Mercury remains well placed in the morning sky during the first half of May for observers in the tropics and Southern Hemisphere. It is visible towards the east-north-east just before sunrise. The planet increases in brightness from mag. 0.0 on May 1st to mag. –1.0 on May 17th as it moves closer to the Sun in the sky.
For Northern Hemisphere observers, Mercury is poorly positioned in May. Despite a reasonable separation from the Sun at the start of the month, it rises only about half an hour before the Sun from London, England. For the remainder of the month, it remains close to the Sun and difficult to observe.
The planet reaches superior conjunction on May 27th and perihelion on May 29th. At perihelion it is located only 0.307495 AU (approx. 46 million km or 28.6 million miles) from the Sun.
Venus begins the month as a brilliant evening star, shining at mag. –4.7, setting four hours after the Sun in Northern temperate latitudes and nearly 2 hours for observers in the tropics and the Southern Hemisphere. On May 6th, a nice conjunction occurs when Venus passes only 49 arcminutes from mag. 1.7 star Elnath (beta Tauri). With a mag. difference of about 6, Venus appears more than 250 times brighter than Elnath!
The planet then draws rapidly towards the Sun as the month progresses and by the last week of May will be difficult to pick out against the bright evening twilight.
Mars has now completed its latest retrograde motion and is now moving direct in Leo. It is visible as soon as night falls and sets in the early hours of the morning. The planet has been moving back and forth in Leo for some time, but now its again moving eastwards the motion of the Red planet against the background stars is noticeably quick. At the beginning of the month Mars is only a few degrees from Regulus, the brightest star in Leo, by the end of the month the distance has more than doubled.
Mars shines at mag. 0.0 with an apparent diameter of 10 arc seconds on May 1st. However, the rapid increase in distance between Mars and the Earth is starting to take its toll; the mag. reduces by months end to 0.5 and the apparent size to 8 arc minutes. Consequently, seeing details with a small telescope may be difficult, although the northern polar cap should be visible at the end of the month.
Jupiter is in conjunction with the Sun on May 13th and is not easily visible this month.
Saturn reached opposition last month and is still well placed for observation during May. The planet is moving retrograde in the constellation of Virgo just north of bright star Spica. At mag. 0.3, Saturn is brighter than mag. 1.0 Spica and appears more yellowish compared with blue-white Spica.
Through a telescope Saturn looks fantastic, the rings are tilted at 14 degrees and are a wonderful sight whatever size instrument you have. On May 4th and 31st, the Moon forms a nice triangle with Saturn and Spica.
Uranus is a mag. 5.9 morning object but not easily visible from Northern temperate regions. Observers located in the tropics and Southern hemisphere fair much better with the planet visible up to four hours before sunrise on May 31st.
During May, Uranus crosses the boundary from Pisces into Cetus.
Neptune is also a morning object and like Uranus, is much better placed when viewed from the Southern Hemisphere or the tropics. The planet is located in Aquarius and shines at mag. 7.9. From the Northern hemisphere it may be spotted an hour or so before sunrise at the end of the month. For Southern hemisphere observers, Neptune is visible as a morning object during May and rises around midnight on May 31st.
Solar System Data Table - May 2012
|Date||Right Ascension||Declination||Mag.||Size||Illum. (%)||Distance (AU)||Constellation|
|Sun||5th May 2012||02h 49m 46.3s||16d 18m 15.9s||-26.7||31.7'||100||1.009||Aries|
|Sun||15th May 2012||03h 28m 50.1s||18d 54m 28.2s||-26.7||31.6'||100||1.011||Taurus|
|Sun||25th May 2012||04h 08m 51.1s||20d 58m 47.0s||-26.7||31.6'||100||1.013||Taurus|
|Mercury||5th May 2012||01h 28m 59.9s||06d 29m 41.3s||-0.3||6.1"||70||1.103||Pisces|
|Mercury||15th May 2012||02h 34m 32.3s||13d 28m 48.8s||-0.9||5.4"||86||1.241||Aries|
|Mercury||25th May 2012||03h 56m 02.4s||20d 28m 03.5s||-2.1||5.1"||99||1.320||Taurus|
|Venus||5th May 2012||05h 23m 38.5s||27d 49m 06.8s||-4.7||39.9"||23||0.418||Taurus|
|Venus||15th May 2012||05h 32m 57.1s||27d 21m 54.0s||-4.6||46.8"||14||0.356||Taurus|
|Venus||25th May 2012||05h 25m 27.9s||25d 56m 11.7s||-4.3||53.7"||05||0.311||Taurus|
|Mars||5th May 2012||10h 34m 28.2s||11d 03m 34.9s||0.1||9.6"||91||0.974||Leo|
|Mars||15th May 2012||10h 43m 48.6s||09d 46m 22.2s||0.2||8.9"||90||1.052||Leo|
|Mars||25th May 2012||10h 55m 48.2s||08d 13m 59.3s||0.4||8.3"||89||1.132||Leo|
|Jupiter||5th May 2012||03h 15m 46.3s||17d 15m 45.2s||-2.0||32.9"||100||5.998||Aries|
|Jupiter||15th May 2012||03h 25m 22.4s||17d 52m 43.6s||-2.0||32.8"||100||6.010||Taurus|
|Jupiter||25th May 2012||03h 35m 01.3s||18d 27m 37.5s||-2.0||32.8"||100||6.002||Taurus|
|Saturn||5th May 2012||13h 35m 46.0s||-07d 01m 19.5s||0.3||18.9"||100||8.775||Virgo|
|Saturn||15th May 2012||13h 33m 17.4s||-06d 48m 17.9s||0.3||18.8"||100||8.846||Virgo|
|Saturn||25th May 2012||13h 31m 12.0s||-06d 37m 56.8s||0.4||18.6"||100||8.943||Virgo|
|Uranus||5th May 2012||00h 25m 50.4s||02d 02m 10.4s||5.9||3.4"||100||20.854||Pisces|
|Uranus||15th May 2012||00h 27m 30.6s||02d 12m 43.8s||5.9||3.4"||100||20.741||Cetus|
|Uranus||25th May 2012||00h 28m 59.1s||02d 21m 58.3s||5.9||3.4"||100||20.609||Cetus|
|Neptune||5th May 2012||22h 20m 13.2s||-10d 58m 35.5s||7.9||2.3"||100||30.294||Aquarius|
|Neptune||15th May 2012||22h 20m 45.4s||-10d 55m 51.0s||7.9||2.3"||100||30.130||Aquarius|
|Neptune||25th May 2012||22h 21m 05.4s||-10d 54m 15.9s||7.9||2.3"||100||29.962||Aquarius|