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.
