Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9


Photo of the Week. Raincloud.

Astronomy news for the week starting Friday, July 2, 2010.

Our constant Moon begins the week in the late stages of its waning gibbous phase as it heads towards its third quarter to help celebrate the Fourth of July. Look for the "perfect" quarter in the eastern morning sky during daylight. The Moon then spends the rest of the week fading away in the waning crescent, as it heads towards new next week and a total solar eclipse on July 11 that will be visible on a long track across the Pacific Ocean (and that misses North America altogether). The waning crescent will spend two days making a nice pairing with bright Jupiter. The morning of Saturday the 3rd, look for the planet to the southeast of the Moon, the following night to the southwest of it (the actual conjunction taking place the evening of the 3rd and out of sight). Just five hours before, the Moon passes north of Uranus, the two planets still very much hanging out together.

Earth makes more news than anything else, when about the time of sunrise on Tuesday the 6th, it -- and we -- pass orbital aphelion, where we are farthest from the Sun, at a distance of 152,096,000 kilometers, or 94,508,000 miles, 1.7 percent farther than the average. Since we are farthest from the Sun during North American summer, distance obviously has little to do with the seasons, which are caused by the 23.4 degree tilt of the rotation axis relative to the orbital. All things equal, variation in distance makes the southern hemisphere seasons a bit more extreme than the northern ones, but the distribution of oceans in the south pretty much negates the effect.

Venus still shines brightly in the western evening sky as it converges on Leo's Regulus, which it will pass the night of Friday the 9th (the planet still not setting until after the end of evening twilight). A bit to the east, look for reddish Mars (which sets less than an hour after Venus), then farther along find Saturn. Still hanging out in Virgo between Regulus and Spica, the ringed planet is just short of three degrees to the north of the Autumnal Equinox. As Saturn drops below the horizon at midnight Daylight Time, opposing Jupiter rises just a bit to the east of the VERNAL equinox in western Pisces. Except for the crescent Moon, the giant planet then proceeds to dominate the morning sky.

It's a perfect time to find and admire Scorpius, one of the few constellations that actually looks like what it is named for. Look for bright Antares to the south around 11 PM, the reddish supergiant lying at the heart of the graceful curve of bright stars that makes the celestial Scorpion, Orion's nemesis. To the east is the distinctive Little Milk Dipper of Sagittarius.
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