Skylights featured on Astronomy Picture of the Day

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Skylights featured three times on Earth Science Picture of the Day: 1 , 2 , 3 , 4 .

1998JK 1998JK

Photo of the Week.. Asteroid 1998 JK, newly named as "Asteroid 17581 Kaler," lies at the center of the left hand image. At the right are sequential overlayed images that show the asteroid's motion over a three-hour period. Since 17851 Kaler (a 5-10 km rock at the inner edge of the main asteroid belt) is in these images close to opposition, the motion is east to west, that is, left to right. Images from the Near-Earth Asteroid Tracking Project, Near-Earth Object Program.

Astronomy news for the week starting Friday, August 6, 2004.

The week begins with an almost third quarter Moon, the phase reached on Saturday, August 7. From that point on, our satellite wanes through crescent toward new, which it passes next week. The end of the week sees the slimming crescent moving through Taurus and Gemini as it visits both Venus and Saturn . The morning of Wednesday the 11th, the Moon will appear well above brilliant Venus (which now rises shortly before 3 AM Daylight Time), while the following morning the Moon will be to the left of the planet. With luck, the morning of Friday the 13th will be clear for us to see the Moon passing between Pollux in Gemini (to the left of the Moon) and Saturn (to the right), the trio plus the other stars of Gemini (and of course Venus!) making a fine sight. Of the bright planets, in the evening we can really see only Jupiter, which is getting more difficult observe in bright western twilight. The ancient planets (those known since ancient times) are in fact are all pretty much bundled in the direction of the Sun, Saturn and Venus to the west of it, Jupiter, Mars, and Mercury in a tight group to the east of it, the latter two effectively invisible.

This is the week not for planets, however, but for the famed Perseid meteor shower, which peaks on the morning of Thursday, August 12. To our great advantage, the Moon will not be a factor in lighting the sky, allowing the fainter meteors to be seen. The shower, which may yield one or two meteors a minute, is caused by debris from Comet Swift-Tuttle, which orbits the Sun every 130 years on a long looping path, and last passed into the inner Solar System only a dozen years ago. The stream of little particles -- not much more than grains of sand or small fragile rocks -- follows along the cometary orbit. When our Earth plows through the swarm, perspective makes the meteors (streaks of light caused by the particles hitting our atmosphere tens of miles high and heating up) appear to come out of the constellation Perseus, hence the name. The best place to look, from the darkest site you can find, is however always straight up. The Perseid shower is one of the best of the year, and one that you don't need to wear a winter coat for.

Find Arcturus, the bright orange star now to the west in the evening. Then look close to overhead for an equally bright but white star, Vega. Draw a line from Arcturus to Vega and find two classic northern constellations, first Corona Borealis, the Northern Crown, and then Hercules, the representation of the great Hero of ancient Greek times. At the northern end of the latter a box of stars called the "Keystone," along the western line of which lies one of the great globular clusters of the sky, Messier 13, which is just visible to the naked eye.
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