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‘Curiosity’ Can Be Positioned With Eclipses

December 20, 2012 Leave a comment

Phobos in transit last September. Credit: NASA/JPL-Caltech/MSSS

Phobos in transit last September. Credit: NASA/JPL-Caltech/MSSS

Observations from ‘Curiosity’ when Mars’ moon Phobos crosses in front of the sun, like in September, help us to understand exactly where the rover is on the red planet. Researchers at the Complutense University of Madrid (Spain) have developed a method for achieving precisely this.

The exact location of Curiosity on the surface of Mars is determined using data transmitted from its antennas as well as the space probes that orbit the red planet. It is very unlikely that these systems would fail but in such an eventuality there would be an alternative for determining the location of the rover: ‘ask it’ what eclipses it sees.

“Observing these events offers an independent method for determining the coordinates of Curiosity,” explains Gonzalo Barderas, researcher at the Complutense University of Madrid (UCM) and coauthor of the study.

Full Story: http://alphagalileo.org/ViewItem.aspx?ItemId=126958&CultureCode=en

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Study Reveals A Remarkable Symmetry In Black Hole Jets

December 20, 2012 Leave a comment

Plot of jet power and Brightness. Credit: NASA's Goddard Space Flight Center

Plot of jet power and Brightness. Credit: NASA’s Goddard Space Flight Center

Black holes range from modest objects formed when individual stars end their lives to behemoths billions of times more massive that rule the centers of galaxies. A new study using data from NASA’s Swift satellite and Fermi Gamma-ray Space Telescope shows that high-speed jets launched from active black holes possess fundamental similarities regardless of mass, age or environment. The result provides a tantalizing hint that common physical processes are at work.

“What we’re seeing is that once any black hole produces a jet, the same fixed fraction of energy generates the gamma-ray light we observe with Fermi and Swift,” said lead researcher Rodrigo Nemmen, a NASA Postdoctoral Program (NPP) fellow at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Gas falling toward a black hole spirals inward and piles up into an accretion disk, where it becomes compressed and heated. Near the inner edge of the disk, on the threshold of the black hole’s event horizon — the point of no return — some of the material becomes accelerated and races outward as a pair of jets flowing in opposite directions along the black hole’s spin axis. These jets contain particles moving at nearly the speed of light, which produce gamma rays — the most extreme form of light — when they interact.

Full Story: http://www.nasa.gov/topics/universe/features/black-hole-symmetry.html