Eye on the Night Sky, December

The winter night sky
The winter night sky

Our December Eye on the Night Sky column starts with comet ISON, which we hoped would become a spectacular sight during December.

Unfortunately ISON’s close shave with the Sun resulted in its ultimate disintegration into a debris and rubble pile.

Shame; but that’s how the cookie (comet) crumbles sometimes. Look for the demise of ISON on the internet; it is quite spectacular.

Brilliant Venus remains a conspicuous object over the Christmas period low in the evening twilight sky, but as we head into the New Year it sinks toward the SW horizon and is lost in solar glare by mid January.

A crescent moon lies close by on January 2. Residing in Gemini, prominent Jupiter dominates the night sky reaching opposition on January 5 and therefore visible from dusk till dawn. Look for the dark bands across the disk and nearby Galilean moons should you have a telescope or good pair of binoculars.

The moon lies nearby on January 14. Mars is still a morning object, rising shortly before midnight. The red planet is starting to brighten; although telescopically it remains very small and pretty featureless.

Look for it on Christmas and Boxing Day morning when it lies near the moon. Saturn also resides low in the dawn sky. Look for a bright ‘star’ low in the SE an hour or so before sunrise. The moon lies nearby on December 29.

With a New moon on New Year’s Eve, you may spot some meteors just into the New Year; especially on the evening of the 3rd. These belong to the Quadrantids meteor shower which peaks that night. The peak is quite short lived, however the shower is quite prolific with rates approaching 80 per hour, although actual observed rates will be a third of this. Look midway up in the sky in any direction but the NW.

Finally, the Earth reaches perihelion with the Sun on January 4 when it will be at its closest, just 97 ¾ million miles away.

The Early Winter Sky

Since our last look at the night sky the stellar canopy has altered considerably with seasonal winter constellations now occupying much of the south and east. But our celestial ramble begins directly overhead: a position known as the Zenith.

Throughout the early part of the evening the zenith is occupied in turn by the distinctive ‘W’ pattern of Queen Cassiopeia, then by Perseus, a group of stars that resemble a distorted figure Pi symbol. Later in the evening the stars of Auriga the charioteer, highlighted by brilliant Capella, occupy the station.

The autumnal groups of Andromeda and Pegasus occupy much of the western aspect, part of the latter group (the square of Pegasus) resembling huge a diamond shape as it slides down toward the W horizon. Low to the northwest two stars normally associated with summer nights catch the eye; Vega and Deneb, both members of the ‘summer triangle’.

These stars remain visible all year from our latitude, the third member; Altair, sets earlier in the evening - due west. During the winter months inexperienced sky watchers can mistake Vega for the North Star. The true north or pole star is much less brilliant and located some three hand spans above the N horizon in Ursa Minor, the little bear. If you are unsure, use the ‘pointer’ stars in the bowl of the Plough; the familiar ‘saucepan’ pattern currently standing on its handle in the NNE as locators.

Ranged across the southern and eastern aspect of the sky is the glittering array of winter constellations. Due south, Taurus leads the way, readily identified by the “V” outline of the Hyades star cluster highlighted by fiery hued Aldeberan.

Following Taurus across the southern aspect majestic Orion stands proud dominated by brilliant Rigel, ruddy hued Betelgeuse, and the 3 belt stars. The belt stars point down to the most prominent of all night stars, sparkling Sirius, the Dog star in Canis Major, low to the SE. Some distance above and left, solitary Procyon, in the lesser dog of Canis Minor, is yet another brilliant winter jewel. Above Orion’s left shoulder stands Gemini, marked by bright Castor and Pollux, which is decidedly off white in hue. Extending westwards from these two stars, two lines of less conspicuous stars mark the ‘stick like’ outline of the twins. Prominent Jupiter lies in Gemini. Scuttling after Gemini later in the evening are the faint stars of Cancer. Leo the lion then follows, identified by the ‘Sickle’ asterism at the foot of which shines bright Regulus. The first celestial shoots of spring are already sprouting from the eastern horizon!

And finally...

The Sun reaches its most southerly position on the ecliptic on December 21, the date of the winter solstice.

Earth’s northern hemisphere is then inclined away from the Sun and from our latitude appears to rise just over 12 degrees above S horizon at local noon. Useful daylight amounts to just 7 ½ hrs - the shortest day. Latest sunrise and earliest sunset do not occur on solstice day however. The Sun rises latest near the end of December (27 or 28). Astronomically speaking the winter solstice also marks the first day of winter in the northern hemisphere, but as our ancestors were all too aware, days will start to lengthen shortly. Time to celebrate; Happy Solstice Day to all.

The next public observing nights at the Bruce Observatory at Whitby Community College are December 22 and January 5 from 7.30pm.

The next monthly Whitby and District Astronomical Society meeting is on January 7 at Whitby Community College, room H1 main block from 7.30pm.

Check out www.whitby-astronomers.com