The night sky in December 2016

posted 30 Nov 2016, 11:23 by Pete Collins   [ updated 30 Nov 2016, 12:18 ]
by Anne Holt

Sunrise  1st:   08.02       31st:   08.25
Sunset   1st:   15.54       31st:   16.00

Astronomical darkness begins at around 18.00 throughout the month. 

Full moon:   14th     new moon:   29th 

Not much change in sunrise and sunset times this month, as we approach the Winter Solstice on 21st.   That day lasts 7 hours 28 minutes and 25 seconds  -  about 9 and a half hours shorter than the longest day, in June.
The earliest sunset is at 15.49 on 12th to 14th,  latest sunrise 08.25 on 25th to Jan 2nd.

Highlights

The Geminid meteor shower peaking on the night of 12th/13th (see below).

We have two bright Christmas 'stars' on view this month:  Venus is extremely bright, magnitude  -4.2, but in the Western evening sky, and Jupiter is shining in the East before dawn,  although much less bright than Venus at a magnitude of 'only' -1.7.

On 12th, the Moon passes through the Hyades, the V shaped asterism in Taurus, occulting several of its stars and, in the early hours of 13th, occults Aldebaran, the orange-red giant star which marks the eye of the bull.  This will be between 05.22 and 05.50 when seen from the centre of the UK.

We also have a comet,  45p/Honda-Mrkos-Pajdusakova.  However, it isn't well placed at present, being very low in the SW sky after sunset.  It is also faint - mag 12.2 in early December, though it is expected to brighten to about 7 by the end of the month.  Its position will improve during January.

Constellations

Orion, with the stars of his belt pointing down to the brightest star in the sky, Sirius, is now well above the horizon by midnight, and is a beautiful sight especially from a dark sky site.  By month end these will be visible from 10pm - weather permitting.  Taurus and the Pleiades precede him across the sky.

Gemini, including the 'twins' Castor and Pollux, and Auriga with the bright Capella are also very prominent.
Aries and Pisces, while not particularly bright - or often not even visible in our polluted skies - are both quite high this month.

Perseus, Andromeda and the Great Square of Pegasus  are also well placed for most of the night. The Plough starts the night quite low in the Northern sky, with Cassiopeia high overhead.  Because of the long winter nights, these last two will have changed places before dawn as they rotate around the celestial north pole.

Planets

Mercury:  in Sagittarius. Again  not easy to see this month. On 1st it sets at 16.35, only 40 minutes after the sun.  On this day it is 8 degrees below the waxing crescent moon very low in the West.   It reaches greatest Eastern elongation on 11th, when it sets about an hour after sunset.  Towards month end it will appear to move much closer to the sun, setting a few minutes before it on 31st.

Venus: mag -4.2,  in Sagittarius moving into Capricorn on 8th. Unmissable in the evening sky, despite its fairly low altitude at sunset in early December.   On 1st it sets soon after 18.30 but can easily be seen in the twilit sky.  By month end it sets a few minutes after 20.00 and will have brightened slightly to - 4.4,  though the difference will be more pronounced as it will be much higher in the now darker sky. On 3rd it is 5.5 degrees SW of the 15% lit moon, low in the SSW at around 16.30.   Photographs anyone?

Mars:  mag 0.7 in Capricorn, moving into Aquarius on 16th. Because it is moving Eastwards against the background stars it sets at around the same time throughout.December:  21.00 on 1st and only 20 minutes later on 31st, when it will have faded slightly to mag 0.9.
 
Jupiter  mag -1.8 in Virgo. Shining brightly in the morning sky.  It rises at 02.18 on Dec 1st and about an hour earlier by month end, when it reaches its highest point while the sky is still dark. On 22nd/23rd it is quite close to the waning crescent moon. For those of you who want a Christmas 'star' in the East, on the morning of 25th it rises at about 01.40 and will be quite prominent from just before 3am until the sky brightens at dawn.

Saturn:  mag 0.5 in Ophiuchus. Hardly visible in December.  An evening star at the start of the month, setting about 30 minutes after the sun.  After conjunction on 10th it becomes a morning object.  On 31st it rises at 7am, about 90 minutes before the Sun, so might be spotted low in the pre dawn sky.

Uranus:  mag 5.9  in Pisces. Sets at 3.30 at the start of December, and a couple of hours earlier by 31st. Reaches its highest point in darkness throughout.   At 20.30 on 9th it is 3.5 degrees North of the 76% lit moon. Still at the limits of naked eye visibility (has anyone here ever seen it without optical aid?) it should be an easy binocular target but a scope is needed to show its blue green disc.

Neptune:  mag 7.9,  in Aquarius. Sets just before 23.30 in early December, when it is quite high in the sky as darkness falls.  By month end it is fairly low in the SW as the sky darkens, setting around 21.30.   On 31st it is separated from Mars by only 20 arcminutes (two thirds of a full moon width).  It should be visible in binoculars - if you know where to look - but you need to look through a telescope if you want to see its rich blue colour.

For exact positions on any day see www.in-the-sky-org  or theskylive.com


Meteors

One major shower this month.

Geminids, active 4th to 16th, peak on the night of 12th/13th,  ZHR could be as high as 120. They are very bright, often multicoloured , fairly slow moving meteors.  This is the only major shower to originate from an asteroid- 3200 Phaeton - rather than a comet.  It is usually worth looking for these meteors from about 10pm, when the radiant is high in the sky. Unfortunately, this year all but the brightest will be washed out because of the proximity of the almost full moon throughout the night.

Minor showers

Ursids:  active 17th to 23rd, peak  21st/22nd.  ZHR usually 5 -10 but occasionally as many as 25.   These are medium speed meteors, associated with comet SP/Tuttle.  They will not have as much moon interference as the Gemenids - the 38% lit moon rises at 1am.


Puppa Velids,  peak 9th ZHR 15
The radiant is well below the horizon from our latitude but a few meteors may be seen shooting upwards in the SW.

Coma Berenecids,  active 12th to 23rd,  peak 18th  ZHR 3.  These were once regarded as part of the Leo Minorids but now thought to be a separate shower.

Leo Minorids:  active Dec 5th to Feb 4th,  peak 20th,  ZHR 5.  Should be distinuishable from the Coma Berenecids as they are slightly faster and stronger.
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