The night sky in December 2019

posted 27 Nov 2019, 10:12 by Pete Collins
by Anne Holt

Sunrise        1st:   08.01          31st:   08.25
Sunset         1st:   15.54          31st:   15.58

Astronomical darkness  1st:  18.02  to  05.54       31st:  18.09  to  06.14

The Winter Solstice is on 22nd at 04.19.  This is the day when the Sun reaches its lowest point in the sky in the northern hemisphere.  On this day it is overhead at noon along the Tropic of Capricorn, the furthest south that this can happen.
 
This is also the shortest day at 7hrs 28 minutes and 48 seconds.

The latest sunrise is on 30th at 08.25, earliest sunset on 14th at 15.49.

Full Moon:  12th at 05.12       New Moon:  26th at 05.13

Lunar perigee:  18th at 20.31  (370258km) 
Lunar apogee:   5th at 04.10   (404445km)

December's full Moon is known as the Cold Moon, for obvious reasons. Other names are the Oak Moon, the Long Night Moon, the Moon Before Yule (Anglo Saxon) and the Bitter Moon (Chinese).

Highlights

As always in December, one of the main highlights is the lack of light, we have around 12 hours of astronomical darkness throughout the month.
There's an annular solar eclipse on 26th. This happens when the Moon is near its furthest point from Earth and doesn't appear quite large enough to cover the Sun's disc. The path of this eclipse goes over parts of Saudi Arabia, India, Sri Lanka, Indonesia, Malaysia and the Philippines.
We're losing the gas giants as evening stars, they both appear very close to the Sun this month, but Venus is getting higher in the evening sky and should soon be an unmissable sight - weather and tall buildings permitting. 
And one of the best meteor showers of the year, the Geminids, will be seriously marred this year by the presence of the just past full Moon close to the radiant.  We might have more luck spotting a few Ursids, much lower ZHR but the Moon will be out of the way.

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 light 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 Libra, mag -0.6.
Should be visible for the first week in December.  On 1st it rises a few minutes before 6am and reaches 10 degrees in the SE by 07.15. It moves into Scorpio on 12th, when it rises at 06.44 and is only 5 degrees above the horizon by dawn, so hardly visible.  It goes into Ophiuchus on 15th and Sagittarius on 27th, when it appears only 7 degrees from the Sun.  It's at aphelion (furthest point in its orbit from the Sun) on 30th.

Venus: in Sagittarius, mag -3.9.
Its position in the evening sky improves during the month. On 1st it is 6 degrees above the horizon at dusk, setting at 17.25.  On 11th it is less than 2 degrees south of Saturn, 9 degrees above the SW horizon at  at around 16.15. Venus moves into Capricorn on 20th, slightly brighter at mag -4.0.  On 29th the 3 day Moon passes close to the planet, separated by just under 7 degrees at dusk. On 31st it will be 14 degrees above the SW horizon at dusk, setting at 18.49.

Mars:  in Virgo, mag 1.7.
Rises around 5am throughout December and reaches 12 or 13 degrees in the SE before the sky brightens.  It moves into Libra on 2nd and on 23rd the 9% Moon passes east of the planet, about 3.5 degrees separation at 07.00.

Jupiter:  in Sagittarius, mag  -1.8.
Not visible this month.  On 1st it is only 4 degrees above the horizon at dusk, setting at 17.08.  It is at solar conjunction, on the opposite side of the Sun from the Earth, on 27th and on 31st  it appears separated from the Sun by only 2 degrees.

Saturn:  in Sagittarius, mag 0.6.
Very low in the evening twilight. On 1st it is only 10 degrees above the horizon at dusk and sets at 18.36.  On 27th the one day old crescent Moon passes 1 degree 12 minutes south of the planet, in daylight.  The pair, slightly further apart, are only 4 degrees above the horizon at dusk.  By month end it is on the horizon as the sky begins to darken.

Uranus:  in Aries, mag 5.7.
Best positioned of the major planets, reasonably high in the sky for most of the night, especially in the earlier part of the month.  On 1st it culminates at 21.31 at 48 degrees above the southern horizon, down to 21 degrees in the west by 02.15 and setting at 04.46. On 8th at around 6pm the Moon passes 5.5 degrees to the SE.  By month end it culminates at 19.30, still at 48 degrees, setting at 02.44.  It should be easily visible in binoculars, maybe even with the naked eye under ideal conditions.

Neptune:  in Aquarius mag 7.9.
An early evening object which should be visible in a reasonable sized amateur scope, maybe even in binoculars from a dark sky site.  On 1st it culminates at 18.36 at 29 degrees in the south. It should be high enough for telescopic observing or imaging until around 21.00, setting at 00.28.  By 31st it culminates in astro twilight and will be at 29 degrees in the south as the sky darkens, reasonably high for a couple of hours and setting at 22.08.

Dwarf Planets

Ceres:  in Sagittarius, mag 9.
The closest of the dwarf planets, orbiting in the asteroid belt beyond Mars, is not currently at its best. It's almost at its furthest from us and appears close to the Sun.  On 1st it is only 9 degrees above the horizon at dusk, setting at 17.08.  It appears to move closer to the Sun during the month, by 31st the two are separated by only 9 degrees.

The others are very faint, targets for only very experienced astrophotographers with really good equipment, using the 'spot the difference' - sorry that should say Blink Comparator - method used by Clyde Tombaugh to find Pluto.


Pluto:  in Sagittarius, mag 14.8
The brightest of the distant Kuiper Belt objects has a very eccentric orbit, perihelion distance is 29.7AU aphelion 49.3AU, (one AU, or astronomical unit is the mean distance between the Earth and Sun)  It  is sometimes closer to the Sun than Neptune.  The last time this happened was from Feb 7th 1979 to Feb 11th 1999. It is currently too low in the sky to be successfully imaged and, because it moves so slowly around the sky, taking 248 years to complete one orbit, it will be several decades before there's any improvement.

Haumea:  in Bootes mag 17.4.
Also has a very eccentric (elliptical) orbit, it's distance from the Sun ranging between 35AU and 51.6AU.  Also, it's inclined to the plane of the major planets by 28 degrees, so its path round the sky doesn't follow the ecliptic and the zodiac constellations.  It's currently a morning object, quite well placed for imaging in the early hours. On 1st it rises at 02.18 and reaches 34 degrees in the east by 06.30, as the sky begins to brighten. On 31st it rises at 00.22 and gets to 49 degrees in the SE by dawn.

Makemake:  in Coma Berenices, mag 17.2.
Also has an eccentric orbit (38.6AU to 52.8AU), inclined to the ecliptic.  Currently a morning object. On 1st it rises at 00.16 and reaches 49 degrees in the SE by dawn. On 31st it rises at 22.14 and culminates, 59 degrees above the southern horizon, at 06.43, just before the sky brightens.

Eris:  in Cetus, mag 18.8.
The most massive (but only second largest) of the known dwarf planets is also the most distant, 38AU at perihelion and 98AU at aphelion.  It orbits, at an inclination of 44 degrees to the ecliptic, in the outer edges of the Kuiper Belt, a region known as the Scattered Disc. It is currently an early evening target, but only for the best astrophotographers. On 1st it culminates at 21.11, at 34 degrees in the south, setting at 03.08. On 31st it is at 30 degrees in the SE at 17.30, just before the start of astro darkness, and culminates at 19.12, still at 34 degrees, and sets at 01.09.

Comets

Only one which may, or may not, be at a reasonable magnitude for viewing through amateur scopes.

C/2017 T2 (PANSTARRS) in Auriga, mag 8.5 (or maybe 10 - or somewhere in between)
Circumpolar throughout December, and reasonably high for most of the night.  At the start of the month it is only 4 degrees west of the bright star Capella, about 28 degrees above the NE horizon at 17.20 and 35 degrees in the NW when astro darkness ends. It moves into Perseus on 4th, Camelopardalis on 21st and back into Perseus on 31st, when it should be slightly brighter and still quite high for most of the night, almost overhead at 21.00.

C/2018 N2 (ASSASSN) in Andromeda, mag 11.7
Again circumpolar but much fainter so only a target for the more experienced. On 1st it will be 65 degrees in the SE as the sky darkens, higher at 75 degrees in the south by 19.18 and down to 21 degrees in the NW at 02.30.  By 31st it is expected to have faded to mag 12.1 and be slightly lower in the sky - 75 degrees in the south at 17.30 and 21 degrees in the NW soon after midnight.

A couple more faint comets are still around:
260P/McNaught in Andromeda, moving into Perseus towards the end of the month. Very faint at mag 12.8 fading to 13.9 - though one site says that it will brighten during December.  Still fairly high in the sky for most of the night, on 1st it reaches 85 degrees in the south around 10pm, on 31st it is at 80 degrees at 20.15.

289P/Blanpain in Aquarius, mag around 11.
Too low for imaging in early December.  Moves into Pisces on 23rd and Pegasus on 28th.  By 31st it reaches 52 degrees in the south by 16.30, down to 17 degrees soon after 11pm, maybe a little brighter.

For detailed positions and more info on all solar system objects


Meteor Showers

One major shower in December

Geminids:  active 4th to 17th, peak 14th. ZHR given as 120 -150, but this is under ideal conditions, far fewer can be seen in the light polluted Manchester sky.  The radiant is high from 22.00, so some may be seen then, but the shower is best around 2am.  They are bright, often colourful, medium paced meteors, not usually leaving trails.  Unusually, they do not originate from debris left by a comet but an asteroid - 3200 Phaeton.
The bad news is that at the peak the 96% Moon will be shining brightly in Gemini, close to the radiant.  However, some of these meteors are so bright that quite a few should still be visible in the glare.

Minor Showers

Monocerotids:  active Dec 5th to 20th, peak 9th, ZHR 3 - though this is said to be variable, so there could be more. Or fewer. They are medium paced meteors best seen around 2am.  This shower will also be adversely affected by moonlight, the Moon is only 3 days from full and doesn't set until 04.37.

Alpha Hydrids:  active 3rd to 15th, peak 12th, ZHR 3.  Best seen around 3am but the Moon is full on this night.

Coma Berenecids: active 12th to 23rd, peak 16th, ZHR 3. Best seen before dawn and again after 22.15 on this day.   These meteors used to be regarded as part of the Geminids but is now considered as a separate shower.  Again there will be Moon interference, 82% full, rising at 20.40.

December Leonis Minorids:  active Dec 5th to Feb 4th, peak Dec 20th, ZHR 5. A weak, long lasting shower, a few meteors might be seen at any time between 19.30 and dawn around the peak.  The crescent Moon rises at 00.49 on 20th and 02.11 on 21st.

Ursids: active 17th to 26th, peak 23rd, ZHR 10. These are medium paced meteors, parent comet 8P/Tuttle.  Best seen around 3am on 23rd.  the 20% Moon rises at 04.56 on this day.  Some sources say that they have detected a dust filament which could result in a very short outburst on 22nd at around 21.40, maybe as many as 30 per hour.







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