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Gibbous Moon

Photo of the Week. A waxing gibbous Moon floats among the clouds.

Astronomy news for the week starting Friday, May 11, 2007.

The Moon begins our week by waning in its crescent phase toward new, which it will reach on Wednesday, May 16th. Before and after that invisible phase, it acts as a guide to two elusive planets. The morning of Saturday the 12th the slimming crescent will lie to the west of Mars, while by the following morning it will have flipped to the other side. Then after new Moon try to find the thin waxing crescent in the west-northwest during twilight the evening of Thursday the 17th just above Mercury, which is an even more difficult target. Looking ahead (always good to plan ahead), during the following week, the Moon takes aim on Venus for a particularly good conjunction the night of Saturday the 19th, so stay tuned. Looking back, the Moon also encounters Uranus, the crescent passing north of it on Friday the 11th. The day before new, the Moon is once again at perigee, allowing those on the coasts to enjoy especially high and low tides.

Dominating western evening skies, Venus's show is now close to its peak. Though still setting ever later, a bit after 11:30 PM Daylight Time, the night-to-night difference is getting less as the planet approaches its maximum elongation in early June. Even then, it will continue to get brighter until early July as it gets ever closer to Earth. Sandwiched between Venus and the north-south celestial meridian, find Saturn. While brighter than all but the most luminous stars (if a star, it would now rank ninth), it is still only 1/70 Venus's brilliance, the result of the latter planet's proximity to us.

Well before Saturn sets at 2 AM, Jupiter steals the show as it makes something of a transition to evening by rising just as twilight ends, around 10 PM. It then transits the meridian half an hour after Saturn sets. Look for the star Antares in Scorpius to the southwest of the giant planet. Particularly note the color contrast, Jupiter a creamy yellow-white, Antares reddish-orange (the star a "red supergiant"). In the morning, Mars ever so slowly begins to break away from dawn, rising in the east about half an hour before morning twilight commences.

While Saturn lies in between Cancer and Leo, we tend to refer it to much brighter Leo (to the east of the planet) rather than to dim Cancer (to the west). Best known for its Beehive Cluster (a pretty sight in binoculars), were Cancer not along the ecliptic path, it might never have made it as a constellation at all. Farther west, northwest really, in the early evening you can still admire bright Castor and Pollux in Gemini, which appear to look down upon us like a pair of celestial eyes.
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