astrophysics Do not (pass) Supernova, go directly to Black Hole -- and LIGO told us which Stars are doing it!

[Unobscured Vision]

Article Link | Ars Technica Website

 

Now this is both terrifying and fascinating at the same time .. and it turns out the Stars that this happens to are ones we already know about and have been studying for a while. And ... it happens to be my favourite star in the sky, and my second favourite Nebula Complex just after the Eagle Nebula Complex (the "Pillars of Creation" formation).  

 

Quote

LIGO’s first black hole merger may have been 10 billion years in the making --
Big, luminous stars might simply be blinking out of existence.

by John Timmer - Jun 22, 2016 1:48pm EDT

 

Walt Feimer, NASA/Goddard Space Flight Center

 

The LIGO detector has now seen at least two black hole mergers. The second merger it spotted was about what we would expect given a binary system of two massive stars. Both explode, leaving black holes behind that are just a bit more massive than the Sun; these later go on to merge.

 

But the first merger detected by LIGO was something rather unusual given that both black holes were around 30 times the Sun's mass. So far, we have not observed anything that could produce black holes in that mass range. Now, a new modeling study suggests that mergers with these sorts of masses might be common—but only if stars can collapse directly into a black hole without exploding first. This situation would require some of the Universe's most luminous stars to simply be winking out of existence.

 

The black holes involved in these mergers almost certainly began their existence as binary star systems. So in the new study, the authors performed a massive number of simulations of these systems using a modeling package called StarTrack. The simulations took into account the different amount of heavy elements present at different times in the Universe's existence—there are 32 different levels of heavy elements, and the team ran 20 million simulations at each of them. The simulations also took into account various models of the collapse of massive stars, as well as whether the process generated an asymmetrical force that could kick the resulting black hole into an energetic orbit.

 

With the simulations run, the authors could sift through the results and look for systems that produced the sorts of heavy black holes that LIGO detected merging. They could then play back the simulation and examine the process that produced the black holes in the first place.

 

The models indicate that the systems that produce LIGO-like mergers started out as giant stars with very few heavier elements. Giant stars have only 10 percent of the metal levels found in the Sun, but they're somewhere between 40 to 100 times more massive. These sorts of stars were much more common in the early Universe, and 75 percent of the simulations indicate that the binary system formed within the first two billion years of the Universe's existence.

 

In the simulations, helium and heavier elements form quickly at the core of these stars. The core then ejects its outer layer of hydrogen. This action creates a pair of Wolf-Rayet stars, extremely bright and compact objects.

 

At this point, one of the two stars does something unusual: it collapses directly into a black hole without exploding in a supernova. While there has been a lot of theoretical work that indicates it should be possible, we've never actually observed a star collapsing out of existence.

 

Assuming it happens, the resulting black hole should be in the right mass range to produce a LIGO-like merger. But the merger doesn't happen immediately (indeed, it may take 10 billion years after the birth of the stars). Because of the lack of explosion, the black hole would continue to orbit close to its companion. Over time, it would help draw out the outer layers of the companion star, creating a situation where the black hole's orbit would be inside the envelope of the star.

 

After the star contracts, the result would look like what we call X-ray binaries: an X-ray source orbiting a massive, luminous star. The authors point out that we've observed two systems that look like the modeled results (IC10 X-1 and NGC 300 X-1). Given a bit more time, however, the second star also undergoes a direct collapse, creating a pair of orbiting black holes, each about 30 times as massive as the Sun. These black holes then take about 5 billion years to spiral into each other and merge.

Well, we certainly know where to find those.  

 

Carinae Nebula Complex (Wikipedia) | Eta Carinae (Wikipedia) | Homunculus Nebula (Wikipedia)

 

 

 

The Primary star meets the conditions theorized to perform the "trick of all tricks". No "badda boom", just a "fwump" and an echo as it snuffs out of existence. Suddenly n-Carinae B finds its' immediate environment strangely quiet ... and begins moving inward on its' orbital track toward some object that now looks like Gargantua.  

Edited June 22, 2016 by Unobscured Vision

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Galactus lives large