4 ms·

Couldn’t it just be a normal, non-collapsed star? I’m sure they thought of that, just curious how they ruled it out.

dandare 6y ago
It would be probably ripped apart into an accretion disc thus no gravitational waves. But i like your question and I hate it when articles omit the to mention and explain layman's explanations.
- dmurray 6y ago
  Yeah, the article really seems to be missing an important point. It's written something like - we never observe any super dense thing between 2 solar masses and 5 solar masses - 2 solar masses is the maximum for a neutron star, because otherwise it would collapse and become a black hole - 5 solar masses is the minimum for a black hole, because...?
  - ISL 6y ago
    It is the minimum thought to be possible for a black hole produced by standard stellar evolution. GR has no limit, large or small, on the size of a black hole. Such black holes could be formed by another mechanism -- in the big bang ("primordial" black holes) or from the merger of neutron stars. What has everyone atwitter about this is that, given the standard plan for things, these objects should be very rare. To have seen even one example this early in the history of gravitational-wave observation is a surprise. Either there are more primordial black holes than people think, supernovae don't work like we expect (historically a pretty good bet), neutron stars find each other and merge more often than people think, or there's another process for making mass-gap objects that people don't know about.
    - gliese1337 6y ago
      I would think neutron stars accumulating material from a binary companion ought to be reasonably common. Unlike white dwarfs, they won't be able to blow themselves apart in supernovae, so they should just keep accumulating mass until they collapse into very small black holes.
infogulch 6y ago
It was detected by gravitational waves via LIGO & friends as a merger of two very dense objects, much denser than your average star. Normal star densities would tear themselves to pieces/devolve into a novae instead of merging like this.

It would be probably ripped apart into an accretion disc thus no gravitational waves. But i like your question and I hate it when articles omit the to mention and explain layman's explanations.

dmurray 6y ago
Yeah, the article really seems to be missing an important point. It's written something like - we never observe any super dense thing between 2 solar masses and 5 solar masses - 2 solar masses is the maximum for a neutron star, because otherwise it would collapse and become a black hole - 5 solar masses is the minimum for a black hole, because...?
- ISL 6y ago
  It is the minimum thought to be possible for a black hole produced by standard stellar evolution. GR has no limit, large or small, on the size of a black hole. Such black holes could be formed by another mechanism -- in the big bang ("primordial" black holes) or from the merger of neutron stars. What has everyone atwitter about this is that, given the standard plan for things, these objects should be very rare. To have seen even one example this early in the history of gravitational-wave observation is a surprise. Either there are more primordial black holes than people think, supernovae don't work like we expect (historically a pretty good bet), neutron stars find each other and merge more often than people think, or there's another process for making mass-gap objects that people don't know about.
  - gliese1337 6y ago
    I would think neutron stars accumulating material from a binary companion ought to be reasonably common. Unlike white dwarfs, they won't be able to blow themselves apart in supernovae, so they should just keep accumulating mass until they collapse into very small black holes.

infogulch 6y ago

It was detected by gravitational waves via LIGO & friends as a merger of two very dense objects, much denser than your average star. Normal star densities would tear themselves to pieces/devolve into a novae instead of merging like this.