Astronomy – October 2019

SKY THIS MONTH

Visible to the naked eye

Visible with binoculars

Visible with a telescope

PISCES

ARIES

CETUS

j k

j

j

1°

N

E

Uranus

Jupiter and Saturn

continue their reign

during October, shining

brightly in the southwestern sky

as darkness falls. Mercury and

Venus present a bigger challenge

— the inner planets hug the

horizon after sunset and will be

hard to see without optical aid.

Uranus takes center stage dur-

ing the overnight hours. The ice

giant world reaches opposition

and peak visibility this month,

climbing higher in our sky than

it has in more than 50 years.

And for those of you who have

missed Mars these past few

months, it returns to view

before dawn in late October.

You’ll need to look low in the

southwest after sunset to see

Mercury and Venus. Venus

shows up more easily because

it gleams at magnitude –3.8 in

mid-October. It then stands

only 2° high a half-hour after

sundown, however, so you’ll

need a haze-free sky and unob-

structed horizon to spot it.

Use Venus as a guide for

finding Mercury. At greatest

elongation October 19, the

innermost planet lies 25° east

of the Sun and 7° to Venus’ left.

If you place Venus at the right

edge of the field through your

binoculars, you should see its

magnitude –0.1 neighbor near

the field’s left edge.

The two planets approach

each other as the month pro-

gresses. On the 29th, Mercury

slides 3° due south (lower left)

of Venus. You can find the pair

with the aid of a two-day-old

crescent Moon. Our satellite

stands 8° high a half-hour after

sunset with Venus 5° to its

lower right and Mercury 6°

directly below the Moon.

While you may struggle to

locate the two inner planets,

the solar system’s gas giants

pose no problem. Jupiter shows

up as a brilliant point of light in

the gathering darkness. On

October 1, the magnitude –2.0

world stands 20° above the

An ice giant reaches its peak

Uranus peaks at opposition the night of October 27/28, when it resides in a

fairly desolate part of Aries the Ram. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY

October 2019

Uranus rides high in the Ram

36 ASTRONOMY • OCTOBER 2019

THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY.

BY MARTIN RATCLIFFE AND ALISTER LING

Uranus’ blue-green color

shows up through amateur

instruments, but you won’t

see the clouds and rings

the Keck Telescope

reveals. LAWRENCE SROMOVSKY

(UW-MADISON)/KECK OBSERVATORY