After reaching greatest eastern elongation at the start of last month, fast moving Mercury moves out west of the Sun hitting greatest western elongation on August 16. The elongation is 19 degrees but sadly not a good one regardless of observer's location. Northern hemisphere planet watchers have the best chance of glimpsing the illusive world. On August 16, Mercury (mag. 0.0) will appear only 7 degrees above the ENE horizon about one hour before sunrise. Unfortunately for southern hemisphere observers the angle is not favourable; the planet appears low down before sunrise and unlikely to be seen in the dawn twilight.
Like Mercury, Venus also reaches greatest western elongation this month when on August 16 it will be positioned 46 degrees from the Sun. As a result, the planet is a brilliant morning object, rising four hours before the Sun for northern temperate latitudes. For southern hemisphere observers the visibility is about an hour or so less. During the month, the magnitude of the planet decreases slightly from –4.5 to –4.3 with the phase increasing from 41% to 58%.
Venus starts the month in Taurus. Unusually for planets, it then moves into the non-zodiac constellation of Orion, staying there between August 5 and August 13. At this time it will be located only twelve or so degrees north of first magnitude red supergiant star Betelgeuse. Venus then leaves Orion, spending the rest of the month in Gemini.
The waning crescent Moon will appear close to Venus on the morning sky on August 14.
Mars is visible in the early evening sky as soon as it gets dark but sets less than two hours after the Sun. The planet is located in Virgo with its rapid eastward motion carrying it past Saturn in mid-August. A good time to look is on August 14 when Mars (mag. 1.1) will pass between Saturn (mag. 0.9) and Spica (mag. 1.0). Look out for the contrasting colours; Mars will appear reddish, Saturn yellowish and Spica bluish-white.
Mars during August has an apparent diameter of only about 5.5 arc seconds.
Jupiter is now a brilliant morning object. The largest of all planets is located in Taurus and is currently moving closer to Earth. It starts the month at mag. –2.1 with an apparent diameter of 36 arc seconds and ends the month at mag. –2.3 with an apparent diameter of 39 arc seconds. The brightness and apparent size of Jupiter will increase until it reaches opposition in December.
The waning crescent Moon will appear close to Jupiter on the morning of August 12.
Saturn shines at mag. 0.9 this month and is located in the constellation of Virgo. The planet is visible as soon as darkness falls and is located just a few degrees north of mag. 1.0 star Spica. The month offers perhaps the last real chance with enough time to have a decent look at Saturn through a telescope. The planet has a good 16 arc seconds of apparent diameter and the rings are wide open, although Saturn now sets less than two hours after the Sun.
Mars is also in Virgo and starts the month to the west of Saturn. The red planets rapid eastward motion soon carries it towards and then past the much slower moving Saturn.
Uranus is located in the constellation of Cetus and is now well placed in the late evening / morning sky. It rises before midnight at the start of the month. The distant planet is only one degree east of star 44 Piscium, which at mag. 5.8 is almost equal in brightness.
Neptune reaches opposition on August 24 and is visible all night. It is located in the constellation of Aquarius and only three degrees south of mag. 4.2 star Ancha (theta Aquarii). At mag. 7.8, Neptune is not visible to the naked eye but quite an easy binocular target.
Solar System Data Table August 2012
|Date||Right Ascension||Declination||Mag.||Size||Illum. (%)||Distance (AU)||Constellation|
|Sun||5th Aug 2012||09h 01m 47.8s||16d 54m 46.9s||-26.7||31.5'||100||1.014||Cancer|
|Sun||15th Aug 2012||09h 39m 42.6s||13d 59m 05.0s||-26.7||31.6'||100||1.013||Leo|
|Sun||25th Aug 2012||10h 16m 45.5s||10d 41m 10.0s||-26.7||31.6'||100||1.011||Leo|
|Mercury||5th Aug 2012||08h 13m 10.3s||15d 44m 59.3s||3.0||10.2"||07||0.659||Cancer|
|Mercury||15th Aug 2012||08h 24m 06.8s||17d 51m 23.7s||0.1||07.8"||36||0.864||Cancer|
|Mercury||25th Aug 2012||09h 18m 27.6s||16d 37m 46.1s||-1.0||06.0"||75||1.126||Cancer|
|Venus||5th Aug 2012||05h 50m 26.6s||19d 28m 53.0s||-4.5||26.6"||44||0.626||Orion|
|Venus||15th Aug 2012||06h 29m 11.3s||19d 58m 00.0s||-4.4||23.7"||50||0.705||Gemini|
|Venus||25th Aug 2012||07h 11m 17.5s||19d 50m 56.0s||-4.4||21.3"||55||0.782||Gemini|
|Mars||5th Aug 2012||13h 07m 41.0s||-07d 22m 29.0s||1.1||05.7"||90||1.652||Virgo|
|Mars||15th Aug 2012||13h 30m 28.8s||-09d 47m 56.2s||1.1||05.5"||91||1.711||Virgo|
|Mars||25th Aug 2012||13h 54m 20.5s||-12d 11m 08.9s||1.2||05.3"||91||1.767||Virgo|
|Jupiter||5th Aug 2012||04h 37m 55.5s||21d 18m 45.1s||-2.2||36.4"||99||5.415||Taurus|
|Jupiter||15th Aug 2012||04h 44m 29.1s||21d 30m 47.0s||-2.2||37.4"||99||5.276||Taurus|
|Jupiter||25th Aug 2012||04h 50m 08.5s||21d 40m 12.8s||-2.3||38.4"||99||5.130||Taurus|
|Saturn||5th Aug 2012||13h 32m 47.4s||-07d 06m 25.6s||0.9||16.6"||100||10.034||Virgo|
|Saturn||15th Aug 2012||13h 35m 21.0s||-07d 23m 44.0s||0.9||16.3"||100||10.186||Virgo|
|Saturn||25th Aug 2012||13h 38m 22.7s||-07d 43m 24.2s||1.0||16.1"||100||10.326||Virgo|
|Uranus||5th Aug 2012||00h 31m 48.3s||02d 37m 40.9s||5.8||03.6"||100||19.472||Cetus|
|Uranus||15th Aug 2012||00h 31m 02.3s||02d 32m 28.3s||5.8||03.6"||100||19.343||Cetus|
|Uranus||25th Aug 2012||00h 30m 02.0s||02d 25m 46.8s||5.8||03.7"||100||19.235||Cetus|
|Neptune||5th Aug 2012||22h 17m 53.4s||-11d 14m 29.2s||7.8||02.4"||100||29.036||Aquarius|
|Neptune||15th Aug 2012||22h 16m 53.7s||-11d 20m 16.8s||7.8||02.4"||100||28.996||Aquarius|
|Neptune||25th Aug 2012||22h 15m 51.5s||-11d 26m 14.7s||7.8||02.4"||100||28.984||Aquarius|