SkyEye

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

September 2012

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	Sat
2	Sun
3	Mon
4	Tue
5	Wed	NASA's Dawn spacecraft leaves orbit around 4 Vesta and heads to dwarf planet 1 Ceres. Expected arrival date: February 2015.
6	Thu
7	Fri	Moon at apogee
7	Fri	Jupiter at west quadrature
8	Sat	Last Quarter Moon occults Jupiter: visible from most of South America (except northern areas) from about 10:30 UT.
9	Sun
10	Mon	Mercury at superior conjunction
11	Tue
12	Wed
13	Thu
14	Fri
15	Sat
16	Sun	New Moon
17	Mon
18	Tue	Moon occults Spica: visible from Madagascar and parts of Antarctica from about 02:00 UT.
19	Wed	Moon at perigee
19	Wed	Moon occults Mars: visible from southern South America (except the southernmost tip) from about 20:25 UT.
20	Thu
21	Fri
22	Sat	Equinox on Earth
22	Sat	First Quarter Moon
23	Sun
24	Mon	2 Pallas at opposition
25	Tue
26	Wed
27	Thu
28	Fri
29	Sat	Uranus at opposition
30	Sun	The Full Moon nearest to the equinox is traditionally known as the 'Harvest Moon'.

Coming up next month...

Neither the Draconids nor the Orionids (meteor showers) should be too inconvenienced by the Moon next month.

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: Leo » Virgo
The solar north pole is most inclined toward the Earth early this month. An equinox occurs on Earth on 22 September. The word equinox means 'equal night' so that on this day, the (centre of the) Sun spends an equal amount of time above and below the horizon everywhere on the planet.
Mercury: Leo » Virgo
Mercury vanishes from view early in the month as it reaches superior conjunction on 10 September. It reappears in the west after sunset at the end of the month and is best observed from southern latitudes.
Venus: Gemini » Cancer » Leo
Northern hemisphere observers find Venus very high in the east before sunrise but it gets lower as the month progresses. The 'morning star' also continues to sink towards the horizon from the viewpoint of those in the southern hemisphere.
Mars: Virgo » Libra
Mars now sets early in the evening. The red planet is occulted by the Moon on 19 September.
2 Pallas: Ceti
The second asteroid discovered, 2 Pallas is at opposition on 24 September, shining at eighth magnitude near the star Iota Ceti.
Jupiter: Taurus
Many of the inhabitants of South America are treated to the sight of Jupiter disappearing behind the disc of the Last Quarter Moon on 8 September. On the previous day, the largest planet in the solar system undergoes west quadrature, making it an interesting telescopic object since the shadows cast by the planet and its largest moons are most pronounced. This bright planet rises before midnight.
Saturn: Virgo
The ringed planet can be found in the west where it sets soon after the Sun.
Uranus: Cetus » Pisces
Uranus is at its brightest this month as it achieves opposition on 29 September.
Neptune: Aquarius
A small telescope is necessary to view the most distant planet in the solar system. Opposition was last month so it sets only just before dawn.

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 supernova remnant known as the Crab Nebula. Six light years wide and 6500 light years distant, this expanding nebula is the shattered remains of a star that blew up nearly a thousand years ago. At its heart beats a pulsar, a neutron star which spins at the incredible rate of 30 times per second. The supernova explosion which produced this object was observed in 1054 in China, Japan and Arabia. It was also seen in North America by the Anasazi people who lived in what is now New Mexico and who depicted it in a petroglpyh. This image is a composite assembled from 24 individual exposures taken by the Hubble Space Telescope in October 1999, January 2000 and December 2000, and is courtesy of NASA, ESA, Jeff Hester and Allison Loll (Arizona State University). The colours represent different elements which were expelled during the explosion: neutral oxygen (blue), doubly-ionised oxygen (red) and singly-ionised sulphur (green). These elements will find their way into the next generation of stars and planets (and extra-terrestrial life?).