What do a cow, a koala, a camel, a Tasmanian devil and now a finch all have in common? It’s not the plot of a new movie in the “Madagascar” series. They are nicknames given to a weird class of space explosions scientists can’t explain. “We’ve been naming these things after animals just for fun,” said Daniel Perley, of Liverpool John Moores University in England. The latest, the Finch, was first spotted April 10 using the Palomar Observatory in California.

So, what are these things? They are more technically called luminous fast blue optical transients, or LFBOTs. These space explosions are much brighter than supernovas (which occur when stars explode), hence the “luminous” designation. They brighten quickly – hence “fast” – and are extremely hot, reaching 70,000 degrees Fahrenheit, and thus emitting “blue” light. “Typically supernovae brighten and fade over weeks to months,” said Deanne Coppejans, an astronomer at Warwick University in England. “These LFBOTs brighten in just three to four days and fade on much faster time scales.”
The first to be found, in 2018, was the Cow (AT2018cow). Among the half dozen since discovered are ZTF18abvkwla (the Koala) and AT2022tsd (the Tasmanian devil). AT2023fhn (the Finch) is the latest, given its name in a paper led by Ashley Chrimes, an astrophysicist from the Netherlands – although Perley and colleagues had been referring to it as “the Fawn” and may continue to do so. “We’re a little bit annoyed that they decided it was up to them to name the object,” he said.

Chrimes’ paper highlights the most unusual feature of the Finch, namely that it was found outside any galaxy, seemingly exploding in intergalactic space near two potential host galaxies about 3 billion light-years from our own. “At that distance you don’t expect to have many, or any, stars, Chrimes said. That could help astronomers clarify what an LFBOT is. At the moment, there are a few leading ideas. The most promising one is that it is a giant star, about 20 times the mass of our sun, that has undergone a failed supernova. Another possibility is that LFBOTs are tidal disruption events, where a black hole is eating material from a companion star, shining brightly in the process. LFBOTs could also be caused by the merger of two neutron stars, the remnant cores of dead massive stars. Anna Ho, an astronomer at Cornell University, isn’t ready to jump to any conclusions. Finding more LFBOTs could give hints to their origin. “There aren’t that many of them yet. So we haven’t run out of animals.”