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Felt mildly like a clickbait title (in my opinion) It still absorbs stars... and other matter... lots of it... but those somewhat more familiar with black hol

Felt mildly like a clickbait title (in my opinion) It still absorbs stars... and other matter... lots of it... but those somewhat more familiar with black holes know not everything is sucked in... black holes (commonly? -- I never looked into prevalence of this) have "jets" that push material away, often at high speed. The "revelation" of this article is that we have the first photographic evidence supporting the fact these "jets" can contribute to the creation of stars.

pdonis 5y ago
> black holes (commonly? -- I never looked into prevalence of this) have "jets" that push material away, often at high speed. This is quite common. The jets are present in most black holes that are rotating with significant angular momentum compared to their mass, which is, AFAIK, a substantial majority of all black holes that have been observed.
- eyegor 5y ago
  Is it even possible for a black hole (or any stellar body) to form without angular momentum? Or somehow consume all of its angular momentum without decomposing? I know that it's used in some bits of general relativity around the schwarzchild solution but I've never seen an attempt to prove that they could ever form in the first place. I'd appreciate links to research papers if you know of any.
  - mr_toad 5y ago
    Only if the matter that comprised it had zero net angular momentum before hand. Angular momentum is conserved. It’s totally possible in theory for a black hole to have zero angular momentum, but not so likely in practice.
    - eyegor 5y ago
      Oh of course, it's just a sum after all. Reminds me of forgetting the zero roots when solving differential equations.
  - pdonis 5y ago
    > Is it even possible for a black hole (or any stellar body) to form without angular momentum? In principle, yes. In fact, one of the earliest papers on black holes was the one by Oppenheimer and Snyder in 1939 that derived an explicit solution for the case of perfectly spherically symmetrical (i.e., exactly zero angular momentum) collapse to a black hole. In practice, any blob of matter is most likely going to have some angular momentum, and it's unlikely that it will shed all of it if it collapses to a black hole, so we would expect black holes without any angular momentum at all to be rare. But there could be significant numbers of them that have small angular momentum compared to their mass.
    - candiodari 5y ago
      Black hole formation will massively accelerate rotation for the same reason ice skaters rotate faster when drawing their arms closer. If the origin star had a tiny rotation the black hole will be incredibly smaller, and incredibly faster rotation.

pdonis 5y ago

> black holes (commonly? -- I never looked into prevalence of this) have "jets" that push material away, often at high speed. This is quite common. The jets are present in most black holes that are rotating with significant angular momentum compared to their mass, which is, AFAIK, a substantial majority of all black holes that have been observed.

eyegor 5y ago
Is it even possible for a black hole (or any stellar body) to form without angular momentum? Or somehow consume all of its angular momentum without decomposing? I know that it's used in some bits of general relativity around the schwarzchild solution but I've never seen an attempt to prove that they could ever form in the first place. I'd appreciate links to research papers if you know of any.
- mr_toad 5y ago
  Only if the matter that comprised it had zero net angular momentum before hand. Angular momentum is conserved. It’s totally possible in theory for a black hole to have zero angular momentum, but not so likely in practice.
  - eyegor 5y ago
    Oh of course, it's just a sum after all. Reminds me of forgetting the zero roots when solving differential equations.
- pdonis 5y ago
  > Is it even possible for a black hole (or any stellar body) to form without angular momentum? In principle, yes. In fact, one of the earliest papers on black holes was the one by Oppenheimer and Snyder in 1939 that derived an explicit solution for the case of perfectly spherically symmetrical (i.e., exactly zero angular momentum) collapse to a black hole. In practice, any blob of matter is most likely going to have some angular momentum, and it's unlikely that it will shed all of it if it collapses to a black hole, so we would expect black holes without any angular momentum at all to be rare. But there could be significant numbers of them that have small angular momentum compared to their mass.
  - candiodari 5y ago
    Black hole formation will massively accelerate rotation for the same reason ice skaters rotate faster when drawing their arms closer. If the origin star had a tiny rotation the black hole will be incredibly smaller, and incredibly faster rotation.