SN2019ein is a Type 1a supernova. It happened when matter from one star fell onto another--a nearby white dwarf, pushing the mass of the dwarf over the threshold for a supernova explosion. This special kind of supernova is a "standard candle", which cosmologists have used to show that the expansion of the universe is accelerating. Monitoring the light curves of Type 1a supernova literally helps us understand the fate of the cosmos.
"To me, as a dedicated observer of the night sky for over 50 years and an avid underwater photographer, satellite megaconstellations such as Starlink are the equivalent of polluting our oceans with plastics", notes Williams. "I hope we take every measure possible to mitigate the effects of satellite light pollution of our night skies."
The International Astronomical Union seems to agree. Read their statement here.