An extremely rare and strange burst of extremely bright light in the universe just got even stranger, thanks to the eagle eye of NASA/ESA’s Hubble Space Telescope. The event, called the fast light blue optical transit (LFBOT), erupted in a scene far from any large galaxy where it was not expected to be detected. Only Hubble was able to determine its location. Hubble’s results suggest that astronomers know less about these objects than previously thought, as it rules out some possible theories.

Fast-light blue optical transients (LFBOTs) are among the brightest known visible-light events in the universe, bursting unexpectedly like camera flashes. Only a few have been found since the first discovery in 2018. LFBOTS is now discovered about once a year.

Since its initial detection, the newest LFBOT has been observed with a variety of telescopes across the electromagnetic spectrum, from X-rays to radio waves. Only Hubble’s extremely sharp resolution was able to pinpoint its location. The transient, called AT2023fhn and nicknamed “Finch,” exhibited all the characteristic features of LFBOT. It glowed intensely in blue light and evolved rapidly, peaking in brightness and fading again within a few days, unlike supernovae that take weeks or months to fade.

But unlike other LFBOTs seen before, Hubble found that Finch lies in apparent isolation between two nearby galaxies (about 50,000 light-years away from a nearby spiral galaxy and about 15,000 light-years away from a smaller galaxy), an unexplained location for celestial bodies . . was previously thought to exist in host galaxies.

“The Hubble observations were really decisive. “They made us realize that this was unusual compared to similar ones, because we wouldn’t know anything without the Hubble data,” said Ashley Crimes, lead author of the Hubble paper reporting the discovery. He is also based at the European Space Center, formerly Radboud University, in Nijmegen, the Netherlands. He is a research assistant at the Agency.

The study will be published in the next issue Monthly Notices of the Royal Astronomical Societyand the article is now available on the preprint server arXiv.

Although these surprising explosions are considered a rare type of supernova (called core collapse supernova), giant stars that go supernova are short-lived by stellar standards. Therefore, large supernova precursor stars do not have time to move away from their birthplace (a cluster of newborn stars). All previous LFBOTs have been found in the spiral arms of galaxies where star formation is ongoing.

“The more we learn about LFBOTs, the more they surprise us,” Crimes said. “We have now shown that LFBOTs can occur at very great distances from the center of the nearest galaxy, and Finch’s location is not what we would expect for any type of supernova.”

The Zwicky Transient Facility, an extremely wide-angle, ground-based camera that scans the entire northern sky every two days, first alerted astronomers to Finch on April 10, 2023. Once detected, the researchers began a pre-planned monitoring program. Those who are waiting and ready to turn their attention to the rapidly emerging potential LFBOT candidates.

Spectroscopic measurements made with the Gemini South telescope in Chile revealed Finch’s temperature to be 20,000 degrees Celsius. The twins also helped determine its distance from Earth so that its brightness could be calculated. These findings, along with data from other observatories, including the Chandra X-ray Observatory and the Very Large Array radio telescope, confirmed that the burst was indeed LFBOT.

LFBOTs can be the result of a star being ripped apart by an intermediate-mass black hole (between 100 and 1000 solar masses). The high resolution and infrared sensitivity of the NASA/ESA/CSA James Webb Space Telescope could eventually be used to reveal that Finch exploded inside a globular star cluster in the outer halo of one of two nearby galaxies. The most likely place to find an intermediate-mass black hole is in a globular cluster.

To explain Finch’s unusual location, researchers are considering the alternative possibility that it is caused by the collision of two neutron stars that have been spiraling towards each other for billions of years, traveling far outside their host galaxy.

Such collisions give rise to a kilonova, an explosion 1000 times more powerful than an ordinary supernova. However, according to a highly speculative theory, if one of the neutron stars was highly magnetized (a magnetar), this could greatly increase the power of the explosion, even reaching up to 100 times the brightness of a typical supernova.

“This discovery raises many more questions than it answers,” Crimes said. “More work is needed to find out which of the many possible explanations is correct.”

Because astronomical transients can occur anywhere, anytime and are relatively transient in astronomical terms, researchers rely on wide-field surveys that can continuously monitor large areas of the sky to detect them and alert other observatories, such as Hubble, to further action. observation.

Researchers say a larger sample size is needed to better understand the phenomenon. Future all-sky telescopes may reveal more, depending on the underlying astrophysics. Source