Ask the Astronomer
Why do some stars supernova and other stars have a smaller explosion called a nova?
What distinguishes the giant cataclysmic explosion of a supernova from the smaller explosion that astronomers call a nova is the original mass of the star before the explosion. A G-class star like our own sun does not have enough mass to supernova. Blue and red giant stars do have enough mass to become a supernova. Examples of massive stars include Antares in the constellation Scorpius and Betelgeuse and Rigel in the constellation Orion.
For example, Antares in the constellation Scorpio is so large that if you superimposed this star on our own solar system, Antares would be larger than the orbit of Mars. Interestingly, these massive stars actually burn cooler than smaller stars like our own Sun. Scientists have conjectured that a massive supergiant star could have its native hydrogen harvested by an extraterrestrial civilization. The atmosphere of that large star would be cool enough on its leading outer edge to allow sophisticated equipment to harvest the raw hydrogen of which that giant star is made.
So in determining the size of the explosion of a dying star, scientists calculate the size and age of that star and then they can reasonably predict when the star will explode and how large that explosion will really be. This is why our name a galaxy program is so exciting. You never know when a participant in our name a galaxy program will have adopted a galaxy that contains a star that is going to supernova. Such an event would be front page astronomical news!
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