Nasa's Chandra X-ray Observatory has taken a stunning image of the Crab Nebula, the remnant of a stellar explosion seen in 1054.

Sensitive to X-rays from superhot gas, Chandra has revealed something never seen before: a brilliant ring around the nebula's heart.

As particles lose their energy, visible light can be detected in the Crab (Paloma Observatory)

Astronomers know that the stellar wreckage is expanding into space and that at the very heart of the nebula is a tiny, rapidly-spinning, superdense object called a pulsar.

It is the slowing down of this pulsar, which is spinning many times a second, that is powering the nebula, keeping it hot and radiating the X-rays that Chandra sees.

"The inner ring is unique," said Professor Jeff Hester of Arizona State University. "It has never been seen before, and it should tell us a lot about how the energy from the pulsar gets into the nebula. It's like finding the transmission lines between the power plant and the light bulb."

Professor Mal Ruderman of Columbia University, New York, agrees. "The X-rays Chandra sees are the best tracer of where the energy is. With images such as these, we can directly diagnose what is going on."

Knots and wisps

What is going on, according to Dr. Martin Weisskopf, Chandra Project Scientist from Nasa's Marshall Space Flight Center, is awesome. "The Crab pulsar is accelerating particles up to the speed of light and flinging them out into interstellar space at an incredible rate."

The image shows tilted rings or waves of high-energy particles that appear to have been flung outward over the distance of a light year (10 million, million km) from the central pulsar as well as high-energy jets of particles blasting away at right angles to the rings.

The Keck Observatory took this infrared image, which captures particles with even lower energies than visible light

Detailed Hubble Space Telescope images have shown moving knots and wisps around the pulsar, and previous X-ray images have shown the outer parts of the jet and hinted at the ring structure.

But with Chandra's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears.

The Crab Nebula, is one of the most studied objects beyond our Solar System. It is the remnant of a star that was observed to explode in AD 1054 by Chinese astronomers.