• Question: Is it true that black holes actually glow? If so, why?

    Asked by anon-106860 to Adrian, Gaia, Jim, Scott, Vicky on 10 Mar 2016.
    • Photo: Adrian Buzatu

      Adrian Buzatu answered on 10 Mar 2016:

      Are you referring to the Hawking radiation of a black hole? A pair of matter and antimatter particle appear out of vacuum for a brief period of time. Normally they would collide, disappear and release the energy borrowed from the vacuum back to the vacuum. If during this brief time one of these particles falls in a black hole, the other particle has no partner to annihilate to. It appears as if it is emitted by the black hole. That is called a black hole radiation. It was predicted by Stephen Hawking. Hence, Hawking radiation!

    • Photo: Scott Lawrie

      Scott Lawrie answered on 11 Mar 2016:

      Hawking radiation is predicted to exist around black holes but there aren’t any black holes close enough to see and prove it. If it’s true, then the particles of Hawking radiation could be trapped a boiling ring of fire around the black hole. So even if you could get close enough to the hole and not get ripped to shreds by the intense gravity, you still have to get through an impenetrable wall of fire!

      Much more easy to see from Earth are accretion disks. These are big disks of matter from things falling into the black hole (like planets!) They can’t just fall right in, like a golf ball in a hole, things have to wait patiently in a queue in a disk around the black hole. This disk gets INCREDIBLY hot and bright, so that might be the ‘glow’ you are thinking of, rather than Hawking radiation.

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