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  sci-tech > space > story pagecorner  

Telescope finds 'power lines' in stellar remnant

crab nebula
A false color image taken by NASA's Chandra X-ray Observatory of an ionized ring that links intense energy from a central pulsar with the Crab Nebula surrounding it.  

September 21, 1999
Web posted at: 2:04 p.m. EDT (1804 GMT)

In this story:

Pulsars are gigantic dynamos

Progress with instrument problem


By Robin Lloyd
CNN Interactive Senior Writer

(CNN) -- Scientists have found the long-sought "power lines" in the most studied object in the sky that connect a powerful, spinning, collapsed star with the luminous gas remnant around it.

For decades, astronomers have known that the pulsing neutron star somehow transferred its energy at a rate 100,000 times that of our sun's radiation rate to the Crab Nebula surrounding it.

The nebula, about 10 light years across, is a remnant of a stellar explosion that occurred about 1,000 years ago and was so bright that Chinese observers reported seeing it in daylight. A light year is about 6 trillion miles -- the distance light travels in 365 days.

This NASA animation shows an artist's representation of the Chandra telescope moving past the Crab Nebula. The image first shows a composite of Hubble space telescope and Chandra data of the nebula, then reveals simply Chandra's X-ray data and the interior ring.
Quicktime Movie 576k
Star gazing
Clickable Chandra

Now high-resolution images taken by NASA's Chandra X-ray Observatory currently orbiting Earth show a fine ring of ions and gas around the pulsing star exactly where the pulsar's blasts are thought to energize the stellar remnant like the "lights of Las Vegas."

The ring never was fully visible to the less powerful telescopes of the past.

"That ring is where energy from the pulsar is running into the nebula," said Jeff Hester of Arizona State University. "This thing sticks out like a sore thumb. We're finally seeing the place where the pulsar and the larger nebula couple themselves together."

The image shows tilted rings or waves of high-energy particles that appear to have been flung from the central star, as well as high-energy jets of particles blasting away from the neutron star in a direction perpendicular to the spiral.

Astronomers also are intrigued by a "thumbprint" of dark space that impinges on the right edge of the nebula.

Overall, the Chandra image provides data that astrophysicists will use to develop new models of high-energy explosions in the universe, said Martin Weisskopf, Chandra project scientist at NASA's Marshall Space Flight Center in Alabama.

Shuttle astronauts released the $1.5 billion telescope into orbit in July.

Pulsars are gigantic dynamos

Columbia University astronomer Malvin Ruderman said the pulsar can be thought of as an incredibly compact celestial dynamo or generator that powers the nebula around it. There are about 100 million rotating neutron stars in the universe, he said.

This particular pulsar, the size of a small city, spins 33 times a second like a generator on Earth, but it's 10,000 times bigger and its magnetic field is a billion times that of a common generator. It is so dense that a teaspoon full would weigh a billion tons, Hester said.

Weisskopf offered another metaphor, a twirling ice skater that suddenly transfers all her energy to light up the audience around her.

So how does the energy get out to the nebula?

That's still not clear, and the question has baffled scientists who used all manner of telescopes, including the Hubble Space Telescope, to study the Crab Nebula, Weisskopf said.

But at least the ring provides a clue to the path and vehicle for the energy's movement.

The nebula is about 6,000 light years from Earth in the constellation Taurus. The neutron star, discovered in 1968, formed in the seconds before a supernova explosion when gravity crushed the central core of the star to densities 50 trillion times that of lead.

Progress with instrument problem

The Crab Nebula image was taken to calibrate Chandra, or make sure its instruments readings match those returned by other telescopes studying the same object in the past.

During calibration work, engineers found a resolution problem involving the front side of chips on Chandra's spectrometer instrument.

In the past week, engineers have solved the problem by moving the instrument out of focus when the telescope passes through radiation belts that surround Earth. They are unsure why that works but hope to learn more in the coming weeks.

"Since we have done that we have seen no further degradation," Weisskopf said.

If the problem did recur, scientists using the telescope would have to collect data on larger celestial objects in pieces and match them like a patchwork quilt rather than imaging them all at once, he said.

Chandra reveals new features of cosmic explosions
September 21, 1999
Instrument falling short on X-ray telescope
September 15, 1999
Chandra telescope snaps traces of exploded star
September 10, 1999
First Chandra images show stellar explosion, X-ray jet
August 26, 1999
NASA to unveil first Chandra telescope images Thursday
August 24, 1999

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