Astronomy - USA (2021-12)

To chase down the Moon’s shadow this month,

you’ll need to put yourself on ice. BY MICHAEL E. BAKICH

44 ASTRONOMY • DECEMBER 2021

LEFT: A total solar eclipse is a not-to-be-missed event that will leave you breathless. This processed image is a single frame

from an HD video shot through a 106mm refractor at f/5.8 during the Nov. 14, 2012, eclipse over Lakeland Downs, Queensland,

Australia. RIGHT: These brightly colored clam tents serve as guests’ Antarctic home away from home at Union Glacier Camp.

ALAN DYER; CHRISTIAN IVERSEN STYVE/ALE

ON DEC. 4, a three-way celestial

tango will once again occur as the Sun and

the Moon line up with Earth to produce the

greatest of nature’s spectacles: a total solar

eclipse. And while many eclipses occur in

faraway places, this one takes the cake. The

darkest part of the Moon’s shadow during

December’s eclipse will touch only the con-

tinent of Antarctica. So, pack your camera,

your eclipse glasses, and your winter sur-

vival gear if you’re going to chase this event.

What’s going on

Total solar eclipses occur more often than

total lunar ones, but more people have seen

a total lunar eclipse (although the number

of observed solar eclipses has been rising in

recent years). The reason for the disparity

is simple. During a lunar eclipse, anyone on

the nightside of our planet under a clear sky

can see the Moon passing through Earth’s

shadow. Even at the Moon’s distance of

about 238,000 miles (383,000 kilometers),

that shadow is much larger than Luna. If

the Moon passes through the center of our

planet’s shadow, totality can last as long

as 106 minutes — though it’s usually less

because the Moon passes either above or

below the shadow’s center.

On the other hand, the Moon’s diameter

is a quarter of our planet’s, so its shadow

barely reaches Earth’s surface to create solar

eclipses. If you’re beneath the lighter, outer

region of that shadow — called the

penumbra — you’ll see a partial solar

eclipse. As long as you’re wearing your

eclipse glasses, a partial is nothing to scoff

at, but there won’t really be any noticeable

dimming of the Sun’s brilliance. The lucky

individuals under the dark inner shadow

— the umbra — will witness the daytime

twilight of a total solar eclipse. Making that

event even more dramatic is the fact that it

doesn’t last long. Solar totality lasts a maxi-

mum of 7 minutes 29 seconds.

ANTARCTICA

A TOTAL SOLAR

ECLIPSE OVER