Free Astronomy Magazine November-December 2023

43 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING BOTs. While these rare explosions have been assumed to be a rare type of supernova, the gargantuan stars that turn into supernovae live short lives by stellar standards, meaning that no such star would have time to travel such a great dis- tance from its home galaxy before exploding. “The more we learn about LFBOTs, the more they surprise us,” says as- tronomer Ashley Chrimes, lead au- thor of the paper reporting the discovery. “We’ve now shown that LFBOTs can occur a long way from their nearest galaxy, and the loca- tion of the Finch is not what we ex- pect for a supernova.” Astronomers have been on the hunt for more of these enigmatic events since the Cow was discov- ered in 2018. Since astronomical transients can pop up anywhere and at any time, and are relatively fleeting in astronomical terms, re- searchers rely on wide-field surveys that can continuously monitor large areas of the sky to detect them. It was one such survey — the NSF- funded Zwicky Transient Facility — that first alerted astronomers to the Finch earlier this year. Once it was spotted, the researchers trig- gered a pre-planned program of observations that had been on standby, ready to quickly turn their attention to any potential LFBOT candidates that arose. This included observations with the Gemini Multi-Object Spectrograph (GMOS) instrument on the Gemini South telescope. GMOS measured the temperature of the Finch to be a scorching 20,000 degrees Celsius (approxi- mately 36,000 Fahrenheit) and helped determine its distance from Earth so its luminosity could be cal- culated. Together with other obser- vations, these findings confirmed the explosion was indeed an LFBOT. However, the mystery of the Finch’s origin, as well as how it ended up so far away from its host galaxy, re- mains. Besides the speculation that LFBOTs are a particularly rare class of su- pernova, scientists have several other ideas about how they could form. For example, they could be the result of stars being torn apart by black holes, but Chrimes notes that finding a black hole so far from a galaxy is also not expected. To explain the unusual location of the Finch, the researchers are con- sidering the possibility that it was the explosion of an extremely fast- moving star. Alternatively, it could be the culmination of a much longer process, such as a collision of two neutron stars that have been spiraling toward each other for bil- lions of years, though these are mere speculations. The Finch may have caused prob- lems for current theories of the na- ture of LFBOTs, but in science it is often the surprising results that re- veal the gaps in our knowledge and lead to advances in our under- standing of the Universe. “The dis- covery poses many more questions than it answers,” says Chrimes. “More work is needed to figure out which of the many possible expla- nations is the right one.” Answers to the curious nature of LF- BOTs are on the horizon with the upcoming Legacy Survey of Space and Time (LSST), conducted with Vera C. Rubin Observatory in Chile. As a survey telescope, the Rubin Ob- servatory will observe and take im- ages of the entire southern night sky every few nights, which means it will detect millions of objects that change brightness over time, includ- ing LFBOTs. As the sample size of these mysterious objects grows, so will astronomers’ understanding of them. What cosmic zoological crea- ture will be discovered next? Unlike any other LFBOTs seen be- fore, the Finch is an unusually long way from either of its two nearest galaxies — about 50,000 light-years from a nearby spiral galaxy and about 15,000 light-years from a smaller satellite galaxy. Not only does this discovery not align with past LFBOT locations within star- forming galaxies, but it raises prob- lems for some of the existing explanations of the origin of LF- ! A rtist’s impression of a Luminous Fast Blue Optical Transient that is unusually far from its host galaxy. [NOIRLab/NSF/ AURA/M. Garlick/ M. Zamani]