APOD: Animation: Black Hole Destroys Star (2021 Apr 27)

[APOD Robot]

Animation: Black Hole Destroys Star

Explanation: What happens if a star gets too close to a black hole? The black hole can rip it apart -- but how? It's not the high gravitational attraction itself that's the problem -- it's the difference in gravitational pull across the star that creates the destruction. In the featured animated video illustrating this disintegration, you first see a star approaching the black hole. Increasing in orbital speed, the star's outer atmosphere is ripped away during closest approach. Much of the star's atmosphere disperses into deep space, but some continues to orbit the black hole and forms an accretion disk. The animation then takes you into the accretion disk while looking toward the black hole. Including the strange visual effects of gravitational lensing, you can even see the far side of the disk. Finally, you look along one of the jets being expelled along the spin axis. Theoretical models indicate that these jets not only expel energetic gas, but create energetic neutrinos -- one of which may have been seen recently on Earth.

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[alter-ego]

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

[Chris Peterson]

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

The star was murdered by the tides. The jets are just the system burping a little of that star back out again.

[Ann]

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

Indeed. My guess is that the only red dwarf stars that have ever died since the Universe began are those that blundered into a black hole.

Ann

[Chris Peterson]

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

Indeed. My guess is that the only red dwarf stars that have ever died since the Universe began are those that blundered into a black hole.

Although stellar collisions are rare, they must occur. It's worth noting that were the black hole in today's simulation a red dwarf, those two would have collided. The nature of the resulting mess would have been different, but whatever came out of it wouldn't be at all like what went in!

[Ann]

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

Indeed. My guess is that the only red dwarf stars that have ever died since the Universe began are those that blundered into a black hole.

Although stellar collisions are rare, they must occur. It's worth noting that were the black hole in today's simulation a red dwarf, those two would have collided. The nature of the resulting mess would have been different, but whatever came out of it wouldn't be at all like what went in!

Of course, Chris. I should have said that the only red dwarf stars that have ever died since the Universe began are those that have collided with something that changed their status from red dwarfs to something else.

Ann

[rj rl]

Why does some of the material immediately fall back and start orbiting close to the black hole while some of it is propelled so far away? Why such difference in speeds, is that merely to do with the diameter of the star?

[MarkBour]

Wow, that's a nice simulation and a gorgeous depiction of it!

When it comes to murdering a star, black-hole jets sure look to be the smoking gun.

Nice one, alter-ego.

Why does some of the material immediately fall back and start orbiting close to the black hole while some of it is propelled so far away? Why such difference in speeds, is that merely to do with the diameter of the star?

In a word, yes, you are right, it has to do with the diameter of the star.

If the star had been a body that could have retained a rigid shape, it would have likely gone into an elliptical orbit around the BH. But the star is made of gas, which only holds together (as does our own sun) because its mutual gravitation among the gas atoms is a huge force.

As they briefly indicate in the caption, the star is an extended object and when it encounters the great gravitational pull of the BH, its own gravity is outmatched. The part of the star that passes nearest the BH is pulled much more strongly than the part of the star that is farthest from it. So, it gets shredded (this is commonly called a tidal force, but it's just a difference between forces). Put one way, it's just that all of the parts of the star end up in their own orbit, but the orbits of different parts are very different here. Some parts end up with not enough orbital velocity to stay in orbit and they spiral in.

I assume this simulation took many, many tiny chunks of the star and plotted what trajectory each piece would take, by massively calculating the gravitational field they moved through. Then, the video makers may have also calculated the effects of gravitational lensing to show not just where each piece really went, but also where it would appear to be from our perspective. If they didn't do this in the first part of the video, they at least did this in the 4th segment where we're shown a close-up of the black hole.

[rj rl]

Makes sense, thank you Mark!

[orin stepanek]

th.jpg (8.17 KiB) Viewed 12841 times

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And we thought that the Empire was powerful!

[De58te]

I found it interesting how in the last few seconds as the camera pans up it looks like rising billowing smoke from a bonfire. Even though they say in space combustion doesn't happen due to lack of oxygen. I wonder if this has something to do with fractals, that the microscopic world ( here on Earth) reflects an identical shape in the gigantic cosmos. Also in the last couple seconds did you see a bright point of light similar to Tinker Bell in Peter Pan shoot up and away at great speed. could this be the animation of the energetic neutrino mentioned?

[Chris Peterson]

If the star had been a body that could have retained a rigid shape, it would have likely gone into an elliptical orbit around the BH.

A single rigid body can't capture another single rigid body. Unless the star was already in a closed orbit around the black hole before the near pass, it would exit on a hyperbolic orbit.

[johnnydeep]

If the star had been a body that could have retained a rigid shape, it would have likely gone into an elliptical orbit around the BH.

A single rigid body can't capture another single rigid body. Unless the star was already in a closed orbit around the black hole before the near pass, it would exit on a hyperbolic orbit.

Hmm. What about the many presumably captured moons of planets?

[Chris Peterson]

If the star had been a body that could have retained a rigid shape, it would have likely gone into an elliptical orbit around the BH.

A single rigid body can't capture another single rigid body. Unless the star was already in a closed orbit around the black hole before the near pass, it would exit on a hyperbolic orbit.

Hmm. What about the many presumably captured moons of planets?

These involve three-body (or more) interactions. For instance, an body in orbit around the Sun can lose angular momentum through an encounter with Jupiter, and then be captured by Saturn.

[Psnarf]

In the linked article on the neutrino, the observatory "spotted a neutrino with relatively high energy that appeared to come from beyond our galaxy." How can you tell from where a particular neutrino came? Is there some characteristic of intra-galactic neutrinos different than a Milky-Way neutrino?

[ta152h0]

Fantastico! Appropriate music too. Pass the ice cold one.

[Chris Peterson]

In the linked article on the neutrino, the observatory "spotted a neutrino with relatively high energy that appeared to come from beyond our galaxy." How can you tell from where a particular neutrino came? Is there some characteristic of intra-galactic neutrinos different than a Milky-Way neutrino?

The energy of the neutrino was such that the only known mechanisms for generating it involve cataclysmic events around supermassive black holes. And the direction of this neutrino corresponded to such an event, observed optically, in a galaxy in Delphinus.

[neufer]

Click to play embedded YouTube video.

"Will you walk into my parlour?" said a spider to a fly;
" 'Tis the prettiest little parlour that ever you did spy.
The way into my parlour is up a winding stair,
And I have many pretty things to shew when you are there."
"Oh no, no!" said the little fly, "to ask me is in vain,
For who goes up your winding stair can ne'er come down again."

"I'm sure you must be weary, with soaring up so high,
Will you rest upon my little bed?" said the spider to the fly.
"There are pretty curtains drawn around, the sheets are fine and thin;
And if you like to rest awhile, I'll snugly tuck you in."
"Oh no, no!" said the little fly, "for I've often heard it said,
They never, never wake again, who sleep upon your bed!"

Said the cunning spider to the fly, "Dear friend, what shall I do,
To prove the warm affection I've always felt for you?
I have, within my pantry, good store of all that's nice;
I'm sure you're very welcome—will you please to take a slice?"
"Oh no, no!" said the little fly, "kind sir, that cannot be,"
I've heard what's in your pantry, and I do not wish to see."

"Sweet creature!" said the spider, "you're witty and you're wise.
How handsome are your gauzy wings, how brilliant are your eyes!
I have a little looking-glass upon my parlour shelf,
If you'll step in one moment, dear, you shall behold yourself."
"I thank you, gentle sir," she said, "for what you're pleased to say,
And bidding you good morning now, I'll call another day."

The spider turned him round about, and went into his den,
For well he knew, the silly fly would soon come back again:
So he wove a subtle web, in a little corner, sly,
And set his table ready, to dine upon the fly.
Then he went out to his door again, and merrily did sing,
"Come hither, hither, pretty fly, with the pearl and silver wing;
Your robes are green and purple---there's a crest upon your head;
Your eyes are like the diamond bright, but mine are dull as lead."

Alas, alas! how very soon this silly little fly,
Hearing his wily, flattering words, came slowly flitting by;
With buzzing wings she hung aloft, then near and nearer drew,
Thinking only of her brilliant eyes, and green and purple hue:—
Thinking only of her crested head, poor foolish thing!—At last
Up jumped the cunning spider, and fiercely held her fast.

He dragged her up his winding stair, into his dismal den,
Within his little parlour—but she ne'er came out again!
—And now, dear little children, who may this story read,
To idle, silly, flattering words, I pray you ne'er give heed:
Unto an evil counsellor, close heart, and ear, and eye,
And take a lesson from this tale, of the Spider and the Fly.

• — Mary Howitt (1829)

[johnnydeep]

A single rigid body can't capture another single rigid body. Unless the star was already in a closed orbit around the black hole before the near pass, it would exit on a hyperbolic orbit.

Hmm. What about the many presumably captured moons of planets?

These involve three-body (or more) interactions. For instance, an body in orbit around the Sun can lose angular momentum through an encounter with Jupiter, and then be captured by Saturn.

Ok, I think I see what you meant. In a universe with just two moving bodies, there are only three possibilities: the bodies collide; they orbit their common center of mass; or they make a close approach, but then miss each other and never get that close again.

And I suppose in the orbiting case, their orbit won't decay or get larger over time if they are both perfectly rigid.

[Chris Peterson]

Hmm. What about the many presumably captured moons of planets?

These involve three-body (or more) interactions. For instance, an body in orbit around the Sun can lose angular momentum through an encounter with Jupiter, and then be captured by Saturn.

Ok, I think I see what you meant. In a universe with just two moving bodies, there are only three possibilities: the bodies collide; they orbit their common center of mass; or they make a close approach, but then miss each other and never get that close again.

And I suppose in the orbiting case, their orbit won't decay or get larger over time if they are both perfectly rigid.

In the latter case, they're still orbiting their common center of mass. But the orbit is open, not closed. That is, the (Keplerian) orbits have eccentricities greater than or equal to one.

And even if they were the only two bodies in the Universe, and they were in closed (elliptical) orbits around their common center of mass, those orbits would decay because both would be losing angular momentum to gravitational radiation. For most bodies, we're talking a very, very long time. But it's a major factor in the last stages of neutron star or black hole mergers.

[WWW]

Fantastico! Appropriate music too. Pass the ice cold one.

With sound effects too.
Never wouldn't have guessed that a star being violently ripped apart like that would make a tiny swishing sound...

[johnnydeep]

These involve three-body (or more) interactions. For instance, an body in orbit around the Sun can lose angular momentum through an encounter with Jupiter, and then be captured by Saturn.

Ok, I think I see what you meant. In a universe with just two moving bodies, there are only three possibilities: the bodies collide; they orbit their common center of mass; or they make a close approach, but then miss each other and never get that close again.

And I suppose in the orbiting case, their orbit won't decay or get larger over time if they are both perfectly rigid.

In the latter case, they're still orbiting their common center of mass. But the orbit is open, not closed. That is, the (Keplerian) orbits have eccentricities greater than or equal to one.

And even if they were the only two bodies in the Universe, and they were in closed (elliptical) orbits around their common center of mass, those orbits would decay because both would be losing angular momentum to gravitational radiation. For most bodies, we're talking a very, very long time. But it's a major factor in the last stages of neutron star or black hole mergers.

Thanks for the nuance. There's much more than I'll ever be able to appreciated here - https://en.wikipedia.org/wiki/Two-body_ ... relativity

[MarkBour]

Ok, I think I see what you meant. In a universe with just two moving bodies, there are only three possibilities: the bodies collide; they orbit their common center of mass; or they make a close approach, but then miss each other and never get that close again.

And I suppose in the orbiting case, their orbit won't decay or get larger over time if they are both perfectly rigid.

In the latter case, they're still orbiting their common center of mass. But the orbit is open, not closed. That is, the (Keplerian) orbits have eccentricities greater than or equal to one.

And even if they were the only two bodies in the Universe, and they were in closed (elliptical) orbits around their common center of mass, those orbits would decay because both would be losing angular momentum to gravitational radiation. For most bodies, we're talking a very, very long time. But it's a major factor in the last stages of neutron star or black hole mergers.

Thanks for the nuance. There's much more than I'll ever be able to appreciated here - https://en.wikipedia.org/wiki/Two-body_ ... relativity

Interesting points! I appreciated the follow-up discussion.

In the simulation in the APOD, I'm guessing they "fed" the star to the BH in their initial conditions, so I would still bet that if it were rigid enough to maintain its integrity, it would end up in an orbital configuration. Such as: https://www.eso.org/public/videos/eso1825e/

But of course they purposely sent it in to a point way beyond its strength, so they could watch its demise. I never thought about the term "Roche limit" applied to a star, but of course it does apply just as well. So, they sent it inside the Roche limit.

[Chris Peterson]

In the latter case, they're still orbiting their common center of mass. But the orbit is open, not closed. That is, the (Keplerian) orbits have eccentricities greater than or equal to one.

And even if they were the only two bodies in the Universe, and they were in closed (elliptical) orbits around their common center of mass, those orbits would decay because both would be losing angular momentum to gravitational radiation. For most bodies, we're talking a very, very long time. But it's a major factor in the last stages of neutron star or black hole mergers.

Thanks for the nuance. There's much more than I'll ever be able to appreciated here - https://en.wikipedia.org/wiki/Two-body_ ... relativity

Interesting points! I appreciated the follow-up discussion.

In the simulation in the APOD, I'm guessing they "fed" the star to the BH in their initial conditions, so I would still bet that if it were rigid enough to maintain its integrity, it would end up in an orbital configuration. Such as: https://www.eso.org/public/videos/eso1825e/

But of course they purposely sent it in to a point way beyond its strength, so they could watch its demise. I never thought about the term "Roche limit" applied to a star, but of course it does apply just as well. So, they sent it inside the Roche limit.

The only way it could be "fed" into the simulation where it would end up in orbit around the BH would be if it was already in a closed orbit around it.

[neufer]

...even if they were the only two bodies in the Universe, and they were in closed (elliptical) orbits around their common center of mass, those orbits would decay because both would be losing angular momentum to gravitational radiation. For most bodies, we're talking a very, very long time. But it's a major factor in the last stages of neutron star or black hole mergers.

<<The Hulse–Taylor binary is a binary star system composed of a neutron star and a pulsar (known as PSR 1913+16) which orbit around their common center of mass. It is the first binary pulsar ever discovered.

The pulsar was discovered by Russell Alan Hulse and Joseph Hooton Taylor, Jr., of the University of Massachusetts Amherst in 1974. Using the Arecibo 305m dish, Hulse and Taylor detected pulsed radio emissions and thus identified the source as a pulsar, a rapidly rotating, highly magnetized neutron star. The neutron star rotates on its axis 17 times per second; thus the pulse period is 59 milliseconds.

After timing the radio pulses for some time, Hulse and Taylor noticed that there was a systematic variation in the arrival time of the pulses. Sometimes, the pulses were received a little sooner than expected; sometimes, later than expected. These variations changed in a smooth and repetitive manner, with a period of 7.75 hours. They realized that such behavior is predicted if the pulsar were in a binary orbit with another star, later confirmed to be another neutron star. The pulsar and its neutron star companion both follow elliptical orbits around their common center of mass. The two neutron stars are believed to be nearly equal in mass, about 1.4 solar masses.

The minimum separation at periastron is about 1.1 solar radii; the maximum separation at apastron is 4.8 solar radii. The orientation of periastron changes by about 4.2 degrees per year in direction of the orbital motion (relativistic precession of periastron). In January 1975, it was oriented so that periastron occurred perpendicular to the line of sight from Earth.

The total power of the gravitational waves emitted by this system presently is calculated to be 7.35 × 10²⁴ watts. For comparison, this is 1.9% of the power radiated in light by the Sun. With this comparatively large energy loss due to gravitational radiation, the rate of decrease of orbital period is 76.5 microseconds per year, the rate of decrease of the [~3 solar radii] semimajor axis is 3.5 meters per year, and the calculated lifetime to final inspiral is 300 million years.>>