APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4407
Joined: Fri Dec 04, 2009 3:27 am

APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

Post by APOD Robot » Wed Jul 14, 2021 4:06 am

Image GW200115: Simulation of a Black Hole Merging with a Neutron Star

Explanation: What happens when a black hole destroys a neutron star? Analyses indicate that just such an event created gravitational wave event GW200115, detected in 2020 January by LIGO and Virgo observatories. To better understand the unusual event, the featured visualization was created from a computer simulation. The visualization video starts with the black hole (about 6 times the Sun's mass) and neutron star (about 1.5 times the Sun's mass) circling each other, together emitting an increasing amount of gravitational radiation. The picturesque pattern of gravitational wave emission is shown in blue. The duo spiral together increasingly fast until the neutron star becomes completely absorbed by the black hole. Since the neutron star did not break apart during the collision, little light escaped -- which matches the lack of an observed optical counterpart. The remaining black hole rings briefly, and as that dies down so do the emitted gravitational waves. The 30-second time-lapse video may seem short, but it actually lasts about 1000 times longer than the real merger event.

<< Previous APOD This Day in APOD Next APOD >>

Deathfleer

Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

Post by Deathfleer » Wed Jul 14, 2021 8:49 am

    Are we looking perpendicular to the plane of the orbit of the star?

    De58te
    Science Officer
    Posts: 413
    Joined: Mon Sep 30, 2013 6:35 pm

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by De58te » Wed Jul 14, 2021 10:41 am

    This question is in the what if category.
    What if a giant blue star 7 times the Sun's mass approached and collided with a yellow star 2 times the Sun's mass. (Both stars being on the main sequence burning hydrogen) Would the video be the same? (Except that the stars would be shinning a lot brighter.)

    User avatar
    orin stepanek
    Plutopian
    Posts: 6802
    Joined: Wed Jul 27, 2005 3:41 pm
    Location: Nebraska

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by orin stepanek » Wed Jul 14, 2021 11:41 am

    BHmerger_LIGO_3600.jpg
    From the mass sizes of the Black hole & Neutron star; I take it that
    the Black hole isn't very large! :roll:
    Any how today's lesson was very interesting!
    black-white-cats-yin-yang-70-5824837231803__605.jpg
    Kitties sharing bed to take their nap
    You do not have the required permissions to view the files attached to this post.
    Orin

    Smile today; tomorrow's another day!

    VictorBorun
    Science Officer
    Posts: 313
    Joined: Fri Oct 16, 2020 10:25 pm

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by VictorBorun » Wed Jul 14, 2021 1:34 pm

    I wonder what are the radii of the starring oblects:

    1) a non-rotating black hole, 6.1 solar masses (event horizon, photon orbits sphere)
    2) a non-rotating neutron star, 1.4 solar masses (surface sphere)

    Is the movie in scale at all?

    User avatar
    Fred the Cat
    Theoretic Apothekitty
    Posts: 704
    Joined: Mon Feb 22, 2016 4:09 pm
    AKA: Ron
    Location: Eagle, Idaho

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by Fred the Cat » Wed Jul 14, 2021 2:35 pm

    VictorBorun wrote:
    Wed Jul 14, 2021 1:34 pm
    I wonder what are the radii of the starring oblects:

    1) a non-rotating black hole, 6.1 solar masses (event horizon, photon orbits sphere)
    2) a non-rotating neutron star, 1.4 solar masses (surface sphere)

    Is the movie in scale at all?
    That is one "obvious" question as stated in the link. Today's APOD topic brings up so many other questions to ponder. One that comes to mind, since little light is observed, are there no jets emitted :?:
    Freddy's Felicity "Only ascertain as a cat box survivor"

    User avatar
    neufer
    Vacationer at Tralfamadore
    Posts: 18354
    Joined: Mon Jan 21, 2008 1:57 pm
    Location: Alexandria, Virginia

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by neufer » Wed Jul 14, 2021 2:47 pm

    VictorBorun wrote:
    Wed Jul 14, 2021 1:34 pm

    I wonder what are the radii of the starring oblects:

    1) a non-rotating black hole, 6.1 solar masses (event horizon, photon orbits sphere)
    2) a non-rotating neutron star, 1.4 solar masses (surface sphere)

    Is the movie in scale at all?
    The starring 'oblects' are probably not to scale:
    • 5.7 solar mass BH => Schwarzschild radius of 16.8 km
      1.4 solar mass neutron star => radius of 11.9 km
    https://www.mpg.de/14575466/how-big-is-a-neutron-star wrote:
    “We find that the typical neutron star, which is about 1.4 times as heavy as our Sun has a radius of about 11 kilometers,” says Badri Krishnan, who leads the research team at the AEI Hannover. “Our results limit the radius to likely be somewhere between 10.4 and 11.9 kilometers. This is a factor of two more stringent than previous results.”
    Art Neuendorffer

    kerberos

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by kerberos » Wed Jul 14, 2021 4:23 pm

    Here's what I want to know...Whenever I see things about falling into a black hole, it's always said that an outside observer would never actually see the entity fall in...it would appear frozen right on the event horizon...So, why wouldn't this be the same, and we would just see the Neutron star hovering on the edge?

    Or, is this about the idea that it is still there, and is just smeared across the accretion disk?

    User avatar
    MarkBour
    Subtle Signal
    Posts: 1180
    Joined: Mon Aug 26, 2013 2:44 pm
    Location: Illinois, USA

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by MarkBour » Wed Jul 14, 2021 4:25 pm

    Fred the Cat wrote:
    Wed Jul 14, 2021 2:35 pm
    That is one "obvious" question as stated in the link. Today's APOD topic brings up so many other questions to ponder. One that comes to mind, since little light is observed, are there no jets emitted :?:
    That's a great point. I would think that there must be jets emitted, even if this were all perfectly planar. The radius of the neutron star is comparable to the Schwarzchild radius of the black hole, so a lot of its material would have begun significantly above and below the plane of their mutual orbit.

    Related to that, for a pair of black holes, I imagine that jets might be forbidden, but I could imagine them occurring even then. If there were any jets from a BH-BH merger, that would be very instructive. Of course it might be hard to tell, from any such observation, if the jets came from material in the black holes or were just from material that was in their vicinity. A really outlandish, but fun, idea is that they might emit jets of dark matter.
    Mark Goldfain

    User avatar
    MarkBour
    Subtle Signal
    Posts: 1180
    Joined: Mon Aug 26, 2013 2:44 pm
    Location: Illinois, USA

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by MarkBour » Wed Jul 14, 2021 5:02 pm

    kerberos wrote:
    Wed Jul 14, 2021 4:23 pm
    Here's what I want to know...Whenever I see things about falling into a black hole, it's always said that an outside observer would never actually see the entity fall in...it would appear frozen right on the event horizon...So, why wouldn't this be the same, and we would just see the Neutron star hovering on the edge?

    Or, is this about the idea that it is still there, and is just smeared across the accretion disk?
    I think this is a great question. I find myself tempted to give an answer, based on the limited understanding that I have of this theory. But it's probably better not to try, and to just hope someone will give a helpful answer. Along with your query, I would add related questions:

    For simplicity, assume we're talking about a very small entity, like the size of a single atom. Would the falling entity appear to red-shift as we watched it? As it approached the horizon, even if it were a very luminous object, would it appear to dim? Would its image appear to fade to darkness, simultaneous to it appearing to stop?

    The PBS Space Time guy on YouTube (Matt O'Dowd) sure talks as if he has it all figured out, maybe we could ask him.
    Mark Goldfain

    User avatar
    Fred the Cat
    Theoretic Apothekitty
    Posts: 704
    Joined: Mon Feb 22, 2016 4:09 pm
    AKA: Ron
    Location: Eagle, Idaho

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by Fred the Cat » Wed Jul 14, 2021 9:01 pm

    MarkBour wrote:
    Wed Jul 14, 2021 4:25 pm
    Fred the Cat wrote:
    Wed Jul 14, 2021 2:35 pm
    That is one "obvious" question as stated in the link. Today's APOD topic brings up so many other questions to ponder. One that comes to mind, since little light is observed, are there no jets emitted :?:
    ...emit jets of dark matter.
    Quite fun. They could be called dark waves. :roll:

    You have to admire the naming of current attempts to identify DM candidates. :lol2:
    Last edited by Fred the Cat on Thu Jul 15, 2021 3:54 pm, edited 2 times in total.
    Freddy's Felicity "Only ascertain as a cat box survivor"

    VictorBorun
    Science Officer
    Posts: 313
    Joined: Fri Oct 16, 2020 10:25 pm

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by VictorBorun » Wed Jul 14, 2021 11:17 pm

    neufer wrote:
    Wed Jul 14, 2021 2:47 pm
    • 5.7 solar mass BH => Schwarzschild radius of 16.8 km
      1.4 solar mass neutron star => radius of 11.9 km
    https://www.mpg.de/14575466/how-big-is-a-neutron-star wrote: “We find that the typical neutron star, which is about 1.4 times as heavy as our Sun has a radius of about 11 kilometers,” says Badri Krishnan, who leads the research team at the AEI Hannover. “Our results limit the radius to likely be somewhere between 10.4 and 11.9 kilometers. This is a factor of two more stringent than previous results.”
    Thanks! So after the merging and relaxation the event horizon grows to (5.7+1.4)*16.8/5.7 = 21 km, does it?
    Encompassing the neutron star?
    Which is first tidally stretched, then gradually head to tail gone plaque before the horizon and eaten by the horizon's protuberance reaching the prey?

    VictorBorun
    Science Officer
    Posts: 313
    Joined: Fri Oct 16, 2020 10:25 pm

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by VictorBorun » Thu Jul 15, 2021 1:07 am


    javachip2

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by javachip2 » Thu Jul 15, 2021 8:01 am

    De58te wrote:
    Wed Jul 14, 2021 10:41 am
    This question is in the what if category.
    What if a giant blue star 7 times the Sun's mass approached and collided with a yellow star 2 times the Sun's mass. (Both stars being on the main sequence burning hydrogen) Would the video be the same? (Except that the stars would be shinning a lot brighter.)
    No, the video would be very different. Stellar collisions are rare. If two main sequence stars of 7 and 2 solar masses did merge, they would simply form a larger star of about 9 solar masses. They would not form a black hole or neutron star, because thermonuclear fusion would maintain equilibrium against gravitational contraction. Any gravitational waves radiated in such a merger would be of much lower magnitude than the ones in the video. Also, a stellar merger might take years, rather than the 0.03 seconds in the video.

    User avatar
    MarkBour
    Subtle Signal
    Posts: 1180
    Joined: Mon Aug 26, 2013 2:44 pm
    Location: Illinois, USA

    Re: APOD: GW200115: Simulation of a Black Hole... (2021 Jul 14)

    Post by MarkBour » Fri Jul 16, 2021 4:04 pm

    Fred the Cat wrote:
    Wed Jul 14, 2021 9:01 pm
    Quite fun. They could be called dark waves. :roll:

    You have to admire the naming of current attempts to identify DM candidates. :lol2:
    Thanks, that was indeed a most creative acronym. And I guess these folks are dead serious in their attempts to detect an axion-like particle.
    Mark Goldfain