A star on the verge of becoming a supernova may be metaphorically cool but literally very hot.
Misleadingly, however, a star, which later turned into a supernova, appeared to be literally cool before it exploded, challenging what astronomers thought they knew about this powerful phenomenon. Supernovas only occasionally publish their backstory, as they often surprise us. Sometimes, however, photos taken by a galaxy that later host a supernova can find the star before it breathes before it dies.
One such case was for the Supernova 2019 EVR, which occurred in NGC 4666, a globally smaller event 35-55 million light-years away. As a particularly active star formation galaxy, NGC 4666 has been studied by both amateur and professional astronomers, offering Dr. Charles Kilpatrick of North-Western University with many opportunities to blame the star for 2019Yvr in the old picture. In the Royal Astronomical Society’s monthly notices (preprint rxib.org), Kilpatrick and co-authors reported that the star behind the explosion was as yellow as the sun.
Although hot enough to power life on a planet millions of kilometers away, the yellow stars are much cooler than the blue stars, which represent a lot of supernova presenters. Some yellow stars have turned into supernovas, but in each case there was previously a shroud of hydrogen that prevented us from seeing the interior which was believed to be very hot. In this case, they do not show any sign of such a veil. Kilpatrick said in a statement, “We haven’t seen this scene before.”
“If it explodes without any hydrogen, it should be very blue – really hot. Without hydrogen in the outer layers of stars, it is almost impossible for stars to cool. We’ve seen every single star model that can explain a star like that, and every single star model needs to have hydrogen which we know from its supernova that it isn’t. It expands what is physically possible.” The images of Kilpatrick used to arrive at this conclusion are from the explosion. H took Hubble years ago.
The 2019Yvr spectrum did not indicate that anything unusual had happened. “It seemed like a very normal hydrogen-free supernova,” Kilpatrick says. While studying Hubble images he was usually associated with sorts of explosions like blue stars The sort yellow giant only provided candidates, not found anywhere near the location. Five months after the explosion, however, the elements discarded by 2019Yvr collided with a massive collision of hydrogen. Kilpatrick’s working theory is that the star once had a hydrogen layer but dropped it decades before the explosion. Alternatively, a fellow star could take the hydrogen away.
