Astronomers Find Evidence Of Most Powerful Pulsar In Distant Galaxy

Astronomers find evidence of most powerful pulsar in distant Milky Way

The astronomers plan to conduct further observations to learn more about the object


Astronomers using data from the VLA Sky Survey have discovered one of the youngest known neutron stars, possibly as young as just 14 years. The dense remnant of a supernova explosion was revealed when bright radio emissions, propelled by the pulsar’s powerful magnetic field, emerged from behind a thick shell of debris from the explosion.

The object, called VT 1137-0337, is located in a dwarf galaxy 395 million light-years from Earth. It first appeared in a VLASS image taken in January 2018. It did not appear in an image of the same region taken by the VLA’s FIRST Survey in 1998. It continued to appear in subsequent VLASS observations in 2018, 2019, 2020, and 2022.

“What we’re probably seeing is a pulsar wind nebula,” said Dillon Dong, a Caltech graduate who will begin a Jansky Postdoctoral Fellowship at the National Radio Astronomy Observatory (NRAO) later this year. A pulsar wind nebula forms when the powerful magnetic field of a rapidly spinning neutron star accelerates surrounding charged particles to nearly the speed of light.

“Based on its characteristics, this is a very young pulsar — ​​possibly as young as just 14, but no older than 60 to 80,” said Gregg Hallinan, Dong’s Ph.D advisor at Caltech. The scientists reported their findings at the American Astronomical Society meeting in Pasadena, California.

Dong and Hallinan discovered the object in data from VLASS, an NRAO project that began in 2017 to survey the entire sky visible from the VLA — about 80 percent of the sky. Over a period of seven years, VLASS performs three full scans of the sky, with the aim of finding ephemeral objects. The astronomers found VT 1137-0337 in the first VLASS scan from 2018.

Comparing that VLASS scan to data from an earlier VLA sky survey called FIRST revealed 20 particularly luminous temporal objects that could be associated with known galaxies.

“This one stood out because its galaxy is experiencing a burst of star formation, and also because of the characteristics of its radio emission,” Dong said. The galaxy, called SDSS J113706.18-033737.1, is a dwarf galaxy about 100 million times the mass of the Sun.

While studying the features of VT 1137-0337, the astronomers considered several possible explanations, including a supernova, gamma-ray burst or tidal disturbance in which a star is shredded by a supermassive black hole. They concluded that the best explanation is a pulsar wind nebula.

In this scenario, a star much more massive than the sun exploded as a supernova, leaving a neutron star behind. Most of the original star’s mass was blown out as a shell of debris. The neutron star spins rapidly and as its powerful magnetic field sweeps through surrounding space, it accelerates charged particles, causing a strong radio emission.

Initially, the radio emission was hidden from view by the grenade of explosive remains. As that shell expanded, it became less dense until eventually the radio waves from the pulsar wind nebula could pass through it.

“This happened between the FIRST observation in 1998 and the VLASS observation in 2018,” Hallinan said.

Probably the best-known example of a pulsar wind nebula is the Crab Nebula in the constellation Taurus, the result of a supernova that shone brightly in the year 1054. The Crab is easily visible in small telescopes today.

“The object we found appears to be about 10,000 times more energetic than the crab, with a stronger magnetic field,” Dong said. “It’s probably an emerging ‘super crab’,” he added.

While Dong and Hallinan consider VT 1137-0337 to be a pulsar wind nebula, it’s also possible that its magnetic field is strong enough to qualify the neutron star as a magnetar — a class of supermagnetic objects. Magnetars are a leading candidate for the origin of the mysterious Fast Radio Bursts (FRBs) now under intense study.

“In that case, this would be the first magnetar to be caught appearing, and that, too, is extremely exciting,” Dong said.

Indeed, it has been established that some rapid radio bursts are associated with persistent radio sources, the nature of which is also a mystery. They bear a strong resemblance in their properties to VT 1137-0337, but have not shown evidence of strong variability.

“Our discovery of a very similar source being turned on suggests that the radio sources associated with FRBs could also be luminescent pulsar wind nebulae,” Dong said.

The astronomers plan to conduct further observations to learn more about the object and track its behavior over time.

The National Radio Astronomy Observatory is a National Science Foundation facility operated under a collaborative agreement by Associated Universities, Inc.

(Except for the headline, this story has not been edited by NDTV staff and has been published from a syndicated feed.)

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