Astronomy - USA (2021-12)

SOUTHERN SKY BY MARTIN GEORGE

February 2022

A parade of predawn planets

Early February offers a

final chance to glimpse

Jupiter in evening twilight.

On the 1st, the giant world

stands only 7° high in the west

45 minutes after sunset. The

planet shines brightly at magni-

tude –2.1, however, so it shows

up easily if you have an unob-

structed horizon. Jupiter disap-

pears in the Sun’s glow by

mid-February and will be lost

from view until it returns on

mornings in late March.

Once Jupiter sets, skygazers

have a long wait before the next

bright planet emerges. The

action picks up starting around

3 a.m. local time (4 a.m. day-

light time), when Mars pokes

above the eastern horizon. The

Red Planet remains rather dim

this month, brightening slightly

from magnitude 1.4 to 1.3

against the backdrop of

Sagittarius the Archer. Despite

this constellation’s fame, its

luminary — magnitude 1.8

Epsilon (ε) Sagittarii — appears

noticeably fainter than Mars. A

telescope shows the planet as a

featureless disk spanning 5".

Not long after Mars clears

the horizon, Venus joins the

scene. Although the inner

planet always shines brightly, it

appears especially stunning this

month. Venus peaks at magni-

tude –4.9 when it hits greatest

brilliancy February 12. That

makes it not only 300 times

brighter than Mars but also 25

times brighter than Sirius, the

night sky’s most dazzling star.

Telescopic observers will be

rewarded with spectacular

views of Venus all month. At

the beginning of February,

Earth’s neighbor spans 49" and

appears just 15 percent lit. The

disk is large enough that good

binoculars can reveal the plan-

et’s delightful crescent. As

Venus moves away from us

during the month, its apparent

size shrinks as its phase waxes.

But even by February 28, its

disk measures 32" across and

appears 37 percent illuminated.

Although Venus appears well

clear of the horizon by the time

dawn starts to break, many

observers find it a more tempt-

ing subject during twilight

because the background light

cuts the planet’s glare.

The morning sky grows

more crowded about an hour

after Venus rises. February

finds Mercury putting on its

finest predawn show of 2022.

The innermost planet begins

the month 17° west of the Sun

and rising some 70 minutes

before sunup. Glowing at mag-

nitude 1.1, Mercury stands out

low in the east-southeast as

twilight starts to brighten.

The inner world grows more

prominent as it climbs higher

and grows brighter during the

next two weeks. At greatest

western elongation February 16,

the magnitude 0.1 planet rises

two hours before the Sun and

appears 12° high an hour later.

Although Mercury sinks closer

to the Sun as February winds

down, it remains conspicuous

through month’s end.

As you might expect,

February mornings also

provide an excellent oppor-

tunity to observe Mercury

through a telescope. The best

views come early in the month

when the planet shows a large

crescent. On the 1st, its disk

spans 9.4" and appears 20 per-

cent lit. On the morning of its

greatest elongation, Mercury

measures 6.9" across and the

Sun illuminates 60 percent of

its Earth-facing hemisphere.

As if these three terrestrial

planets weren’t enough, a gas

giant world adds to the spec-

tacle. Although Saturn passes

behind the Sun from our view-

point February 4, it reappears

in morning twilight during the

month’s final 10 days. To find it

on the 18th, simply draw a line

from Mars to Mercury and

extend it an equal distance

toward the horizon. By the

28th, Saturn stands 4° directly

below Mercury. The gas giant

shines at magnitude 0.7 and

appears half as bright as its

neighbor. Unfortunately, the

ringed planet won’t look like

much through a telescope until

it climbs higher next month.

Be sure to watch the waning

crescent Moon slide past these

planets on the final two morn-

ings of February (and the first

of March). To capture a great

photo, shoot during twilight

with a striking terrestrial scene

in the foreground.

The starry sky

Northern Hemisphere observers

wax poetic about the Summer

Triangle: the bright stars Altair,

Deneb, and Vega that appear so

prominent on northern sum-

mer evenings. For us in the

Southern Hemisphere, of

course, that triangle lies in the

winter sky and isn’t impressive

because only Altair climbs high.

So let’s focus instead on the

Southern Hemisphere’s Summer

Triangle. February evenings are

the perfect time to appreciate

the geometric shape formed by

Betelgeuse, Procyon, and Sirius,

all three of which rank among

the night sky’s 10 brightest stars.

I find our Summer Triangle

more aesthetically pleasing

because it creates a nearly per-

fect equilateral triangle. The

angular distance from ruddy

Betelgeuse to Procyon is 26.0°,

from Procyon to brilliant Sirius

is 25.7°, and from Sirius back to

Betelgeuse is 27.1°. Compare

that with the Northern

Hemisphere’s far less symmet-

ric Summer Triangle: The lon-

gest side of the triangle runs

from Deneb to Altair and spans

38.0°, Altair to Vega spans

34.2°, and Vega back to Deneb

covers just 23.8°.

Of course, any three celes-

tial objects can form a triangle.

One of my favorites appears

late on February evenings and

provides a convenient way to

locate the sky’s brightest globu-

lar cluster, Omega (ω) Centauri

(NGC 5139), with just your

naked eye. Omega forms the

northern vertex of a nearly

equilateral triangle with the

bright stars Beta (β) Cen and

Gamma (γ) Crucis. The tri-

angle’s three sides measure

12.4°, 12.8°, and 14.0°.