Astronomy

SOUTHERN

SKY

MARTIN GEORGE describes the solar system’s changing landscape

as it appears in Earth’s southern sky.

June 2018: Saturn dazzles all night

Four bright planets adorn

the evening sky in June. The

brightest of the lot is Venus,

which lurks low in the north-

west during twilight. It shines

brilliantly at magnitude –4.0

and appears conspicuous even

in twilight. Venus stands 13°

high an hour after sundown

in early June, and its altitude

nearly doubles by month’s end.

During that same period, the

inner world moves from central

Gemini to western Leo.

Venus’ travels take it

through the much dimmer

background stars of Cancer in

mid-June. Be sure to target the

planet through binoculars on

the 20th, when it passes less

than 1° north of the bright

Beehive star cluster (M44).

Telescopic views of Venus won’t

be as grand, however. Although

the planet’s disk grows from

13.1" to 15.6" across during

June, it shows a rather unim-

pressive gibbous phase.

After taking a good look

at Venus, swing your gaze to

the east and pick up Jupiter.

The giant planet shines at

magnitude –2.4 during most of

June. Although that’s only one-

quarter as bright as Venus, it is

still the sky’s second-brightest

point of light. Jupiter resides

against the faint backdrop of

Libra, a region that climbs

highest in the north around

9 p.m. local time in mid-June.

Although Jupiter reached

opposition and peak visibility

in early May, its telescopic

appearance doesn’t suffer much

in June. The gas giant spans 43"

at midmonth and shows a

wealth of atmospheric detail

through any telescope. Look for

two dark equatorial belts, one

on either side of a bright zone

that coincides with the planet’s

equator. Also track the move-

ments of Jupiter’s four bright

moons as they change positions

from night to night.

But the real showpiece

of June’s sky is Saturn. The

ringed planet peaks at opposi-

tion June 27, when it shines

at magnitude 0.0 against the

star-studded backdrop of

Sagittarius. It then appears

3° from both 3rd-magnitude

Lambda (λ) Sagittarii and the

great globular cluster M22, but

the planet’s slow movement

means the three objects remain

close all month.

Because Saturn now lies

opposite the Sun in our sky, it

rises around sunset and climbs

highest in the north near mid-

night local time. At its peak, it

stands more than 70° above the

horizon from most Southern

Hemisphere locations. Its great

altitude means we view it

through a minimal amount of

Earth’s atmosphere, so tele-

scopes of all sizes should

deliver spectacular results. At

opposition, Saturn’s equator

measures 18" across while the

rings span 42" and tip 26° to

our line of sight. The large tilt

affords impressive views of the

Cassini Division, a dark gap

separating the outer A ring

from the brighter B ring.

Mars resides in Capricornus,

one constellation east of Saturn,

and follows about two hours

after its sibling. The Red Planet

appears to the ringed world’s

lower right as they climb in the

eastern evening sky. Mars more

than doubles in brightness this

month, climbing from magni-

tude –1.2 to –2.1, as it heads

toward a stunning opposition

in late July. It appears far more

conspicuous than Saturn and

comes close to rivaling Jupiter

by June’s close.

Telescopes also reveal the

approach of opposition. Mars’

apparent diameter swells from

15.3" to 20.7" during June, a

35 percent increase. The plan-

et’s south pole tilts 15° toward

us, so the white south polar cap

should stand out. Observers

also should keep an eye out for

dusky surface features.

Mercury passes behind the

Sun from our viewpoint June 6,

and it remains lost in the Sun’s

glare during the month’s first

three weeks. But by late June,

the innermost planet lies low in

the northwest during evening

twilight. On the 30th, magni-

tude –0.2 Mercury appears to

the lower left of Venus and

stands 10° above the horizon

45 minutes after sunset. It will

improve dramatically in July as

it makes its finest evening

appearance of 2018.

The starry sky

Eighty-eight constellations

spread across the night sky,

with no gaps and no overlaps.

But the star groups that seem

so familiar today represent only

a fraction of those used or sug-

gested in the past. Some of my

favorites of these extra constel-

lations are the “Christian” ones

Julius Schiller proposed in the

early 17th century.

Schiller produced a magnifi-

cent atlas of the sky, Coelum

Stellatum Christianum, using

figures from the Bible to replace

each of the 48 constellations

listed by Ptolemy. For example,

he replaced Orion the Hunter

with the figure of St. Joseph. A

careful examination of the atlas

shows that Schiller drew his

figures as if the celestial sphere

were being viewed from the

outside — a God’s-eye view —

so the star patterns are reversed

compared with the way they

actually appear in the night sky.

Schiller replaced the south-

ern constellations with figures

from the Old Testament and

the northern ones with charac-

ters from the New Testament.

Perhaps the most obvious

replacement was Argo, which,

as you might expect, became

Noah’s Ark, so it retained its

status as a ship.

A less obvious one repre-

sents the biblical character Eve.

She occupies the area now cov-

ered by three constellations:

Chamaeleon, Musca, and Apus.

This area lies in the southern

sky on June evenings.

Examining Schiller’s map,

it’s easy to identify the dis-

torted rectangle created by the

stars Beta (β), Gamma (γ),

Delta (δ), and Epsilon (ε)

Chamaeleontis. These form

Eve’s left thigh. A trail of three

stellar pairs leading from Delta

and ending at Alpha Cha mark

her left leg.

Schiller’s star positions are

far from accurate compared

with those of today. But his

atlas, despite not showing the

more accepted constellations,

was the most accurate of his

time. It remained so until

Johannes Hevelius published

Firmamentum Sobiescianum

several decades later.