Possible detection of a black hole with a mass thought to be impossible
quantamagazine.org
quantamagazine.org
https://news.ycombinator.com/item?id=20819902
However there is an update to the article posted today:
[Update: On September 2, 2020, researchers confirmed [1] that the colliding black holes had masses 65 and 85 times that of our sun. The resulting black hole was 150 times more massive than the sun.]
[1] https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12...
> Chris Belczynski, an astrophysicist at Warsaw University, previously felt so sure that such a large specimen wouldn’t be seen that in 2017 he placed a bet with colleagues. “I think we are about to lose the bet,” Belczynski said, “and for the good of science!”
LIGO has existed for decades and by 2017 had already detected a merger. My guess is he considered black holes in this range rare enough that we were unlikely to detect any. If he believed they were impossible the article certainly doesn’t elucidate on that fact.
Neither side was saying that they wouldn't be found.
I presume that different masses of black holes result in different frequency waves, and that LIGO is not uniformly sensitive to all frequencies. Depending on the actual numbers, this would make these intermediate sized mergers either over or under represented in our data.
I would think after supernova, the companion star(s) would end up in a modified orbit that would result in more destructive gravitational interactions (collisions, mass transfer, feeding or creating a black hole). To the layperson it feels like a matter of 'when', not 'if'.
Perhaps it's that I'm thinking that in a universe of a billion billion distinct examples of orbital mechanics, surely we are going to spot a lot of exceedingly lucky/unlucky events out there. Especially if we are doing any kind of observation that filters for those events.
After all, a one-in-a-billion probability event on earth happens to about eight people. If you know how to find them, it's a good human interest story.
> The million- and billion-solar-mass supermassive black holes that anchor galaxies’ centers formed differently, and rather mysteriously, in the early universe. LIGO and Virgo are not mechanically capable of detecting the collisions of supermassive black holes.
After the event horizon surfaces contact, does it become spherical in minimal time, or does it keep a complicated shape for an extended period? (E.g., until gravitational waves carry off enough energy?) And does the very large rotational momentum affect properties of the resulting black hole?
As to the second part, I'd think it becomes axially symmetric in very minimal time. I don't have a good answer as to why, except that my intuition says the GW signature of blackhole mergers at the point of the merger has a frequency that appears to get infinitely fast as it radiates away the axial asymmetry.
This black hole is big enough to fall into a mass RANGE that shouldn't exist, but isn't the largest found (which I feel the title of the article implies).
Supermassive black holes are on the scale of BILLIONS of solar masses.
https://en.wikipedia.org/wiki/List_of_most_massive_black_hol...
Obviously black holes are colliding otherwise we probably wouldn't have supermassive black holes, so it doesn't seem unexpected that two smaller black holes would collide and form one bigger than the limit imposed by pair-instability supernova, except as a statistical improbability.
Is it because the amplitude is so big it "pegs the needle" above its limit?
It now makes perfect sense to me that more massive objects wouldn't revolve quickly enough to create high frequency waves.
The ground-based detectors are most sensitive at 100Hz, which is around the frequency of the binary black hole inspiral. Supermassive black holes are more like millihertz. We do not have any concrete way yet to measure the gravitational waves from supermassive black holes, but there are some ideas. For example we can look at the time dilation of frequencies of nearby pulsars (https://en.wikipedia.org/wiki/Pulsar) as a kind of gravitational wave interferometer in space, however to get a signal-to-noise ratio greater than one many years (decades) of data is needed.
I would guess "no" but then again I'm not a physicist, maybe there's a surprise down the road.
Humorous and rarely shared in science articles and gives some great context for the personalities involved!
<3s!!!
In order to reach LIGO's frequency band, the objects must be very compact. If they are too large, they touch before they can orbit each other at sufficiently-high (audio!) frequencies.
The Schwarzschild radius of the black holes in question are less than 100km in size, while the size of a star as small as our Sun is ~700,000 km in size.
Moreover, the compact objects (neutron stars, black holes) that LIGO can observe are exceptionally dense ( > 3x10^17 kg/m^3), while stars have roughly the density of water (1000 kg/m^3) on average, and much less at their extremities. Compact objects can disrupt nearby stars long before they could touch, spreading the "merger" across many, many years (many, many millenia, I suspect), rather than the fraction-of-a-second typical of a LIGO black-hole observation.
For a visual image of the interaction of a large/fluffy star with a compact object, have a gander at a few of these images: https://www.google.com/search?q=roche+lobe+accretion
https://www.frontiersin.org/articles/10.3389/fspas.2020.0002...
Absolutely, the question was only how frequently it happens. The bet was within the first 100 detections — with one side only saying they're rarer than that.