Australian Sky & Telescope — November-December 2017

46 AUSTRALIAN SKY & TELESCOPE November | December 2017

SUN, MOON & PLANETS by Jonathan Nally

Jupiter’s planetary pairings

The planets are coming and going in our summertime sky.

T

he summer months begin with

three planets visible in the

morning sky and two in the

evening sky. Mercury is well placed

for observation in the west at sunset,

reaching its greatest elongation (22°)

from the Sun on November 24. Look

for Saturn nearby in the last week

of November. Entering December,

Mercury will soon become lost in

the Sun’s glare, reaching inferior

conjunction on the 13th. But give it

a few weeks, and the tiny planet will

reappear in the eastern pre-dawn sky

around the end of the month.

Venus is low on the eastern horizon

in the pre-dawn sky at the beginning

of November. On the 13th and 14th

the planet will be close to Jupiter, but

the pair will be very hard to see due to

theirlowaltitude—you’llneedeither

an extremely clear horizon, or to be on

topofahillwithagoodview.Moving

into December, Venus will become lost

SLeft: Saturn and Mercury team up in November.Middle:Jupiter,theMoonandMarsformatrio.Right:AfineconjunctiononNewYear’sEve.

in the solar glare as it heads toward

the other side of the Sun and superior

conjunction (on January 9).

Mars, too, is visible in the eastern,

pre-dawn sky, climbing higher as

November progresses. Look for the Moon

nearby on the 15th. By the end of the

month, the red planet and Venus will be

close together and make an attractive

pairing. By the start of December, Mars

will be rising at around 2:00am and

starting to move closer to Jupiter — at

the end of the month they’ll be only

three degrees apart.

Speaking of Jupiter, it is making its

reappearance in the eastern sky after

having spent time around the other

side of the Sun. As mentioned above,

Jupiter and Venus will be close together

in the middle of November, low on the

horizon. As December opens, Jupiter

will rise higher and higher, dominating

proceedings in the eastern pre-dawn sky.

Saturnbegins November low on the

western horizon at sunset, dropping

lower and becoming more enveloped in

the twilight as the month progresses.

Come mid-December, the planet will

be lost to view, reaching superior

conjunction with the Sun on the 22nd.

The ringed planet will return to our

morning skies in late January.

Finally, on December 22 the Earth

will reach the southern summer

solstice, which is when the Sun is

at its southern-most point in the sky

(declination –23.5°). In many parts of

the world, the solstice is taken to be the

point in time at which the new season

begins — summer or winter, depending

upon which hemisphere you’re in — but

here in Australasia, we take it as the

approximate mid-point of the season.

Oops! In the subheading in our last issue,

we suggested that Uranus would reach

‘conjunction’ in October. It should have

read ‘opposition’.