What is a supernova, and why is it an important tool in gauging the universe’s behavior?
A supernova is the explosive death of a star, which unleashes a burst of light through the cosmos. These violent deaths occur once every 100 years in a typical spiral galaxy like our Milky Way. Some astronomers call some types of supernovas nature’s “60-watt light bulbs” because they burn at nearly the same brightness. By measuring their predictable light output, astronomers can estimate how far they are from Earth. Many of them are billions of years away. But supernovas blaze so brightly that they can be seen far across space. That’s why some astronomers also call them “cosmic mile markers”: their light provides important information about the universe’s behavior. Supernovas illuminate the dark corners of space, allowing astronomers to map the history of the universe’s expansion.
