Supermassive black hole turns unlucky star into spaghetti
- Reference: 1602565506
- News link: https://www.theregister.co.uk/2020/10/13/black_hole_spaghetti/
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AT2019qiz was ripped apart by a supermassive black hole in the constellation of Eridanus. Though it is 215 million light years from Earth, it is the closest star we've seen annihilated in such a way. The extreme tidal forces exerted on the sun stretched it into long noodle-like strands that were torn apart as it was gobbled up, a violent affair that set off bright flares of electromagnetic energy.
[1]
My god, it's full of spaghetti ... An illustration of AT2019qiz being torn apart. Credit: ESO/M. Kornmesser. Click to enlarge
“When an unlucky star wanders too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole shreds the star into thin streams of material," [2]said Thomas Wevers, a research fellow at the European Southern Observatory, on Monday.
Although spaghettification is a well-described process in theoretical physics, observing it in the real world is difficult. The telltale emissions of energy from such events are normally obscured by thick dust from the stellar destruction. A team of astronomers led by the UK's University of Birmingham was able to spot the spaghettification of AT2019qiz by catching it early before a cloak of dust had settled around the supermassive black hole. The researchers [3]published their results in a paper in the Monthly Notices of the Royal Astronomical Society on Monday.
“Because we caught it early, we could actually see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10,000 kilometers per second," said Kate Alexander, co-author of the study and a NASA Einstein Fellow at Northwestern University in the US.
What would happen if Earth fell into a black hole? [4]READ MORE
"This unique 'peek behind the curtain' provided the first opportunity to pinpoint the origin of the obscuring material and follow in real time how it engulfs the black hole."
Alexander told El Reg the first sign of the spaghettification of AT2019qiz was a bright blue flash from the center of a nearby galaxy.
“The blue light alerts us to the presence of hot gas, debris from the star that has been heated by the disruption process,” she said. The researchers observed AT2019qiz over six months in various wavelengths, including radio, optical, X-ray, and ultraviolet. They were able to study the relationship between the radiation emitted during the black hole’s feast, and the material erupting from the star as it was eaten for the first time.
“The observations showed that the star had roughly the same mass as our own Sun, and that it lost about half of that to the monster black hole, which is over a million times more massive," said Matt Nicholl, first author of the paper and a lecturer at the University of Birmingham. The other half of its mass was dispersed as a stream of gas into the surrounding space.
“Although black holes have a reputation as 'cosmic vacuum cleaners,' a star has to get extremely close to the black hole, in fact, before the gravitational tidal forces are strong enough to tear it apart,” Alexander told us. “Most stars in galaxies are on stable orbits that keep them far away from the danger zone, so in any specific galaxy, a star is only torn apart in this way about once every 10,000 to 100,000 years.”
Scientists reckon that analyzing spaghettification events could uncover secrets of how supermassive black holes accrue such giant masses. “Studying spaghettification allows us to get a better picture of exactly how a black hole eats, and how it expels material back into its surroundings,” she concluded. ®
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[1] https://regmedia.co.uk/2020/10/13/spaghetti.jpg
[2] https://www.eso.org/public/news/eso2018/
[3] https://academic.oup.com/mnras/article/499/1/482/5920142
[4] https://www.theregister.com/2016/02/17/what_would_happen_if_earth_fell_into_a_black_hole/
[5] https://whitepapers.theregister.com/
yes or no ?
This article says that the supermassive black hole spaghettified an infalling star. The sidebar linked article " what would happen if Earth fell in" says that only normal black holes spaghettify and that with a supermassive BH, you fall inside the event horizon before the field gradient gets big enough.
Re: yes or no ?
There are all kinds of hidden and non-hidden assumptions here, but perhaps the most obvious difference is that stars are just big balls of gas; but the earth is rocky, and so has more intrinsic structural integrity.
Re: yes or no ?
Getting my head around the (truly mind boggling) forces involved here required some serious reading. Gravity can literally pull any object apart because it's operating at the sub-atomic level and everything has a structural limit while gravity just keeps on increasing as you add mass.
From the perspective of the singularity in a supermassive, the difference in structural integrity between a gas cloud and a neutron star is insignificant, both will arrive as a particle stream, the only difference is how far away it happens.
Re: From the perspective of the singularity ...
The event horizon is not the (or even any sort of [1]) singularity; so the relative "structural strengths" of a rocky planet vs that of a star might well be relevant when considered in relation to the tidal forces near the event horizon of some particular black hole.
.
[1] Wll, ok, if you pick bad coordinates you might get a sort of "coordinate singularity"', but that's a problem with the description, and not an indication of any physics.
Re: yes or no ?
In a supermassive the spaghettification happens after passing the event horizon, it's just that there's no way to view the process from outside. Theres quite a distance (many AU) between event horizon and the actual singularity itself.
Anything with less mass than a star wouldn't have the inbuilt gravity to hold itself together long enough to reach the event horizon.
Re: yes or no ?
> In a supermassive the spaghettification happens after passing the event horizon
Does it though? Crossing the event horizon means there's no way back. The gravitational field is more than strong enough prior to that to pull the star apart.
Re: yes or no ?
No way back, but there's still an ever increasing gravity pull that will eventually rip anything apart down to the sub atomic level.
The more massive an object is, the nearer it will be able to approach a singularity before it's own gravity is swamped.
Re: yes or no ?
The answer to this is that what disrupts objects falling into a BH is not the strength of the gravitational field, it's the variation of that strength over the extent of the object falling in. This is normally called a 'tidal' effect because it's the same effect that causes the Moon to raise tides on the Earth.
As an object falls towards a BH, the difference between the field it feels on the side away from the BH and that it feels on the side closest to it increases, and it increases without bound (it becomes as large as you like) as you approach the singularity. At some point this difference in field overcomes whatever is holding the object together and it falls apart, becoming spaghettified.
Any large object like a planet or a star is held together entirely by gravity – in particular planets don't have significantly more 'structural integrity' than stars. So it is not that planets are somehow stronger than stars that means that planets will get spaghettified later.
Rather it is that stars are much larger than planets, so they experience hugely larger tidal forces as they approach the BH, and thus get disrupted much sooner.
A nice way of thinking about it is to realise that what matters, really, is how large the infalling object is compared to the radius of the BH's event horizon. The larger it is, the larger the tidal forces across it and the sooner it will get disrupted. If it is very dense, like a neutron star or something, it will tend to hold together for longer (neutron stars are also rather small, of course).
If the object is small enough compared to the radius of the BH's event horizon, it won't get disrupted until after it has passed the horizon (at least not classically). If it's much larger, it will.
In this case you can see that the star being disrupted is indeed pretty large compared to the BH: from the paper referenced in the article the BH has a mass of about a million solar masses while the star has a mass of about 1. This means that the radius of the BH's event horizon is only about 4 times the radius of the Sun. If we assume the star had a radius about the same as the Sun you can see it's really fairly large compared to the BH, which is why it will get disrupted.
For the technically-minded there is a rather easy expression for the distance at which an object will be disrupted: R_t = R_* (M_h / M_*)^(1/3) (approximately). Here R_t is the radius at which a star will be disrupted, the 'tidal radius', R_* is the radius of the star, M_h is the mass of the black hole and M_* is the mass of the star.
For a million-solar-mass BH, this means that the Sun would be disrupted about at about 23 times the radius of the event horizon, while Earth would be disrupted only about 14 times the radius. For a hundred-million solar-mass BH the Earth would only be disrupted inside the event horizon.
Note that there are other nasties that happen as you approach a BH even if you dont get disrupted. You probably don't want to be too close to an active accretion disk, for instance.
FSM?
Truly 'tis a glimpse of his noodly appendage!
Re: FSM?
That's one noodle of his I'd rather not be touched by though...
Though it does raise the question... Are his meatballs made of black holes... Or are black holes made of his meatballs?
Re: FSM?
Dam! was just about to make the same observation.
Clearly the star is being offered as a living sacrifice to the FSM in some unimaginable Cosmic Alien ritual. May I suggest that we terminate all efforts to contact alien civilizations, with immediate effect?
Confusion
You're getting confused with meatyorites.
spaghettification
Possibly the best word ever to have come from the study of black holes.