In the year 1054, something strange happened in the night sky. A new star seemed to appear out of nowhere.
The Chinese called it “the great guest star”.
The Swiss described it as “a star of unusual magnitude, shimmering brightly, in the extreme south, beyond all the constellations.”
What they didn’t realise, however, was that they hadn’t witnessed the birth of a star. They had witnessed the death of one.
The Crab Nebula
The Crab Nebula is one of my favorite historical objects because it was the first to be identified historically. Hundreds of years later, when we point our telescopes towards the same point in the sky that had been described by people from all over the world, this is what we see - a giant, expanding shell of gas, surrounding an incredibly dense neutron star:
When a massive star reaches the end of its life, it goes supernova (that is, it explodes, big time!). The result is unbelievably bright. For a short period of time, the dying star can become brighter than entire galaxies, which contain hundreds of billions of stars.
The Crab Nebula 6,523 light years away; that is, if you were to travel at the speed of light, it would take you 6,523 years to get there. Yet this object exploded so brightly that it was visible to millions of people on Earth in 1504.
What’s perhaps even stranger is that because the light took so long to reach Earth, the explosion itself occurred not in 1054 (when it was first observed), but 6,523 years earlier, in 5469 BCE!
At the core of the Crab Nebula is what astronomers call the Crab Pulsar - a rapidly rotating star made almost entirely of neutrons. You can see it at the centre of the purple (representing X-Rays) cloud here:
This object is so dense that a teaspoon of it would weigh around a 5 million elephants. Oh, and it rotates 33 times in a single second.
Will you and I ever get to see one?
We just might. Astronomers have calculated that the chance of us being able to see a supernova from earth with the naked eye this century are about 20%. Fingers crossed!
Let me know what your favourite astronomical object is in the comments.
Thanks for reading!