICER’s agility, allowing it to monitor virtually any part of the sky for extended durations, proved invaluable in the analysis of this unusual cosmic event.
“NICER’s ability to steer and observe for weeks has been key to our findings,” said Dheeraj Pasham, a researcher from the Massachusetts Institute of Technology (MIT). “Its precision is crucial in deciphering these mysterious explosions.”
The Future of Cosmic Exploration
The ongoing research showcases the potential for new discoveries in cosmic phenomena. EP240408A might indeed represent the first confirmed jetted TDE, opening a new frontier in astronomy.
“We’re thrilled about the prospect of uncovering more unusual cosmic explosions,” Pasham added. “The excitement in astronomy comes with the unknown, and we’re not deterred by it.”
The findings from this EP240408A study were published on January 27 in The Astrophysical Journal Letters, appending significant evidence to our understanding of the universe.
Your Turn: Participate in the Discussion
What do you think caused the cosmic explosion EP240408A? Is it likely a jetted TDE, or could there be another explanation? Share your thoughts in the comments below or on social media. Join us in following this remarkable journey of discovery as astronomers continue to unravel the mysteries of the cosmos.