Leading Killer Wears Two Faces

Diabetes is the 6th leading cause of death in the United States. About 17 million people (6.2% of the population) have diabetes. But the disease usually wears two faces. Type 1 diabetes affects young people and Type 2 diabetes affects adults. Doctors have determined that the causes are not the same. The effect though, is a manageable, but often ...

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GM: Not For General Motors Anymore

Genetically Modified plants have been given genes from other plants or even other species, that make them better able to resist diseases and pests, or more nutritious, or more productive. The list of ... Continue reading


The Mineral Chalcedony

Chalcedony is a catch all term that includes many well known varieties of cryptocrystalline quartz gemstones. They are found in all 50 States, in many colors and color combinations, and in ... Continue reading


How Sublime

Show of hands. How many of you can't resist playing with dry ice? Dry ice is carbon dioxide frozen to -109.3 degrees F (-78.5 C). Throw a piece in water and it bubbles and boils. Expose a piece to air ... Continue reading


318 Times as Massive as Earth

What is 318 times more massive than Earth? Jupiter, the fifth planet from the Sun (next in line after Earth and Mars). Jupiter is the largest planet in our Solar System. If you decided to take a ... Continue reading


Rossi X-ray Timing Explorer Solves Mystery of Pulsar 'Speed Limit'

RossiXrayTimingExplorerGravitational radiation, ripples in the fabric of space predicted by Albert Einstein, may serve as a cosmic traffic enforcer, protecting reckless pulsars from spinning too fast and blowing apart, according to a report published in the July 3 issue of Nature. Containing the mass of our Sun compressed into a sphere about 10 miles across, pulsars are the core remains of exploded stars. Pulsars are born spinning, but can gain speed by pulling in gas from a neighboring star, reaching spin rates of nearly one revolution per millisecond, or almost 20 percent the speed of light. Scientists have long wondered how these 'millisecond' pulsars keep from accelerating their spin rate and blowing apart. Thanks to observations using the Rossi Explorer, they now speculate that the cause is gravitational radiation.

'Nature has set a speed limit for pulsar spins,' said Prof. Deepto Chakrabarty of the Massachusetts Institute of Technology in Cambridge, lead author on the journal article. 'Just like cars speeding on a highway, the fastest-spinning pulsars could technically go twice as fast, but something stops them before they break apart. It may be gravitational radiation that prevents pulsars from destroying themselves.' The faster a pulsar spins, its spherical shape changes, developing distortions in its crust and allowing it to radiate gravitational waves. Eventually, the pulsar's spin rate balances out when the momentum lost in gravitational radiation is matched by momentum gained when gas is pulled in from the nearby star.

A short burst of X-ray light, emitted by a massive thermonuclear explosion on some pulsars' surface, serves as a direct measure of spin rate. Scientists have studied these 'burst oscillations' from 11 pulsars and have found none spinning faster than 619 times per second. From a statistical analysis of those pulsars, they concluded that pulsars must stay below 760 revolutions per second in order to stay intact. Gravitational radiation has not been directly detected just yet, but the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Hanford, Wash., and in Livingston, La., are expected to make the detection and study of the relationship between pulsars and gravitational radiation much easier.