                        Astronomy Picture of the Day

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      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2021 July 14

      GW200115: Simulation of a Black Hole Merging with a Neutron Star
    Video Credit: Simulation: S.V. Chaurasia (Stockholm U.), T. Dietrich
                            (Potsdam U. & MPIGP);
       Visualization: T. Dietrich (Potsdam U. & MPIGP), N. Fischer, S.
                        Ossokine, H. Pfeiffer (MPIGP)

   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.

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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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