Mercury reaches superior conjunction on the far side of the Sun on June 6th. The fast moving planet then moves rapidly out from the Sun to become an early evening object, visible low down above the western horizon, during the second half of the month. It subsequently improves in altitude each evening, although fading in brightness at the same time. However from northern temperate locations, Mercury has to battle against the bright evening twilight and therefore best glimpsed towards the end of month. On June 15th, the planet shines at magnitude -1.2 but by months end it will have dropped to magnitude -0.2. Mercury then sets up to 90 minutes after the Sun. Much brighter Venus, is located in the same region of sky, although considerably higher above the horizon.
On June 25th, Mercury passes 5 degrees south of Pollux (mag. +1.1). At magnitude +0.4, Mercury will be the brighter of the pair.
Venus continues to illuminate the western sky after sunset. The brilliant "evening star" is visible as soon as it's dark enough and dominates the view. Brighter than all other planets, Venus continues to increase in brightness, improving from magnitude -3.9 to -4.1 as the month progresses. During this time, its angular size increases slightly from 13 to 15 arc seconds. Venus begins June in Gemini, close to Pollux (mag. +1.1), before moving into Cancer on the June 11th. Later on June 19th and 20th, it passes near to M44, also know as the Praesepe or Beehive Cluster. Throughout the month the planet sets between 2.5 to 3 hours after the Sun.
On June 16th, the thin waxing crescent Moon passes a couple of degrees south of Venus, providing pleasant early evening viewing.
Mars, in Capricornus, brightens quite dramatically this month as it heads towards its much anticipated opposition in July. The red planet starts the month at magnitude -1.2, but by months end it will have more than doubled in brightness to magnitude -2.1. During the same time period, its apparent size improves from 15 to 21 arc seconds. With a small telescope, it's now possible to spot details, such as Syrtis Major, on its pink surface. Since Capricornus is a faint constellation with no stars above 3rd magnitude, Mars dominates this region of sky.
From northern temperate locations, the planet rises about midnight at the start of the month, improving by about 90 minutes at months end. Further south, Mars is superbly placed for observation. For example, from Sydney, Australia it rises just prior to 9:00pm at the onset of June, but by months end is visible from 7:15pm. During the night as it passes the meridian, Mars reaches a peak altitude of some 78 degrees above the northern horizon.
On June 3rd, the waning gibbous Moon passes 3 degrees north of Mars. On June 28th, Mars reaches its first stationary point, which signals the beginning of this year's opposition period. The planet then commences retrograde motion.
Jupiter is now a month past opposition and remains a stunning object moving retrograde in Libra. As soon as it's dark enough, the gas giant is visible towards the east and remains so until the early hours of the morning. Jupiter starts the month at mag. -2.5 with an apparent diameter of 44 arc seconds. By months end it has faded slightly to mag. -2.3 and shrunk to 41 arc seconds.
When viewed through a telescope a wealth of Jovian cloud details are visible including bands, twists, knots and storms. Also easily visible, but not always at the same time, are the four bright Galilean moons: Io, Europa, Ganymede and Callisto.
A lovely pairing occurs on the night of June 23rd when the waxing gibbous Moon passes four degrees north of Jupiter.
Saturn, mag. 0.0, reaches opposition in Sagittarius on June 27th. This month, the sixth planet from the Sun, is at its best for the year and practically visible all night long. With a declination of -22 degrees, Saturn is much better placed from southern and tropical locations. It appears higher in the sky and has a longer visibility period than from northern temperate latitudes.
At opposition, Saturn is 9.049 AU (1,354 million kilometres or 841 million miles) from Earth. Even a small telescope will show its most famous feature, the spectacular ring system. Also easily visible is Titan, the largest and brightest moon, which at 8th magnitude can be spotted with binoculars. Small scopes reveal other moons including Rhea, Tethys and Dione. In total, Saturn's disk spans 18.4 arc seconds in diameter.
On June 1st and 28th, the full Moon passes 2 degrees north of Saturn.
Uranus, mag. +5.9, is located in Aries. For northern temperate observers, the planet is lost to the bright twilight during the first half of the month, but by months end rises over three hours before the Sun. Observers located further south have it better with Uranus visible throughout June. At the end of the month, from such locations, it rises a few hours after midnight.
The waning crescent Moon passes 5 degrees south of Uranus on June 10th.
Neptune, mag. +7.9, is in Aquarius. By months end the distant planet rises a couple of hours after midnight from northern temperate latitudes and before midnight for those located further south. Neptune is located about 30 degrees south and slightly west of the centre of the Great Square of Pegasus. It can be found about a quarter of the way along an imaginary line connecting phi Aquarii (φ Aqr - mag. +4.2) with lambda Aquarii (λ Aqr - mag. +3.7). Although the distance ice giant is the only planet that's not visible to the naked eye, it can easily be seen with binoculars and small telescopes.
On June 6th, the last quarter Moon passes 2 degrees south of Neptune. Later on June 19th, Neptune reaches its first stationary point, which signals the beginning of this year's opposition period. The planet then commences retrograde motion.
Solar System Data Table - June 2018
|Date||Right Ascension||Declination||Mag.||App. Size||Illum. (%)||Dist. (AU)||Constellation|
|Sun||Jun 01||04h 34m 24.1s||21d 58m 47.3s||-26.7||31.5'||100||1.014||Taurus|
|Sun||Jun 15||05h 32m 12.3s||23d 16m 58.7s||-26.7||31.5'||100||1.016||Taurus|
|Sun||Jun 30||06h 34m 32.2s||23d 11m 58.3s||-26.7||31.5'||100||1.017||Gemini|
|Mercury||Jun 01||04h 08m 09.0s||20d 48m 44.8s||-1.7||5.2"||97||1.305||Taurus|
|Mercury||Jun 15||06h 18m 49.5s||25d 09m 40.1s||-1.2||5.3"||91||1.266||Gemini|
|Mercury||Jun 30||08h 13m 56.9s||21d 23m 09.8s||-0.2||6.5"||63||1.040||Cancer|
|Venus||Jun 01||07h 04m 10.3s||24d 31m 26.2s||-3.9||13.1"||80||1.271||Gemini|
|Venus||Jun 15||08h 14m 51.6s||21d 53m 56.9s||-4.0||14.2"||76||1.177||Cancer|
|Venus||Jun 30||09h 25m 23.7s||17d 03m 33.7s||-4.1||15.6"||70||1.068||Leo|
|Mars||Jun 01||20h 32m 49.4s||-21d 46m 51.2s||-1.2||15.3"||91||0.612||Capricornus|
|Mars||Jun 15||20h 46m 20.7s||-21d 55m 28.9s||-1.6||17.8"||93||0.526||Capricornus|
|Mars||Jun 30||20h 50m 55.3s||-22d 46m 58.7s||-2.1||20.7"||96||0.453||Capricornus|
|Jupiter||Jun 01||14h 52m 57.7s||-15d 16m 05.9s||-2.5||44.1"||100||4.468||Libra|
|Jupiter||Jun 15||14h 47m 51.7s||-14d 56m 32.9s||-2.4||43.0"||100||4.580||Libra|
|Jupiter||Jun 30||14h 44m 36.4s||-14d 45m 41.4s||-2.3||41.5"||99||4.746||Libra|
|Saturn||Jun 01||18h 32m 11.0s||-22d 21m 01.9s||0.2||18.2"||100||9.153||Sagittarius|
|Saturn||Jun 15||18h 28m 10.2s||-22d 24m 37.8s||0.1||18.3"||100||9.073||Sagittarius|
|Saturn||Jun 30||18h 23m 26.8s||-22d 28m 40.1s||0.0||18.4"||100||9.050||Sagittarius|
|Uranus||Jun 01||01h 54m 35.9s||11d 10m 44.8s||5.9||3.4"||100||20.656||Aries|
|Uranus||Jun 15||01h 56m 55.8s||11d 23m 17.9s||5.9||3.4"||100||20.488||Aries|
|Uranus||Jun 30||01h 58m 56.7s||11d 33m 58.0s||5.8||3.5"||100||20.271||Aries|
|Neptune||Jun 01||23h 10m 30.0s||-06d 20m 10.8s||7.9||2.3"||100||30.030||Aquarius|
|Neptune||Jun 15||23h 10m 49.2s||-06d 18m 48.1s||7.9||2.3"||100||29.794||Aquarius|
|Neptune||Jun 30||23h 10m 43.4s||-06d 20m 04.2s||7.9||2.3"||100||29.550||Aquarius|