Neutron star jets move at one-third the speed of light

In a world first, the ultra-fast speeds of neutron stars’ powerful jets have been recorded. They have been measured to move at 114,000 km per second – a third of the speed of light.

The measurements were taken using data from the CSIRO’s Australia Telescope Compact Array (ATCA) and the European Space Agency’s Integral observatory. The results are published today in Nature.

Telescope dishes under stars milky way night sky
The Australia Telescope Compact Array, CSIRO. Credit: Alex Cherney.

Neutron stars are among the densest objects in the universe. They form when a supergiant star, 10–25 times the mass of our Sun, runs out of fuel and its core collapses on itself. The neutron star is only a few tens of kilometres across, but weighs 1–3 times as much as the Sun. A single teaspoon of neutron star material weighs about a trillion kilograms.

Because they are so dense, neutron stars have an immense gravitational pull. Sometimes they pull matter in from other nearby stars. This can cause thermonuclear explosions which shoots matter out into space.

Until now, virtually nothing has been known about these jets, including their speed.

In the latest study, the jets were detected by Integral and tracked by ATCA to determine their speed.

“The explosion tells us when the enhanced jets were launched, and we simply time them as they move downstream – just like we would time a 100m sprinter as they move between the starting blocks and the finish line,” says co-author Professor James Miller-Jones, from Western Australia’s Curtin University node of the International Centre for Radio Astronomy Research.

“Radio telescopes are extremely versatile in the research they can do,” says leader of ATCA operations Dr Jamie Stevens.

“Five of ATCA’s six dishes, for instance, take on different configurations by moving along a track. It can be used to look at everything from nearby objects in our galaxy to some of the most distant objects in the universe,” adds Stevens, who is not an author on the recent paper.

“The sensitivity and stability of ATCA allowed this research team to observe rapid changes in the neutron star’s surroundings over 3 days,” says Stevens. “This new method will help astronomers to better understand jets in many different environments and the complex events that build our universe.”

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