Scientists Reveal the Origin of Cassiopeia A: What Should You Know

new research

It is known that massive stars end their existence with energetics blasts, called supernovae. The so-called stripped-envelope supernovae manifest low or no traces of hydrogen in their ejecta. Such a thing means that the star loses most or all of its hydrogen-rich outer layers before popping. 

Scientists hypothesize that those stars are part of some binary star systems, where one of the stars eliminates the outer layers of the other star with its gravitational pull. Some studies claim that the companion star was successfully spotted, but there are many cases where the companion couldn’t be detected. 

One of the most popular cases is Cassiopeia A’s (Cas A), a stripped-envelope supernova remnant. According to scientists, this supernova should have a stellar companion, but nothing has been discovered in its explosive aftermath. 

Recent research, however, promises to shed some light on that case. Here is what you need to know. 

New Research Emerges

The research, led by the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav), proposes a new scenario for these isolated stripped-envelope stars. 

Dr. Ryosuke Hirai, an OzGrav researcher and lead author of the research, released a statement discussing stripped-envelope stars’ features. He said: “[…] they have similar lifetimes, meaning that the explosion of the first star will occur when the second star is close to death, too.”

Massive Stars So Far

In the last million years of their existence, massive stars are known to turn into some red supergiants with puffed-up and unstable outer layers. 

If the first supernova of the binary star system kicks the red puffy red supergiant, it can quickly tear off the outer layers, making it a stripped-envelope star. The stars then disrupt after the supernova, so the secondary star turns into a lonely stellar widow and will be single by the time it bursts 1 million years later. 

Scientists’ Discoveries

The OzGrav scientists realized hydrodynamical simulations of a supernova crashing with a red supergiant to examine how much mass can be ripped off through the whole process. They discovered that if the two stars get closer, the supernova can rip approximately 90 % of the envelope off the companion star. 

If such a scenario ever happens, the stripped-off envelope should be drifting as a one-sided shell at around 30 to 300 light-years away from the second supernova. New observations unveiled indeed that there is a bit of material at almost 30- to 50 light-years away from Cassiopeia A. 

The OzGrav team also predicts that this approach has a much wider range of possible outcomes. For instance, it can realize a similar number of partially stripped stars. 

In the future, it will great to find out what happens to those partially stripped stars and how they could be examined.

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