SkyEye

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

April 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	Fri
2	Sat	Moon at apogee
3	Sun	New Moon
3	Sun	Saturn at opposition
4	Mon
5	Tue
6	Wed	Jupiter at conjunction
7	Thu
8	Fri
9	Sat	Mercury at inferior conjunction
10	Sun
11	Mon	First Quarter Moon
12	Tue
13	Wed
14	Thu
15	Fri
16	Sat
17	Sun	Moon at perigee
18	Mon	Full Moon
19	Tue
20	Wed
21	Thu
22	Fri	The waning gibbous Moon interferes with the Lyrids (theoretical peak activity: from 15:30 UT to 02:30 UT on 23 April).
23	Sat
24	Sun	The Pi Puppids enjoy slightly darker skies than the Lyrids (theoretical peak activity: from 04:00 UT but no unusual activity is predicted this year).
25	Mon	Last Quarter Moon
26	Tue
27	Wed
28	Thu
29	Fri
30	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: Pisces » Aries
Mercury: Pisces » Aries
Mercury is lost in the solar glare as viewed from the southern hemisphere but early in the month, those in the north can catch a glimpse of this elusive planet low in the west after sunset. It soons disappears from view, undergoing inferior conjunction on 9 April.
Venus: Aquarius » Pisces » Cetus » Pisces
The "morning star" is best viewed from southern latitudes, still high above the eastern horizon before sunrise. It is much lower in the sky for northern observers and seems to remain at a steady altitude from day to day.
Mars: Pisces » Cetus » Pisces
A morning sky object, Mars lingers near the Sun and is difficult to view in eastern dawn skies.
Jupiter: Pisces
At conjunction on 6 April, the largest planet in the solar system is lost to view this month.
Saturn: Virgo
Zero-magnitude Saturn is at opposition on 3 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 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.