Meteor showers are typically the result of the Earth passing through the trail of a comet. The bits of rock and debris burn up when they hit the Earth’s dense atmosphere, and streak across the sky.
The Geminids — which radiate out of the constellation Gemini and reach their peak Tuesday night — are not a typical meteor shower.
If you go outside Tuesday night and watch, you’ll be seeing bits of debris from an asteroid named 3200 Phaeton burn up in the night sky.
What’s more, those asteroid bits are denser than typical meteor kindling. That means they move more slowly across the sky as they burn. They also tend to be a bit brighter than the typical meteor. “The brightest often break up into numerous luminous fragments that follow similar paths across the sky, the Royal Observatory Greenwich explains in its annual guide to the night sky.
It should be a great show. Here’s what you need to know.
What causes the Geminids?
3200 Phaethon is an odd asteroid. While Phaethon is a small (3-mile-wide) rocky asteroid, it behaves more like a comet.
It has a highly elliptical orbit like a comet (asteroid orbits tend to be rounder). But more important for the meteor shower, 3200 Phaethon is a rare asteroid that forms a tail. This is likely due to its orbit that brings it very close to the sun (in Greek mythology, Phaethon is the son of Helios, the sun god). The heat of the sun fractures the rock and creates the trail of debris that the Earth is about to slam into. For this reason, 3200 Phaethon is sometimes referred to as a “rock comet.”
How to view the Geminids
In the Northern Hemisphere, the constellation Gemini will rise in the East on the night of December 13 and ascend to the top of the night sky by 2 am, which will make for the best time for viewing.
“The Geminids are typically one of the best and most reliable of the annual meteor showers,” NASA notes, usually producing around 120 meteors an hour at peak.
But there’s a big caveat this year.
The shower will be diminished due to a full “supermoon” out on December 13. (The moon is considered “super” because it will be near its closest orbit to the Earth, which makes it appear a bit bigger and brighter than usual.)
The light from the moon “will wash out all but the brightest Geminids, reducing the rate you can see them significantly,” NASA’s Watch the Skies blog reports.
But fear not: In a Reddit Ask Me Anything session Monday, scientists at NASA’s Meteoroid Environment Office wrote that most people will still be able to see 30 meteors per hour if the skies are clear.
“The best way to view the Geminids,” they write, “is to find a dark place (away from city lights) with an open sky (no trees/buildings in the way) and lie on your back and look straight up.”
The Geminids should also be visible on the night of December 14, too, peaking around 2 am. (And if you totally miss out, there will be one more meteor shower this year — the Ursids, peaking on December 22. But that shower only produces about five to 10 meteors per hour.)
It’s too cold to stargaze. Do I have other options?
If you can’t get outside, or think it’s too cold to go outside past midnight to look at the stars, you’re in luck.
The astronomy education website Slooh will be live-streaming a feed from one of its observatories, which you can watch right here.