SkyEye

Welcome to SkyEye, your guide to this month's celestial events.

December 2013

The Calendar

All times and dates are given in Universal Time (UT).
Nightly darkness estimates are calculated for 45° N and 30° S.
Like total solar eclipses, lunar occultation events can be seen only from limited regions on Earth (and sometimes not at all if the occultation takes place during daylight hours). However, the Moon will appear close in the sky to its 'target' for some hours either side of the actual occultation, regardless of where you are.

Date		Event
1	Sun	The Moon occults Saturn: visible from parts of Antarctica from about 09:00 UT.
2	Mon
3	Tue	New Moon
4	Wed	Moon at perigee
5	Thu
6	Fri	Nearly perfect skies greet this year's return of the Phoenicids (theoretical peak activity: 10:00 UT).
7	Sat	The poorly-established Puppid-Velids are similarly blessed with dark skies.
8	Sun
9	Mon	First Quarter Moon
10	Tue	Venus at its brightest this year, magnitude -4.7
11	Wed
12	Thu
13	Fri
14	Sat	The waxing gibbous Moon will interfere with the reliable Geminids (theoretical peak activity: 05:45 UT).
15	Sun
16	Mon
17	Tue	Full Moon
18	Wed
19	Thu	Moon at apogee
20	Fri
21	Sat	Solstice on Earth
22	Sun	The waning gibbous Moon means light-polluted skies during peak activity (about 14:00 UT) of the Ursids
23	Mon
24	Tue
25	Wed	Last Quarter Moon
26	Thu	Comet C/2012 S1 ISON nearest to Earth (0.4 AU)
27	Fri	The Moon occults the first-magnitude star Spica: visible from Finland, Norway, Russia and Sweden from about 01:45 UT.
28	Sat	The Moon occults Saturn: visible from most of Antarctica from about 23:30 UT.
29	Sun	Mercury at superior conjunction
30	Mon	Uranus at east quadrature
31	Tue

Coming up next month...

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The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies including comets, are not so constrained, often moving far above or below the ecliptic.

Sun: Ophiuchus » Sagittarius
[Although Ophiuchus is not a member of the zodiac, the ecliptic passes through it.] A solstice occurs on Earth on 21 December. The word solstice means 'sun stands still' so that on this day, the solar declination reaches an extreme. In this case, the Sun appears directly over the Tropic of Capricorn in the southern hemisphere. From now until the solstice in June, days will be getting shorter in the southern hemisphere and longer in the northern hemisphere.
Comet C/2012 S1 ISON: Scorpius » Ophiuchus » Serpens » Hercules » Corona Borealis » Hercules » Draco
Did it survive its close brush with the Sun? If it did, it will be visible in both the morning and evening skies for observers in the northern hemisphere. Look towards the eastern (morning) and western (evening) horizons during twilight for a glimpse of the comet.
Mercury: Libra » Scorpius » Ophiuchus » Sagittarius
The smallest planet in the solar system is lost in the morning twilight by mid-month as it keeps its appointment with the Sun on 29 December. It will reappear after sunset next month.
Venus: Sagittarius
The evening star is at its brightest this month but it is plummeting towards the western horizon for those watching it from the southern hemisphere. The descent towards the Sun for observers in northern latitudes is much more gradual.
Mars: Virgo
First-magnitude Mars rises just after midnight. This has not been a good year for observing the red planet but 2014 promises to be much better.
Jupiter: Gemini
On course for opposition early next month, Jupiter is on view most of the night.
Saturn: Libra
At solar conjunction early last month, Saturn is now visible in the morning sky ahead of the Sun. It is occulted by the Moon twice this month but these events are only visible from the Antarctic.
Uranus: Pisces
Uranus reaches east quadrature on 30 December and sets around midnight.
Neptune: Aquarius
A small telescope is necessary to view the most distant planet in the solar system. It sets mid-evening.

The Celestial Sphere

Constellations are patterns of stars in the sky. The International Astronomical Union (IAU) recognises 88 different constellations. The brightest stars as seen from the Earth are easy to spot but do you know their proper names? With a set of binoculars you can look for fainter objects such as nebulae and galaxies or some of the closest stars to the Sun.

Descriptions of the sky for observers in both the northern and southern hemispheres are available for the following times this month. Subtract one hour from your local time if summer (daylight savings) time is in effect.

Local Time	Northern Hemisphere	Southern Hemisphere
1730 hours (1830 hours summer time)	45° N	30° S
1930 hours (2030 hours summer time)	45° N	30° S
2130 hours (2230 hours summer time)	45° N	30° S
2330 hours (0030 hours summer time)	45° N	30° S
0130 hours (0230 hours summer time)	45° N	30° S
0330 hours (0430 hours summer time)	45° N	30° S
0530 hours (0630 hours summer time)	45° N	30° S

For More Information...

Consult our online glossary for non-technical explanations of many of the astronomical terms used in these pages.
Blue moons, eclipses, the dates of Easter and much more can be found at the Interactive Astronomy Pages.
For more information about the objects and events described in SkyEye, visit these astronomy-related sites.

Credits

Much of this information can be found in this month's issue of your favourite amateur astronomy magazine available in your local bookshop. Another excellent source is the current edition of the Astronomical Calendar by Guy Ottewell and published by the Universal Workshop.

The SkyEye banner features interacting galaxies UGC 1810 and UGC 1813, known collectively as Arp 273. The larger of the two spiral galaxies, UGC 1810, has a disc that has been tidally distorted into a rose-like shape by its companion galaxy below, UGC 1813. This smaller galaxy, nearly edge-on to our line of sight, shows signs of intense star formation in its core, possibly triggered by its encounter with its larger neighbour. It is thought that UGC 1813 actually dived through UGC 1810 some time in the distant past. Arp 273 is found in the constellation of Andromeda at a distance of about 340 million light years. The image was taken on 17 December 2010 and is courtesy of NASA, ESA, and the Hubble Heritage Team (STScI/AURA).