1006 AD: Supernova Lights Up Sky
More than a thousand years ago, humans witnessed the brightest, most violent event ever.
Dazzling New Star
What was daily life like in May 1006 AD? Well, it certainly wasn’t your average month!
On 1 May 1006 AD, people from Switzerland to China were startled to see a new, extremely bright star in the southern sky.
“The sky was shining because of its light,” wrote Egyptian astronomer Ali ibn Ridwan at the time. Monks at the Abbey of St Gall in Switzerland described the way “a new star of unusual size appeared; it was glittering in aspect and dazzling the eyes, causing alarm.”
This ‘guest star’, as the Chinese called it, was so bright that it could be seen during the day, and at night people may have read books by its light alone. But it didn’t last. Over the next three years, the star faded from view, leaving only eye-witness accounts and astrologers’ omens as testimony to its brilliance.
We now know that this guest star was a supernova – the violent explosion of a massive, dying star. And it was not just any supernova, but the brightest supernova in recorded history. More than a thousand years later, we still haven’t seen its equal.
Despite its brilliance, the remains of SN 1006, as it’s now called, were not found until 1965. Astronomers spied a circular ring in constellation Lupus, which turned out to be the expanding bubble of the SN 1006 explosion, full of different elements that used to be inside the star.
Today we can see SN 1006 in all its exploded glory, thanks to detailed images from radio, optical, and X-ray telescopes. This colourful image shows expanding debris clouds glowing in X-ray light (blue clouds), radio light (red clouds), and visible light (yellow stripe).
SN 1006 is about 7,200 light years away from us: close enough to make a brilliant sight back in 1006 AD, but far enough away that life on Earth wasn’t affected by its intense radiation. The explosion itself is now a whopping 65 light years across, or about 15 times bigger than the distance between us and our nearest star, Alpha Centauri.
By studying SN 1006 in different types of light, we can reverse engineer the explosion back to its original star. Or stars in this case.
The explosion of one big star leaves behind a dense core – either a neutron star or a black hole. But the remnant of SN 1006 has nothing in the centre. Instead SN 1006 is thought to be triggered by the collision of two dead stars, called white dwarfs.
White dwarfs are the leftover cores of dead stars that were similar to our Sun. If two white dwarfs collide, their combined mass can trigger a runaway nuclear reaction that will destroy both white dwarfs in a supernova explosion, leaving no trace behind.
The chance of two white dwarfs colliding is very rare, which makes SN 1006 all the more fascinating.
Will we see another supernova like SN 1006 in our lifetimes? Chances are pretty good. It’s estimated that an average of 1-3 stars explode in a supernova every century in our galaxy alone. But the last Milky Way supernova occurred more than a hundred years ago. So we’re definitely overdue for a new stellar explosion to light up our night sky.
About the author: Dr Tamela Maciel is the Space Communications Manager at the National Space Centre.