Mercury was well placed for early birds in the tropics and southern hemisphere during the first half of last month before been lost to the Suns glare as it headed towards superior conjunction. Moving into June, Mercury is now past superior conjunction and reappears later this month in the evening sky.
Once again, it is southern hemisphere and tropics observers who have all the luck. From Sydney, Australia (35S), Mercury is visible for a few weeks from the middle of June. At its highest, Mercury will be more than 10 degrees above the horizon at the end of June / beginning of July. Unfortunately, as the planet moves higher in the sky it also dims in brightness, fading from mag. –1.8 to 0.4 as the month goes by. For northern hemisphere observers the planet is visible for a shorter time and located much lower in the sky; at best only 5 degrees or so north of the horizon when seen from London, England (51.5N).
Easily the celestial highlight of the month or even the year takes place on June 5/6 when Venus reaches inferior conjunction and transits the Sun. This extremely rare, only twice in a lifetime event, occur in pairs of 8 years with a gap of more than 100 years between them. For the current cycle, first performance took place on June 8, 2004 when the entire transit was visible from Europe, most of Asia, and almost all of Africa. The second show is on June 5/6 with the complete transit or at least part of it visible from most of the world including Europe, Asia, North America, Central America and Australasia. Missing that, you will have to wait until 2117 to catch this spectacle once more!! The diagram below shows the path of Venus as it moves across the Suns disk.
After the transit, Venus moves into the morning sky rising just before the Sun. As June progresses, the planet will rise a little earlier than the Sun each morning and by June 15, for observers for the tropics and southern hemisphere Venus can be glimpsed low down in the pre-dawn sky before sunrise. By the end of the month the planet will rise up to two-and-a-half hours before the Sun for observers at these latitudes. However, unfortunately Venus this month is inconveniently low for northern hemisphere based planet watchers.
Mars is easily visible in the evening sky as soon as darkness falls but is now well past its best. The great red planet of mystery fades from mag. 0.5 to 0.8 during June and shrinks to less than 7 arc seconds in diameter. Telescopically, it is now nigh on impossible to make out features on the surface with a small instrument although some success is possible with a large telescope. The planet is in direct motion and moves from Leo into Virgo on June 21 with the Moon passing 6 degrees south of Mars on June 26.
During June the distance between the Earth and Mars increases from 178 million km (1.19 AU) to 211 million km (1.41 AU).
Jupiter is also an early morning object this month. Now located in the constellation of Taurus, Jupiter passes south of the famous Pleiades star cluster (M45) during the middle of June. With a magnitude of –2.0, it is a conspicuous object towards the east in the pre-dawn sky. Like Mercury and Venus, Jupiter is better placed for observers from the tropics and southern hemisphere this month and rises just over an hour before the Sun at the start of the month, increasing to more than two-and-a-half hours by months end. Observers from the northern hemisphere will probably have more chance of sighting the planet during the second half of the month.
On June 17, a waning crescent Moon passes just over 1 degree north of Jupiter.
Saturn is currently a prominent night sky object. Although the faintest of the ancient naked eye planets and now past opposition, Saturn is still visible for most of the night, has an apparent size of about 18 arc seconds and the beautiful ring system is nicely positioned for observation.
Even though receding from Earth, Saturn still shines at mag. 0.6 and is easy to find just a few degrees north of mag. 1.0 star Spica. The planet moves retrograde during the start of the month, reaches its stationary point on June 26 and then resumes direct motion.
Uranus is now becoming a prominent morning object. This distance ice world hovers on the fringe of naked eye visibility (mag. 5.9) and unusually for a planet is currently not located in one of the 12 classic zodiac constellations. To find this planet you need to look in northwest Cetus about 1.5 degrees east of almost equal brightness star, 44 Piscium (mag. 5.8).
Like Uranus, Neptune is also becoming a more prominent object in the morning sky. Located in Aquarius, Neptune shines at mag. 7.9 and is a relatively easy binocular object.
Solar System Data Table June 2012
| ||Date||Right Ascension||Declination||Mag.||Size||Illum. (%)||Distance (AU)||Constellation|
|Sun||5th June 2012||04h 53m 46.6s||22d 33m 41.8s||-26.7||31.5'||100||1.015||Taurus|
|Sun||15th June 2012||05h 35m 10.9s||23d 18m 41.5s||-26.7||31.5'||100||1.016||Taurus|
|Sun||25th June 2012||06h 16m 47.1s||23d 22m 40.0s||-26.7||31.5'||100||1.017||Gemini|
|Mercury||5th June 2012||05h 37m 52.2s||25d 01m 17.5s||-1.3||05.3"||91||1.262||Taurus|
|Mercury||15th June 2012||07h 01m 11.0s||24d 42m 46.9s||-0.5||06.1"||70||1.108||Gemini|
|Mercury||25th June 2012||08h 04m 04.8s||21d 33m 24.2s||0.1||07.2"||51||0.932||Cancer|
|Venus||5th June 2012||05h 00m 45.5s||23d 08m 07.8s||-3.7||57.8"||00||0.289||Taurus|
|Venus||15th June 2012||04h 37m 05.5s||20d 10m 34.9s||-4.1||55.4"||03||0.301||Taurus|
|Venus||25th June 2012||04h 25m 45.0s||18d 05m 47.5s||-4.5||49.0"||11||0.340||Taurus|
|Mars||5th June 2012||11h 11m 26.6s||06d 17m 30.7s||0.6||07.7"||89||1.219||Leo|
|Mars||15th June 2012||11h 27m 25.3s||04d 20m 20.6s||0.7||07.2"||89||1.297||Leo|
|Mars||25th June 2012||11h 44m 48.7s||02d 14m 01.7s||0.8||06.8"||89||1.373||Virgo|
|Jupiter||5th June 2012||03h 45m 35.1s||19d 03m 14.0s||-2.0||33.0"||100||5.970||Taurus|
|Jupiter||15th June 2012||03h 55m 03.5s||19d 32m 50.1s||-2.0||33.3"||100||5.921||Taurus|
|Jupiter||25th June 2012||04h 04m 19.1s||19d 59m 37.4s||-2.0||33.7"||100||5.854||Taurus|
|Saturn||5th June 2012||13h 29m 27.9s||-06d 30m 16.2s||0.6||18.3"||100||9.075||Virgo|
|Saturn||15th June 2012||13h 28m 28.2s||-06d 27m 00.0s||0.6||18.0"||100||9.213||Virgo|
|Saturn||25th June 2012||13h 28m 04.6s||-06d 27m 26.7s||0.7||17.7"||100||9.365||Virgo|
|Uranus||5th June 2012||00h 30m 20.7s||02d 30m 23.5s||5.9||03.4"||100||20.447||Cetus|
|Uranus||15th June 2012||00h 31m 19.0s||02d 36m 18.2s||5.9||03.5"||100||20.288||Cetus|
|Uranus||25th June 2012||00h 32m 00.7s||02d 40m 25.5s||5.9||03.5"||100||20.123||Cetus|
|Neptune||5th June 2012||22h 21m 13.1s||-10d 53m 53.3s||7.9||02.3"||100||29.777||Aquarius|
|Neptune||15th June 2012||22h 21m 07.2s||-10d 54m 46.3s||7.9||02.3"||100||29.615||Aquarius|
|Neptune||25th June 2012||22h 20m 49.3s||-10d 56m 46.8s||7.9||02.3"||100||29.463||Aquarius|