Earlier this week scientists announced that the nearest supermassive black hole to Earth erupted in an ‘cataclysmic’ explosion so dramatic it sent a huge gust of radiation ‘slicing’ through the Milky Way.
Now an astronomer who led the research has warned that a similar ‘ancient explosion’ may have sent a death beam hurtling towards Earth.
The gigantic monster at the Milky Way’s heart is called Sagittarius A* and is 25,640 light-years away from humanity’s home planet.
It has appeared to be dormant throughout the history of our species but is capable of roaring dramatically to life.
We now know it emitted blasts of radiation so powerful they scorched through the Milky Way and smashed into the Magellanic Cloud – which lies 200,000 light-years away from the monster’s lair in our galaxy’s centre. You can see what this might have looked like in the video below.
Joss Bland-Hawthorn, director of the Sydney Institute for Astronomy, University of Sydney, was part of the team which this week revealed that the ‘supermassive black hole at the heart of our galaxy spat out an enormous flare of radiation 3.5 million years ago that would have been clearly visible from Earth’.
‘The discovery changes our view of our galaxy’s central black hole, which has appeared dormant throughout recorded human history,’ he went on to write in an article for The Conversation.
‘Astronomers are coming to realise that it has been hugely active, even explosive, in the relatively recent past in galactic terms (measured in millions of years).
‘This activity has been flickering on and off for billions of years. We don’t understand why this activity is intermittent, but it has something to do with how material gets dumped onto the black hole. It might be like water droplets on a hot plate that sputter and explode chaotically, depending on their size.
‘Our situation on Earth resembles living near a largely dormant volcano like Mount Vesuvius that is known to have been explosively active in the past, with disastrous consequences for Pompeii.’
This astonishing cosmic fireworks display would have been visible from Earth.
‘Some three million years ago, our direct ancestor Australopithecus afarensis walked the Earth,’ Bland-Hawthorn continued.
‘They may well have looked up towards Sagittarius and seen cones of light shooting sideways from the Milky Way, brighter than any star in the night sky.
‘The lightshow would have appeared as static beams on a human timescale, only flickering on timescales of thousands of years. Today, the only visible remnant of that immensely powerful event is the cooling gas along the distant Magellanic Stream.’
He went on to say that it’s possible a similar spurt of radiation is coming our way.
‘If the beam was pointing at the Solar System, the jet would have to plough through the Milky Way disc, and it would take about ten million years to reach us,’ he added.
‘So it’s possible that a more ancient explosion could have produced a powerful jet that is yet to reach us.’
Black holes are sometimes surrounded by an ‘accretion disc’ made up of superhot gas and other material.
It’s this disc which sends ‘jets, winds and radiating beams of light’ through the galaxy as it interacts with the black hole.
If a human was hit by a black hole beam, they would almost certainly die.
But we’re happy to report that even if Sagittarius A* has sent a dangerous ray towards Earth, humanity would more or less definitely survive the blast.
The astronomer wrote: ‘We need not worry – at its peak, the intensity of the jet when it reaches us is unlikely to exceed the most energetic solar flares.
‘These are known to knock out satellites, and pose a threat to space-walking astronauts, but our own atmosphere largely protects us on Earth.’
He added: ‘There’s no need to be alarmed: as far as we can tell, we are safe here in orbit about a cool dwarf star far from the centre of the Milky Way.’