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Photo of the Week. Drifting in the evening sky.

Astronomy news for the week starting Friday, June 14, 2013.

The Moon begins the week as a fat waxing crescent, then goes through its first quarter on Sunday the 16th around the time of Moonrise in North America. The rest of the week is spent with it in the waxing gibbous phase, full Moon not reached until early next week. Look for the Moon playing tag with the star Spica (Virgo's luminary) and Saturn. The evening of Monday the 17th, the Moon will lie to the west of Spica, while the following night it will sit sort of between the star and the planet, though closer to Spica. By the evening of Wednesday the 18th, our gibbous companion will have passed them both, then appearing to the east of Saturn, the three in a broken line.

Though Jupiter has retired from the evening skies, we still have Mercury and Venus dancing in evening twilight to entertain us. Look in the west-northwest in dusk for the brighter of the two, Venus, then early in the week up and to the left to find Mercury. By the end of the week, Mercury will be down and to the left, the two passing each other. You'll need a good flat horizon and a very clear sky: binoculars will help. Both will have set before the sky fully darkens. Hovering over them will be Castor and Pollux in Gemini.

Jupiter is more than just "retired," it's gone. On Wednesday the 19th, it passes conjunction with the Sun and thereby transfers to the morning sky, though it will be another month or so before you can catch it in dawn's light. But (as noted earlier) the other giant planet is right up there, transiting the meridian to the south (and east of Spica) around 9:30 PM as twilight draws to a close. And it's on view until close to 3 AM when it sets, shortly before dawn.

The big event is the passage of the Sun across the Summer Solstice in classical Gemini at 12:04 AM CDT the morning of Friday, June 21st (1:04 AM EDT, 11:04 and 10:04 MDT and PDT the night of Thursday June 20) to announce the beginning of astronomical summer. At that moment the Sun will be as far north as possible, 23.4 degrees north of the celestial equator, and we will have maximum daylight and minimum night. However, because of the Earth's orbital eccentricity and the 23.4 degree tilt of its axis against the orbital perpendicular, the year's earliest sunrise took place a week earlier, on Friday the 14th, though you won't notice much difference.

If you are very far south, the Southern Cross will be just past the meridian as the sky darkens. Between it and the sky's south pole is little but the modern constellation of Musca, the Fly. Better perhaps to find the Northern Cross (Cygnus upside down), with great Deneb at its top, as it rises on its side in the northeast in late evening.
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