Black holes are a fierce beast. Anything that strays too close – be it a gas cloud, asteroid or star – will be violently ripped apart and sucked into its yawning mass of nothingness, suspended in the void for eternity.
Fun.
Luckily for us, the supermassive black hole at the centre of our own galaxy, Sagittarius A* (Sgr A*), is both 26,000 light years away and largely dormant, having already swallowed up everything within its reach.
However, a team of international researchers have discovered that around 200 years ago Sgr A* briefly woke up – hungry – and for up to a year consumed all the gas and dust around it. But as the matter fell into the black hole’s grip and was torn apart, it emitted bursts of bright x-ray light.
This phenomenon led to the ring of light around Sgr A* shining a million times brighter than it is today. The light was reflected by nearby galactic molecular clouds, which caught the eye of astronomers.
‘To get an idea of the increase in intensity of the x-ray emission when the black hole emerged from its quiescent state, it is as if a single glow-worm hidden in a forest suddenly became as bright as the Sun,’ said co-author Dr Frederic Marin, of Strasbourg University in France.
‘These findings explain why galactic molecular clouds near Sgr A* are shining more brightly than usual. It is because they are reflecting the X-rays emitted by Sgr A* 200 years ago.’
The team combined data from space telescope IXPE (Imaging X-ray Polarimetry Explorer) and the Chandra X-ray Observatory to pinpoint the origin of the x-rays. The paper is published in the journal Nature.
‘It reveals the past awakening of this gigantic object – which is four million times more massive than the Sun,’ said Dr Marin.
Even more incredibly, the team has recorded the echo that bounced off those nearby clouds for everyone on Earth to listen to. The soundwaves have been converted into an audio spectrum 51 octaves below the true frequencies, enabling the human ear to hear them.
‘Our work presents the missing piece of evidence that x-rays from the giant molecular clouds are due to reflection of an intense, yet short-lived flare produced at or nearby Sagittarius A*,’ added Dr Marin.
Black holes are formed when a dying star collapses inward under the pressure of its own weight. This leads to a supernova, a star’s extremely powerful explosion.
Last year, astronomers unveiled the first image of Sagittarius A*, produced using a worldwide network of radio telescopes by the Event Horizon Telescope Collaboration.
MORE : Awe-inspiring image of supermassive black hole expelling a powerful jet unveiled
