Sky.and.Telescope_

OBSERVING

Sun, Moon && Planets

48 August 2014 sky & telescope

Venus Meets Jupiter at Dawn

The two brightest planets have a remarkably close conjunction in August.

Two planetary conjunctions add extra

excitement and beauty to our late-summer

skies. In the evening, Mars passes Saturn

near the end of August. In the dawn sky,

bright Jupiter climbs out of the Sun’s

glow and engages even brighter Venus in

a spectacular, very close conjunction on

August 18th.

DUSK

Mercury is easy to spot from the South-

ern Hemisphere after sunset in late

August. But from mid-northern latitudes,

Mercury appears very low and will be dif-

fi cult to spot even with optical aid.

EARLY EVENING

Mars and Saturn come into view in the

southwest at dusk, and modestly dimmer

Spica becomes visible shortly afterward.

As August begins, Saturn, Mars, and

Spica are lined up in that order, from

upper left to lower right. Mars is the

brightest of the three, shining at mag-

nitude 0.4. That’s slightly brighter than

0.5-magnitude Saturn 13° to Mars’s

upper left, and signifi cantly brighter than

1.0-magnitude Spica 10° lower right of

Mars. But as the month progresses, Mars

closes the gap on Saturn as both move

eastward relative to the stars. Mars nudges

1½° under 3rd-magnitude Alpha Librae

(Zubenelgenubi) on the American evening

of August 21st, then 3½° under Saturn

from August 23rd through 26th. By then

the two planets are identically bright,

magnitude 0.6. Can you distinguish them

by their colors alone?

With a telescope, observe them early

before they sink too low. Saturn’s 17′′-wide

globe and its much larger rings are still

impressive even when viewed through the

unsteady air near the horizon. But Mars

shrinks from 8′′ to 7′′ wide in August and

will probably appear featureless.

Dim Pluto, in northern Sagittarius, is

near its highest in the south at nightfall

— but that’s still not very high for mid-

northerners. See page 50 of the June issue

if you wish to seek it.

LATE NIGHT TO DAWN

Neptune comes to opposition on August

29th, but even then this most distant

offi cial planet shines only at magnitude

7.8 and shows a disk just 2.4′′ wide in

telescopes. It’s best observed at its highest,

an hour or two after midnight (daylight-

saving time). Neptune is currently retro-

grading westward in Aquarius, but it will

resume its slow eastward trek in Novem-

ber. It will cross into Pisces in 2022.

Uranus is in Pisces now and will

remain there until 2018. It rises about

1½ hours after Neptune (at mid-northern

latitudes) and is fairly high just before

the sky begins to brighten. At that point,

the 5.8-magnitude planet may be faintly

visible to the unaided eye from a dark site,

and its 3.6′′-wide disk should be apparent

through a telescope at 100×. For fi nder

charts, see skypub.com/urnep.

Dusk, Aug 1– 4

1 hour after sunset

Spica

Mars

Saturn

Moon

Aug 1

Moon

Aug 2

Moon

Aug 3

Moon

Aug 4

t Looking Southwest

10 °

α Lib

Dusk, Aug 29 –Sept 2

1 hour after sunset

Spica

Mars

Saturn

Moon

Aug 29

Moon

Aug 30

Moon

Aug 31

Looking Southwest

β Lib

α Lib

These scenes are

drawn for near the

middle of North

America (latitude

40 ° north, longitude

90 ° west); European

observers should

move each Moon

symbol a quarter of

the way toward the

one for the previ-

ous date. In the Far

East, move the Moon

halfway. The blue 10°

scale bar is about

the width of your fi st

at arm’s length. For

clarity, the Moon is

shown three times its

actual apparent size.