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MARS & SATURN: Mars and Saturn are pleasingly close together in the western sky tonight. Look for the pair, only a few moon-widths apart, in the constellation Gemini after sunset. Saturn looks like a bright yellow star; Mars is dimmer and red, right beside Saturn. Point a small telescope at Saturn and you can easily see the planet's rings. [sky map]
Saturn is 1.4 billion km from Earth. Mars is closer, only 349 million km away. So why is Saturn brighter? Simple. Saturn, a gas giant with bright rings, is 18 times wider than little rocky Mars, so it reflects more sunlight.
VENUS ECLIPSE: On May 21st, sky watchers across Europe saw a rare daytime eclipse of Venus by the crescent Moon. In Hungary, Zsolt Kereszty made this movie of Venus, a thin crescent, splitting in two then disappearing behind the Moon's dark limb.
more images: from Douglas Cooper of Stirling, Scotland; from Wolf Manfred of Köngetried, Bavaria, Germany; from Jörgen Blom of Stockholm, Sweden; from Riccardo Di Nasso of Pisa, Italy; from Rijk-Jan Koppejan of Middelburg, The Netherlands; from Anthony Ayiomamitis of Athens, Greece; from Pete Lawrence of Selsey, West Sussex, UK; from Beom-Seok Yeom of Gyeonggi-do, South Korea; from Vladimi Ladinsky of Moscow, Russia; from Arne Danielsen of Oslo, Norway; from tianjixing.com of Beijing, China.
STRANGE RAINBOW: A severe thunderstorm was approaching Laurel, Maryland, last week when Julie Deth-Rhoden Hutto looked up and saw something strange: a rainbow peeking out from behind a cloud. "The colors were intense at times and had cloud shadows falling back over it," she says "It was an unusual sight." (continued below)
Atmospheric optics expert Les Cowley explains what Julie saw: "This is iridescence in a 'pileus cloud' above the head of the thunder cloud. During the day, warm and moist cumulus clouds billow upward. Sometimes they push a layer of moist air above them. This moist air expands and cools; suddenly, the water vapor condenses forming a misty veil-like layer of water droplets above the thunder cloud. This is the pileus cloud named from the Latin word for cap. Any cloud formed suddenly like this has all its droplets of a similar size. This is an absolutely ideal condition for iridescence, a light diffraction effect by the tiny individual droplets." more images: #1, #2, #3