'Black neutron star' discovery changes astronomy.

[Notebook]

Scientists have discovered an astronomical object that has never been observed before.
It is more massive than collapsed stars, known as "neutron stars", but has less mass than black holes.
Such "black neutron stars" were not thought possible and will mean ideas for how neutron stars and black holes form will need to be rethought.
The discovery was made by an international team using gravitational wave detectors in the US and Italy.

https://www.bbc.co.uk/news/science-environment-53151106

 

[Linguofreak]

Might I suggest that a better title for the thread would be "gravitational wave event in mass gap", as those are the keywords that people following gravitational wave astronomy will be looking for?

"Black neutron star" appears either the what BBC journalists without much knowledge of the field took away from the announcement, or maybe wording that the LIGO PR department came up with to try to make things accessible to the public, but it is rather confusing for anyone following the field (it doesn't actually make it obvious that this was a GW observation without reading in to the article, for example).

It appears to reference this LIGO detection:

https://www.ligo.org/detections/GW190814.php

 

[jedidia]

Such "black neutron stars" were not thought possible and will mean ideas for how neutron stars and black holes form will need to be rethought.

Again? Oh, for crying out loud! :lol:

 

[Linguofreak]

Again? Oh, for crying out loud! :lol:

Well, I don't think the "not thought possible" bit is accurate: One of the things that LIGO has explicitly been looking for is events involving a body in the mass gap. This isn't something that they weren't looking for because it wasn't thought possible and therefore came as a huge surprise. Basically, we don't have the equation of state for nuclear matter very tightly constrained, as we only have atomic nuclei and the results of particle collisions to work with in terrestrial laboratories, and there isn't a convenient neutron star in the solar system for us to examine from up close. So we don't know where the boundary between neutron stars and black holes lies, and the set of known objects doesn't contain enough objects close to the boundary to constrain its location well. Gravitational wave observations let us search a larger area of the universe, plus the fact that they involve mergers potentially allows us to probe the interior dynamics of neutron stars by seeing how, e.g, tidal deformation of the neutron star affects the GW spectrum, and/or, for closer events, by analyzing the electromagnetic emissions from the debris.