Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 March 20 
Posted on 03/20/2004 3:49:56 AM PST by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 March 20
Explanation: Twice a year, at the Spring and Fall equinox, the Sun rises due east. In an emphatic demonstration of this celestial alignment, photographer Joe Orman recorded this inspiring image of the Sun rising exactly along the east-west oriented Western Canal, in Tempe,Arizona, USA. But he waited until March 21st, one day after the northern Spring equinox in 2001, to photograph the striking view. Why was the rising Sun due east one day after the equinox? At Tempe's latitude the Sun rises at an angle, arcing southward as it climbs above the horizon. Because the distant mountains hide the true horizon, the Sun shifts slightly southward by the time it clears the mountain tops. Waiting 24 hours allowed the Sun to rise just north of east and arc back to an exactly eastern alignment for the photo. Today's equinox finds the Sun on the celestial equator at 0649 Universal Time.
ASTEROID FLYBY: On March 18th, asteroid 2004 FH flew past Earth only 43,000 km from our planet's surface. There was no danger of a collision, but it was close. For comparison, geosynchronous satellites orbit Earth at an altitude of 35,800 km, only six or seven thousand km below the asteroid. [full story]
Using the 14-inch SoTIE telescope in Las Campanas, Chile, Gianluca Masi and Franco Mallia captured this video of the asteroid: (click on the image to view a larger version)
To make this animation, "we put together twenty-four 5-second exposures," says Masi. "It shows both the motion and the brightness variations of this funny asteroid."
Asteroid 2004 FH is only about 30 meters wide, which astronomers consider small. An object this size, if it struck Earth, would make a spectacular meteor. After passing through the atmosphere, fragments of the rock might cause local damage, but no widespread destruction.
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