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. Above all the beauty of the shore is the blue sky.

Astronomy news for the three weeks starting Friday, July 1, 2011.

Yes, three weeks: it's summertime. We make up for it by presenting a remarkable triple (no, wait, quadruple) star as the "Star of the Week." Skylights will resume its normal weekly schedule on July 22, 2011.

We start our triple week with the Moon right at its new phase, at which time it will eclipse the Sun. But don't get too excited, as it's again just partial and visible only from the South Pacific Ocean and a tiny piece of Antarctica. But it's the third eclipse in a month, June 1 (solar), June 15 (lunar), and now July 1, showing that if conditions are right for one, they are for another.

Following that event, such as it is, the Moon then waxes through its crescent phase until it reaches first quarter about the time of Moonset the night of Thursday, July 7. We then see a waxing gibbous that grows to full phase the evening of Thursday th 14th. Seen at near-perfection around midnight, the "Thunder Moon" will be in between the classical figures of Sagittarius and Capricornus. The remainder of our period sees the Moon gibbously waning, but not reaching third quarter until Friday the 22nd. We also note the Moon running the gamut of distance from Earth as it moves from perigee (closest to us) on Thursday the 7th to apogee (farthest) on Thursday the 21st, though the effect is not noticeable to the eye.

Many are the planetary passages. The evening following that of new, Saturday, July 2, finds the ultrathin crescent almost directly beneath Mercury in bright western twilight, while the following evening will be better with the Moon off to the left of the little planet, allowing you to find it easily, at least given a good flat horizon. Then we can celebrate the Fourth of July by admiring the crescent below Regulus in Leo. The next visit is with Saturn, the growing crescent well down and to the right of the planet the evening of Wednesday the 6th, down and to the left of it the following night, and then to the left of Spica the night of Friday the 8th, Saturn, the star, and the Moon all in a nice line. Note the star Porrima just to the west of the planet. Neptune and then Uranus get passed the nights of Sunday the 17th and Wednesday the 20th, these events however hardly worth the notice. The latter planet, though, does get a bit of its own notice by beginning retrograde motion the night of Sunday the 9th. But it's really Neptune's time for glory, as on Tuesday the 12th, it will have gone around once in orbit since its discovery in 1846.

Saturn has now become strictly an evening object, as during our period the setting time goes from local midnight (1 AM daylight) to 11:30 PM Daylight. As noted above, Mercury also makes a decent appearance, going through greatest eastern elongation relative to the Sun on the night of Tuesday the 19th. The morning sky, though, contains much brighter Jupiter, which, rising about half an hour after Saturn sets, makes its own transition to local evening (rising before 1 AM Daylight) while pulling away from Mars, which does not pop up until roughly just after 3 AM. It passes five degrees north of similarly-colored Aldebaran in Taurus the morning of Wednesday the 6th. Venus, rising in bright twilight, is essentially gone.

That leaves Earth, which adds to the Fourth of July celebration by going through aphelion, when and where it is farthest from the Sun, a distance of 94.512 million miles (152.102 million kilometers), just 1.7 percent greater than average. Obviously, given summer's heat, solar distance has little to do with the seasons, which are caused by the 23.4 degree tilt of the Earth's rotation axis against the orbital perpendicular.

The middle of our three-week evening action sees the Big Dipper beginning to slip off to the west. Above the southern horizon look for the dramatic figure of Scorpius with bright Antares to cross the meridian around 10:30 PM. Up and to the right of it are two modest stars, Zubenelgenubi (the southern one) and Zubeneschamali. Though well within Libra (the Scales), they also represent the Scorpion's outstretched claws.
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