NASA’s Chandra captures pulsar in X-ray velocity trap

NASA’s Chandra captures pulsar in X-ray velocity trap

The supernova remnant G292.0+1.8 contains a pulsar moving at more than 1 million miles per hour, as shown in the Chandra image and the optical image of the Digital Sky Survey. Pulsars orbit neutron stars rapidly, and neutron stars form when massive stars run out of fuel, collapse, and explode. These explosions sometimes create “shocks” that send the pulsar through the remnants of the supernova explosion. Other images show a close-up of the pulsar in Chandra’s X-rays, which he detected in 2006 and 2016 to measure this impressive speed. The red cross on each panel indicates the position of the pulsar in 2006. Image credits: X-rays: NASA/CXC/SAO/L. Shi et al; Optics: Palomar DSS2

  • one[{” 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 supernova remnant G292.0+1.8 contains a pulsar moving at over a million miles per hour. The image contains data from NASA’s Chandra X-ray Observatory (red, orange, yellow and blue) that was used to make this discovery. X-rays are combined with optical images from the Digitized Sky Survey, an all-sky ground survey.

Pulsars, fast-spinning neutron stars, form when massive stars run out of fuel, collapse, and explode. These explosions sometimes produce “shocks,” which are what caused this pulsar to pass through the remnants of the supernova explosion. The inset shows a close-up view of the pulsar in Chandra X-rays.

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 changes in the pulsar’s position over a 10-year period. The change in source location is negligible because the pulsar is about 20,000 light-years from Earth, but it has traveled about 190 billion kilometers during that time. The researchers were able to measure this by combining high-resolution images from Chandra with precise techniques to verify pulsar coordinates and other X-ray sources using precise positions from the Gaia satellite.

Pulsar positions, 2006 and 2016

Pulsar site, 2006 and 2016. Image credit: X-ray: NASA/CXC/SAO/L. Stone et al.

The team calculated that the pulsar was moving down and left from the center of the supernova remnant at a speed of at least 1.4 million miles per hour. This velocity is about 30 percent higher than previous estimates of the pulsar’s velocity, which were based on an indirect method of measuring the pulsar’s distance from the center of the explosion.

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

At that time, many civilizations around the world were recording supernova explosions, opening the possibility of directly observing G292.0+1.8. However, for most Northern Hemisphere civilizations you might observe, G292.0+1.8 is below the horizon, and no recorded instances of supernovae have been observed in the Southern Hemisphere in the direction of G292.0+1.8.

G292 + 1.8 close-up

Close-up view of the center of the G292+1.8 Chandra image. The direction of the pulsar’s motion (arrow) and the location of the center of the explosion (green ellipse) are shown based on the debris motion seen in the optical data. The position of the pulsar was extrapolated 3000 years ago, and the triangle represents the uncertainty of the induction angle. The coincidence of the induction point with the epicenter of the explosion gives the age of the pulsar and G292 + 1.8 about 2,000 years. The centroid (intersection) of the X-ray elements (Si, S, Ar, Ca) detected in the debris lies opposite the center of motion of the exploding pulsar. The asymmetry of the debris in the upper right corner of the explosion kicked the pulsar into the lower left corner, preserving momentum. Image credits: X-rays: NASA/CXC/SAO/L. Shi et al; Optics: Palomar DSS2

In addition to learning more about the age of G292.0+1.8, the research team also studied how pulsar supernovae can be so powerful. There are two main possibilities, both involving the supernova not ejecting material uniformly in all directions. One possibility is that the neutrinos output in the explosion are ejected asymmetrically from the explosion, and the other possibility is that the fragments produced by the explosion are ejected asymmetrically. If matter had a preferred direction, the pulsar would be pushed in the opposite direction, due to a physical principle called the conservation of momentum.

In the last result, the amount of neutrino asymmetry required to explain the high velocity would be extreme, supporting the explanation that the asymmetry in the blast debris gave the pulsar the impetus.

The energy delivered to the pulsar by this explosion was enormous. Although the pulsar is only about 16 kilometers in diameter, the pulsar is 500,000 times the mass of Earth and orbits 20 times faster than Earth orbits the sun.

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