SN 2020tlf was a Type II supernova that occurred 120 million light years away in the galaxy NGC 5731. The supernova marked the first time that a red supergiant star had been observed before, during, and after the event,[2][1] being observed up to 130 days before.[2] The progenitor star was between 10 and 12 solar masses.
The star was first observed by the Pan-STARRS telescope in the summer of 2020, with other telescopes such as ATLAS also observing it. It was initially believed that red supergiants were quiet before their demise; however, SN 2020tlf was observed emitting bright, intense radiation and ejecting massive amounts of gaseous material.[3][4] Observations were also made throughout the electromagnetic spectrum, such as in the X-ray, ultraviolet, infrared and radio wave spectrums.[1]
