Australian Sky & Telescope — January 01, 2018

46 AUSTRALIAN SKY & TELESCOPE January 2018

SUN, MOON & PLANETS by Jonathan Nally

become an evening object, on its way

to reaching opposition (and prime

viewing) in May.

Saturn (0.5, 15.2 ́) returns to our

morning skies after reaching superior

conjunction during December. You’ll

find it rising at about 4:40 am at

month’s start, and by around 2:40am

by the end of January. As mentioned

above, the ringed world will do a dance

with Mercury and the Moon during the

middle of January.

The Earth will reach perihelion

(closest point the Sun) on January

3. On that day, we will be separated
   from our parent star by 147,097,193
   kilometres, or 0.983284 astronomical
   units.
   Finally, don’t forget the total
   lunar eclipseon January 31, the
   firstoftwothisyearforAustralasian
   observers.Seepages54–55foryourfull
   observing guide.

Gatherings in the east

The pre-dawn darkness is the place to spot four planets this January.

F

our naked-eye planets will grace

our morning skies during January.

Mercury (magnitude –0.4,

diameter 6.5 arcseconds decreasing to

5.0 by the end of the month) is visible

to the east in the pre-dawn twilight

this month, and will reach its greatest

elongation from the Sun (22.7 degrees

west) on the 2nd. But despite that

separation, it will be still be very low

down on the horizon. Have a look on

the 13th and 14th and you’ll see Saturn

less than 1 degree away — Mercury will

be the brighter of the two, with Saturn

a slightly yellowish colour compared to

Mercury’s white. (Saturn might be hard

to see at this time, but it’ll be easier

to spot later in the month when it has

climbed higher.) On the 15th, the very

thin crescent Moon will join the party,

just above and to the left of the pair.

Venus (–3.9, 9.8 ́) is out of the

picture at the moment, reaching

superior conjunction (ie. on the

opposite side of the Sun to us) on

January 9. But don’t worry, it will return

to our western evening skies at the

end of February, and remain there for

almost all the rest of the year — until

the end of October in fact — shining

brightly as the evening star.

Mars (1.4, 5.1 ́) is an early morning

object during January, rising around

1:30 am at the beginning of the month

and by 1:00 am by month’s end. (These

and other times in this article are

given in Australian Eastern Standard

Time, so you’ll need to adjust for your

own time zone as well as daylight

saving, if it’s in force where you live.)

The Red Planet will get up close with

its larger sibling, Jupiter, this month,

and the pair will be close from the 5th

to the 10th — on the 7th they’ll be just

15 arcminutes apart. On the 12th, the

Moon will join them, sitting about five

degrees below Mars. SFOUR WORLDSMarsandJupiter,andMercuryandSaturn,aretheonestowatchinJanuary.

This is going to be a great year

for Mars watchers, with the planet

reaching opposition — when the Sun,

Earth and Mars, in that order, are in a

line — in late July. This will be around

the same time as the planet reaches

perihelion, putting it somewhat closer

than usual, at 57.59 million kilometres

from Earth. The closer it is, the bigger

it will appear through a telescope — for

this year, that will be 24.3 arcseconds.

This year’s apparition will be only

marginally poorer than 2003’s, which

was itself billed as the opposition with

the best viewing circumstances during

the previous tens of thousands of years.

As mentioned above, Jupiter (–1.9,

34.2 ́) will join Mars in the early

morning sky. The giant planet will rise

alittleearliereachweek—fromabout

1:40 am at the beginning of Januar y

to around midnight by month’s end.

By the end of February it will have