Starship Asterisk*

Chris Peterson wrote: ↑Sat Jun 17, 2023 9:05 pm

johnnydeep wrote: ↑Sat Jun 17, 2023 8:38 pm

Chris Peterson wrote: ↑Fri Jun 16, 2023 9:56 pm

It's far from certain that there even is a BH in the center. And the model used to offer it as a possibility suggests a mass of about 2000 solar masses to be consistent with the orbital dynamics of the innermost stars.

Ok. And if such a 2000 solar mass BH vanished, would the stars in the cluster care? Perhaps only the very close ones, for some value of "close"?

The impact would depend on where they were. The closer, the more it would matter. But broadly, the BH isn't what's determining the dynamics of the stars in the cluster.

johnnydeep wrote: ↑Sat Jun 17, 2023 8:38 pm

Chris Peterson wrote: ↑Fri Jun 16, 2023 9:56 pm

johnnydeep wrote: ↑Fri Jun 16, 2023 9:12 pm

Hmm, so if the black hole were to suddenly vanish, along with it's mass, would the stars know? I wonder how big the central black hole is. It's described as having "intermediate mass" in the linked paper, and Wikipedia says those are in the range of 100 - 100000 solar masses. The cluster as a whole is said to have about 100000 stars. If the black hole were only a few thousand solar masses, that would be pretty insignificant compared to the overall mass, and it's sudden vanishing might not have much of an effect.

It's far from certain that there even is a BH in the center. And the model used to offer it as a possibility suggests a mass of about 2000 solar masses to be consistent with the orbital dynamics of the innermost stars.

Ok. And if such a 2000 solar mass BH vanished, would the stars in the cluster care? Perhaps only the very close ones, for some value of "close"?

Chris Peterson wrote: ↑Fri Jun 16, 2023 9:56 pm

johnnydeep wrote: ↑Fri Jun 16, 2023 9:12 pm

Chris Peterson wrote: ↑Fri Jun 16, 2023 3:54 am

Neither. They mostly don't even feel the effects of the black hole. All of the stars are simply orbiting the common center of mass of the cluster. Those closer to the center are in shorter, faster orbits... just like the planets on the Solar System.

Hmm, so if the black hole were to suddenly vanish, along with it's mass, would the stars know? I wonder how big the central black hole is. It's described as having "intermediate mass" in the linked paper, and Wikipedia says those are in the range of 100 - 100000 solar masses. The cluster as a whole is said to have about 100000 stars. If the black hole were only a few thousand solar masses, that would be pretty insignificant compared to the overall mass, and it's sudden vanishing might not have much of an effect.

It's far from certain that there even is a BH in the center. And the model used to offer it as a possibility suggests a mass of about 2000 solar masses to be consistent with the orbital dynamics of the innermost stars.

johnnydeep wrote: ↑Fri Jun 16, 2023 9:12 pm

Chris Peterson wrote: ↑Fri Jun 16, 2023 3:54 am

Avalon wrote: ↑Fri Jun 16, 2023 3:10 am So would those central stars with "increasing velocities" be falling inward toward the black hole on a straight course, or circling in toward it in a spiral pattern?

Neither. They mostly don't even feel the effects of the black hole. All of the stars are simply orbiting the common center of mass of the cluster. Those closer to the center are in shorter, faster orbits... just like the planets on the Solar System.

Hmm, so if the black hole were to suddenly vanish, along with it's mass, would the stars know? I wonder how big the central black hole is. It's described as having "intermediate mass" in the linked paper, and Wikipedia says those are in the range of 100 - 100000 solar masses. The cluster as a whole is said to have about 100000 stars. If the black hole were only a few thousand solar masses, that would be pretty insignificant compared to the overall mass, and it's sudden vanishing might not have much of an effect.

Chris Peterson wrote: ↑Fri Jun 16, 2023 3:54 am

Avalon wrote: ↑Fri Jun 16, 2023 3:10 am So would those central stars with "increasing velocities" be falling inward toward the black hole on a straight course, or circling in toward it in a spiral pattern?

Neither. They mostly don't even feel the effects of the black hole. All of the stars are simply orbiting the common center of mass of the cluster. Those closer to the center are in shorter, faster orbits... just like the planets on the Solar System.

Avalon wrote: ↑Fri Jun 16, 2023 3:10 am So would those central stars with "increasing velocities" be falling inward toward the black hole on a straight course, or circling in toward it in a spiral pattern?

Avalon wrote: ↑Fri Jun 16, 2023 3:10 am So would those central stars with "increasing velocities" be falling inward toward the black hole on a straight course, or circling in toward it in a spiral pattern?

Rauf wrote: ↑Thu Jun 15, 2023 2:47 pm

Chris Alex wrote: ↑Thu Jun 15, 2023 12:13 pm

Locutus76 wrote: ↑Thu Jun 15, 2023 9:44 am There are maybe 10 stars within 10 lightyears from Earth. Imagine it being 50,000! The night sky would never be black, but instead have a ‘milky’ glow, perhaps even perpetual daylight, and be absolutely covered with stars that could shine as bright as a full moon. But (inter)stellar radiation might be way too high for any life to evolve in such clusters… still, impressive

That would be quite a sight indeed! I always like to Imagine what the sky would look like if we lived right next to or inside any given awesome cosmic object. - As for the challenges of life evolving in M15, in addition to the constant intense radiation, some ten neutron stars have been identified in there, so life would have had to survive ten nearby supernovae! Good luck with that.

There was an APOD about this very long ago.
https://apod.nasa.gov/apod/ap011005.html

Well, I know this APOD's been made with birds shining, but still a hilarious sight!

Chris Alex wrote: ↑Thu Jun 15, 2023 12:13 pm

Locutus76 wrote: ↑Thu Jun 15, 2023 9:44 am There are maybe 10 stars within 10 lightyears from Earth. Imagine it being 50,000! The night sky would never be black, but instead have a ‘milky’ glow, perhaps even perpetual daylight, and be absolutely covered with stars that could shine as bright as a full moon. But (inter)stellar radiation might be way too high for any life to evolve in such clusters… still, impressive

That would be quite a sight indeed! I always like to Imagine what the sky would look like if we lived right next to or inside any given awesome cosmic object. - As for the challenges of life evolving in M15, in addition to the constant intense radiation, some ten neutron stars have been identified in there, so life would have had to survive ten nearby supernovae! Good luck with that.

Locutus76 wrote: ↑Thu Jun 15, 2023 9:44 am There are maybe 10 stars within 10 lightyears from Earth. Imagine it being 50,000! The night sky would never be black, but instead have a ‘milky’ glow, perhaps even perpetual daylight, and be absolutely covered with stars that could shine as bright as a full moon. But (inter)stellar radiation might be way too high for any life to evolve in such clusters… still, impressive