SOUTHERN METEOR SHOWER: Earth is entering a stream of dusty debris from Halley's Comet, the source of the annual eta Aquarid meteor shower. Forecasters expect the shower to peak on Wednesday morning, May 6th, with as many as 85 meteors per hour over the southern hemisphere. Rates in the northern hemisphere will be less, 20 to 30 per hour. The best time to look is during the dark moonless hour before local sunrise.
LUNAR X-MOVIE: On Friday night, May 1st, a luminous X appeared on the Moon. "We saw it easily through our 5-inch telescope," report Enzo De Bernardini and Rodolfo Ferraiuolo of San Rafael, Argentina. Using a digital camera attached to the telescope's eyepiece, they made a movie of the X emerging from the shadows:
Click to view the movie
What is this "Lunar X"? Once a month when the sun rises over Crater Werner in the Moon's southern hemisphere, sunlight floods the region's high terrain and makes a luminous criss-cross shape. "Observing the X has little or no scientific value. It is a trick of the light. But the effect is striking, and it is exciting to rediscover each month," writes David Chapman in "A Fleeting Vision near Crater Werner" (Journal of the Royal Astronomical Society of Canada, Vol. 101, Issue 2, p.51).
The next apparition: May 31, 2009. Mark your calendar with an X.
MAINE SUNRISE: In Cape Elizabeth, Maine, the last sunrise of April was a doozy. Standing on the shore of Casco Bay on April 30th, photographer John Stetson captured this sequence of images:
"Our sun can appear in interesting shapes," says Stetson with understatement. "This is a result of Earth's atmosphere acting as a lens to refract the light that we see."
Atmospheric optics expert Les Cowley elaborates: "In John’s sequence the solar image struggles upwards through multiple atmospheric temperature inversion layers. Each has unusually cooler air trapped beneath warmer, and each splits the sun’s light into two images – one rising, one inverted and sinking. Where they overlap we see a bulging 'spare tire'! Such mirages are the stuff of a special type of green flash, a 'mock-mirage' that is frequently photographed but is very rarely seen with the unaided eye."
A close-up look at the distorted sun reveals even more: "John has caught several instances of the green upper rim flash and lower 'red flashes' where the last fragment of an image caught between inversion layers is reddened and vertically stretched."
What kind of sunrises will May bring? Stay tuned.
April 2009 Aurora Gallery
[previous Aprils: 2008, 2007, 2006, 2005, 2004, 2003, 2002]
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