Over a million miles per hour: NASA’s Chandra catches Pulsar in an X-Ray speed trap

• 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 NASA Chandra X-ray Observatory images of G292.0+1.8 taken in 2006 and 2016.
• Pulsars can form when massive stars run out of fuel, collapse, and explode — leaving behind a rapidly spinning dense object.
• This result may help explain how some pulsars are accelerated to such remarkably high speeds.

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

Pulsars spin fast neutron stars which can form when massive stars run out of fuel, collapse and explode. Sometimes these explosions produce a “kick”, which sent this pulsar through the remnants of the supernova explosion. An inset shows a close-up of this pulsar in Chandra’s X-rays.

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

The team calculated that the pulsar was moving at least 1.4 million miles per hour from the center of the supernova remnant to the lower left corner. This speed is about 30% higher than a previous estimate of the pulsar’s speed which was based on an indirect method, by measuring the distance between the pulsar and the center of the explosion.

The newly determined speed of the pulsar indicates that G292.0+1.8 and its pulsar could be much younger than astronomers previously thought. The researchers estimate that G292.0+1.8 would have exploded about 2,000 years ago as seen from Earth, rather than 3,000 years ago as previously calculated. This new age estimate for G292.0+1.8 is based on extrapolating the pulsar’s position backward in time to coincide with the center of the explosion.

Several civilizations around the globe were recording supernova explosions at this time, opening up the possibility that G292.0+1.8 was directly observed. However, G292.0+1.8 is below the horizon for most northern hemisphere civilizations that might have observed it, and there are no recorded examples of a supernova observed in the southern hemisphere in the direction of G292.0 + 1.8.

Along with finding out more about the age of G292.0+1.8, the research team also looked at how the supernova gave the pulsar its mighty kick. There are two main possibilities, both of which imply that matter is not ejected uniformly by the supernova in all directions. One possibility is that neutrinos products in the explosion are ejected from the explosion asymmetrically, and the other is that the debris from the explosion is ejected asymmetrically. If the material has a preferred direction, the pulsar will be thrown in the opposite direction due to the principle of physics called conservation of momentum.

The amount of neutrino asymmetry needed to explain the high speed of this latter result would be extreme, supporting the explanation that asymmetry in the debris from the explosion kicked the pulsar.

The energy transmitted to the pulsar by this explosion was gigantic. Although it is only about 10 miles in diameter, the mass of the pulsar is 500,000 times that of Earth and it is moving 20 times faster than the speed of Earth orbiting the Sun.

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

Reference: “The Proper Motion of the 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, The 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.