Mercury reaches greatest elongation east on May 25th. On this date, the closest planet to the Sun is positioned 23 degrees east of the Sun and hence visible as an evening star low down above the western horizon just after sunset. As is often the case with Mercury apparitions, one hemisphere of the Earth is favoured over the other. This time, observers at northern temperature latitudes have it slightly better than their southern counterparts with the added bonus that this also happens to be the north's most favourable evening apparition of the year.
For example, from latitude 52N (e.g. London, England) Mercury should be visible from about May 7th. The best time to search for the planet is during the period just before and after it reaches its highest point in the sky (May 25th). On this date 45 minutes after sunset, Mercury will be 10 degrees above the horizon and shine at magnitude +0.3. Before this, Mercury will be brighter but lower down.
Mercury fades from magnitude -1.7 to +1.3 during May. From the Southern Hemisphere, Mercury is visible from about the middle of May, appearing closer to the horizon than from locations further north.
Venus remains a superb early morning object. Although continuing to fade slightly from magnitude -4.1 to -4.0 during May, the planet is dazzling, an unmistakable beacon of light towards the east before sunrise.
While Mercury is better seen from the Northern Hemisphere this month, Venus is very much a Southern Hemisphere object. Observers from these locations continue to enjoy more than 3 hours of visibility before dawn, whereas for northern-based observers, Venus is visible for just 1 hour before sunrise.
On May 15th, Venus passes 1.3 degrees south of the much fainter Uranus. Uranus is at mag. +5.9 and the pair should be visible with binoculars or a wide field telescope, especially from southern latitudes. Later in the month (May 25th) the thin waning crescent Moon passes 2 degrees north of Venus.
Mars is now just past opposition but remains well paced for observation during May. The "Red Planet" is located in Virgo, visible as soon as it's dark enough and easily recognizable due to its colour and brilliance; the brightest object in that part of the sky.
Mars starts May moving slowly continuing its westerly retrograde motion just south of Porrima (γ Vir - mag. +2.7). On May 20th the planet reaches its second stationary point, marking the end of the Martian opposition period. Subsequently the planet resumes direct motion once again and heads eastwards. What's particularly noticeable during May is the brightness fading of Mars, from magnitude -1.2 to -0.5. The apparent size also decreases from 14.5 to 11.9 arc seconds. Despite the small size of Mars, even a 100mm (4-inch) telescope at high magnifications - under good seeing conditions - will show the Martian polar cap as well as other major surface features such as Syrtis Major and various dusty shadings.
On May 11th, the waxing gibbous Moon passes 3 degrees south of Mars.
Jupiter dominates the early evening sky and the first half of the night. The planet is now moving direct amongst the stars of Gemini and fades very slightly from magnitude -2.0 to -1.9 during May. Despite this, Jupiter remains brighter than both other nighttime planets on view, Mars and Saturn. It's apparent diameter decreases slightly from 35 to 33 arc seconds as the month progresses.
From northern temperate latitudes Jupiter sets at around midnight by months end, but much earlier for those located further south. On May 4th, the waxing crescent Moon passes 5 degrees south of Jupiter forming a nice evening pairing.
Saturn reaches opposition on May 10th and is subsequently visible all night as it continues its slow retrograde motion through the faint constellation of Libra. The favourite planet of many astronomers is at it's best this month with an apparent diameter of almost 19 arc seconds, rings wide open, beautifully displayed with a tilt of 22 degrees. The apparent diameter of the planet including the rings spans some 42 arc seconds.
Through telescopes, Saturn's rings are a wonderful sight and visible even in the smallest of instruments, along with Titan, the largest and brightest moon of Saturn. Larger telescopes reveal subtle planet details and many of the planets other moons.
At opposition, Saturn shines at magnitude +0.1 and is positioned 8.90 AU or approximately 1331 million kilometres (827 million miles) from Earth. The full Moon passes 0.6 degrees south of Saturn on May 14th with an occultation visible from Australia and New Zealand.
Uranus at magnitude +5.9 is currently located in Pisces. For the first half of May from northern temperate latitudes the planet is too down low to be seen against the bright morning twilight. However, the situation quickly improves and by months end Uranus rises over 2 hours before the Sun; hence visible through binoculars and telescopes against the now darker backdrop. Observers located further south have it even better with Uranus well placed in the early morning sky throughout the month. At the start of the May, the planet rises 2 hours before the Sun, more than doubling the time by May 31st.
A nice conjunction occurs on May 15th when Venus (mag. -4.1) passes less than 1.5 degrees south of Uranus. The difference in brilliance between the two planets is stark, Venus being about 10,000x brighter than the much larger but distant Uranus! Wide field scopes will show both planets together although Uranus is challenging from northern latitudes due to its low altitude. For those located further south, altitude is not a problem and a pair of binoculars should suffice.
The waning crescent Moon passes 2 degrees north of Uranus on May 24th.
Neptune, mag. +7.9, is an early morning in Aquarius. The planet is now two months past solar conjunction and like Uranus remains an early morning object towards the east, best seen from southern latitudes.
As the month progresses the planets visibility improves as it gains altitude each subsequent morning. Neptune is the only planet that's not visible to the naked eye, although when dark enough it can be spotted with binoculars, rising more than an hour earlier than Uranus.
On May 22nd, the waning crescent Moon passes 5 degrees north of Neptune.
Solar System Data Table May 2014
|Date||Right Ascension||Declination||Apparent Magnitude||Apparent Size||Illum. (%)||Distance from Earth (AU)||Constellation|
|Sun||5th May 2014||02h 47m 06.8s||16d 06m 36.0s||-26.7||31.7'||100||1.008||Aries|
|Sun||15th May 2014||03h 26m 06.5s||18d 44m 50.0s||-26.7||31.6'||100||1.011||Taurus|
|Sun||25th May 2014||04h 06m 02.6s||20d 51m 27.8s||-26.7||31.6'||100||1.013||Taurus|
|Mercury||5th May 2014||03h 27m 20.3s||20d 01m 22.3s||-1.4||05.4"||91||1.243||Aries|
|Mercury||15th May 2014||04h 45m 21.2s||24d 37m 56.3s||-0.6||06.4"||63||1.046||Taurus|
|Mercury||25th May 2014||05h 42m 48.7s||25d 26m 48.7s||0.4||08.1"||37||0.834||Taurus|
|Venus||5th May 2014||00h 09m 42.2s||00d 32m 30.7s||-4.1||16.5"||68||1.011||Pisces|
|Venus||15th May 2014||00h 52m 22.2s||03d 38m 47.0s||-4.1||15.4"||72||1.085||Pisces|
|Venus||25th May 2014||01h 35m 46.4s||07d 50m 42.5s||-4.0||14.4"||75||1.156||Pisces|
|Mars||5th May 2014||12h 40m 08.2s||-02d 46m 07.4s||-1.1||14.3"||97||0.657||Virgo|
|Mars||15th May 2014||12h 34m 35.0s||-02d 38m 48.2s||-0.9||13.4"||95||0.700||Virgo|
|Mars||25th May 2014||12h 33m 54.7s||-03d 00m 28.1s||-0.7||12.4"||93||0.753||Virgo|
|Jupiter||5th May 2014||07h 06m 54.6s||22d 51m 16.2s||-2.0||34.9"||99||5.649||Gemini|
|Jupiter||15th May 2014||07h 14m 01.7s||22d 39m 53.9s||-2.0||34.1"||99||5.785||Gemini|
|Jupiter||25th May 2014||07h 21m 46.1s||22d 26m 07.9s||-1.9||33.4"||100||5.908||Gemini|
|Saturn||5th May 2014||15h 13m 57.5s||-15d 24m 30.3s||0.1||18.7"||100||8.905||Libra|
|Saturn||15th May 2014||15h 10m 57.3s||-15d 12m 51.4s||0.1||18.7"||100||8.902||Libra|
|Saturn||25th May 2014||15h 08m 00.7s||-15d 01m 46.9s||0.1||18.6"||100||8.930||Libra|
|Uranus||5th May 2014||00h 52m 49.5s||04d 57m 07.1s||5.9||03.4"||100||20.891||Pisces|
|Uranus||15th May 2014||00h 54m 38.8s||05d 08m 23.7s||5.9||03.4"||100||20.796||Pisces|
|Uranus||25th May 2014||00h 56m 18.1s||05d 18m 33.4s||5.9||03.4"||100||20.680||Pisces|
|Neptune||5th May 2014||22h 36m 07.3s||-09d 34m 12.1s||7.9||02.2"||100||30.352||Aquarius|
|Neptune||15th May 2014||22h 36m 44.7s||-09d 30m 51.5s||7.9||02.3"||100||30.192||Aquarius|
|Neptune||25th May 2014||22h 37m 10.5s||-09d 28m 40.7s||7.9||02.3"||100||30.025||Aquarius|