NASA has just witnessed a new first, spotting the moment a supermassive black hole shoots a giant beam of X-ray light out of its core, lending further clues to how coronas are shaped.
Coronas are sources of extremely energetic particles that produce some of the light in black holes, though their shape and position within one of space’s biggest mysteries has been up for debate by astronomers for years.
Now, though, thanks to some opportune collaboration between NASA’s Explorer mission Swift and the Nuclear Spectroscopic Telescope Array, or NuSTAR, we may know a fair bit more.
Black holes are a giant question mark for astronomers, but one that we’re learning more and more about. Consisting of immensely powerful gravity, nothing can escape them.
They fire out flares from their core, the epicentre of their power, though the light they emit is borrowed from other things, with black holes entirely, well, black.
Laying down a marker
One such black hole called Markarian 335 was monitored a decade ago by Swift and scientists noticed that its power was fading, markedly.
Situated around the centre of our galaxy, Markarian 335 used to be the brightest X-ray source in the sky. It still rifles out flares, but they are of lesser brightness than at its peak, with nobody knowing why.
A year ago Swift finally caught Markarian 335 shooting out a huge flare, so the team behind it put out a call to NuSTAR to drop everything and take a look.
NuSTAR set its X-ray eyes on the target and witnessed the final half of the flare event and, after careful scrutiny of the data, the astronomers realised they were seeing the ejection, and eventual collapse, of the black hole’s corona.
This three-staged graphic shows how a shifting corona can create a flare of X-rays around a black hole. The corona gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right), via NASA/JPL-Caltech
Shedding some light on the subject
They essentially learned that the flares could well be black holes firing X-rays out as coronas shoot away from the centre.
Supermassive black holes don’t give off any light themselves, but they are often encircled by disks of hot, glowing material.
The gravity of a black hole pulls swirling gas into it, heating this material and causing it to shine with different types of light, which astronomers look out for.
They also look for the light of the corona and, having noticed that one moved in the Markarian 335’s emission, NASA now thinks it knows what’s going on.
The corona gathered inward at first and then launched upwards like a jet. Putting this all together, the results show that the X-ray flare from this black hole was caused by the ejected corona.
A first for NASA
“This is the first time we have been able to link the launching of the corona to a flare,” said Dan Wilkins of Saint Mary’s University in Halifax, Canada, lead author of a new paper on the results appearing in the Monthly Notices of the Royal Astronomical Society.
“This will help us understand how supermassive black holes power some of the brightest objects in the universe.”
NASA’s researchers now think that coronas are “lampposts”, compact sources of light, similar to light bulbs, that sit above and below the black hole, along its rotation axis.
Many other black hole brainteasers remain, though. For example, astronomers want to understand what causes the ejection of the corona in the first place.
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