Sky & Telescope - December 2020 - 49

and after totality, when bits of the
solar photosphere briefly shine through
gaps along the Moon's rugged limb. As
always during a solar eclipse, you must
use a safe solar filter or eclipse glasses
except during totality, when the solar is
completely covered by the Moon.
During totality, have a pair of binoculars at the ready to inspect the bright
pinkish-red chromosphere. Chances
are you'll see one or more prominences
of incandescent hydrogen poking out
beyond the dark lunar limb.
Most eclipse watchers would agree
that the Sun's corona is the event's
most mesmerizing sight. The pearly,
unearthly nimbus of light dramatically
frames the blackened Moon. Wide-field
binoculars reveal the corona's magnetic
nature. You can clearly see filaments
and whorls of hot gas that recall iron
filings around a magnet, as hot coronal gases bend to the will of the solar
magnetic field. During solar minimum
(currently underway), the corona often
appears asymmetric, with long, taffylike structures on either side of the
Sun's equator and vertical field lines
streaming from polar coronal holes.
We actually see two coronas during a total eclipse. There's the inner
portion called the K corona, comprising
free electrons illuminated by sunlight.
Beyond that, the F corona or "dust
corona" begins. Here, sunlight scatters
off particles shed by comets and asteroids along the plane of the solar system.
The F corona expands into the zodiacal
light, visible at dawn in autumn and
dusk in spring.
During totality's brief twilightdarkness, listen for night insects - such
as crickets - feel the sudden chill in the
air, and relish the fact that you're part
of a cosmic alignment along with the
Sun and the Moon. Take a few moments
to look around the sky, too. Four planets will be visible: Mercury and Venus
(found 3° and 24° west of the Sun,
respectively), and the close duo of Jupiter and Saturn 35° to the Sun's east.
Before you know it the eclipse will
come to an end. Baily's Beads make a
final appearance, and the shadow that
descended in apocalyptic haste when

totality began now hurries away ahead
of the returning daylight. Yes, it all goes
by too fast.
Two-thirds of South America and
a portion of Antarctica will witness a
partial eclipse, with 79% of the Sun
covered in Santiago, Chile; 74% in

Buenos Aires, Argentina; 32% in São
Paulo, Brazil; 17% in Lima, Peru; and
1.4% in Guayaquil, Ecuador. For details
of the eclipse along the entire path
of totality, check out Xavier Jubier's
interactive eclipse map at https://
is.gd/2020eclipse.

December's "Other" Meteor Shower
Ursid Meteor Shower
Dec 21, early evening
Polaris
10°

URSA
MINOR
Little
Dipper

Ursid
radiant

DRACO

Big
Dipper

URSA
MAJOR

Mizar

Looking North
S The Ursid radiant is visible all night from most locations north of the equator. You can view the
shower beginning in the early evening of December 21st, but the display peaks in the predawn
hours of the 22nd.

THE GEMINIDS (see page 14) rightly
steal the headlines when it comes to
annual meteor showers, but the lesser
known Ursids are also worth a look.
This shower originates from particles
released by Comet 8P/Tuttle in its
13-year orbit around the Sun. Like the
Geminids, Ursid meteoroids move relatively slowly, striking the atmosphere at
a speed of 33 kilometers per second.
The Ursids are active from December 17-26, and this year they peak in
the predawn hours of December 22nd
(at around 4 a.m. EST) when 5 to 10

meteors per hour shoot from just near
2nd-magnitude Kochab, the brightest
star in the bowl of the Little Dipper. The
Moon will be at first-quarter phase and
sets around midnight, leaving a dark
sky during the shower's peak for observers across North America.
I like to think of the Ursid shower
as a little bear briefly emerging from
hibernation at the winter solstice and
flinging a few meteoroids our way. Playful fella. Follow his lead and leave your
warm bed for an hour or so to see what
he kicks up.
sk yandtelescope.org * DECEMBER 2 02 0

49


https://www.is.gd/2020eclipse https://www.is.gd/2020eclipse http://www.skyandtelescope.org

Sky & Telescope - December 2020

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