Chuck Bednar for redOrbit.com – Your Universe Online
Sweeping a laser pointer across the surface of the moon or a passing asteroid can create spots that actually move faster than light, and doing so could reveal previously unknown information about those objects, according to a new study.
As Robert Nemiroff, a physics professor at Michigan Technological University, explained Friday at a meeting of the American Astronomical Society (AAS) in Seattle, sweeping beams of light at high speeds typically begins with a flash known as a “photonic boom.”
These flashes, named because they are directly comparable to sonic booms, could reveal three-dimensional information about the scattering object that was previously unknown. Photonic booms may be detectable on the moon or asteroids, as well as on fast-moving shadows that cast dust clouds near variable stars and on objects illuminated by a pulsar’s rapidly rotating beam.
Nemiroff said that this unusual, theoretical phenomenon could he put to a practical use in space, and that if it can be detected, it could provide unique information to observers. For example, a laser beam could be swept across the surface of an asteroid thousands of time per second. Those flashes could be recorded with a high-speed camera and reveal an asteroid’s surface features.
“The concept, although not proven in practice, is quite intriguing,” said Rosanne Di Stefano, a researcher at the Harvard-Smithsonian Center for Astrophysics. Nemiroff’s study is scheduled to appear in the journal PASA – Publications of the Astronomical Society of Australia.
These photonic booms could also be visible much farther out in the universe, Nemiroff noted. For instance, shadows that are cast by clouds moving between the bright star “R Mon,” which is located in Hubble’s Variable Nebula in the constellation of Monoceros, move so fast that they are capable of creating photonic booms which remain visible for a period of days or even weeks.
The physics behind the photonic boom are linked to the faster-than-light sweep speeds of the illuminating spots and cast shadows, the MTU professor explained. A flash can be seen by an observed when the speed of the scattered spot towards that individual drops from above the speed of light to below it.
This can only happen because the spots contain no mass, meaning that they are capable of moving faster than light and decelerating past the speed of light without violating Einstein’s theory of special relativity.
The specifics of this effect depend upon the interaction that takes place during the time when the light beam travels through the depths of the object. As a result, measuring photonic booms can provide researchers with data on the depth of the scatterer, provided it is not just a flat object. In those cases, no photonic booms would occur.
“Photonic booms happen around us quite frequently – but they are always too brief to notice,” said Nemiroff. “Out in the cosmos they last long enough to notice – but nobody has thought to look for them!”
He added that the light flash from a photonic boom is far different from well-known Cherenkov radiation, which light emitted when a charged object moves faster than the speed of light inside of transparent matter.
—–
Follow redOrbit on Twitter, Facebook, Instagram and Pinterest.
Comments