The Milky Way's fastest observed pulsar is speeding out of the galaxy at more than 670 miles a second, propelled largely by a kick it received at its birth 2.5 million years ago.

Using the Very Long Baseline Array (VLBA), 10 radio telescopes spanning 5,000 miles from Hawaii to the U.S. Virgin Islands, James Cordes, professor of astronomy at Cornell University, his former student Shami Chatterjee, now of the Harvard-Smithsonian Center for Astrophysics, and his colleagues studied the pulsar (a fast-spinning neutron star) B1508+55, about 7,700 light years from Earth. With the ultra-sharp radio vision of the continentwide VLBA, they precisely measured both the distance and the speed of the pulsar.

The team then plotted the star's motion backward to a birthplace among groups of giant stars in the constellation Cygnus, which contains stars so massive they inevitably explode as supernovae.

Commenting on the research, which was published last fall in Astrophysical Journal Letters, Chatterjee said, "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding. This discovery is very difficult for the latest models to explain." Chatterjee is also a Jansky fellow at the National Radio Astronomy Observatory (NRAO).

The VLBA measurements show the pulsar moving at nearly 1,100 kilometers (more than 670 miles) per second. At this speed, it could travel from London to New York in five seconds.

To measure the pulsar's distance, the astronomers had to detect a very slight wobble in its position caused by the Earth's motion around the sun. This enabled them to calculate the pulsar's speed by measuring its motion across the sky.

"The motion we measured with the VLBA The team then plotted the star's motion backward to a birthplace among groups of giant stars in the constellation Cygnus, which contains stars so massive they inevitably explode as supernovae.

Commenting on the research, which was published last fall in Astrophysical Journal Letters, Chatterjee said, "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding. This discovery is very difficult for the latest models to explain." Chatterjee is also a Jansky fellow at the National Radio Astronomy Observatory (NRAO).

The VLBA measurements show the pulsar moving at nearly 1,100 kilometers (more than 670 miles) per second. At this speed, it could travel from London to New York in five seconds.

To measure the pulsar's distance, the astronomers had to detect a very slight wobble in its position caused by the Earth's motion around the sun. This enabled them to calculate the pulsar's speed by measuring its motion across the sky.

"The motion we measured with the VLBA was about equal to watching a home run ball in Boston's Fenway Park from a seat on the moon," Chatterjee said. "However, the pulsar took nearly 22 months to show that much apparent motion. The VLBA is the best possible telescope for tracking such tiny apparent motions."



Source: Cornell University

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