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5 December 2013 11:26 am ,
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Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Sizing Up a Neutron Star
9 September 2004 (All day)
NEW ORLEANS, LOUISIANA--A neutron star seems stranger than fiction, with more than a sun's worth of mass crushed into a sphere weighing 3 billion tons per teaspoon. Now, the first solid measurement of a neutron star's size has made that tale more real. The diameter--about 23 kilometers--matches predictions for a star consisting of a dense soup of neutrons rather than more exotic particles.
Neutron stars are the corpses of huge stars that die in supernovas. Theorists think they contain the densest matter we can see, because anything more compact would collapse into a black hole. Popular models call for a superfluid inferno of nearly pure neutrons, about 20 kilometers wide and 1.5 times as massive as our sun. Some physicists have proposed that the objects could be smaller if their cores contain an even denser brew of quarks, Bose-Einstein condensates, or nuggets of "strange matter." But neutron stars are so far away that gauging their size has been impossible.
In the new study, graduate student Adam Villarreal of the University of Arizona, Tucson, and astrophysicist Tod Strohmayer of NASA's Goddard Space Flight Center in Greenbelt, Maryland, examined light from a neutron star that pulls gas from a companion. The gas piles up on the spinning star and ignites in fierce bursts every few hours. Peering from halfway across the Milky Way, a NASA x-ray satellite detected 38 such bursts during occasional observations over 7 years. When the researchers combined all bursts into a single statistical analysis, they concluded that the explosions flicker 45 times every second. The neutron star must spin at that rate, Villarreal and Strohmayer reported here on 8 September at a meeting of the American Astronomical Society's High-Energy Astrophysics Division.
Then, the team relied on an estimate of the strength of the neutron star's gravitational field, published in 2002 by other scientists. That measurement yielded a wide range of plausible sizes and masses. The new spin rate limits the diameter to between 19 and 30 kilometers, with a most likely value of 23 kilometers, Strohmayer says.
The deductions are complex but reliable, says astrophysicist M. Coleman Miller of the University of Maryland, College Park. "This does constrain the radius in the most interesting range," Miller says. "A 'strange matter' star would have to be much smaller than this."