SkyEye

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

April 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	Sun
2	Mon
3	Tue
4	Wed
5	Thu
6	Fri	Full Moon
7	Sat	Moon at perigee
8	Sun
9	Mon
10	Tue
11	Wed
12	Thu
13	Fri	Last Quarter Moon
14	Sat
15	Sun	Saturn at opposition
16	Mon
17	Tue
18	Wed	Mercury at greatest elongation west
19	Thu
20	Fri
21	Sat	New Moon
22	Sun	A moonless sky greets the Lyrids (theoretical peak activity: from 21:30 UT the previous evening to 08:30 UT today).
22	Sun	Moon at apogee
23	Mon	A relatively new shower (they've only been detected since 1972), the southern hemisphere's Pi Puppids enjoy dark skies (theoretical peak activity: 10:30 UT but no unusual activity is predicted this year).
24	Tue
25	Wed
26	Thu
27	Fri
28	Sat
29	Sun	First Quarter Moon
30	Mon

Coming up next month...

The closest perigee of the year, at almost the exact moment of Full Moon, occurs early in the month.

An annular solar eclipse takes place on 20 May.

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: Pisces » Aries
Mercury: Pisces » Cetus » Pisces
The tiniest planet in the solar system is at greatest elongation west on 18 April and is visible in the east before sunrise. It is difficult to see from a northern observation point but early morning risers in southern latitudes will see it rise high above the eastern horizon.
Venus: Taurus
The 'evening star' passes through the Pleiades open cluster early in the month and is at its brightest (an amazing -4.5 magnitude) at the end of April. The planet is still very high in the sky for northern hemisphere viewers but is finally starting to descend towards the Sun. For those in the southern latitudes, Venus continues to sink slowly in the west.
Mars: Leo
The red planet was at opposition last month and is up nearly all night, not setting until well after midnight.
Jupiter: Aries
At conjunction next month, the largest planet in the solar system can still be viewed in the west after sunset.
Saturn: Virgo
Zero-magnitude Saturn is at opposition on 15 April and is visible all night.
Uranus: Pisces
With conjunction only last month, this distant gas giant is still lost in the glare of the rising Sun.
Neptune: Aquarius
A small telescope is necessary to view the most distant planet in the solar system. It rises about an hour and a half before its outer solar system neighbour Uranus.

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?).