UAlberta astronomer tapped for expertise on NASA pulsar discovery

The University of Alberta's Jeanette Gladstone, a world-leading astrophysics researcher, weighs in on the surprising discovery of the brightest pulsar ever recorded.

News Staff - 16 October 2014

(Edmonton) Astronomers have found a pulsating, dead star beaming with the energy of about 10 million suns. This is the brightest pulsar-a dense stellar remnant left over from a supernova explosion-ever recorded. The discovery was made with NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR.

Pulsars belong to a class of stars called neutron stars. Like black holes, neutron stars are the burnt-out cores of exploded stars, but puny in mass by comparison. Pulsars send out beams of radiation ranging from radio waves to ultra-high-energy gamma rays. As the star spins, these beams intercept Earth like lighthouse beacons, producing a pulsed signal.

The surprising discovery is helping astronomers better understand mysterious sources of blinding X-rays, called ultraluminous X-ray sources (ULXs). They also are suspected to be the long-sought-after "medium-size" black holes-missing links between smaller, stellar-size black holes and the gargantuan ones that dominate the hearts of most galaxies. Until now, all ULXs were thought to be black holes, but new data from NuSTAR show at least one ULX, about 12 million light-years away in the galaxy Messier 82 (M82), is actually a pulsar.

Jeanette Gladstone, formerly a post-doctoral fellow in the University of Alberta's Department of Physics and a world leader in ULX research, was asked by NASA to comment as an external expert on the finding.

"We were starting to settle on the opinion that these [ULXs] were black holes in an extreme state, but this one is smaller and even more extreme than we thought," she says.

"We thought the question was, how massive are these black holes? Are they smaller, stellar remnant black holes eating at extreme rates? Or are they intermediate-mass black holes-the missing link between the smaller sources we see scattered around galaxies and the gargantuan supermassive black holes found in galaxy centres?" Gladstone explains. "Yet here we have a neutron star, much smaller in mass, but on a massive black hole's diet. It's competition eating to the extreme."

Looking at the bigger picture, Gladstone believes this discovery could significantly change our understanding about the rapid growth of black holes in the early universe, shedding light on critical topics including galaxy formation and the evolution of the universe.

Gladstone has recently taken a public outreach role for the U of A observatory that hosts more than 4,000 community visitors and school groups each year. In her new role, she will be working to provide outreach programming to school groups and the public, including the ongoing Thursday viewings at lunchtime and in the evenings.

"We want to give you a chance to see the wonders of astronomy, to explore the night sky and chat with an astronomer. So come along and enjoy the fun."