Australian Sky & Telescope - June 2018

46 AUSTRALIAN SKY & TELESCOPE July 2018

SUN, MOON & PLANETS by Jonathan Nally

Mars assumes control

The Red Planet rules the night as it reaches perihelion and closest approach.

Y

ou’re going to hear a lot about

Mars this month, but actually

the whole of July is superb as

far as planet observing goes, as all five

naked-eye planets will be visible in the

evening sky for the entire period. So

keep your fingers crossed for some good

weather!

Let’s begin with Mercury (mag.

–0.1 and diameter 6.7 ̋ at the start of

the month; 1.5 and 10.0 ̋ by month’s

end). Reaching greatest elongation on

the 12th, the innermost planet will

be on display in the western evening

sky, setting almost two hours after the

Sun on July 1 and 75 minutes post-

sunset by the end of the month. The

tiny world will be seen skirting the

Beehive Cluster (Messier 44) on the

4th, having a close encounter with the

Moon on the 15th, and appearing close

to 1st-magnitude Regulus on the 25th.

Venus (–4.2, 17.5 ̋) is a western

evening object, too, setting just after

8:00pm at the start of July and just

before 9:00pm by month’s end. Slowly

moving through Leo, the bright planet

will appear close to Regulus on the

10th, with the thin crescent Moon

coming close on the 16th.

Jupiter reached opposition in May

and Saturn in June, but now it’s Mars’

turn, with the Red Planet coming to

opposition on the 27th. This will be

its best apparition since 2003, with

the planet reaching an apparent

diameter of 24 ̋ by the last week of

July and magnitude –2.8 on the night

of opposition. Mars will be closest to

Earth a few nights later, on July 31, at a

distance of 57,589,196 kilometres.

Being at opposition, the Red Planet

will of course rise in the east around

the time of sunset and will therefore

be visible all night long. Grab your

telescope and see if you can spot any

features, such as the south polar cap

or Syrtis Major. And if you’re feeling

adventurous, why not try for one

or both of its moons, Phobos and

Deimos? Turn to pages 36-41 for a full

rundown on when, where and how to

see the Red Planet.

Jupiter (–2.2, 39.8 ̋), now two

months past opposition, is a still a fine

sight high in the northern evening

sky, setting around 2:30am at the start

of the month and by about 1:00am

at month’s end. The planet has been

undergoing retrograde motion for

the past few months but will reach

its stationary point on the 11th,

whereupon it will start heading east

again. Take a look on the 21st, and

you’ll see the nine-day-old Moon

nearby.

S Venus and Mercury shine together in the

west after sunset.

S Jupiter, now two months past opposition,

is still a ine sight.

S Mars reaches its best opposition for

15 years on July 27.