Tip:
Highlight text to annotate it
X
Salutations celestial sight seers! I'm David Fuller, welcome to Eyes on the Sky; what's
up this week?
On December 12-st at 17:11 Universal Time, the winter solstice occurs for the Northern
Hemisphere. So what can we expect to see in the sky for the coming season? In the north
around 9 pm, the circumpolar stars for many of us well north of the equator rotate 90
degrees or so from December to March. Cassiopeia begins the season high to the northwest, with
the easily-seen Big Dipper or Plough low to the north east. Directly north, Kocab hangs
directly below Polaris, with the seemingly blank Camelopardalis and Lynx sections of
the sky above the north star. Fast forwarding three months, Cassiopeia drops, Ursa Major
rises, and Kocab is now towards the east. This is direct evidence of our planet having
revolved 90 degrees over those three months, with its axis still pointing the same direction.
To the west, many autumn favorites are visible early, such as Pegasus and Andromeda -- so
look for the sights within their borders in early winter. As the season progresses, many
of the dimmer water constellations like Pisces, Cetus and Eridanus replace them, but a fair
number of the prominent winter constellations aren't far behind. We'll look at constellations
to the south next.
Dark Sky Fact: Giving any gifts this holiday season? Why not get some silver crown bulbs
for post lamps, or some shields for floodlights? Many of us buy ourselves a gift or two, so
consider giving yourself -- and others - the gift of slightly darker skies, along with
being an example for friends, family and neighbors.
Orion, perhaps the most easily recognized pattern in the sky, graces the southeast.
Orange-appearing Betelgeuse is the bright star at the hunter's shoulder on the left,
and blue-white Rigel is at his knee to our right. The nearly straight and similarly bright
belt stars help us locate several winter constellations nearby to Orion. Up and to the right of the
belt is Aldebaran, the red-giant symbolizing the eye of Taurus. The Bull appears to protect
the Seven Sisters of the Pleiades from the hunter, although this does not entirely follow
the mythology of these characters. Down and to the left of the belt is the brightest night-time
star in the sky, Sirius, punctuating the hunter's dog Canis Major. 25 degrees up from Sirius
and away from Orion is first magnitude Procyon, one of two stars that mark the unremarkable
Canis Minor. But swinging up and over Orion from there is Gemini, the twins. Normally
we would be excited about the similarities and differences of Castor and Pollux, but
a brighter visitor graces the twins all season long: Jupiter slides it's way through here
during winter. As if rounding out a circle, 4-th brightest northern hemisphere star Capella
helps us find Auriga. This constellation appears to share a star with Taurus, with Alnath often
forming not only a horn of the bull, but completing the shape of Auriga -- though the reality
is the star is Beta Tauri, so Auriga technically loses out there.
All of these stars move quickly across the sky in winter, so look for objects within
them as the cross or are near the meridian, and they will arrive there earlier in the
evening as the season grows later. Towards the east, the stars of spring are making their
way up from the horizon, the ones of most interest to us being Cancer, Leo, Canes Venatici
and Coma Berenices.
Along The Ecliptic: On Tuesday, the Moon is both full, but also a few days before apogee,
giving us the smallest full Moon of 2013, or mini-Moon. In the evening, Venus goes on
an extreme diet, slimming down from 17% to 11% illumination, yet growing in angular diameter
from 48 arc seconds to 53 arc seconds; use a small telescope to see that change. An hour
before sunrise, Spica splits the distance between Saturn closer to the horizon, and
Mars further west along the ecliptic. And for outer gas giant stargazers, Uranus crosses
the border of Cetus into Pisces near the 5-th magnitude star 44 Piscium. Neptune sets earlier
in the evening three and a half degrees from Theta Aquarii.
That's all for this week. Keep your eyes on the sky and your outdoor lights aimed down,
so we can all see, what's up. I'm David Fuller, wishing you clear and dark skies.