Skywatch - 2021 - 69

LUNAR ECLIPSE AND FULL MOON: GARY SERONIK;
NEOWISE: BOB KING

plow into Earth's atmosphere at speeds
of tens of kilometers per second.
At various times of the year, the
Earth passes through clouds of particles
left behind by crumbling asteroids and
comets. On such occasions we get to
enjoy a meteor shower. Meteor showers
are named after the constellations from
which the flashes of light appear to
originate. The most famous examples
are the Perseids in August and the Geminids in December. Under dark, moonless skies these displays can produce
up to 100 meteors per hour at the peak
of activity! Some shooting stars leave
behind long-lasting trails - in particular, the biggest and brightest meteorites,
called fireballs.
Atmospheric phenomena are best
seen with the unaided eye, too. The
most famous is the aurora borealis (from
the Latin for dawn and northern,
respectively), also known as the northern
lights (analogously, the aurora australis,
or southern lights, shimmer for those
south of the equator). Generally, the
closer to the Earth's magnetic poles you
are, the more often you'll get to see this
amazing light show.
Aurorae occur when fast-moving,
charged particles (mostly electrons)
from the Sun are funneled down toward
Earth's poles by our planet's magnetic
field and slam into oxygen and nitrogen
atoms in the upper atmosphere, causing those gases to glow. During intense
displays aurorae appear as glorious rippling curtains or rays in mostly greenish and red hues that can be seen even
from relatively southerly locations. A
good aurora display is an unforgettable
experience.

peach of a moon During a total lunar
eclipse, the Moon passes through the darkest part
of Earth's shadow, bathing the Moon in sunset
shades of red and orange.

S The

light of a silvery moon Full Moon
is the ideal time for viewing the lunar seas (the
dark areas shown here) and ray craters. Binoculars
or a small telescope will readily reveal both.

narrow track that the lunar shadow
traces across a portion of the globe.
The eclipse path can be about 16,000
km (10,000 miles) long, but just 160 km
wide. (A strong word of caution for viewing solar eclipses: During the partial
phases - any time before the Sun is
completely covered by the Moon - you
must use eclipse glasses if you're viewing
without optical aid or a specialized solar
fi lter on your instrumentation to avoid
the Sun's blindingly bright light. Safety
must come fi rst!)
Are any solar eclipses coming up this
year? Yes, but both are viewable only
from remote locations. On June 10th,
an annular solar eclipse (when the Moon
is too distant, and thereby presenting a
smaller disk, to fully hide the Sun - in
these cases, a ring, or annulus, of sunlight
encircles the lunar disk) is visible from

northeast Canada and the North Pole,
while a totally eclipsed Sun occurs over
Antarctica on December 4th. For eclipse
watchers in North America, there is an
annular eclipse on October 14, 2023,
but the big one is a total eclipse on April
8th, 2024. Mark your calendar!
A lunar eclipse, on the other hand,
occurs when the Moon passes directly
through Earth's shadow. Unlike a
solar eclipse, the lunar variety can
be seen anywhere the Moon happens
to be above the horizon at the time,
which means almost half the planet
can observe the event simultaneously,
weather permitting. A lunar eclipse
is also a far more leisurely aﬀair,
with totality (when the Moon is fully
immersed in the umbra, the dark, central
region of Earth's shadow) often taking
more than an hour to unfold.

T Icy

visitor Comets are often described as "dirty snowballs" from the outer solar system. Although
quite common, those that rise to naked-eye brightness and sprout impressive tails only appear once a decade or so on average. This photo shows Comet NEOWISE (C/2020 F3) - the ﬁnest comet since 2007.

Eclipses of the Sun and Moon
Both the Earth and the Moon are illuminated by the Sun, and they cast long
shadows into space. When the Moon
passes precisely between the Earth and
the Sun, it can blot out the blinding
glare of our nearest star for up to 7½
awesome minutes in some cases, giving
rise to a total solar eclipse. It's truly one
of nature's grandest spectacles. But to
see one, you have to position yourself
somewhere along the path of totality, the
SK Y WATCH 2021

Skywatch - 2021

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