Sky & Telescope - December 2019 - 49

ON THURSDAY, DECEMBER 26TH,

weather permitting, parts of Africa,
most of Asia, the western Paciﬁc, and
northern and western Australia will
see a partial solar eclipse. The event
lasts more than three hours, from
the moment the Moon ﬁrst brushes
the Sun's face to when the Sun again
appears perfectly round. For observers
in western Asia and eastern Africa, the
eclipse is already in progress as the Sun
rises, with the ﬁnal partial phase wrapping up while the Sun is still low in the
morning sky. South and Central Asia
see the eclipse begin in early morning
and end before or near noon local time.
Those on the eastern end of the eclipse
path see a partial eclipse in the afternoon. Some Paciﬁc islanders should see
the Sun drop below the horizon before
the eclipse concludes.
Observers situated along a narrow track that runs from Saudi Arabia
through the United Arab Emirates,
Oman, southern India, Sri Lanka,
Indonesia, and Malaysia to the Philippines will see a special type of partial
solar eclipse known as an annular, or
ring, eclipse. Typically, when the Moon
passes directly between the Sun and
Earth, its umbra (shadow cone) reaches
Earth's surface, with the Sun completely hidden. We experience this as
a total solar eclipse. But if the Moon is
closer to apogee, and so slightly farther
from us, when it passes between Earth
and Sun, its disk appears smaller and
doesn't cover the entire Sun. Instead,
the Sun's chromosphere shows as a
brilliant ring of ﬁre, blazing along
the Moon's perimeter.

p Takeshi Kuboki used a Nikon D7000 to capture this image of an annular eclipse through
clouds above Amagasaki, Japan, on the morning of May 21, 2012.

Because the Sun isn't fully blocked
during an annular eclipse (in this case
it's just 97% hidden at maximum),
observers need proper eye protection,
even when the Moon is centered in
front of the solar disk. Certiﬁed eclipse
glasses or a properly ﬁltered telescope
will provide excellent views of the
action. Pinhole projectors and telescopic
projection are also good options (see
https://is.gd/SolarProjection).
The duration of annularity depends
on the observer's location along the
central path of the eclipse. Greatest
eclipse occurs over eastern Sumatra
(Indonesia) at 05:18 UT; annularity
lasts 3 minutes and 40 seconds for that
spot. For more detailed information,
visit https://is.gd/2019annular.
Lunar eclipses often take place two
weeks before or after a solar eclipse.
This ﬁnal solar eclipse of 2019 is followed by a penumbral lunar eclipse on
January 10, 2020.
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A NNUL A R ECLIPSE IM AG E: TA K ESHI K UBOK I / CC BY 2.0;
A NNUL A R ECLIPSE DIAG R A M: S&T, SOURCE: FRED ESPEN A K

Ring of Fire

u The annular eclipse begins at sunrise
in Saudi Arabia, crosses the United
Arab Emirates, Oman, southern India,
and Sri Lanka in the morning and the
Bay of Bengal, Malaysia, and Singapore
through most of the day, then finishes
late in the afternoon and at sunset for
parts of the Pacific. Interpolate between
the horizontal red or black lines to find the
approximate maximum percentage of the Sun's
diameter (up to 97% along the central path)
that the Moon covers for a given location.

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25 %
50 %

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75%

N U L A R ECLIP

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the range of 30 to 80, however. That's
not bad! If your sky is transparent,
you could see more than 20 meteors
per hour between midnight and 4
a.m., when the radiant is highest. The
Geminids tend to be rich in bright
meteors, which are often spectacular
even under very bright skies. Turn
your back to the Moon to protect
your night vision; the Geminids can
appear anywhere in the sky, so you
needn't look toward Gemini.
Since the radiant (near Castor)
rises just ahead of the Moon on the
14th, consider going out in the early
evening. You might be lucky enough
to catch a few earthgrazers - slow,
bright meteors that angle upward
from the eastern horizon - before or
as the Moon makes its appearance.
The Geminids are intrinsically
interesting thanks to their parent
object. Unlike most meteor showers, which spring from dust and
rock particles left behind by active
comets, the Geminids are produced
by the semi-dead "rock comet" 3200
Phaethon. Phaethon acts as if it's
both an asteroid and a comet. Most
of the time, it's inert like an asteroid and loses very little material as
it hurtles through the solar system.
However, when it approaches the
Sun, Phaethon behaves more like a
comet. Its rocky surface responds
to the intense solar heat (as great as
800°C / 1,500°F) by cracking, which
releases enough material to produce
a modest dust tail. Only one other
object in the solar system has been
observed to act in a similar manner.
Despite being one of the most
productive and reliable meteor showers, the Geminids remains a somewhat underreported event, possibly
because December is often cold and
cloudy over much of the Northern
Hemisphere. The IMO encourages
observers to watch a few nights
before and after the predicted maximum, even under moonlit skies. For
more detailed instructions regarding recording and reporting, visit
the IMO Visual Observations page
(https://is.gd/IMOvisual).

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sk yandtele scope.com * D EC E M B E R 2 019

https://www.is.gd/SolarProjection https://www.is.gd/2019annular https://www.is.gd/IMOvisual http://www.skyandtelescope.com

Sky & Telescope - December 2019

Table of Contents for the Digital Edition of Sky & Telescope - December 2019