The Planets this Month - July 2016

Mercury

Mercury passes through superior conjunction on July 7th but it's not long before the rapid moving planet moves out from the Sun and into the early evening sky. During the second half of the month it re-appears after sunset low down towards the west-northwestern horizon from equatorial and southern latitudes. Observers should note that although Mercury's altitude improves slightly each subsequent evening it dims from magnitude -1.2 to -0.2 between July 15th and 31st. From northern temperate latitudes the planet struggles against the lengthy summer twilight making observations almost impossible.

There are a couple of interesting conjunctions coming up. On July 16th, Mercury passes 0.5 degrees north of much brighter Venus, with Mercury (mag. -1.1) 13 times fainter than its mag. -3.9 neighbour. However, this is a challenging event to observe since both planets remain low down. For example, from latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury and Venus appear just 4 degrees above the horizon, 30 minutes after sunset. Binoculars are recommended and safe-viewing techniques should be followed. Ensure that the Sun is below the horizon before scanning the sky. Two weeks later on July 30th, Mercury (mag. -0.2) passes 0.3 degrees north of Regulus (mag +1.4) the brightest star in Leo.

Venus

Venus returns to the evening sky this month for the first time since August 2015. The brilliant planet shines at mag. -3.9 and from mid-July can be seen after sunset low down above the west-northwestern horizon for observers at tropical and southern latitudes. As previously noted, Mercury passes close by Venus on July 16th.

Venus then climbs slightly higher in the sky each subsequent evening and by the third week of July should be visible from locations such as Florida and the Mediterranean. However, those living in northern Europe, Canada, northern Russia and northern Asia will find it more difficult to spot the planet (if at all) due to the bright evening twilight.

Mars

Mars is visible as soon it's dark enough as it moves direct (eastwards) among the stars of Libra. Now well past opposition the "Red planet" fades in brightness from magnitude -1.4 to -0.8 and shrinks in apparent diameter from 16.3 to 13.1 arc seconds this month. However, it still remains large enough for telescope observers to make out a reasonable amount of surface detail. By the end of the month, Mars sets about midnight for northern temperate latitudes but a couple of hours later from more southerly locations.

The surrounding region of sky also contains Saturn (mag. +0.2) east of Mars and first magnitude red supergiant star Antares (α Sco - mag. +1.0) to the southeast. Of the three objects Mars is the brightest followed by Saturn then Antares.

A nice evening pairing occurs on July 14th when the waxing gibbous Moon passes 8 degrees north of Mars.

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

Jupiter

Jupiter is located in Leo. Even though long past opposition and heading towards solar conjunction it remains a lovely evening object this month, visible towards the west just after sunset. However, by months end from northern temperate latitudes the giant planet sets only 1.5 hours after the Sun although observers in the Southern Hemisphere have a couple of extra hours visibility. During July, the brightness of Jupiter decreases slightly from mag. -1.9 to -1.7 with its apparent size shrinking from 34 to 32 arc seconds.

On July 9th, the waxing crescent Moon passes 0.9 degrees south of Jupiter. An occultation is visible from the southern tip of Africa (10:11 UT).

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

Saturn

Saturn is only one month passed opposition and can be seen after sunset towards the south from northern temperate latitudes or towards the northeast from southern temperate latitudes. It remains observable for most of the night. Bright red Mars is positioned about 15 degrees west of Saturn with both planets better seen from southern and equatorial locations.

The beautiful "Ringed planet" continues it's retrograde motion through the constellation of Ophiuchus close to the border with Scorpius. As the Earth slowly distances itself from Saturn the apparent brightness and size of the planet continue to decrease. Its magnitude fades from +0.2 to +0.4 with its apparent diameter shrinking from 18.2 to 17.6 arc seconds as the month progresses.

Saturn's wonder of course is its ring system. They are currently wide open and even a small 80mm (3.1-inch) scope will easily show them. Larger telescopes with their increased light gathering and power capabilities display much more detail. For example, a 200mm (8-inch) scope under good seeing conditions at 250 to 300x magnification reveals 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.

On July 16th, the waxing gibbous Moon passes 3 degrees north of Saturn.

Uranus

Uranus, mag. +5.8, is located among the stars of Pisces. At the beginning of the month from northern temperate locations, the planet rises 4 hours before sunrise improving to midnight by months end. The visibility period from locations further south is slightly better still.

Under dark skies Uranus is faintly visible to the naked eye, although from most populated areas optical aid is required. The planet is currently positioned close to the mid point of an imaginary line connecting omicron Psc (ο Psc - mag. +4.3) and epsilon Psc (ε PSc - mag. +4.3).

On July 26th, the last quarter Moon passes 3 degrees south of Uranus. Four days later the planet reaches its first stationary point signaling the beginning of this year's opposition period. It then commences retrograde motion.

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

Neptune

Neptune continues to move retrograde in Aquarius. The distant planet is approaching a September 2nd opposition date and is therefore well placed for observation throughout the month. At the start of July, it rises about midnight from northern temperate latitudes and even earlier still for those located further south. By months end it can be seen in late evening.

Neptune is positioned approx. 30 degrees south of the Great Square of Pegasus and half a degree southeast of lambda Aqr (λ Aqr - mag. +3.7). First magnitude star Fomalhaut (α Psc - mag. +1.2) is located 20 degrees south of the planet. Neptune is the only planet that's never bright enough to be seen with the naked eye but it's relatively easy with binoculars or small scopes. During July, it marginally brightens from mag. +7.9 to +7.8.

On July 23rd the waning gibbous Moon passes a degree north of Neptune with an occultation visible from central and eastern North America at 5:36 UT.

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

Solar System Data Table July 2016