Photonic Booms Faster-Than-Light Could Unlock Astronomical Secrets

""If you sweep a laser pointer across the Moon fast enough, you can create spots that actually move faster than light. Anyone can do it.

This image depicts Hubble's Variable Nebula.

At a meeting of the American Astronomical Society in Seattle, Wash., today, Robert Nemiroff, a physics professor at Michigan Technological University, reported that this theoretical curiosity may turn out to be practically useful out in the cosmos. When a superluminal sweep occurs, it typically starts with a flash that may reveal previously unknown three-dimensional information about the scattering object.

Flashes, dubbed "photonic booms" because they are directly analogous to sonic booms, may be detectable on the Moon, on passing asteroids, on fast moving shadows cast on reflecting dust clouds near variable stars, and on objects illuminated by the rapidly rotating beam of a pulsar, said Nemiroff, author of a study accepted for publication by the Publications of the Astronomical Society of Australia, with a preliminary version available online at http://arxiv.org/abs/1412.7581. "And if detected, we could learn more about all of these objects," said Nemiroff.

To reveal the size and surface features of asteroids passing near the Earth, a laser beam might be swept across the rock's surface thousands of times a second, with each sweep forcing a harmless but telling photonic boom. The flashes could be recorded with high-speed cameras attached to large telescopes, potentially mapping out major features on the asteroid."The concept, although not proven in practice, is quite intriguing," said Rosanne Di Stefano, a leading researcher at the Harvard-Smithsonian Center for Astrophysics.

Photonic booms could also be seen much farther out in the universe. An example occurs in Hubble's Variable Nebula in the constellation of Monoceros. There, shadows cast by clouds moving between the bright star "R Mon" and reflecting dust move so fast that they might create photonics booms visible even for days or weeks.

The physics that creates the photonic boom is tied to the faster-than-light sweep speeds of the illuminating spots and cast shadows. Specifically, a flash is seen by an observer when the speed of the scattered spot toward the observer drops from above the speed of light to below the speed of light. The phenomenon is possible only because the spots contain no mass and so cannot only move faster than light, but decelerate past the speed of light without violating Einstein's theory of special relativity""

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http://www.innovations-report.com/html/reports/physics-astronomy/photonic-booms-may-help-illuminate-astronomical-secrets.html

Massive Millions Collection of Stars and Galaxies Released from Astronomy Database Data Now Available to the Public

"This set of observations is one of the largest astronomical databases ever assembled," remarked Donald Schneider, Distinguished Professor of Astronomy and Astrophysics at Penn State. Images are online at http://science.psu.edu/news-and-events/2015-news/SDSS1-2015


"The more than 70 terabytes we collected during the third epoch of this survey, SDSS-III, contain information on nearly half-a-billion stars and galaxies, including three-dimensional cosmic structures that formed billions of years before the sun began to shine," Schneider said. "This data release will undoubtedly form the basis for many future scientific investigations." Schneider is the SDSS-III survey coordinator and the project's scientific publication coordinator.

"The most astonishing feature of the SDSS is the breadth of groundbreaking research it enables," said SDSS-III Director Daniel Eisenstein of the Harvard-Smithsonian Center for Astrophysics. "We've searched nearby stars for planets, probed the history of our Milky Way and measured 9 billion years of our universe's accelerated expansion. Our data also provide the first direct probe of the expansion rate of the universe 10 billion years ago."

Niel Brandt, Penn State's Verne M. Willaman Professor of Astronomy and Astrophysics, is the SDSS-III leader of a number of projects investigating the properties of quasars, which are supermassive black holes that are devouring enormous amounts of matter, releasing amazing amounts energy in the process. "SDSS-III consists of four independent surveys," he said. "The fields range from searches for planets around nearby stars, to the chemical and dynamical evolution of our galaxy, to the large-scale structure of our universe."

After a decade of design and construction, the SDSS team began mapping the cosmos in 1998, using the dedicated 2.5-meter Sloan Foundation Telescope at Apache Point Observatory in New Mexico. Each phase of the project has used this telescope, which is equipped with a succession of powerful instruments, for a distinct set of astronomical surveys. SDSS-III started observations in July 2008 and completed its six-year, $45 million program in June 2014. The SDSS-III Collaboration includes 51 member institutions and 1,000 scientists from around the world.

University Released Article:

http://news.psu.edu/story/339942/2015/01/08/research/massive-new-astronomy-database-now-available-public

Dark Matter Mystery Deepens: We Know Less About Dark Matter Than We Did Before," Asserts Lead Author Matt Walker, a Hubble Fellow at the Harvard-Smithsonian Center For Astrophysics.

"""Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data," Walker stated.

Dwarf galaxies are composed of up to 99 percent dark matter and only one percent normal matter like stars. This disparity makes dwarf galaxies ideal targets for astronomers seeking to understand dark matter.

Walker and his co-author Jorge Peñarrubia (University of Cambridge, UK) analyzed the dark matter distribution in two Milky Way neighbors: the Fornax and Sculptor dwarf galaxies. These galaxies hold one million to 10 million stars, compared to about 400 billion in our galaxy. The team measured the locations, speeds and basic chemical compositions of 1500 to 2500 stars.

"Stars in a dwarf galaxy swarm like bees in a beehive instead of moving in nice, circular orbits like a spiral galaxy," explained Peñarrubia. "That makes it much more challenging to determine the distribution of dark matter."

Their data showed that in both cases, the dark matter is distributed uniformly over a relatively large region, several hundred light-years across. This contradicts the prediction that the density of dark matter should increase sharply toward the centers of these galaxies.

"If a dwarf galaxy were a peach, the standard cosmological model says we should find a dark matter 'pit' at the center. Instead, the first two dwarf galaxies we studied are like pitless peaches," said Peñarrubia.

Some have suggested that interactions between normal and dark matter could spread out the dark matter, but current simulations don't indicate that this happens in dwarf galaxies. The new measurements imply that either normal matter affects dark matter more than expected, or dark matter isn't "cold." The team hopes to determine which is true by studying more dwarf galaxies, particularly galaxies with an even higher percentage of dark matter.

The paper discussing this research was accepted for publication in The Astrophysical Journal and is available online.""

http://www.cfa.harvard.edu/news/2011/pr201129.html