4 ms·

absolutely not confirmed to be a boson star. Most likely a black hole found its way there under unusual circumstances

by metalliqaz 3y ago

eterevsky 3y ago
Still exciting. Do we have any other examples of stars closely orbiting around black holes?
- daniel-thompson 3y ago
  [1] S62 comes within 16 AU at closest approach to Sag A* but its orbit is highly elliptical. The distance between objects in this system 1.4 AU, which is _incredibly_ close. https://en.wikipedia.org/wiki/S62_(star) https://en.wikipedia.org/wiki/S62_(star)
  - dylan604 3y ago
    Do we know the distance to the event horizon for Sgr A*? I'm no astrophysicist, but 1.4AU sounds really _incredibly_ close. In my sci-fi thoughts, something at 1.4AU would be attempting to go "in, through, and beyond" and not orbiting. So excuse me while I try to re-evaluate whatever pre-existing notions I might have
    - daniel-thompson 3y ago
      I'm no astrophysicist, but the paper and some web data show - Sag A* has a mass of ~4,000,000 times the sun, and an event horizon of approximately 12,000,000 km (0.08 AU). This is just the event horizon; Sag A*'s accretion disk has a diameter of about 150,000,000,000 km (1000 AU). So your intuition would certainly be right about Sag A* - there is a huge disk of gas and other junk you'd be flying through. - This object has a mass of at most ~12 times the sun, and (if it's a black hole) an event horizon of approximately 35 km. The paper doesn't say anything about an accretion disk given that it's exploring the idea that the object is not a black hole. Regardless, a star orbiting at 1.4 AU would probably clear out everything in the immediate neighborhood.
- wrycoder 3y ago
  Yes, that's why they published it.
spuz 3y ago
This paper doesn't seem to agree: > the scenario of a central black hole requires unreasonable amount of fine-tuning within the usual evolutionary channels. In particular, if the system is expected to have formed as a binary in isolation, a common envelope formation scenario is rather unlikely, given the system’s arrangement. This requires an extreme, and possibly unphysical, tuning of the relevant parameters of the evolutionary channel under consideration. Moreover, formation within a globular cluster is also improbable given the geometrical characteristics of the observed orbit. Other evolutionary channels such as formation without a common envelope or via a hierarchical triple also seem unlikely for similar reasons. What makes you think their proposal isn't more likely than a black hole?
- daniel-thompson 3y ago
  More likely != confirmed
- nawgz 3y ago
  Is a "boson star" even a confirmed physical construct? I can see confirmed neutron stars like RXJ1856 that they think might be a strange star, but... Just based on what is a confirmed physical construct in the universe, a black hole seems far likelier. Obviously they address this in a way I'm not knowledgeable enough to argue against. Regardless, it will be an interesting scenario to watch evolve!
  - pja 3y ago
    > Is a "boson star" even a confirmed physical construct? No. We don’t even have evidence of a candidate boson you could use to make one.
    - dboreham 3y ago
      First catch your boson.
- jwuphysics 3y ago
  > What makes you think their proposal isn't more likely than a black hole? Because a boson star is purely theoretical and I have a much stronger observational prior that the object is a black hole.

absolutely not confirmed to be a boson star. Most likely a black hole found its way there under unusual circumstances

eterevsky 3y ago

Still exciting. Do we have any other examples of stars closely orbiting around black holes?

daniel-thompson 3y ago
[1] S62 comes within 16 AU at closest approach to Sag A* but its orbit is highly elliptical. The distance between objects in this system 1.4 AU, which is _incredibly_ close. https://en.wikipedia.org/wiki/S62_(star) https://en.wikipedia.org/wiki/S62_(star)
- dylan604 3y ago
  Do we know the distance to the event horizon for Sgr A*? I'm no astrophysicist, but 1.4AU sounds really _incredibly_ close. In my sci-fi thoughts, something at 1.4AU would be attempting to go "in, through, and beyond" and not orbiting. So excuse me while I try to re-evaluate whatever pre-existing notions I might have
  - daniel-thompson 3y ago
    I'm no astrophysicist, but the paper and some web data show - Sag A* has a mass of ~4,000,000 times the sun, and an event horizon of approximately 12,000,000 km (0.08 AU). This is just the event horizon; Sag A*'s accretion disk has a diameter of about 150,000,000,000 km (1000 AU). So your intuition would certainly be right about Sag A* - there is a huge disk of gas and other junk you'd be flying through. - This object has a mass of at most ~12 times the sun, and (if it's a black hole) an event horizon of approximately 35 km. The paper doesn't say anything about an accretion disk given that it's exploring the idea that the object is not a black hole. Regardless, a star orbiting at 1.4 AU would probably clear out everything in the immediate neighborhood.
wrycoder 3y ago
Yes, that's why they published it.

spuz 3y ago

This paper doesn't seem to agree: > the scenario of a central black hole requires unreasonable amount of fine-tuning within the usual evolutionary channels. In particular, if the system is expected to have formed as a binary in isolation, a common envelope formation scenario is rather unlikely, given the system’s arrangement. This requires an extreme, and possibly unphysical, tuning of the relevant parameters of the evolutionary channel under consideration. Moreover, formation within a globular cluster is also improbable given the geometrical characteristics of the observed orbit. Other evolutionary channels such as formation without a common envelope or via a hierarchical triple also seem unlikely for similar reasons. What makes you think their proposal isn't more likely than a black hole?

daniel-thompson 3y ago
More likely != confirmed
nawgz 3y ago
Is a "boson star" even a confirmed physical construct? I can see confirmed neutron stars like RXJ1856 that they think might be a strange star, but... Just based on what is a confirmed physical construct in the universe, a black hole seems far likelier. Obviously they address this in a way I'm not knowledgeable enough to argue against. Regardless, it will be an interesting scenario to watch evolve!
- pja 3y ago
  > Is a "boson star" even a confirmed physical construct? No. We don’t even have evidence of a candidate boson you could use to make one.
  - dboreham 3y ago
    First catch your boson.
jwuphysics 3y ago
> What makes you think their proposal isn't more likely than a black hole? Because a boson star is purely theoretical and I have a much stronger observational prior that the object is a black hole.