Astronomers Find Speed Limit for Whirling Pulsars

Wed Jul 2, 5:27 PM ET

Reckless pulsars -- spinning searchlights in space -- might tear themselves apart if they whirled too fast, but ripples in the cosmic fabric first predicted by Albert Einstein may set a celestial speed limit. That limit is still extremely high, about 760 revolutions per second, astronomers said on July 2, 2003. But scientists figure some of the fastest pulsars could technically go two or three times that speed. Image is a still from a supernova animation of 'Birth of a Pulsar.' (NASA (news - web sites)/Reuters)

I love reading this stuff. I also enjoy watching it on television.

I wish I understood half of it.

Thanks for the post.

You're most welcome.

I wish I could understand half of my telephone bill. ;-)

The satellite kept track of the pulsars' spin rate by watching for thermonuclear explosions on their surfaces. Those blasts last only a few seconds but give off bursts of X-ray light and flicker in a distinctive way that lets astronomers figure out how fast the pulsars are twirling.

Is this what passes for hard science nowadays? This is a load of pseudoscientific mumbo-jumbo. They say "watching" as if to imply the science is harder that it is. It implies someone peering through a telescope. "Detecting" would be a better verb. "Thermonuclear explosions on their surfaces"? The pulsars are thermonuclear reactions themselves. "The blasts last only a few seconds"? But the "flicker" is detected at 600 or so times a second? What correlation is there to the detected pulse and a determination that it is the rotation?

"As the gravitational wave comes to me or my instrument, it actually has the effect of stretching space a little bit in one direction and squashing it in another direction," Barish said. "It goes back and forth between stretching and squashing at the rate of several hundred times a second."

So where's the observational data for that? This guy's been watching too many Star Trek shows.

"I wish I understood half of it."

I love reading this stuff too. I wish they understood half of it. Most of it seems to be conjecture and unconfirmed hypotheses.

Speed limits in outer space too.

I don't want to live anymore.

FRom AP,, same stuff, different writer.

Science - AP

Study: Cosmic Brake Slows Spin of Pulsars

By PAUL RECER, AP Science Writer

WASHINGTON - Pulsars are the fastest spinning stars in the universe — rotating at hundreds of revolutions per second — and they could go twice as fast before flying apart. A new study by NASA (news - web sites) suggests that these exotic stars are held together by gravitational radiation that puts on the brakes.

Observations by NASA's Rossi X-ray Timing Explorer of 11 pulsars found that there seems to be a natural limit on how fast the strange stars can spin, astronomers said Wednesday at a news conference.

"The fastest-spinning pulsars could technically go twice as fast, but something stops them before they break apart," said Deepto Chakrabarty, a Massachusetts Institute of Technology (news - web sites) astronomer and the lead author of a study appearing in the journal Nature.

Chakrabarty called the natural brake "a cosmic speed limit" and said it may be the result of rotational energy being emitted from the stars as gravitational waves.

Pulsars are the remnants stars that were once eight to 20 times bigger than the sun. When their fuel was exhausted, the stars exploded and then collapsed into a very dense body equal to about 1.5 solar masses, but measuring only about 10 miles across.

The collapse starts the pulsar spinning at about 30 turns a second.

If there is a nearby star, the pulsar, with its superior density, will begin pulling material from its stellar companion. As this material spirals into the pulsar, the spin of the star rapidly increases.

In theory, said Chakrabarty, the star could spin up to 3,000 revolutions per second and eventually fly apart.

But in the study, Chakrabarty said the researchers found that the maximum speed for the 11 pulsars analyzed was below 760 revolutions per second, a velocity that approaches about 20 percent of the speed of light.

Pulsars give off beams of energy, such as X-rays, from fixed points on their surface. Since the objects are rapidly spinning, the beams appear to rapidly blink on and off, or pulse. By measuring these pulses, astronomers can estimate the rate of spin.

Chakrabarty said that Lars Bildsten, a University of California, Santa Barbara, astrophysicists, had theorized that the spinning speed of pulsars would be limited because irregularities on the star's surface would allow rotational energy to stream away as gravitational waves.

Bildsten, who took part in a NASA news conference, said the observation by Chakrabarty and others was unusual because it actually supported with observations an astrophysical theory.

"We're usually proven wrong," Bildsten, "so this is kind of exciting."

___

On the Net:

Pulsar study: http://www.gsfc.nasa.gov/topstory/2003/0702pulsarspeed.html

"The pulsars are thermonuclear reactions themselves"

Correction. A pulsar is a super dense ball of neutrons, which is why it's also known as a neutron star. It forms when a supernova explosion compresses the core of the star so much so that the atoms collapse and the electrons and protons merge to form neutrons. No thermonuclear reactions take place inside the pulsar, if the theories are correct, as there is no material remaining that can undergo fusion.

As for the thermonuclear reactions on the surface of the pulsar (caused by gas trapped from other stars), they are seen by telescopes such as the Chandra X-ray telescope and they last long enough so that as they rapidly flicker on and off due to the rotation of the pulsar, the scientists can figure out the rate of rotation.

I agree. Every once in a while it is nice to read something healthy. An attempt at pure understanding. No apparent vice, crime, lies, fraud etc. Sigh!

Is this what passes for hard science nowadays?

To be exact, this would be what passes for journalism nowadays...

That's what I thought the first one was trying to say. ;-)

I got a couple more but I ain't even gonna post 'em now ;-)

Thanks for the post. Einstein was an incredible genius.

Thanks. My daughter loves this stuff.

When I read articles on astrophysics, I can only imagine the genius necessary to 'get it', to theorize and have those theories prove correct.

Some of the more rudimentary mechanics I can understand, but the theoretical/mathematical aspects remind me that I have all the quirks of a tortured genius, without the genius.

Thank you. That makes more sense. But what is there in the observations to indicate that the observed flicker is correlated to the pulsar's rotation? If it is gasses that are drawn into the pulsar's gravity, then it will spiral down at a faster rotational speed than the pulsar rotates just like a satellite orbits the earth at a faster rate than the earth's rotation. Does the flicker always stay the same rate for each pulsar -- never varying?

I've been confused by this stuff all my life; I just don't understand what Einstein's fear of relatives has to do with science.

This is a load of pseudoscientific mumbo-jumbo.

What is your level of expertise, for you to pass such a judgment?

They say "watching" as if to imply the science is harder that it is. It implies someone peering through a telescope. "Detecting" would be a better verb.

I think "watching" is a perfectly good description. In fact, this science is much "harder" than someone peering through the eyepiece of an optical telescope, as the time resolution and sensitivity of a radio telescope are much finer.

"Thermonuclear explosions on their surfaces"? The pulsars are thermonuclear reactions themselves.

That makes no sense.

"The blasts last only a few seconds"? But the "flicker" is detected at 600 or so times a second? What correlation is there to the detected pulse and a determination that it is the rotation?

Suppose you were watching the Earth--yes, "watching", with a radio telescope--from a distant star. Suppose you were looking in a frequency band where there was a particularly powerful radio station. The station isn't always on; for some reason, it only operates for a few weeks at a time, at odd intervals. Over the years, you'd see the signal go on and off. Superimposed over this signal, you'd see the signal go up and down with a period of 24 hours. This "flicker" is caused by the rotation of the Earth: when the transmitter is on the far side of the Earth, it's harder to hear than when it's pointing at you. In the periods when the blast of radio waves is being sent out, you can measure the rotation of the Earth.

It's the same thing with the pulsar. There aren't any radio stations on the surface--so far as we know!--but clumps of matter falling onto the surface of the star (causing huge explosions as they land) serve the same purpose. The radio signals from these explosions, lasting several seconds each, go up and down from the rotation of the star.

So where's the observational data for that?

Although indirect, the measurements from the Hulse-Taylor binary pulsar verify the gravitational radiation predictions of Einstein's Theory of General Relativity to many decimal places. This research was awarded the Nobel Prize for Physics in 1993. The theory dates to 1915, and has withstood many experimental tests since.

This guy's been watching too many Star Trek shows.

As you say, but Barry Barish is also a world-class physicist, and what he says in this case is correct.

Speed limits in outer space too.

But imposed by the laws of nature, not the laws of the nanny state and other assorted ne'er do wells.

Like not spitting in the wind, or redlining an engine for an extended period of time...

*SPINNING PINK MATTER ALERT*
It's really amazing! A spinning (symetrical) mass can give off gravity waves!! I'd really like to know the mechanism involved.
All a spinning electric charge does is create a steady state magnetic field, which does not propagate. A spinning symettrical magnet creates a steady state non propagating electric field.
Gravitational radiation supposedly requires a quadripole moment to radiate (propagate) energy. This would seem to contradict that, in fact it would be a unipolar source of radiation. Could it be the strange dark matter or dark energy at play again?