If the universe has a lesson for humanity, it is that everything comes to an end. This includes stars, which must also die, albeit on a time scale of billions of years. But new research shows that when some stars die, they don’t do so alone, potentially solving a long-standing mystery surrounding a special class of cosmic explosions called interacting supernovae.
When stars more massive than the Sun reach the end of their lives, their cores collapse, sending shockwaves through their outer layers that trigger explosions. supernova and leaving behind stellar remnants neutron stars Or black hole. Interacting supernovae differ because the shockwave generated by these explosions crashes into a cocoon of pre-existing material. The big mystery has always been: Where does this cocoon of gas and dust come from?
Humanity is somewhat biased when it comes to the stars; After all, Sun dominates our existence, and it is a lonely stellar body. But by contrast, most stars are not so antisocial, existing in binary partnerships held together by gravity. This new research shows that these stars don’t just stay together; They may even die together. Understanding this dual existence may be important in solving the origin of the dust envelope in supernova interactions.
“Our study shows that many stars do not die alone,” said team member Ke-Jung Chen of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA). said in a statement. “His ultimate appearance may be shaped by a long and intimate partnership with a fellow star.”
How some stars become drains
Before stars reach the end of their lives, they enter a relatively short-lived red giant phase. This allows them to expand to hundreds or thousands of times their original radius.
For a binary stellar pairing, this leads to a situation called “Roche Lobe overflow,“Which basically sees the swollen star dumping material onto its companion. However, not all of that material is captured by the companion star, which escapes to form a giant cocoon around the binary stars.
When the evolved and swollen star reaches the end of its life and “goes nova”, shockwaves surge forward and slam into this cocoon of matter at speeds of thousands of miles per second. The kinetic energy becomes light, creating a strange and intensely bright interaction supernova.
However, this leaves an obvious question. If stellar binaries are so common, and have become even more common for stars massive enough to go supernova, why aren’t supernova interactions becoming more common?
Turns out, just like comedy, the secret is…timing.
Chen and colleagues ran hundreds of computer simulations of mass transfer between binary stars and found that the key to generating interacting supernovae is that when it mass transfer Occurs late in the life of stars.
If mass transfer occurs very early, say millions of years before the last supernova explosion, the team found that material spreads far away from the binary stars, destroying the surrounding cocoon. For the onslaught of shockwaves to hang around the cocoon, mass transfer must occur a few thousand years before the final explosive death of one of the binary stars.
“We found that binary stars can set the stage for supernova interactions with remarkable timing,” said ASIAA team member Sung-Han Tsai. “The companion star helps form a dense cocoon around the dying star just before it explodes, providing the fuel that powers it.” cosmic fireworks“
The team’s research shows that there are many ways for stars to die, and these explosive fates are determined by the way they lived.
The team’s research was published June 30 The Astrophysical Journal Letters.
