AURORA WATCH: Sporadic auroras are likely tonight and tomorrow over Alaska, Canada and Scandinavia. The cause: a high speed solar wind stream blowing around Earth. Mushers, look up!
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ROSETTA FLYBY: The European Space Agency's Rosetta probe streaked past Earth on March 4th, only 1900 km from our planet. The close encounter was a "gravity assist maneuver" slingshotting the spacecraft on its way to land on a comet.
Astronomers at the CAST Observatory in Italy caught the flyby on film:
At closest approach, Rosetta was only about as bright as a 9th magnitude star--much too dim for the human eye. Nevertheless, many amateur astronomers were able to photograph the spacecraft using CCD cameras and backyard telescopes.
more images: from Christian Riou at La Seyne sur mer, France; from Gianluca Masi, Franco Mallia and Roger Wilcox using the SoTIE telescope at Las Campanas, Chile; from V. Terno and W. Borghini of Casasco (AL), Italy;
LOOMING LIGHTHOUSE: Walking along a beach in France on Feb. 28th, Laurent Laveder watched in amazement as an island materialized above the waves. First a lighthouse appeared, then the ground beneath it--all floating in midair!
It was, of course, a mirage:
Atmospheric optics expert Les Cowley explains: "We have all seen mirages over a hot road. Air near the road heats, expands and becomes less dense. Down-going light rays bend upwards again as they pass between the different density layers to make upside down images of vehicles." There's no road in Laveder's image, but the sea serves the same purpose: warm water heated the cold morning air just above it. The warm air, in turn, bent light rays from the island in surprising ways.
"Sailors had their own words for mirage effects," adds Cowley. "Ships raised up over the horizon were 'looming.' Vertically stretched images were 'towering' and squashed ones 'stooping.'" Click here to view an animation of Laveder's looming lighthouse.