I magine a cosmic explosion some 100 times the size of our Solar System and 2 trillion times brighter than the Sun. This enormous fireball blasted bright for more than a year. But astronomers only spotted it by chance. Since its discovery, researchers have been doing their utmost to work out what could have caused the flare-up, which has now been observable for more than three years. It’s certainly intriguing, not to mention very rare, potentially paving the way for even more of these huge mystery explosions being discovered.
The mystery began when the Zwicky Transient Facility in California detected an explosion in 2020 during routine nightly scans of the sky. The facility was looking for anything unusual by comparing the difference between new images and a set of reference images. The blast was picked up by the Asteroid Terrestrial-impact Last Alert System (ATLAS), but escaped being noticed by humans until the following year. “At that point it was given its official name: AT 2021lwx,” Dr Philip Wiseman, a research fellow at the University of Southampton, tells All About Space. “Once it was registered as a ‘real’ transient object, rather than an artefact in the images, it got picked up by algorithms that search the data for things like supernovae and tidal disruption events.” Despite efforts to analyse the spectrum of the explosion’s light to discover more about its chemical composition, velocity and geometry, it still took a few more months
