Luminous Fast Blue Optical Transient: Light that has perplexed even astronomers

The astronomical power of NASA’s Hubble Space Telescope has made a very uncommon burst of bright light in the cosmos even stranger.  The phenomenon, known as a Luminous Fast Blue Optical Transient (LFBOT), suddenly appeared in a location where it wasn’t anticipated, distant from any host galaxy. Astronomers are even more perplexed by the outcomes. They were unaware of LFBOTs, and by disproving certain potential explanations, the Hubble data imply they know even less.

LFBOTs go off abruptly and are among the brightest known visible-light phenomena in the cosmos. Only a few have been discovered since the first detection in 2018 – an event roughly 200 million light-years away known as “the Cow”. LFBOTs are now discovered roughly once a year.

The newest LFBOT was spotted by several telescopes spanning the electromagnetic spectrum, from X-rays to radio wavelengths. The transitory occurrence, designated AT2023fhn and dubbed “the Finch,” exhibited all of the hallmarks of an LFBOT. It shone brightly in blue light and developed quickly, reaching peak brightness and then fading in a couple of days, as opposed to supernovae, which take weeks or months to fade.

But unlike any other LFBOT seen before, Hubble found that the Finch is located between two neighbouring galaxies – about 50,000 light-years from a nearby spiral galaxy and about 15,000 light-years from a smaller galaxy. “The Hubble observations were really the crucial thing. They made us realise that this was unusual compared to the other ones like that, because without the Hubble data we would not have known,” said Ashley Chrimes, lead author of the Hubble paper reporting the discovery in an upcoming issue of the Monthly Notices of the Royal Astronomical Society (MNRAS).

While these spectacular explosions have been considered to be a rare sort of supernova known as core-collapse supernovae, the massive stars that become supernovae are rather short-lived by stellar standards. As a result, the enormous progenitor stars do not have much time to travel from their birthplace — a cluster of young stars – before exploding. All prior LFBOTs were discovered in the spiral arms of galaxies where star formation occurs, but the Finch is not located in any galaxy.

“The more we learn about LFBOTs, the more they surprise us”, Chrimes added. “We’ve now shown that LFBOTs can occur a long way from the centre of the nearest galaxy, and the location of the Finch is not what we expect for any kind of supernova.”

Image credit: vijaifoon via iStock

Image description: Artistic impression of a luminous fast blue optical transient