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 -- Full List Restored!

Mountain cloud

Photo of the Week. While it may look like an alien spacecraft, it's really a cloud forming over the mountain.

Astronomy news for the two weeks starting Friday, December 18, 2015.

The next skylights will appear January 1, 2016. Best wishes for the holiday season.

The last Skylights of the year begins with the Moon right at its first quarter, which takes place shortly before its daytime rise, allowing you to enjoy it most of the day. Three days later it goes through perigee, where it is closest to Earth. It then waxes in the gibbous phase as it heads towards full Moon around the time of moonset on Christmas morning. With the Sun near the winter solstice, the full and near-full Moon will be high in the nighttime sky and will flood the countryside with pale moonlight. The Moon then enters the waning gibbous phase, which concludes at third quarter on New Year's night, January 1, 2016. The night of Tuesday the 22nd, the fading Moon will appear to the west of Aldebaran and the Hyades, while by the following night it will have moved to the other side. As the year draws to a close, the Moon glides to the south of the zodiacal constellation Leo. The night of Wednesday, December 30, the Moon will present itself southwest of Jupiter and on New Year's Eve will be to the southeast of the giant planet, which rises just after midnight and transits the celestial meridian around dawn. .

The planets put on a bit of a show for us as well. The morning of Monday the 21st, Mars, which now rises shortly before 2 AM, passes four degrees north of Spica in Virgo, the blue-white color of the star contrasting smartly with the reddish glow of the planet. Then take a look the morning of the last day of the year to see brilliant Venus rising north of the star Antares. Now it's the star's turn to look reddish against Venus's creamy white. Rising around 4 AM, Venus will appear to the upper right of Saturn, which rises about an hour and a half later, the two planets and the star making a nifty triangle. And shortly before midnight up comes Jupiter.

As augured above, the Big Event is the passage of the Sun over the Winter Solstice in Sagittarius at 10:48 PM CST on Monday the 21st (11:48 EST, 9:48 MST, 8:48 PST), at which time astronomical winter begins in the northern hemisphere. At that special moment, the Sun will rise and set as far to the southeast and southwest as possible. In the temperate northern hemisphere, daytime will be shortest, nighttime longest, as the Sun begins its annual trek to the north. Already the evenings are longer, as, because of the Earth's axial tilt and orbital eccentricity, the earliest sunset took place on December 8, while the latest sunrise will be on January 5. Welcome to winter.

Three other planets make news. Mercury reaches its greatest eastern elongation on Monday the 28th, when it sets around the end of evening twilight, making for decent visibility. Uranus, still in Pisces, ceases retrograde motion on Saturday the 26th. Finally, images of Pluto keep flooding in from the New Horizons spacecraft, revealing extraordinary detail of its ice mountains.

The autumn constellations of the Andromeda myth slowly move out. Orion, made obvious by his three-star Belt (with reddish Betelgeuse to the upper left, blue-white Rigel to the lower right), now dominates the nightly scene, Sirius shining brightly to the southeast. Look to the northeast of the Hunter to find the stars of Gemini with Pollux and Castor on top, and directly north of him for Auriga, the Charioteer, who carries bright Capella.
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