Skylights featured on Astronomy Picture of the Day

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Skylights featured five times on Earth Science Picture of the Day:
1 , 2 , 3 , 4 , 5


Photo of the Week.. Trees stand before the glory of the rising Sun...

Astronomy news for the two week period starting Friday, June 24, 2005.

Skylights will next appear on Friday, July 8.

During this fortnight, the Moon glides through its waning phases, beginning with the waning gibbous, passing through third quarter on Tuesday, June 28th, then continuing with the waning crescent. On Friday the 24th, our companion passes five degrees south of Neptune (in Capricornus) and then on Sunday the 26th, three degrees to the south of Uranus (in Aquarius). The morning of Wednesday the 29th will be Mars's turn, the Moon passing a couple degrees to the north of the red planet.

The grand event, one of the fine ones of the year, is a tight gathering of planets that will appear low in the west-southwest in the evening twilight sky (the low altitude and brightness of the sky making it rather difficult to view). The best time is around the nights of Friday the 24th and Saturday the 25th, when you will see (from left to right) Saturn , Venus , and Mercury all in a row only a couple degrees long, Venus by far the brightest. Farther to the right will be Gemini's Pollux and Castor. The motions of the planets will be easily visible from night to night. On Saturday the 25th, Venus will pass 1.3 degrees to the north of Saturn, while on Monday the 27th, Venus will have switched places with Mercury and will pass a mere tenth of a degree north of the smaller planet, making one of the closest planetary couplings anyone is likely to see. The two will hang together for a few days, while Saturn sinks ever farther into twilight. Find a clear horizon, and take binoculars.

The low altitudes of these planets then leaves the evening nighttime sky to Jupiter. As twilight ends, the giant planet will lie well to the southwest, moving slowly eastward against the stars back towards Spica in Virgo. Around Saturday the 26th, Jupiter does a sort of "crossover" with Mars, the former setting near local midnight (1 AM Daylight Time) as the latter, now in Pisces, rises.

The last passage the period involves our own planet, which goes through aphelion, our farthest point from the Sun, about midnight the night of Monday, July 4, coincidentally to the sight and sound of fireworks in the US. At that time, the Earth will be 94,512,036 miles (152,102,378 kilometers) from the Sun, about 1.7 percent farther than average. Obviously, given that greatest distance corresponds to the hottest time of the year, the solar distance has nothing to do with the seasons, which are caused exclusively by the tilt of the Earth's rotation axis relative to its orbital axis and the varying altitude of the Sun during the day (which affects the heating of the ground).

Two of the most famed figures of the sky oddly lie at about the same separation from their respective celestial poles. In the south, Crux, the Southern Cross, is just 30 degrees from the South Celestial Pole, while in the north, The Big Dipper of Ursa Major lies between 30 and 40 degrees from the North Celestial Pole (and Polaris in Ursa Minor). Residents a bit south of 30 degrees south latitude then see the Cross as circumpolar (never setting), while those north of about 40 degrees north latitude see the Dipper as circumpolar. An even better match is between Crux and the "W" of Cassiopeia, which is closer (only 30 degrees from) the North Celestial Pole and is circumpolar for those only a bit north of 30 degrees north latitude.
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