Using telescopes from the European Southern Observatory (ESO) in Chile and other organizations around the world, astronomers including researchers from DTU Space at the Technical University of Denmark, have spotted a rare blast of light from a star being ripped apart by a supermassive black hole.
The phenomenon, known as ‘a tidal disruption event’, is the closest such flare recorded to date. It took place some 215 million light-years from Earth, and the event has now been studied in unprecedented detail with a wide suite of telescopes.
“Our prompt and extensive observations in ultraviolet, optical, X-ray and radio light, revealed, for the first time, a direct connection between the material flowing out from the star and the bright flare of light emitted as it is was ‘eaten’ by a black hole,” says PhD student Panos Charalampopoulos at DTU Space who is one of the co-authors of the study.
“This research helps us to get a better understanding of supermassive black holes and how matter behaves in the extreme gravity environments around them”.
The new research has now been published in the scientific journal Monthly Notices of the Royal Astronomical Society.
“The idea of a black hole ‘sucking in’ a nearby star sounds like science fiction. But this is exactly what happens in a tidal disruption event,” says Matt Nicholl, lecturer and Royal Astronomical Society research fellow at the University of Birmingham and the lead author of the new study.
The star went through the ‘spaghettification’ process
The tidal disruption events, where a star experiences what is called ‘spaghettification’ as it is being sucked in by a black hole, are very rare and not always easy to study.
The team of researchers pointed ESO’s Very Large Telescope (VLT) and ESO’s New Technology Telescope (NTT) at a new flash of light that occurred last year close to a supermassive black hole, to investigate in detail what happens when a star is devoured by such a monster.
Exciting times in astrophysics
Astronomers know what should happen in theory: When a star is getting too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole will shred the star into thin streams of material, the so-called ‘spaghettification’. As some of these thin strands of stellar material fall into the black hole during this ‘spaghettification’ process, a bright flare of energy is released, which astronomers can detect.
“These are very exciting times in our field. Just last week the Nobel prize in Physics was awarded for the proof that a supermassive black hole exists in the centre of our galaxy. This discovery was possible by observing the motion of the stars around a black hole that weighs 6 million Suns over many years,” says Giorgos Leloudas, astrophysicist and senior researcher at DTU Space and co-author of the new study.
“Now, thanks to this star that ‘committed suicide’ as we describe i our article it was possible for us to briefly get a glimpse of another supermassive black hole at the centre of another galaxy. This is the only way we could do that, as we would never be able to observe the motions of individual stars at such a far distance.”
Difficult to observe
Although powerful and bright, up to now astronomers have had trouble investigating this burst of light, which is often obscured by a curtain of dust and debris. Only now have astronomers been able to shed light on the origin of this curtain.
When a black hole devours a star, it can launch a powerful blast of material outwards that obstructs the view from the researchers. This happens because the energy, released as the black hole eats up stellar material, propels the star’s debris outwards.
The discovery was possible because the tidal disruption event the team studied, called AT2019qiz, was found just a short time after the star was ripped apart. This made it possible for the researchers to see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10.000 km/s.
They could ‘look beyond’ this curtain and pinpoint the origin of the obscuring material and then follow in real-time how it engulfed the black hole. This was done by pointing a suite of ground-based and space telescopes in the direction of the event to see how the light from it was produced.
Six months of observations
The team carried out observations of AT2019qiz, located in a spiral galaxy in the constellation of Eridanus, during six months. The scientists estimate that the star had roughly the same mass as our own Sun and that the black hole was over a million times more massive.
The observations of the event were taken with multiple facilities that included X-shooter and EFOSC2, powerful instruments on ESO’s VLT and ESO’s NTT, which are situated in Chile as well as instruments in space.
When ESO’s Extremely Large Telescope (ELT) come into service later in this decade it will enable researchers to detect increasingly fainter and faster evolving tidal disruption events, to solve further mysteries of black hole physics and give us new insight into this extreme phenomenon in space.