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Posted by: TrappistPlanets Apr 22 2021, 11:48 AM

Yesterday my friend on Discord sent me an article on this new black hole called The unicorn
and i got very intersted and i found these articles for other people to read up on
https://www.space.com/tiny-black-hole-unicorn-closest-to-earth

and here is the arxiv.org article
https://arxiv.org/abs/2101.02212

apparently it orbits a big bloated red giant star

Posted by: Greenish Apr 23 2021, 02:02 AM

I wouldn't have any context for this if I hadn't recently listened to https://www.youtube.com/watch?v=As7vWYmb5L8of PBS Spacetime (consistently amazing content, by the way), where Matt O'Dowd explains how a recent gravitational wave observation helps clarify the boundary/mass gap between neutron stars and black holes ... sounds like this is another related piece of that puzzle? Neat stuff.

Posted by: JRehling Apr 23 2021, 03:56 AM

Given that the star has a companion, the first thing I think of is Type 1a supernovae. If a white dwarf (the pre-nova star) in a binary system can gradually accumulate matter from its companion until the white dwarf suddenly goes supernova, could the Unicorn be part of a similar pair, but where a neutron star gradually accumulated matter from its companion until it suddenly becomes a black hole? In which case, it would initially have basically the minimum possible mass for a black hole, and not be indicative of the minimum possible mass for a black hole to form directly from the collapse of a giant star?

Posted by: HSchirmer Apr 23 2021, 12:56 PM

There is also the interesting / bizarre possibility that colliding stars of degenerate matter (electron, proton, neutron or quark) could form a "synestia"- https://www.ucdavis.edu/news/synestia-new-type-planetary-object

In that case, the central core collapses to a fly-weight black hole (boxing reference) while the remainder of the degenerate matter is flung out into a torus where it is under comparatively low gravity.

Hmm, is it theoretically possible to create a "degenerate matter eutectic"?
In simplest terms, you'd have a white-dwarf "sauce" mixed in with a neutron star's "nuclear pasta"?

Posted by: JRehling Apr 23 2021, 03:35 PM

Greenish, that Matt Dowd video is a very good connection to make. The Unicorn paper discusses LIGO discoveries as comparable cases; they may not be the same thing, but they're part of the same range of mass and density and presence in a coorbital binary. The Dowd video gives a good sense of what we do and don't know about bodies in this mass range so far.

Posted by: TrappistPlanets Apr 24 2021, 11:23 PM

yeah scientists use what they already have (other black holes) to compare to something new (The Unicorn)

could Unicorn and its companion star once ben a binary star system, and "The Unicorn" died first and became a neutron star then sucked material from its companion witch is now a red giant and became a black hole as JRehling said in his comment