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Mercury

Mercury the innermost and smallest planet reaches greatest eastern elongation (20 degrees) on December 29th and therefore is visible as an early evening object during the latter part of the month. For observers at tropical and southern latitudes it appears low down above the western horizon from about the middle of December. Try looking for the planet from about 30 minutes after sunset. Mercury is more difficult to spot from mid-latitude northern locations. Only during the last few evenings of December will observers have their latest change to glimpse this elusive World, low down towards the southwest, 35 minutes after sunset.

During December the magnitude of Mercury fades slightly from -0.8 to -0.5 with the thin waxing crescent Moon passes 7 degrees north of the planet on the 12th.

Venus

Venus remains a superb morning object although its period of visibility is now decreasing. At the start of December from northern temperate latitudes the planet rises over 4 hours before the Sun decreasing to about 3 hours by months end. For observers located further south, Venus is visible for less time. For example from Sydney, Australia (33.5 S) it rises 2.5 hours before the Sun on December 1st, decreasing to 2 hours by December 31st.

Venus fades slightly from magnitude -4.2 to -4.0 with its illuminated phase increases from 67% to 77% this month. It continues its rapid eastwards motion crossing the constellation boundary from Virgo into Libra on December 11th. By the end of the month, Venus is now 30 degrees southeast of much fainter Mars (mag. +1.4).

On December 7th, the waning crescent Moon passes 0.7 degrees north of Venus and an occultation is visible from North and Central America at 16:56 UT.

Venus during December 2015 (credit:- freestarcharts)

Venus during December 2015 - pdf format (credit:- freestarcharts)

Venus, Jupiter, Mars and the Moon - 3 hours before sunrise on December 7th as seen from mid Northern Latitudes (credit:- Stellarium)

Venus, Jupiter, Mars and the Moon - 2 hours before sunrise on December 7th as seen from mid Southern Latitudes (credit:- Stellarium)

Mars

Mars is located in Virgo and continues to gradually improve in brightness and apparent size as the distance between the "Red planet" and Earth continues to decrease. It remains a morning object throughout December, starting it at magnitude +1.5 and ending it at magnitude +1.3. The apparent size increases from 4.8 to 5.5 arc seconds.

From northern temperate latitudes you can almost set you watch by Mars this month. As a consequence of its current eastwards and southwards motion Mars rises at approx. the same time each morning; between 2 am and 3 am depending on location. For observers at tropical and southern latitudes the planet rises slightly earlier each morning and by the end of the year it's visible just after midnight.

It's generally regarded among amateur astronomers that an apparent size of 5 arc minutes is the minimum required to begin serious Martian telescopic work. Mars crosses that threshold this month and although obviously still small in diameter, a medium 150mm (6-inch) scope at high powers on nights of good seeing should reveal the more prominent markings.

The waning crescent Moon passes 0.1 degrees south of Mars on December 6th with an occultation visible from Australia, Central and East Africa, Indonesia, Southern India (2:42 UT). Later on December 21st, Mars passes 4 degrees north of Spica (α Vir - mag +1.0).

Mars during December 2015 (credit:- freestarcharts)

Mars during December 2015 - pdf format (credit:- freestarcharts)

Venus, Jupiter, Mars and the Moon - 3 hours before sunrise on December 6th as seen from mid Northern Latitudes (credit:- Stellarium)

Venus, Jupiter, Mars and the Moon - 2 hours before sunrise on December 6th as seen from mid Southern Latitudes (credit:- Stellarium)

Jupiter

Jupiter the major dominant planet in the Solar System is now a brilliant morning object moving direct in southeastern Leo. The giant planet rises after midnight at the start of the month improving to before midnight by months end and remains visible until dawn. It increases in magnitude from -2.0 to -2.2 with the apparent size growing from 36 to 39 arc seconds as the month progresses.

Jupiter as imaged by Hubble Space Telescope on April 21, 2014 (credit:- NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

Through a pair of binoculars the four large Galilean moons, Io, Europa, Ganymede and Callisto are easily visible. They constantly change position as they orbit the planet and sometimes all four can be seen at once but more often than not some are hidden from view as they pass behind or in front of Jupiter's disk. On rare alignment occasions none of the four can be seen at all, just the planet itself.

When viewed through a telescope, Jupiter is a stunning sight. Even a small 80mm (3.1 inch) refractor will show the main Northern and Southern equatorial cloud belts. Larger telescopes reveal much more finer details, including smaller belts, ovals, festoons, darker regions and of course the famous "Great Red Spot".

The waning crescent and last quarter Moon pass 2 degrees and 1.5 degrees south of Jupiter on December 4th and 31st respectively.

Jupiter during December 2015 (credit:- freestarcharts)

Jupiter during December 2015 - pdf format (credit:- freestarcharts)

Saturn

Saturn passed through solar conjunction late last month and subsequently re-appears low down in the southeastern sky before sunrise during the second half of December. The "Ringed" planet is located in Ophiuchus, shinning at magnitude +0.6.

Uranus

Uranus, mag +5.8, is now two months past opposition but remains well placed for observation in the evening sky among the stars of Pisces. During December, the second furthest planet from the Sun is visible as soon as it's dark enough, remaining so until around midnight. It's easy to spot with binoculars.

Uranus starts the month moving slowly retrograde. It then reaches its second stationary point on December 26th - signaling the end of this year's opposition period - after which direct motion is once again resumed. The planet is positioned 15 degrees south and 20 degrees east of the centre of the "Great Square of Pegasus" and 2 degrees south of epsilon Psc (ε Psc - mag. +4.3).

On December 20th, the waxing gibbous Moon passes 1.2 degrees south of Uranus with an occultation visible from Southern South America, Falkland Islands at 0:50 UT.

Uranus during December 2015 (credit:- freestarcharts)

Uranus during December 2015 - pdf format (credit:- freestarcharts)

Neptune

Neptune, mag. +7.9, is located in Aquarius and is visible with binoculars and small telescopes. The Solar System's distant far planet can be seen towards the west for a few hours after sunset. It's positioned some 30 degrees southwest of the "Great Square of Pegasus" and two degrees northeast of sigma (σ) Aqr (mag. +4.8).

On December 17th, the waxing crescent Moon passes 3 degrees north of Neptune.

Neptune during December 2015 (credit:- freestarcharts)

Neptune during December 2015 - pdf format (credit:- freestarcharts)

Solar System Data Table December 2015

 DateRight AscensionDeclinationApparent MagnitudeApparent SizeIllum. (%)Distance from Earth (AU)Constellation
Sun5th Dec 201516h 43m 15.1s-22d 15m 55.8s-26.832.5'1000.986Ophiuchus
Sun15th Dec 201517h 27m 08.5s-23d 13m 19.9s-26.832.5'1000.984Ophiuchus
Sun25th Dec 201518h 11m 28.9s-23d 24m 40.1s-26.832.5'1000.984Sagittarius
Mercury5th Dec 201517h 24m 12.1s-25d 03m 20.8s-0.704.8"961.394Ophiuchus
Mercury15th Dec 201518h 32m 13.3s-25d 30m 18.2s-0.605.3"901.281Sagittarius
Mercury25th Dec 201519h 34m 53.3s-23d 32m 23.3s-0.706.1"731.094Sagittarius
Venus5th Dec 201513h 53m 12.5s-09d 14m 00.7s-4.216.9"680.985Virgo
Venus15th Dec 201514h 38m 43.9s-13d 04m 29.7s-4.115.8"721.054Libra
Venus25th Dec 201515h 26m 11.5s-16d 31m 08.9s-4.114.9"751.121Libra
Mars5th Dec 201512h 49m 46.3s-03d 44m 36.5s1.504.8"931.934Virgo
Mars15th Dec 201513h 11m 19.1s-05d 57m 28.4s1.405.1"921.845Virgo
Mars25th Dec 201513h 32m 39.2s-08d 04m 18.5s1.305.3"921.751Virgo
Jupiter5th Dec 201511h 29m 30.2s04d 30m 38.9s-2.036.0"995.475Leo
Jupiter15th Dec 201511h 32m 48.5s04d 12m 11.9s-2.137.1"995.316Leo
Jupiter25th Dec 201511h 35m 04.3s04d 00m 33.3s-2.138.2"995.157Leo
Saturn5th Dec 201516h 25m 19.2s-20d 00m 01.1s0.615.1"10010.989Ophiuchus
Saturn15th Dec 201516h 30m 15.8s-20d 11m 15.4s0.615.2"10010.963Ophiuchus
Saturn25th Dec 201516h 35m 05.8s-20d 21m 27.9s0.615.2"10010.911Ophiuchus
Uranus5th Dec 201501h 01m 54.5s05d 53m 37.3s5.803.6"10019.407Pisces
Uranus15th Dec 201501h 01m 23.7s05d 50m 49.4s5.803.6"10019.557Pisces
Uranus25th Dec 201501h 01m 11.4s05d 49m 57.5s5.803.6"10019.720Pisces
Neptune5th Dec 201522h 35m 37.0s-09d 43m 54.5s7.902.3"10030.037Aquarius
Neptune15th Dec 201522h 36m 04.3s-09d 41m 01.6s7.902.3"10030.207Aquarius
Neptune25th Dec 201522h 36m 43.9s-09d 36m 57.0s7.902.2"10030.369Aquarius