Cannonball Pulsar speeds its way through space

Astronomers have observed a pulsar travelling through space at immense speeds after a powerful ‘kick from a massive supernova explosion.

Observations using the Very Large Array (orange) reveal the needle-like trail of pulsar J0002+6216 outside the shell of its supernova remnant, shown in an image from the Canadian Galactic Plane Survey. The pulsar escaped the remnant some 5,000 years after the supernova explosion (Jayanne English, University of Manitoba; F. Schinzel et al.; NRAO/AUI/NSF; DRAO/Canadian Galactic Plane Survey; and NASA/IRAS).

Astronomers have used the Very Large Array (VLA) telescopes to find a pulsar speeding away from its presumed birthplace at nearly 700 miles per second, with its trail pointing directly back at the centre of a shell of debris from the supernova explosion that created it.

The discovery provides vital new insights into how pulsars — superdense neutron stars left over after a massive star explodes — can get a speed boost from the explosion.

Frank Schinzel, from the National Radio Astronomy Observatory (NRAO, says: “This pulsar has completely escaped the remnant of debris from the supernova explosion.

“It’s very rare for a pulsar to get enough of a kick for us to see this.”

The pulsar, dubbed PSR J0002+6216, about 6,500 light-years from Earth, was discovered in 2017 by a citizen-science project called Einstein@Home — which uses computer time donated by volunteers to analyze data from NASA’s Fermi Gamma-ray Space Telescope. So far, using more than 10,000 years of computing time, the project has discovered a total of 23 pulsars.

Artist’s animation of Pulsar J0002+6216 speeding away from its birthplace and escaping the shell of debris from the supernova explosion that created it (Sophia Dagnello, NRAO/AUI/NSF).

Radio observations with the VLA clearly show the pulsar outside the supernova remnant, with a tail of shocked particles and magnetic energy some 13 light-years long behind it. The tail points back toward the centre of the supernova remnant — the pulsar is now 53 light-years from the centre of the explosion.

Matthew Kerr, of the Naval Research Laboratory (NRAO), says: “Measuring the pulsar’s motion and tracing it backwards shows that it was born at the centre of the remnant, where the supernova explosion occurred.”

Dale Frail, one of Kerr’s colleagues at the NRAO, adds: “The explosion debris in the supernova remnant, originally expanded faster than the pulsar’s motion.

“However, the debris was slowed by its encounter with the tenuous material in interstellar space, so the pulsar was able to catch up and overtake it.”

The astronomers say that the pulsar has caught up with the shell 5,000 years after the explosion. The system is currently 10,000 years after the explosion, as we see it.

In comparison with previous observations, the pulsar’s speed of nearly 700 miles per second is very fast indeed — the average pulsar speed only about 150 miles per second. Frail says that as a consequence of its speed the pulsar will eventually escape our galaxy — the Milky Way.

Astronomers have long known that pulsars get a kick when born in supernova explosions, but they are still are unsure just how that happens.

As Frail points out: “Numerous mechanisms for producing the kick have been proposed. What we see in PSR J0002+6216 supports the idea that hydrodynamic instabilities in the supernova explosion are responsible for the high velocity of this pulsar.”

Schinzel believes this discovery points to an exciting future for research into similar objects and their origins: “We have more work to do to fully understand what’s going on with this pulsar, and it’s providing an excellent opportunity to improve our knowledge of supernova explosions and pulsars.”