Science & Technology

Scientists observe consumption of a star by a supermassive black hole for the first time

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The consumption of stars by supermassive black holes which lie at the centre of most galaxies is believed to be a fairly common event in the Universe, but astronomers have been unable to observe such proceedings unfold. That was until recently. It was revealed today that scientists at  Astrophysical Institute of Andalusia in Granada, Spain have used two specialised telescopes to observe the violent event in its full glory.  

Although most galaxies are believed to harbour supermassive black holes, those observed thus far have been fairly dormant only absorbing small amounts of material accreted from neighbouring stars. Not devouring the stars themselves.

The researchers observed the formation and expansion of a jet of material moving at close to light-speed emitted by the unfortunate star as it is ripped apart by the black hole’s massive gravity. The emission is similar to that observed when material spirals from a star towards a black hole forming a glowing disc of ionised gas and dust around the black hole known as an accretion disc.

The forces that tear the star apart are known as tidal forces and are similar to those encountered in the moon-earth system but far more powerful and violent. Such extreme tidal forces are expected to ‘spaghettify’ objects falling into the black hole. That means to stretch vertically whilst compressing horizontally any such object, practically atomizing it before it can reach the event horizon, the point of no escape, of the black hole. Such events when they occur to stars or other massive bodies are known as ‘tidal disruption events or TDEs.

Although common, astronomers believe that TDEs have been obscured by interstellar material such as dust clouds which absorb the emitted radiation and re-emit it in the less-energetic radio and infrared frequencies of the electromagnetic spectrum.

The research team discovered this remarkable sight by observing two colliding galaxies 150 million light-years from Earth. One of the galaxies involved in the collision referred to as Arp 299 harboured a star with roughly twice the mass of the Sun. This unfortunate star encountered a black hole with a mass approximately 20 million times that of the sun and the results were a foregone conclusion.

The colliding galaxies, collectively known as Apr299 have provided remarkable evidence of TDEs

This encounter is believed to form a disc similar to that mentioned above which emits strongly in the X-ray and visible light portions of the electromagnetic spectrum. It is also the believed that the process would cause jets of material to be blasted from the poles of the disk at relativistic speeds.

Now, these jets have been observed, a major development for astrophysics. These violent events should give astronomers, cosmologists and astrophysicists a greater insight into the physics around black holes.  The search now continues for more similar objects using infrared and radio telescopes with the aim of revealing the hungry cosmic giants that surround us in the universe and their unfortunate meals.

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About

Robert is a member of the Association of British Science Writers, qualified in Physics, Mathematics and Contemporary science. As well as contributing articles on topics as diverse as quantum physics, cosmology, medical science and the environment at Scisco media, he also writes the Null Hypothesis blog which examines pseudoscience and poor science reporting in the news media.

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