Charleston WV Gazette wrote:January 17, 2006
Green Bank Telescope scores big finds in space
Fastest pulsar, ‘Slinky’ magnetics, ‘superbubble’ of hydrogen ID’d
By Rick Steelhammer
Staff writer
The fastest-spinning pulsar ever observed, a magnetic field coiled around a gas cloud like a “giant, magnetic Slinky” and a “superbubble” of hydrogen gas rising 10,000 light years above the Milky Way galaxy are among recent discoveries made using the Green Bank Telescope.
The three discoveries were announced last week during an American Astronomical Society meeting in Washington, D.C.
The Green Bank Telescope, the world’s largest fully steerable radio telescope, is operated by National Radio Astronomy Observatory in Pocahontas County. It’s construction began in 1991 and was completed in 2000.
The fast-spinning pulsar was discovered about 28,000 light years from Earth in a globular cluster of stars in the constellation Sagittarius.
Twenty miles in diameter, the newly discovered pulsar spins at a rate of 716 times per second, easily beating the previous rotational speed record of 642 times per second by a pulsar discovered in 1982. By comparison, the fastest speeds for common kitchen blenders range from 250 to 500 revolutions per second.
“Our observations of such a rapidly rotating star set a hard upper limit on its size, and hence, how dense the star can be,” said Jason Hessels, a graduate student at McGill University in Montreal, a member of the research team that discovered the fast-spinning “millisecond” pulsar.
Hessels and his colleagues maintain that the object’s fast rotational speed means that it cannot be any larger than about 20 miles across. “If it were any larger, material from the surface would be flung into orbit around the star,” said Hessels.
Pulsars are spinning neutron stars that sling “lighthouse beams” of radio waves or light around as they spin, according to the NRAO. Neutron stars are what are left after massive stars explode at the end of their “normal” lives.
So far, Hessels and his colleagues have found 30 new fast-spinning “millisecond” pulsars in the same Sagittarian star cluster. Other astronomers have observed three others pulsars there, bringing the total for that star cluster to 33, and making it the site of the largest known concentration of pulsars.
The great sensitivity of the giant, 100-meter diameter Green Bank Telescope and the attachment of a special signal processor called the “Pulsar Spigot” made possible the discovery of so many fast-spinning pulsars in the Sagittarian star cluster known as Terzan 5.
“We think there are many more pulsars to be found in Terzan 5 and other clusters, and given that the fast ones are often hidden by eclipses, some of them may be spinning even faster than this new one,” said Scott Ransom, an astronomer at the NRAO and one of Hessels’ collaborators.
Another discovery announced last week was what might be the first coil-shaped magnetic field ever seen in interstellar space. It was observed wrapped around a gas cloud in the constellation Orion.
“You can think of this structure as a giant, magnetic Slinky wrapped around a long, finger-like interstellar cloud,” said Timothy Robishaw, a graduate student in astronomy at the University of California at Berkeley. “The magnetic field lines are like stretched rubber bands — the tension squeezes the cloud into its filamentary shape.”
Astronomers have long hoped to find specific cases in which magnetic forces directly influence the shape of interstellar clouds, but according to Robishaw, “telescopes just haven’t been up to the task — until now.”
Robishaw and his colleagues observed hydrogen radio waves across the Orion Molecular Cloud, a star nursery 1,750 light years from Earth. They found that the magnetic field reversed its direction, pointing toward Earth on the upper side of the cloud, and away from it on the bottom, and used previous observations of starlight to see how the magnetic field in front of the cloud is oriented.
When all measurements were combined, the picture emerged of a corkscrew pattern wrapping around the cloud.
“Measuring magnetic fields in space is a very difficult task,” said Robishaw, “because the field in interstellar space is very weak and because there are systematic measurements that can produce erroneous results.”
But the Green Bank Telescope is located in the 13,000-square-mile National Radio Quiet Zone, allowing astronomers to observe weaker radio waves coming from space without interference from man-made sources.
According to Robishaw and his associates, the Green Bank Telescope might be the only radio telescope capable of reliably detecting weak magnetic fields.
The third Green Bank-related discovery announced last week involved observations made 23,000 light years from Earth, where a huge “superbubble” of hydrogen gas was observed rising nearly 10,000 light years above the plane of our Milky Way galaxy.
Astronomers from the National Radio Observatory and Ohio University discovered the huge bubble by combining numerous smaller images made with the Green Bank Telescope into one large image, then adding images of ionized hydrogen in the region made by a University of Wisconsin optical telescope on Kitt Peak, Ariz.
“We see that all the hydrogen gas in this region of the galaxy is disturbed, with many smaller outflows closer to the plane of the galaxy and then a giant plume of gas that forms a sort of cap on the whole thing,” said Yuri Pidopryhora of the NRAO and Ohio University.
Ionized hydrogen, with atoms violently stripped of their electrons, seems to fill the interior of the superbubble, while neutral hydrogen forms its walls and cap, according to the NRAO.
The Milky Way, about 100,000 light years across, somewhat resembles a vast dinner plate, with most of its stars and gases lingering in a flat disk.
“Gas driven outward from the plane of the galaxy’s disk has been seen many times before,” said NRAO astronomer Jay Lockman, “but this superbubble is particularly large. The eruption that drove this much mass so far out of the plane has to have been unusually violent.”
More information on the discoveries can by found online by accessing the “news” sections at www.nrao.edu and www.berkeley.edu.
New Pulsars, Slinkys, and SuperBubbles in Space
Moderator: Alyrium Denryle
New Pulsars, Slinkys, and SuperBubbles in Space
Me: Nope, that's why I have you around to tell me.
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Goddamn thing spins faster than my blender too...
I'm somewhat amazed as to how something like that can spin so fast. 20 miles in diameter would probably be a less massive pulsar (IIRC they get smaller as they get more massive, due to gravity squeezing them tighter) 20 x pi = 62.8 mile radius x 716 rotations per second =45000 miles per second.
That's roughly a quarter the speed of light.
I'm somewhat amazed as to how something like that can spin so fast. 20 miles in diameter would probably be a less massive pulsar (IIRC they get smaller as they get more massive, due to gravity squeezing them tighter) 20 x pi = 62.8 mile radius x 716 rotations per second =45000 miles per second.
That's roughly a quarter the speed of light.
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