SkyEye

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

December 2011

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	Thu
2	Fri	First Quarter Moon
2	Fri	Mars at west quadrature
3	Sat
4	Sun	Mercury at inferior conjunction
5	Mon
6	Tue	The waxing gibbous Moon should not interfere too badly with viewing the Phoenicids (theoretical peak activity: from 21:40 UT).
6	Tue	Moon at apogee
7	Wed	The Puppid-Velids enjoy similar observing conditions to last night's shower.
8	Thu
9	Fri
10	Sat	Total lunar eclipse
10	Sat	Full Moon
11	Sun
12	Mon
13	Tue
14	Wed	The waning gibbous Moon seriously interferes with observing the Geminids.
15	Thu
16	Fri
17	Sat
18	Sun	Last Quarter Moon
19	Mon
20	Tue
21	Wed
22	Thu	Moon at perigee
		Solstice on Earth
		Uranus at east quadrature
23	Fri	Dark skies greet this year's appearance of the Ursids (theoretical peak activity: several predictions ranging from 16:00 UT the previous day to 02:00 UT).
23	Fri	Mercury at greatest elongation west
24	Sat	New Moon
25	Sun
26	Mon
27	Tue
28	Wed
29	Thu
30	Fri
31	Sat

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 22 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.
Mercury: Ophiuchus » Sagittarius » Ophiuchus
At inferior conjunction on 4 December, Mercury reappears at sunrise by mid-month. It spends most of the rest of the month climbing ever higher ahead of the rising Sun.
Venus: Sagittarius » Capricornus
The "evening star" appears to stop climbing in height above the western horizon when seen from southern latitudes but northern observers are finally getting some good views of the bright planet.
Mars: Leo
Rising just before midnight, the red planet reaches west quadrature on 2 December. Mars has not been well-placed for viewing this year but is now brightening towards zero magnitude and is finally visible in the evening sky.
Jupiter: Aries » Pisces
This bright gas giant is well-placed for viewing in the evening hours, not setting until well after midnight.
Saturn: Virgo
The ringed planet is on view from the early hours of the morning.
Uranus: Pisces
Uranus reaches east quadrature on 22 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 the beautiful planetary nebula NGC 2818. A planetary nebula is a glowing shell of gas surrounding a dying star. When a star begins to run out of fuel and expands into a red giant, the outer layers of the star are expelled into space, enriching the surrounding area with the heavy elements manufactured by the parent star. The remaining hot stellar core ionises the ejecta, causing it to glow for a few tens of thousands of years. Eventually the star fades away and nebula is no longer visible. This image was taken by the Hubble Space Telescope in November 2008 and is courtesy NASA, ESA, and the Hubble Heritage Team (STScI/AURA). The red colour represents nitrogen, green represents hydrogen and blue represents oxygen.