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Mercury

Mercury passed inferior conjunction on May 30th and was therefore positioned too close to the Sun to be observable. However, it moves rapidly out from the Sun so that two weeks later it becomes visible as a morning object for observers in the tropics and Southern Hemisphere. The planet subsequently climbs higher in the sky and brightens each day until it reaches a peak altitude on June 24th, the date of greatest elongation west (22.5 degrees from the Sun). Also on this day Mercury passes 2 degrees north of orange giant star Aldebaran (α Tau) the brightest star in the constellation of Taurus "the Bull". At magnitude +0.4 Mercury is half a magnitude brighter than the star with the pairing making a lovely early morning binocular / small telescope view.

It should also be noted that once past greatest elongation west, Mercury continues to brighten as it begins to draw into the Sun. For example, the planet shines at mag. +1.7 on June 15 but by month's end it has brightened to magnitude -0.1. From northern temperate latitudes, Mercury is a more difficult catch as it battles against the long morning twilight. The best time to try and catch it is for a few days on and around June 24th when it should be visible low down above the east-northeast horizon just before sunrise. A pair of binoculars will easily show the magnitude +0.4 planet although be careful not to confuse it with nearby Aldebaran.

The diagram below shows the June / July morning apparition of Mercury from a latitude of 35S (approx. equal to Sydney, Cape Town and Santiago).

June / July morning apparition of Mercury from a latitude of 35S

Venus

The brightest object in western sky after sunset is Venus with the planet remaining well placed for observation throughout the month. On June 6th it reaches greatest elongation and on this day is positioned 45 degrees east of the Sun.

Currently moving eastward the declination of Venus decreases by 10 degrees as it moves from Gemini into Cancer and then into Leo. Consequently, the planets period of visibility decreases from 3.5 hours to less than 2 hours for observers located at Northern Hemisphere latitudes. For those living in the Southern Hemisphere the period of visibility remains around the 3-hour mark for the complete month.

Venus and Jupiter during June 2015

Jupiter and Venus during June 2015 - pdf format

There are three superb Venus conjunctions visible during June. On June 12th and 13th the planet slides less than a degree north of splendid open star cluster M44 "The Beehive", making a wonderful binocular sight. Then on June 20th, the waxing crescent Moon passes 6 degrees south of the planet. Finally Venus closes the gap on Jupiter and on the last day of June the two planets will be less than half a degree apart. To the naked eye they will appear stunning. Through binoculars and a telescope at low power both planets will appear in the same field of view, although Venus is about 10x the brighter of the pair.

The magnitude of Venus increases slightly from -4.3 to -4.4 with its phase decreasing from 53% to 34% during June.

Mars

Mars reaches solar conjunction on June 14th and therefore is unobservable throughout the month.

Jupiter

Jupiter remains an early evening object throughout June although it's now long past opposition and heading towards solar conjunction. The largest planet of the Solar System is visible towards the west as soon as it gets dark, but sets before midnight by months end. It's brightness decreases slightly from magnitude -1.9 to -1.8 as the month progresses.

The giant planet continues on a direct motion path, starting the month in Cancer before passing into Leo on June 10th. At the start of June, brighter Venus (mag. -4.3) is located about 20 degrees from Jupiter. It then closes the gap each subsequent evening before catching Jupiter at the tail end of the month. On June 30th, the two planets will be less than half a degree apart.

On June 21st, the waxing crescent Moon passes 5 degrees south of Jupiter.

Saturn

This month Venus and Jupiter dominate the early evening sky with Mercury visible for a time in the morning sky but the night belongs to Saturn. The planet is only just past opposition (May 23rd) and remains superbly placed for observation during June. It's currently moving retrograde in western Libra and visible towards the southeast (NH) / east (SH) as darkness falls. Saturn can be observed practically all night and is better seen from southern latitudes where it's situated much higher in the sky.

Since now past opposition the apparent brightness and apparent size of Saturn will gradually decrease as the Earth moves away. During June, its magnitude decreases from 0.0 to +0.2 with the apparent diameter shrinking slightly from 18.5 to 18.0 arc seconds.

Saturn imaged by the Cassini space probe (NASA)

Saturn's wonder of course is its ring system. They are currently tilted at 24 degrees from our perspective and even a small 80mm (3.1-inch) telescope will easily show them. At magnification 100x the rings are nicely visible, tightly circling the central gem of Saturn. Increase the magnification to 200x or greater (seeing permitting) and the ring shadow on the planet, the darker outer A ring, the lighter B ring, subtle shadings and colour changes on Saturn's surface may be detected.

A good quality larger telescope, with its increased light gathering capability and higher magnification capability will of course show greater detail. For example, a 200mm (8-inch) scope can under good seeing be used to up to 400x magnification and will also reveal the 0.7 arc seconds wide Cassini division, the Enke division, the hazy C-ring as well as up to half a dozen of Saturn's satellites.

The almost full Moon passes 2 degrees north of Saturn on June 1st and again on June 29th.

Saturn during June 2015

Saturn during June 2015 - pdf format

Uranus

Uranus starts the month as a morning object in Pisces with the planets visibility steadily improving as the month progresses. For Northern Hemisphere based observers at the start of June, it's visible above the eastern horizon for about an hour before twilight interferes. By months end the planet is much higher in the sky, rising more than 4 hours before the Sun.

Observers located further south have it even better with Uranus well placed in the morning sky throughout the month. At the beginning of the June the planet rises some 4 hours before the Sun and by the end of the month it's visible before midnight.

Uranus is a distant ice giant that shines at magnitude +5.9 and therefore bright enough to be seen with the naked eye from a dark site. Unfortunately most people don't have the luxury of such fine seeing conditions and therefore a pair of binoculars or small telescope is usually required to spot the planet.

On June 11th, the waning crescent Moon passes 0.5 degrees south of Uranus and an occultation is visible from South and East Australia, New Zealand, Fiji and Samoa (20:26 UT).

Uranus during June 2015

Uranus during June 2015 - pdf format

Neptune

Neptune shines at mag. +7.9 and is now well placed for observation amongst the stars of Aquarius. By months end the most distant planet of all rises around midnight from northern temperate latitudes and much earlier for those located further south. It's currently located about 30 degrees southwest of the Great Square of Pegasus and a few degrees southwest of star lambda (λ) Aqr (mag. +3.7).

On June 9th, the last quarter Moon passes 3 degrees north of Neptune. Three days late Neptune reaches its first stationary point, signaling the beginning of this year's opposition period. The planet then commences retrograde motion.

Neptune during June 2015

Neptune during June 2015 - pdf format

Solar System Data Table June 2015

 DateRight AscensionDeclinationApparent MagnitudeApparent SizeIllum. (%)Distance from Earth (AU)Constellation
Sun5th June 201504h 49m 51.8s22d 27m 32.1s-26.731.5'1001.014Taurus
Sun15th June 201505h 31m 14.2s23d 16m 21.3s-26.731.5'1001.016Taurus
Sun25th June 201506h 12m 50.0s23d 24m 16.6s-26.731.5'1001.016Gemini
Mercury5th June 201504h 18m 52.4s18d 00m 48.1s4.512.0"030.562Taurus
Mercury15th June 201504h 14m 12.3s16d 55m 08.3s1.810.2"170.663Taurus
Mercury25th June 201504h 38m 26.8s18d 44m 46.2s0.408.0"370.836Taurus
Venus5th June 201508h 07m 29.4s22d 47m 48.5s-4.423.1"510.724Cancer
Venus15th June 201508h 45m 53.5s20d 06m 24.3s-4.526.0"450.643Cancer
Venus25th June 201509h 18m 40.2s16d 57m 23.6s-4.629.6"380.563Cancer
Mars5th June 201505h 00m 55.4s23d 16m 55.8s1.503.7"1002.553Taurus
Mars15th June 201505h 30m 41.9s23d 53m 20.9s1.503.6"1002.569Taurus
Mars25th June 201506h 00m 21.7s24d 08m 24.6s1.503.6"1002.580Taurus
Jupiter5th June 201509h 18m 51.2s16d 34m 54.7s-1.934.3"995.748Cancer
Jupiter15th June 201509h 25m 01.5s16d 05m 42.2s-1.933.5"995.885Leo
Jupiter25th June 201509h 31m 47.0s15d 33m 01.6s-1.832.8"1006.009Leo
Saturn5th June 201515h 55m 07.2s-18d 07m 33.7s0.018.5"1008.991Libra
Saturn15th June 201515h 52m 17.1s-18d 00m 15.4s0.118.4"1009.044Libra
Saturn25th June 201515h 49m 47.2s-17d 54m 11.5s0.218.2"1009.123Libra
Uranus5th June 201501h 12m 03.0s06d 57m 17.8s5.903.4"10020.565Pisces
Uranus15th June 201501h 13m 21.8s07d 05m 02.5s5.903.5"10020.421Pisces
Uranus25th June 201501h 14m 25.5s07d 11m 13.3s5.903.5"10020.265Pisces
Neptune5th June 201522h 45m 46.1s-08d 41m 34.5s7.902.3"10029.873Aquarius
Neptune15th June 201522h 45m 49.3s-08d 41m 38.7s7.902.3"10029.706Aquarius
Neptune25th June 201522h 45m 40.3s-08d 42m 55.8s7.902.3"10029.546Aquarius