NASA’s Chandra captures pulsar in an X-ray radar trap

NASA’s Chandra captures pulsar in an X-ray radar trap
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The G292.0+1.8 supernova remnant contains a pulsar moving at more than 1 million miles per hour, as seen in the Chandra image along with an optical image from the Digital Sky Survey. Pulsars orbit rapidly around neutron stars, which can form when massive stars run out of fuel, collapse and explode. These explosions sometimes create a “kick” that propels this pulsar through the remnants of a supernova explosion. Additional images show a close-up of this pulsar in X-rays from Chandra, which it discovered in 2006 and 2016 to measure its impressive speed. Red crosses in each panel show the pulsar’s position in 2006. Credit: X-ray: NASA/CXC/SAO/L. Shi et al.; Optical: Palomar DSS2

  • a[{“ attribute=““>pulsar is racing through the debris of an exploded star at a speed of over a million miles per hour.
  • To measure this, researchers compared

    The G292.0+1.8 supernova remnant contains a pulsar moving at over a million miles per hour. This image includes data from NASA’s Chandra X-ray Observatory (red, orange, yellow, and blue) used for this discovery. X-rays are combined with an optical image from the Digitized Sky Survey, a ground-based survey of the entire sky.

    Rapidly spinning pulsars Neutron stars These are formed when massive stars run out of fuel, collapse and explode. These explosions sometimes create a “kick” that caused this pulsar to race through the remnants of the supernova explosion. The inset shows a close-up of this pulsar in X-ray images from Chandra.

    To make this discovery, the researchers compared Chandra images of G292.0+1.8 taken in 2006 and 2016. A pair of complementary images show the change in the pulsar’s position over 10 years. The shift in source location is negligible because the pulsar is about 20,000 light-years from Earth but has traveled about 120 billion miles (190 billion km) in that time period. The researchers were able to measure this by combining high-resolution Chandra images with precise technology to verify the coordinates of the pulsar and other X-ray sources using precise positions from the Gaia satellite.

    Pulsar locations, 2006 and 2016. Credit: X-ray: NASA/CXC/SAO/L. Shi et al.

    The team calculated that the pulsar was moving down-left from the center of the supernova remnant at at least 1.4 million miles per hour. This speed is about 30% faster than the previous estimate of the pulsar’s speed, which was based on an indirect method by measuring how far the pulsar is from the center of the explosion.

    The pulsar’s newly determined velocity suggests that G292.0+1.8 and the pulsar could be much smaller than astronomers previously thought. The researchers estimate that G292.0+1.8 may have erupted around 2,000 years ago as seen from Earth, instead of 3,000 years ago as previously calculated. This new estimate of the age of G292.0+1.8 is based on extrapolating the pulsar’s position in the past to coincide with the blast center.

    Many civilizations around the world were recording supernova explosions at the time, opening up the possibility of directly observing G292.0+1.8. However, G292.0+1.8 is below the horizon for most Northern Hemisphere civilizations you may have observed, and there are no recorded examples of a supernova observed in the Southern Hemisphere toward G292.0+1.8.

    G292 + 1.8 closeup

    Close-up of Chandra’s image center for the G292+ 1.8. The direction of movement of the pulsar (arrow) and the location of the center of the explosion (green oval) are shown based on debris movement in the optical data. The pulsar’s position was extrapolated 3,000 years ago and the triangle shows the uncertainty of the induction angle. Matching the location of the induction with the epicenter of the explosion gives an age of about 2000 years for the pulsar and G292 + 1.8. The center of mass (intersection) of the X-ray elements (Si, S, Ar, Ca) detected in the debris is opposite the explosion center of the moving pulsar. The asymmetry in the debris in the upper right corner of the explosion pushed the pulsar down to the left while maintaining momentum. Photo credit: X-ray: NASA/CXC/SAO/L. Shi et al.; Optical: Palomar DSS2

    In addition to learning more about the age of G292.0+1.8, the research team also studied how the pulsar’s supernova triggered its powerful kick. There are two main possibilities, both of which are that material from the supernova is not being ejected evenly in all directions. One possibility is that the neutrinos ejected in the explosion are ejected asymmetrically from the blast, the other is that the debris produced by the blast is ejected asymmetrically. If matter had a preferred orientation, the pulsar would be pushed in the opposite direction, due to a physical principle called conservation of momentum.

    The amount of neutrino asymmetry that would be required to explain the high velocity in this last result would be extreme and supports the interpretation that the asymmetry in the debris from the explosion gave the pulsar its kick.

    The energy transferred to the pulsar by this explosion was enormous. Although the pulsar is only about 10 miles across, the pulsar has a mass 500,000 times that of Earth and is moving 20 times faster than the speed of Earth orbiting the sun.

    The latest work by Xi Long and Paul Plucinksky (Astrophysics Center | Harvard & Smithsonian) on G292.0+1.8 was presented at the 240th meeting of the American Astronomical Society in Pasadena, California. The findings are also discussed in an article accepted for publication in the Astrophysical Journal. The other authors of the paper are Daniel Patnaud and Terrence Gaetz, both from the Center for Astrophysics.

    Reference: “Proper motion of pulsar J1124-5916 in the galactic supernova remnant G292.0 + 1.8” by Xi Long, Daniel J. Patnaude, Paul P. Plucinsky and Terrance J. Gaetz, Accepted, Astrophysical Journal.
    arXiv: 2205.07951

    NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts and flight operations from Burlington, Massachusetts.

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