What is a supernova?
Andy Briggs in ASTRONOMY ESSENTIALS | November 12, 2020
A supernova is a star’s colossal explosion at the end of its life, potentially outshining its entire galaxy. Read about the causes and types of supernovae here.
A supernova is the name given to the cataclysmic explosion of a massive star at the end of its life. It can emit more energy in a few seconds than our sun will radiate in its lifetime of billions of years.Andy Briggs in ASTRONOMY ESSENTIALS | November 12, 2020
A supernova is a star’s colossal explosion at the end of its life, potentially outshining its entire galaxy. Read about the causes and types of supernovae here.
The sky above us is strewn with alluringly beautiful remnants of ancient supernovae, that is, stars that lived out their lives and then died in these violent explosions. In a galaxy like our Milky Way, consisting of some 200 billion stars, there should be a supernova as often as every 50 years. Yet supernovae visible to the eye alone are exceedingly rare. You might – or might not – witness one in your lifetime.
What we do see are supernova remnants, expanding clouds in space where stars used to be. There are many examples, both inside and outside our galaxy. The most famous supernova remnant visible from the Northern Hemisphere is called the Crab Nebula. It’s located in the direction of the constellation Taurus the Bull. The Chinese recorded witnessing the supernova in the year 1054 CE (although it had occurred 6,523 years earlier, because this star was that many light-years away). They called it a guest star and wrote that it was visible in daylight for a full three weeks, finally fading entirely from view about three months later.
The Crab Nebula | Image via Hubblesite
Later, the Crab Nebula became famous for hosting the first known pulsar, discovered in 1967 by Jocelyn Bell Burnell, when she was a graduate student at Cambridge University in England. The Crab pulsar, as it is known, is a neutron star, the remnant of the supernova that created the Crab Nebula. Like cosmic lighthouses, pulsars give off beams of radio waves as they spin. The beams from the Crab pulsar happen to be aimed our way.