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Don’t miss the Geminids as 3200 Phaethon swings
near |
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December 10, 2017 |
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| 3200
Phaethon (blue orbit) will sweep close
to Earth on December 16, 2017, just days
after the Geminid meteor shower’s peak.
Image via Osamu Ajiki (AstroArts)/Ron
Baalke (JPL) /Ade Ashford (AN)/AstronomyNow. |
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By Bruce McClure and Deborah Byrd
EarthSky.org
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| The Geminids
seem to radiate from near the bright
star Castor in the constellation Gemini,
which lies in the east on December
evenings, highest at around 2 a.m.
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The Geminid meteor shower – always a highlight
of the meteor year – will peak in 2017 around
the mornings of December 13 and 14. Geminid
meteors tend to be few and far between at early
evening, but intensify in number as evening
deepens into late night.
Observing around 2 a.m. is best.
This shower favors Earth’s Northern Hemisphere,
but it’s visible from the Southern Hemisphere,
too.
The Geminids’ parent body – a curious rock comet
called 3200 Phaethon – is exceedingly nearby
this year, due to make a close sweep past Earth
on December 16.
It's likely to be cloudy over the region around
North Idaho through the nights the Geminids are
most active, December 13-15, and it's going to
be cold, but there could be breaks in the
clouds, making sightings theoretically possible
at least. Those chances diminish as the Geminid
showers wane December 16, with a 70-percent
chance of snow and freezing rain in Bonners
Ferry, conditions are likely to be too overcast
and too miserable for meteor watching.
Why are these meteors called the Geminids? If
you trace the paths of the Geminid meteors
backward, they all seem to radiate from the
constellation Gemini the Twins.
This shower’s radiant point nearly coincides
with the bright star Castor in Gemini. That’s a
chance alignment, of course, as Castor lies
about 52 light-years away while these meteors
burn up in the upper atmosphere, some 60 miles
(100 km) above Earth’s surface.
Again, you don’t need to find the constellation
Gemini to watch the Geminid meteor shower. These
medium-speed meteors streak the nighttime in
many different directions and in front of
numerous age-old constellations.
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| Watch for
the waning moon, Jupiter and Mars around
the mornings of the Geminids’ peak in
2017. |
You can watch this shower in the evening – late
evening is best.
But the greatest number of meteors will fall in
the wee hours after midnight, centered around 2
a.m. local time (the time on your clock no
matter where you are on Earth), when the radiant
point is highest in the sky. As a general rule,
the higher the constellation Gemini climbs into
your sky, the more Geminid meteors you’re likely
to see.
These meteors are often bold, white and bright.
On a dark night, you can often catch 50 or more
meteors per hour.
You need no special equipment – just a dark,
open sky and maybe a sleeping bag to keep warm.
Plan to sprawl back in a hammock, lawn chair,
pile of hay or blanket on the ground. Lie down
in comfort, and look upward.
By the way, you don’t need to find a meteor
shower’s radiant point to see the shower. The
meteors will appear in all parts of the sky.
It’s even possible to have your back to the
constellation Gemini and see a Geminid meteor
fly by. However, if you trace the path of a
Geminid meteor backwards, it appears to
originate from within the constellation Gemini.
When you’re meteor-watching, it’s fun to bring
along a buddy. Then two of you can watch in
different directions. When someone sees one,
they can call out “meteor!” This technique will
let you see more meteors than one person
watching alone will see.
Be sure to give yourself at least an hour of
observing time. It takes about 20 minutes for
your eyes to adapt to the dark.
Be aware that meteors often come in spurts,
interspersed with lulls.
Every year, in December, our planet Earth
crosses the orbital path of an object called
3200 Phaethon, a mysterious body that is
sometimes referred to as a rock comet and parent
to the Geminid meteors we see on Earth.
The debris shed by 3200 Phaethon crashes into
Earth’s upper atmosphere at some 80,000 miles
(130,000 km) per hour, to vaporize as colorful
Geminid meteors.
In periods of 1.43 years, this small 5-kilometer
(3-mile) wide asteroid-type object swings
extremely close to the sun (to within one-third
of Mercury’s distance), at which juncture
intense thermal fracturing causes it to shed yet
more rubble into its orbital stream.
In 2017, 3200 Phaethon will be exceedingly
nearby around nights of the Geminid meteor
shower’s peak. This object will sweep close to
Earth – just 0.069 astronomical units (6.4
million miles, 10.3 million km, 26
lunar-distances) on December 16, 2017 at 23 UTC;
translate to your time zone.
The proximity of this object might mean a
fantastic year for the Geminids in 2017!
One of the best things about this year’s Geminid
shower is that the moon is out of the way. It’s
a waning crescent in the east before sunup and
so shouldn’t interfere much, if at all, with
your meteor-watching. Plus, the waning crescent
moon will slide past the morning planets, on the
peak mornings on the 2017 Geminid shower.
Look at the chart above. See how the moon gets
closer to the sunrise point each day? That
motion of the moon across our sky is a
translation of its motion in orbit around Earth.
Bring along your binoculars when watching for
the moon and planets, on the nights of the
Geminids’ peak. They won’t help you watch
meteors, but you’ll be able to see Jupiter in
the same binocular field of view with the star
Zubenelgenubi in the constellation Libra the
Scales. Look closely, and you’ll see that
Zubenelgenubi is a double star – two stars in
one!
You won’t see as many Geminid meteors when the
constellation Gemini sits close to the eastern
horizon during the evening hours. But the
evening hours are the best time to try to catch
an earthgrazer meteor.
An earthgrazer is a slow-moving, long-lasting
meteor that travels horizontally across the sky.
Earthgrazers are rarely seen but prove to be
especially memorable, if you should be lucky
enough to catch one. |
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