Mercury

Mercury reaches greatest elongation on June 5th when it's positioned 24.2 degrees west of the Sun. Despite this at northern latitudes the angle of the ecliptic is unfavourable and the planet will be challenging to spot low down above the eastern horizon. However it's a different story from the Southern Hemisphere where elusive Mercury puts on a respectable morning show for the first three weeks of the month. During week one it rises more than two hours before the Sun and can be seen 10 degrees above the east-northeastern horizon an hour before sunrise. After that Mercury slips back towards the Sun until it's finally lost to the bright twilight during the last week of June. It should be noted that the planet gains in brightness from mag. +0.8 to -1.0 during the visibility period.

On June 3rd, the thin waning crescent Moon passes 0.7 degrees south of Mercury (mag. +0.5) with an occultation visible from southern Africa and Madagascar (9:47 UT).

Venus

Venus reaches superior conjunction on June 6th. Since the planet is currently located on the far side of the Sun it's not suitably placed for observation. Indeed from June 5th to June 7th, Venus passes directly behind the Sun as seen from Earth. This "occultation" lasts some 46 hours and for its duration no Earth based instrument will be able to detect the planet.

At conjunction Venus and the Earth are separated by 1.74 AU (260 million kilometers or 161 million miles).

Mars

Mars is just past opposition and remains well situated for observation throughout June. The "Red planet" is visible after sunset and remains so until the early hours of the morning. It's better placed from tropical and southern latitudes where it appears higher in the sky and has a longer visibility period than at mid-northern latitudes. Although still shining brightly it does fade from mag. -2.0 to -1.4 as the month progresses.

Mars as imaged by the Hubble Space Telescope on August 26, 2003 (credit:- NASA/ESA)

Mars starts the month moving retrograde among the faint stars of Libra. On the last day of June it reaches its second stationary point, which is often regarded as the end of the opposition period, thereafter direct motion is once again resumed.

The apparent size of the planet decreases from 18.6 to 16.5 arc seconds this month but remains large enough that major surface details such as the Polar Cap and Syrtis Major are visible even with a small scope. On initial observation the surface may appear bland but with patience it's possible to tease out subtle details. Also don't be afraid to push up the magnification, Mars will take it.

The surrounding region of sky also contains Saturn (mag. 0.0) about 15 degrees east of Mars and first magnitude red supergiant star Antares (α Sco - mag. +1.0) approx. 15 degrees to the southeast. Of the three objects Mars is the brightest followed by Saturn then Antares.

On June 17th the waxing gibbous Moon passes 7 degrees north of Mars.

The Moon, Mars and Saturn as seen after sunset on June 17, 2016 from London, England (credit:- stellarium/freestarcharts)

Mars and Saturn during June 2016 (credit:- freestarcharts)

Mars and Saturn during June 2016 - pdf format (credit:- freestarcharts)

Jupiter

Although now fading Jupiter remains visible as a brilliant evening object towards the west as soon as it's dark enough. However the planet's visibility is reducing and by June 30th it sets before midnight from northern temperate latitudes and slightly earlier for those living further south. During the month, Jupiter continues its direct eastwards motion among the faint stars of Leo, some way south of the main constellation pattern.

As the month progresses, Jupiter fades from mag. -2.0 to -1.9 with its apparent size decreasing from 37 to 34 arc seconds. On June 11th the waxing crescent Moon passes 1.5 degrees south of Jupiter offering a nice early evening pairing.

The Moon and Jupiter after sunset on June 11th from New York City (credit:- stellarium/freestarcharts)

Jupiter during June 2016 (credit:- freestarcharts)

Jupiter during June 2016 - pdf format (credit:- freestarcharts)

Saturn

Saturn, mag. 0.0, reaches opposition in Ophiuchus on June 3rd. The famous "Ringed planet" is visible all night long and at its best for the year. With a declination of -20.5 degrees it's much better placed from southern and tropical locations where it appears higher in the sky and has a longer visibility period than from northern temperate latitudes.

Saturn as imaged by the Cassini spaceprobe (credit:- NASA/ESA)

At opposition, Saturn is located 9.015 AU (1349 million kilometres or 838 million miles) from Earth. Even a small telescope will show its most famous feature, the spectacular rings. Also visible is the largest and brightest moon of Saturn, eighth magnitude Titan which can be seen with binoculars. Small scopes will also show additional moons including Rhea, Tethys and Dione.

A good opportunity exists this month to spot bizarre moon Iapetus. This world is famous for its "two-tone" colouration with one side being much darker in colour than the other. As a result when Iapetus is positioned on the western side of Saturn (when viewed from Earth) it appears brighter than from the opposite side. This happens on June 22nd with Iapetus peaking at mag. +10.1 and easily within the range of small scopes.

Before that on June 19th, the full Moon passes 3 degrees north of Saturn.

Mosaic of Iapetus images taken by the Cassini spacecraft on Dec 31, 2004 (NASA/Cassini_Probe/Matt McIrvin)

Uranus

Uranus, mag. +5.9, is now a morning object in Pisces. For northern temperate observers the planet is swamped by the bright early morning twilight sky for most of June. Nevertheless, towards the end of the month it can be seen with binoculars and small scopes above the eastern horizon an hour or so before sunrise.

Observers located further south have it much better with Uranus well placed in the morning sky throughout June. At the beginning of the month it rises some 4 hours before the Sun improving to before midnight by months end.

On June 1st and 28th, the waning crescent Moon passes a couple of degrees south of Uranus.

Uranus during June 2016 (credit:- freestarcharts)

Uranus during June 2016 - pdf format (credit:- freestarcharts)

Neptune

Neptune shines at mag. +7.9 and is now well placed for observation in Aquarius. By months end the most distant planet rises around midnight from northern temperate latitudes but much earlier for those located further south. It's positioned about 30 degrees south of the Great Square of Pegasus. Locating Neptune is easy at the moment since star lambda Aqr (λ Aqr - mag. +3.7) is just 0.5 degrees northwest of the planet. Neptune is the only planet that's not visible to the naked eye but it can be readily seen with binoculars and small telescopes.

On June 14th, Neptune reaches its first stationary point signaling the beginning of this year's opposition period. The planet then commences retrograde motion. Later on the 26th the waning gibbous Moon passes close by Neptune with an occultation visible from central and Northern Europe (0 UT).

Neptune during June 2016 (credit:- freestarcharts)

Neptune during June 2016 - pdf format (credit:- freestarcharts)

Solar System Data Table June 2016

 DateRight AscensionDeclinationApparent MagnitudeApparent SizeIllum. (%)Distance from Earth (AU)Constellation
Sun5th June 201604h 52m 55.5s22d 32m 30.7s-26.731.5'1001.015Taurus
Sun15th June 201605h 34m 19.8s23d 18m 21.9s-26.731.5'1001.016Taurus
Sun25th June 201606h 15m 54.0s23d 23m 12.9s-26.731.5'1001.016Gemini
Mercury5th June 201603h 16m 41.6s14d 25m 41.7s0.508.3"370.745Aries
Mercury15th June 201604h 04m 17.0s18d 18m 35.2s-0.306.7"581.005Taurus
Mercury25th June 201605h 59m 15.0s23d 47m 51.6s-1.505.3"941.275Taurus
Venus5th June 201604h 50m 44.2s22d 24m 02.7s-4.009.6"1001.735Taurus
Venus15th June 201605h 43m 53.9s23d 41m 56.5s-4.009.6"1001.734Taurus
Venus25th June 201606h 37m 37.7s23d 50m 35.4s-3.909.7"1001.726Gemini
Mars5th June 201615h 36m 52.2s-21d 14m 39.5s-1.918.5"990.505Libra
Mars15th June 201615h 25m 40.3s-20d 59m 56.8s-1.818.0"970.522Libra
Mars25th June 201615h 19m 42.0s-20d 55m 59.8s-1.517.0"950.551Libra
Jupiter5th June 201611h 03m 14.7s07d 26m 53.3s-2.036.8"995.354Leo
Jupiter15th June 201611h 06m 29.8s07d 04m 34.2s-2.035.8"995.510Leo
Jupiter25th June 201611h 10m 37.2s06d 36m 50.2s-1.934.8"995.663Leo
Saturn5th June 201616h 46m 12.8s-20d 32m 19.7s0.018.4"1009.015Ophiuchus
Saturn15th June 201616h 43m 06.5s-20d 27m 34.3s0.118.4"1009.035Ophiuchus
Saturn25th June 201616h 40m 11.3s-20d 23m 17.2s0.118.3"1009.084Ophiuchus
Uranus5th June 201601h 26m 26.6s08d 25m 38.3s5.903.4"10020.578Pisces
Uranus15th June 201601h 27m 50.8s08d 33m 42.3s5.903.4"10020.439Pisces
Uranus25th June 201601h 29m 00.4s08d 40m 17.3s5.903.4"10020.286Pisces
Neptune5th June 201622h 54m 06.1s-07d 54m 45.6s7.902.3"10029.890Aquarius
Neptune15th June 201622h 54m 11.2s-07d 54m 39.4s7.902.3"10029.723Aquarius
Neptune25th June 201622h 54m 04.1s-07d 55m 46.8s7.902.3"10029.562Aquarius


Sky Highlights - September 2017

Opposition
Neptune reaches opposition on September 5th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for September

Northern Hemisphere
Evening
West:- Jupiter (mag. -1.7)
Southwest:- Saturn (mag. +0.5)
East:- Neptune (mag. +7.8)
Midnight
South:- Neptune
East:- Uranus (mag. +5.7)
Morning
West:- Neptune
South:- Uranus
East:- Venus (mag. -3.9), Mars (mag. +1.8) (from second week), Mercury (mag. +0.5 to -1.3) (from second week)

Southern Hemisphere
Evening
West:- Jupiter
Northwest:- Saturn
East:- Neptune
Midnight
West:- Saturn
North:- Neptune
Northeast:- Uranus
Morning
West:- Neptune
Northwest:- Uranus
Northeast:- Venus
East:- Mars (end of month)

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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