New gamma-ray eyes spot hidden pulsars
NASA’s new Fermi gamma-ray telescope has captured the faint gamma-ray glimmer of pulsars invisible to radio telescopes. The enhanced ability to detect pulsars may help theorists flesh out the life stories of massive stars.
Pulsars are spinning neutron stars, the dense and fiercely magnetized remnants of massive stars that underwent gravitational collapse. Astronomers can observe them with a radio telescope only when the slender streams of radio waves broadcast from their magnetic poles point Earthward. The newly identified pulsars appear to emit gamma-rays in broad plumes originating in their intense magnetic atmospheres well above the neutron stars’ surfaces.
The new pulsars weren’t simple to spot. To detect periodic patterns in emissions from extremely faint objects rotating at an unknown rate, a team led by the Santa Cruz Institute for Particle Physics (SCIPP) ran five months of data through a series of brute force guess-and-check calculations. Their computations turned up 16 pulsars rotating between 2 and 20 times per second (Science, DOI: 10.1126/science.1175558). Since then, they have identified at least 8 more. The newly discovered pulsars are 10,000 to 100,000 years old, young by astronomical standards.
“Certainly there are a lot that we haven’t seen,” says Robert Johnson, the SCIPP physicist who designed the telescope’s gamma-ray sensors. Astronomers have already identified more than 1800 radio pulsars, but Johnson said the new gamma-ray telescope may double the number of pulsars they can detect.
Caption: New pulsars: blink and you’ll miss them.
Showing posts with label short. Show all posts
Showing posts with label short. Show all posts
Tuesday, October 27, 2009
Tuesday, October 20, 2009
in the style of Smithsonian's Wild Life
Timed Flight
How do tiny monarch butterflies migrate more than 2,000 miles without a map and end up in the same grove of fir trees in central Mexico, year after year? They navigate by the sun, just as the Vikings did. The monarchs’ internal sun compass needs a clock to work correctly because the sun is “a moving target, and butterflies need to compensate for that movement,” says Steven Reppert of the University of Massachusetts. Until recently, scientists assumed that butterflies navigated with a light-sensitive clock built into their brains. Reppert and his colleagues discovered that monarchs have two such clocks – and that they navigate with the one in their antennae.
The researchers put tiny leashes on the monarchs and let them take wing in an outdoor flight simulator. Normal butterflies flew southwest, toward Mexico. Butterflies with their antennae snipped off couldn’t orient properly and took off every which way. Painting the monarchs’ antennae black didn’t affect their brain clocks, but a few days without time cues from the sun set the butterflies and their antenna clocks adrift. Bees, ants, and other insects that navigate by the sun may rely on antenna clocks, too.
How do tiny monarch butterflies migrate more than 2,000 miles without a map and end up in the same grove of fir trees in central Mexico, year after year? They navigate by the sun, just as the Vikings did. The monarchs’ internal sun compass needs a clock to work correctly because the sun is “a moving target, and butterflies need to compensate for that movement,” says Steven Reppert of the University of Massachusetts. Until recently, scientists assumed that butterflies navigated with a light-sensitive clock built into their brains. Reppert and his colleagues discovered that monarchs have two such clocks – and that they navigate with the one in their antennae.
The researchers put tiny leashes on the monarchs and let them take wing in an outdoor flight simulator. Normal butterflies flew southwest, toward Mexico. Butterflies with their antennae snipped off couldn’t orient properly and took off every which way. Painting the monarchs’ antennae black didn’t affect their brain clocks, but a few days without time cues from the sun set the butterflies and their antenna clocks adrift. Bees, ants, and other insects that navigate by the sun may rely on antenna clocks, too.
Tuesday, October 13, 2009
in the style of New Scientist expert Q&A
How does ultraviolet light kill microbes in drinking water?
-J. Welsh, Santa Cruz, Calif.
Sandra Chung, who wrote her master’s thesis on microbial drinking water quality at the University of North Carolina School of Public Health, shines a spotlight on waterborne germs:
Many municipal wastewater treatment plants use ultraviolet, or UV, light to disinfect wastewater. The particles in raw sewage absorb or scatter UV light and make it less effective, so UV disinfection usually happens after crude steps like settling and filtration remove most of the solids from the water. UV light disinfects by penetrating the outer membranes of bacteria and viruses and frying the DNA inside. Massive DNA damage kills the microbes or prevents them from reproducing; either way, they’re unlikely to make you sick.
UV light is simpler to use than chlorine, and it doesn’t change the way water tastes or smells. But it’s expensive and requires a lot of energy to do on a large scale. If you have time to spare in a sunny climate, you can leave drinking water in clear plastic bottles on a hot tin roof or other reflective surface. After six or more hours in direct sunlight, a healthy dose of solar UV and heat should kill most of the harmful bacteria in the water.
-J. Welsh, Santa Cruz, Calif.
Sandra Chung, who wrote her master’s thesis on microbial drinking water quality at the University of North Carolina School of Public Health, shines a spotlight on waterborne germs:
Many municipal wastewater treatment plants use ultraviolet, or UV, light to disinfect wastewater. The particles in raw sewage absorb or scatter UV light and make it less effective, so UV disinfection usually happens after crude steps like settling and filtration remove most of the solids from the water. UV light disinfects by penetrating the outer membranes of bacteria and viruses and frying the DNA inside. Massive DNA damage kills the microbes or prevents them from reproducing; either way, they’re unlikely to make you sick.
UV light is simpler to use than chlorine, and it doesn’t change the way water tastes or smells. But it’s expensive and requires a lot of energy to do on a large scale. If you have time to spare in a sunny climate, you can leave drinking water in clear plastic bottles on a hot tin roof or other reflective surface. After six or more hours in direct sunlight, a healthy dose of solar UV and heat should kill most of the harmful bacteria in the water.
Subscribe to:
Posts (Atom)
