• Question: Thanks for your answer earlier I was wondering if you had anything to add about why partial beams shoot from black holes

    Asked by hgddgrfbg to Bella on 25 Mar 2020.
    • Photo: Bella Boulderstone

      Bella Boulderstone answered on 25 Mar 2020:


      Hey! I’m so glad that you dropped me an ask. Legit, best question!

      Strap in!

      So black holes are like, giant 3D holes in space. A lot of people think that this means that they’re like a big hover and suck everything inside them BUT actually they’re a bit more like a big space funnel (at home experiment: roll some marbles around in a funnel, watch how they are able ‘orbit’ the central hole). Black holes are just like any other gravitational body (like a star or a planet) in that it’s able to have things orbit around it. It’s just when you get to the event horizon (the edge) that things get weird and you’re not able to come out and then there’s all the weird spacey-wacey-timey-wimey stuff that happens.

      So, black holes tend to come in two types: on and off. Which means: ones that are ‘active’ or ‘accreting’ and ones that aren’t. The words ‘active’ and ‘accreting’ here means that they’re eating stuff: things are falling into them. And because it’s just like any other gravitational body, the stuff falling into it settles into what’s called an ‘accretion disc’. It’s a thin disc that’s allowing the black hole to do the accreting. The accretion disc is hot, bright and violent. It’s made up of the 4th state of matter: plasma.

      Plasma is like superheated gas that’s also able to conduct electricity and (importantly for us) magnetic fields. Now, astronomers aren’t able to deal that much with magnetic fields because (awkwardly) they’re invisible and (annoyingly) we can’t visit the stars to figure out what’s going on with magnetic fields. BUT we do have some theories for how jets shoot or ‘launch’. And not just partial jets, full-on-fantastic-bigger-than-its-own-galaxy-super-duper-beautiful jets, go ahead and google ‘M87’ for a really spectacular jet.)

      We think that jets launch is because plasma gets stuck to magnetic field lines, like beads on a string. Then when it gets close to the event horizon of the black hole (the edge where things can’t come back from), the stringy-line things get all tangled up and when they are finally sucked down into the black hole, the string is cut & the beads (if you imagine tangling up a necklace and then pulling it apart) pop off and are able to be ‘launched’.

      Partial jets, we think, happen because there isn’t enough energy to ‘launch’ the full jet. We think that it tried its best, but there wasn’t enough tension or energy stored (when you pull the necklace apart, the beads will scatter more if you rip that necklace up really fast and hard. If you gently cut the necklace, the beads will scatter less) in the magnetic fields to allow for the full launch: not enough fuel in the weird magnetic engine.

      So essentially, the beams shoot from the processes that occur at the event horizon of the black hole where the plasma and magnetic field lines get all tangled, and when there’s finally a disconnection, energy is released in the form of this jet.

      HOWEVER, there’s a lot we don’t know about jet launching. Actually loads. It’s a really active area of research, especially in the UK. There are a lot of people looking at all sorts of different types of jets and black holes and all sorts. I hope this answers your question properly!

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