SkyEye

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

July 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	Partial solar eclipse: visible from the Southern Ocean between Africa and Antarctica.
1	Fri	New Moon
2	Sat
3	Sun	Saturn at east quadrature
4	Mon	Earth at aphelion
5	Tue
6	Wed
7	Thu	Moon at perigee
8	Fri	First Quarter Moon
9	Sat
10	Sun
11	Mon
12	Tue	Neptune completes its first orbit since its official discovery on 23 September 1846.
13	Wed
14	Thu
15	Fri	Full Moon
16	Sat	NASA's Dawn spacecraft enters orbit around 4 Vesta for a year-long visit.
17	Sun
18	Mon
19	Tue
20	Wed	Mercury at greatest elongation east
21	Thu
22	Fri
23	Sat
24	Sun
25	Mon
26	Tue
27	Wed
28	Thu
29	Fri	2 Pallas at opposition
30	Sat	If the second Full Moon in a month is popularly known as a "Blue Moon", what is the second New Moon in a month called?
30	Sat	Whatever it's called, the New Moon provides perfect conditions for observing the Delta Aquariids.
31	Sun

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: Gemini » Cancer
A partial solar eclipse occurs on the first day of the month. Then, three days later, the Earth reaches its farthest point from the Sun on 4 July. The date of aphelion can range from 2 July to 6 July.
Mercury: Cancer » Leo
The smallest planet in the solar system soars above the western horizon after sunset. Best seen from southern latitudes, Mercury reaches greatest elongation east on 20 July and begins losing altitude by the end of the month.
Venus: Taurus » Gemini » Cancer
The "morning star" is sinking towards the eastern horizon as it heads towards superior conjunction next month.
Mars: Taurus
The red planet finally begins to leave the solar glare of the dawn sky behind, now rising a couple of hours after midnight.
2 Pallas: Sagitta
The second of the asteroids to be discovered, 2 Pallas reaches a feeble tenth magnitude at opposition on 29 July. A five-centimetre or two-inch telescope will be necessary to see it.
Jupiter: Aries
This bright gas giant rises shortly after midnight.
Saturn: Virgo
At east quadrature on 3 July, the ringed planet now sets before midnight. Look for it high in the west during evening hours. This is an excellent time to observe the interplay of shadows between the planet, its rings and its satellites.
Uranus: Pisces
This faint planet, on the edge of naked-eye visibility, rises mid-evening, about 90 minutes ahead of its much brighter outer solar system neighbour Jupiter.
Neptune: Aquarius
A small telescope is necessary to view the most distant planet in the solar system. Galileo actually spotted Neptune in his telescope early in the seventeenth century but he didn't recognise it as a planet so its official discovery had to wait until 23 September 1846. On 12 July, this blue gas giant will complete its first orbit since its nineteenth century discovery! With opposition occurring next month, Neptune rises in the east shortly after sunset.

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.