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. A brilliant "subsun," caused by reflection of sunlight from ice crystals, seems to follow the aircraft.

Astronomy news for the two weeks starting Friday, March 19, 2010.

The next Skylights will appear Friday, April 2.

The Moon begins our fortnight in the waxing crescent phase a few days shy of first quarter, which it passes on the morning of Tuesday, March 23, when it is quite out of sight. It then works its way entirely through the waxing gibbous until it meets its full phase the night of Monday the 29th, when it IS nicely visible and, for North Americans, climbing the eastern sky. The Moon subsequently reverses itself to begin to fade in the waning gibbous until we pick it up again in the next Skylights on April 2. It passes perigee, where it is closest to the Earth, the night of Saturday the 27th.

Our companion will present a fine sight the evening of Saturday the 20th, when it passes just to the left of the Pleiades star cluster in Taurus, the sight well worth a look. The following evening, it will appear above and to the right of the Hyades, the cluster that makes the Bull's head. The evening of Wednesday the 24th finds it to the southwest of Mars, the planet passed as dawn begins to light the next morning's sky (the Moon appearing to the southeast of the planet that night). Then the night of Sunday the 28th, it's Saturn's turn, with the Moon southwest of the planet, the two more or less exchanging positions by the following evening.

Be sure now to watch for Venus in western evening twilight, as by the end of our period it lingers until twilight is about over. You might even spot fainter Mercury, which is beginning to make an appearance below its brighter neighbor. Then make way for dimming Mars, which crosses the meridian to the south around 9 PM Daylight Time, the planet still northwest of the Beehive Cluster in Cancer and now setting about an hour before dawn. Next it's time to admire Saturn, which comes into opposition with the Sun on Sunday the 21st, when it rises (still in western Virgo) at sunset, sets at sunrise, and crosses the meridian to the south at local midnight.

It is, however, the Earth that makes the top news. At 12:32 PM CDT (1:32 EDT, 11:32 MDT, 10:32 PDT), the Sun crosses the Vernal Equinox in Pisces to announce the beginning of astronomical spring in the northern hemisphere. On that date, when the Earth's axis stands vertically to the line to the Sun, the Sun will rise due east, set due west, be up for 12 hours (or close to it) and be down for about the same amount. The Earth's north pole will also now have full sunlight, while the south pole will be plunging into ever-deepening twilight.

Yet there is still time to admire the winter constellations as they slip west. While Canis Major, with Sirius, is the more famed, look now for Canis Minor to the south between 8 and 9 PM with bright, nearby Procyon, the eighth brightest star in the sky and, at a distance of just a dozen light years, one of the closest.
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