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 .

Mars and the Moon

Photo of the Week.. Mars passes north of the waning gibbous Moon on July 17, 2003, amidst the stars of Aquarius.

Astronomy news for the short week starting Sunday, August 24, 2003.

Skylights will resume its normal schedule on Friday, August 29.

The Moon passes its new phase this week on Wednesday, August 27, and is effectively out of sight for this short period except for dedicated viewers who might see it as a thinning waning crescent the morning of Monday the 25th, or as an equally thin waxing crescent in twilight the night of Thursday the 28th. That evening the Moon will be in conjunction with Mercury, passing well to the north of the nearly invisible planet.

Two planetary oppositions (to the Sun) occur this week, the first one belonging to Uranus (on Sunday, the 24th), rendering the planet about as bright as it gets (at magnitude 5.7) as it moves retrograde within southern Aquarius. The event is overwhelmed, however, as is about everything else, with the favorable opposition of Mars, which will take place on Thursday, August 28th, at around noon in the Americas, not that one or two days makes much difference, as Mars slowly moves into this position and slowly moves away from it as it too retrogrades through southern Aquarius. For the few days bracketing opposition, Mars will rise at close to sunset, set around sunrise, and cross the meridian to the south around midnight, 1 AM Daylight Time. (The opposition is actually not exact, as Mars is seven degrees south of the ecliptic, so in the Northern Hemisphere, it will actually rise after sunset.) The planet's orbit is among the more elliptical of the planets. Its "synodic period," that between successive oppositions, is 2.14 years. When the opposition is at Martian aphelion (farthest from the Sun), the planet is about twice as far away as when it is at Martian perihelion (closest to the Sun), when the opposition is called "favorable." Such favorable oppositions occur on a 15-year cycle. This particular opposition is nearly perfect, and is the closest in over 50,000 years (34,646,418 miles, 55,758,006 kilometers), though the difference with past favorable oppositions is rather marginal (Mars only about one percent closer than it was at the fine 1971 favorable opposition). Because of the eccentricity of the orbit, the closest approach actually occurs a day and a third earlier than the actual opposition, on the morning of Wednesday, the 27th, when the planet will be as bright as it can get as seen from Earth. The angular size of the Martian disk will also be as large as possible, 25.1 seconds of arc across, just under half a minute of arc, which is still unresolvable to the naked eye (that is, Mars will appear as a yellowish to reddish point, depending on your color vision). The telescope will show dark markings and a polar cap. If you stay up late to admire the "red planet" be sure to find Saturn, which rises, beautifully set in Gemini, around 2 AM Daylight Time.

While waiting for Mars to climb above the trees and houses, be sure also to admire Scorpius low in the southwest, Ophiuchus above it, and Sagittarius to the left.
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