Astronomy Essentials

All you need to know: 2020’s Geminid meteor shower

Long, straight bright streak in dark sky above dark nearby mountains.
John Ashley in Glacier National Park, Montana, caught this amazing earthgrazer meteor in December 2018. You’re most likely to catch an earthgrazer in the evening hours. Watch for them! John said this one lasted approximately 4 seconds and left behind a glowing smoke train. He commented: “The meteor went dark just above Dusty Star Mountain, or ‘Iszika-kakatosi’ in Blackfeet, which translates to ‘smoking star.'” Cool! Nikon D750, Rokinon 24mm lens @ f1.4, 30 sec, ISO 3200. Thanks, John!

The Geminid meteor shower – always a highlight of the meteor year – is expected to peak in 2020 on the night of December 13-14 (Sunday evening until dawn Monday). This year’s shower should be grand! The Geminids are typically a very reliable shower if you watch at the best time of night, centered on about 2 a.m. for all parts of the globe, and if you watch in a dark sky. And this year there’s no moon to ruin the shower. Will you see Geminid meteors after the peak? Yes, but not as many. Be sure to look around the peak time of night (2 a.m. for all locations on the globe) and in a dark sky.

Geminid meteors tend to be bold, white and quick. This shower favors Earth’s Northern Hemisphere, but it’s visible from the Southern Hemisphere, too. The curious rock comet called 3200 Phaethon is the parent body of this shower.

On a dark night, near the peak, you can often catch 50 or more meteors per hour. On an optimum night for the Geminids, it’s possible to see 150 meteors per hour … which might happen this year, given the moon-free skies accompanying this year’s Geminid meteor shower. New moon falls on December 14, 2020. On the mornings before that date, you’ll see a waning crescent moon. And – on December 11, 12 and 13, 2020 – after a night of meteor-watching, the slender lunar crescent and dazzling planet Venus will rise into your eastern sky at or near dawn.

What a way to cap a night of meteor-watching!

EarthSky’s lunar calendar shows the moon phase for every day in 2021. Order yours before they’re gone! Makes a great gift.

Sky chart: Moon joins up with Venus in the morning sky along the ecliptic.
In 2020, the 2 brightest orbs of nighttime – the moon and Venus – will be ascending in the east as the predawn darkness gives way to morning dawn on December 11, 12 and 13. What a wonderful sight to behold after a night of meteor-watching!

Why are the Geminids best around 2 a.m.? It’s because that’s when the shower’s radiant point – the point in our sky from which the meteors seem to radiate – is highest in the sky. As a general rule, the higher the constellation Gemini the Twins climbs into your sky, the more Geminid meteors you’re likely to see.

This Geminids’ 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.

Castor is noticeably near another bright star, the golden star Pollux of Gemini. It’s fun to spot them, but you don’t need to find a meteor shower’s radiant point to see these meteors.

Instead, meteors in annual showers 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.

Straight white streak in dark sky with several stars labeled.
Martin Marthadinata in Surabaya, East Java, Indonesia, caught this Geminid fireball in 2014, coming from the shower’s radiant point near the star Castor.
Outlined constellation Gemini with radial arrows near star Castor.
The Geminids radiate from near the bright star Castor in the constellation Gemini, in the east on December evenings, highest around 2 a.m. for all parts of the globe. Learn more about the Geminids’ radiant point.

6 tips for meteor-watchers.

1. The most important thing, if you’re serious about watching meteors, is a dark, open sky.

2. Watch at the peak time of night, around 2 a.m. (or later) for all parts of the globe.

3. When you’re meteor-watching, it’s good to bring along a buddy. Then two of you can watch in different directions. When someone sees one, call out “meteor!” This technique will let you see more meteors than one person watching alone will see.

4. 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.

5. Be aware that meteors often come in spurts, interspersed with lulls.

6. Special equipment? None needed. Maybe bring a sleeping bag to keep warm. A thermos with a warm drink, and a snack, is always welcome. Plan to sprawl back in a hammock, lawn chair, pile of hay or blanket on the ground. Lie back in comfort, and look upward. The meteors will appear in all parts of the sky.

Black sky with fuzzy dot at top and thin red streak near bottom.
Jim Livingston in Custer, South Dakota, caught Comet 46P/Wirtanen in the same field of view as a streaking meteor on December 9, 2018. See more images of Comet Wirtanen. Canon 60D, Skywatcher 8″ reflector, CGX mount. Thanks, Jim!

Earthgrazers are possible in the evening hours. Okay, we said you’ll likely see the most meteors at a time of night centered around 2 a.m. You won’t see as many Geminid meteors in early evening, when the constellation Gemini sits close to the eastern horizon.

But the evening hours are the best time to try to catch an earthgrazer meteor.

An earthgrazer is a slooow-moving, looong-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.

Orange streak with multiple large yellow dots along it in dark blue sky.
Painting of 1860 earthgrazer fireball by Frederic Edwin Church. Image via Wikimedia Commons.

Geminid’s parent – 3200 Phaethon – is a “rock comet.” 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. 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 3-mile (5-kilometer) 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.

There was big excitement about 3200 Phaethon in 2017, because this object was exceedingly nearby around the nights of the Geminid meteor shower’s peak. It swept to within 6.4 million miles (10.3 million km, 26 lunar-distances) on December 16, 2017. In 2019, 3200 Phaethon is much farther away. Visit The Sky Live to know 3200 Phaethon’s present distance from the Earth and sun.

Read more: Mysterious rock comet 3200 Phaethon

Animated image of rotating roundish gray object.
Radar images of near-Earth asteroid 3200 Phaethon generated by astronomers at the Arecibo Observatory on December 17, 2017. The 2017 encounter was the closest the asteroid will come to Earth until 2093. Image via Wikipedia.

Bottom line: The annual Geminid meteor shower peaks on the night of December 13-14, 2020 (Sunday evening to Monday morning). But the preceding weekend nights should offer a decent number of meteors, too. Will you continue to see Geminid meteors after the peak? Yes, but not as many. Be sure to look around the peak time of night (2 a.m. for all locations on the globe) and in a dark sky.

December 13, 2020
Astronomy Essentials

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