'Lord of the Rings' spotted in Milky Way

Astronomers using NASA's Chandra X-ray Observatory have discovered the largest and brightest set of rings from X-ray light echoes ever observed.

These extraordinary rings, produced by an intense flare from a neutron star, provide astronomers a rare chance to determine how far across the Milky Way galaxy the star is from the Earth.

The rings appear as circles around Circinus X-1, a double star system in the plane of our galaxy containing a neutron star, the dense remnant of a massive star pulverised in a supernova explosion.

The neutron star is in orbit with another massive star, and is shrouded by thick clouds of interstellar gas and dust.

"We like to call this system the 'Lord of the Rings', but this one has nothing to do with Sauron," said co-author Michael Burton of the University of New South Wales in Sydney.

"The beautiful match between the Chandra X-ray rings and the Mopra radio images of the different clouds is really a first in astronomy," Burton said.

"It's really hard to get accurate distance measurements in astronomy and we only have a handful of methods," said Sebastian Heinz of the University of Wisconsin in Madison, who led the study.

"But just as bats use sonar to triangulate their location, we can use the X-rays from Circinus X-1 to figure out exactly where it is," Heinz said.

The light echo shows that Circinus X-1 is located about 30,700 light years from Earth, and settles the difference in results published in prior studies.

The detection and characterization of the rings required the unique capabilities of Chandra -- the ability to detect fine details combined with sensitivity to faint signals.

The researchers also determined that the speed of the jet of high-energy particles produced by the system is at least 99.9 percent of the speed of the light.

This extreme velocity is usually associated with jets produced by a black hole.

These results were published in The Astrophysical Journal.