By: Madaline Meagher
When some stars die they explode in a huge supernova. But what separates a “super” nova from an “it’s alright I guess,” nova?
Supernovas the universe’s best fireworks; they explode with a flash brighter than entire galaxies and send shock waves shooting out in all directions. Sadly, our own sun won’t be able to light the giant space firework. Instead the sun, the miasma of incandescent plasma in the sky that has been burning for about 4.6 billion years, which means our sun is approaching a midlife crisis! In another 5 billion years the sun will run out of hydrogen fuel for fusion and then will go through some expansions and contractions. As a last stand to fight off gravity and collapse, the sun will eventually lose its outer layer, leaving behind a little glowing core called a White Dwarf to cool off in space. As star deaths go, the Sun’s will be a pretty peaceful one. Much bigger stars prefer to go out in a blaze of glory or what we call a supernova.
So what separates our sun’s fade to black from a grand finale? The Chandrasekhar limit, named after a Indian physicist, determines what mass a star has to have to go boom. Chandrasekhar discovered mass is the key to the galaxy’s greatest fireworks show, and he did it at the age of 19! Feeling old yet? More specifically, he calculated that if a white dwarf was 1.4 times our sun’s mass, it would not be able to fend off the force of gravity. The star would collapse, and would ignite a runaway chain of fusion reactions and BAM! Supernova!
There are two ways stars can reach the Chandrasekhar limit. A Type Ia supernova occurs by a white dwarf leaching off another nearby star; these two bodies are called a binary system. The white dwarf can pull matter from its partner star until reaches about 1.39 solar masses, only to end with a fiery explosion. A Type II supernova would need a star that would have to be at least 8 times our sun’s mass to have a core heavy enough to light that giant space firework. Unlike our Sun, stars that massive don’t stop at fusing carbon and helium into oxygen. Massive stars burn neon, oxygen, and silicon to keep the fusion going, but once iron is made, they’re done for because iron uses more energy to fuse than it puts out. Once the Chandrasekhar limit is reached we get supernova! The explosion of a supernova frees up elements like carbon,oxygen, and iron that would otherwise have been locked up in the star’s core. Once the explosion dissipates as a nebula, it leaves behind a ball of densely packed neutrons called a neutron star that’s only a few miles across. If the star was really massive, the neutrons will be crushed and form a black hole. Unfortunately, because stars have to be so huge to explode, supernovae and black holes don’t happen very often. In our galaxy, supernovas only occurring about twice a century.
One example of a star on supernova watch is Betelgeuse, burning off the shoulder of Orion. Betelgeuse is a red supergiant at least 430 light years away. When it does go, Betelgeuse’s supernova will be brighter than a full moon but it probably won’t explode for another 100,000 years. Unless you say it’s name three times.
The life of star is a constant battle against gravity. Throughout a star’s life, it’ll perform fusion within it’s core to combat gravity and maintain equilibrium. However a star can’t do this forever, eventually gravity will win and force the star to collapse in on itself. Some stars will meet rather peaceful deaths as white dwarfs, others will go out in a similar fashion the Death Star did as a supernova. Despite it being sad that a star just exploded in supernova, be happy that it’s death gives you life. The explosion creates nebulae which is a nursery for young stars which begins the cycle anew.