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46 AUSTRALIAN SKY & TELESCOPEJULY 2016

T

helong,darknightsof

winter are here, bringing

colder conditions but

hopefully clear, crisp skies

(depending on where you live,

of course). The Milky Way is

stretching from northeast to

southwest, with the Southern

Cross high in the southwest and

Scorpius overhead from mid-

southern latitudes.

Mercuryis lost in the Sun’s

dawn glare for the first week of

July,reachingsuperiorconjunction

(ie.ontheoppositesideofthe

Sunfromus)onthe7th.By

mid-monthitwillhavebegun

to make a reappearance in the

evening sky to the west. On the

17th, the tiny planet will appear

veryclosetoVenus—they’ll

be only half a degree apart, but

low in the twilight less than 3°

above the horizon. You’ll need a

clear western horizon or a hilltop

vantage point, plus eagle eyes (or

maybebinoculars,butbesafe

andensuretheSunhasfully

JONATHAN NALLY

Mercury and Venus meet up

The two inner planets join forces in the western twilight sky.

Celestial Calendar

set) to spot them. A little later in

the month, on the 30th and 31st,

Mercury will appear near Regulus

— the brightest star in Leo and, at

magnitude 1.4, the 21st brightest

star in the night sky.

Venus reached superior

conjunction last month, and so

it too has been lost in the Sun’s

glare. But as mentioned above, it

will return to our western, evening

skies by mid-July, shining at a

dazzling magnitude –3.9. Venus

will be with us in the evening sky

now for the rest of the year.

Mars, which reached opposition

in May, is still well placed for

viewing in the northwestern sky,

not far from its rival, the star

Antares. But the Red Planet is

drawing away from us now and

getting smaller as seen through

a telescope. So make sure you

grab this opportunity to observe

it as over the coming months its

apparent diameter will shrink

from its May maximum of 18.4

arcseconds to as little as 6.1

arcseconds by year’s end. Look for

the Moon nearby on July 14 and 15.

(And speaking of Moons, see pages

58-59 for a guide to spotting Mars’

own moons.)

Shining at magnitude –1.8

and a little over 33 arcseconds

across, Jupiter is prominent in the

northwestern sky after sunset.

Look for the Moon very close

nearby on the 9th — the two

celestial bodies will appear less

than one degree apart. If you

happen to be reading this from

southern Africa, Madagascar or

eastern Antarctica, you’ll actually

see the Moon occult (ie. block out)

Jupiter; but in Australasia we’ll

have to make do with the close

conjunction.

Saturn reached opposition

just last month, so it’s still very

well placed for viewing in the

eastern sky after sunset. Shining

at magnitude 0.2 and about 18

arcseconds across, the ringed world

is always stunning, no matter

whether you’re using the naked eye

or a telescope. Watch for the Moon

nearby on the 16th.

Finally, our own planet will

reach aphelion — its furthest

orbital point from the Sun

— on July 5, at a distance of

152,103,785 kilometres, or 1.016751

astronomical units.

Left: The Moon

and Jupiter will

be less than 1°

apart on July 9.

Middle: Mars,

Saturn, the

Moon and the

star Antares

will make

an attractive

grouping in

mid-July.

Right: After

sunset on July

17, Venus and

Mercury will

be extremely

close together,

but very low on

the horizon and

difficult to see.