The Earth plows through a swarm of asteroid debris this week to give us one of the best meteor showers of the year — the Geminids. The shower is already active and will peak this Friday night December 13-14 when up to 120 meteors per hour might be seen from a dark, moonless sky. Unfortunately, glare from the moon, just two nights past full, will chew into that number, reducing meteor counts to perhaps 20-30 per hour.
But even 20 meteors an hour makes a show especially when you consider that the Geminids are famed for their bright meteors called fireballs. Better yet you don’t have to get up in the wee hours to watch. True, you’ll see more meteors in the early morning hours when Gemini and the radiant stand highest in the sky (around 2 a.m. local time), but the shower starts revving up as early as 9 p.m. when the radiant stands nearly three fists high in the eastern sky.
If you’re a parent, that’s early enough to take the kids out for a look. Meteor shower watching is a relaxing and enjoyable family activity where we can step away from our glowing phones and laptops and focus on something bigger and grander. I recommend a reclining lawn chair for easy and comfortable viewing. Younger children can simply snuggle up with mom or dad but otherwise make sure everyone has their own chair and sleeping bag or blanket to keep warm. Hot chocolate makes a nice enticement. I’ve always been partial to adding a marshmallow to mine.
Last year’s Geminids were moonless and I counted 85 meteors in about 2 hours, the most I’d ever seen in one session. Besides shooting stars, you can use the opportunity to get reacquainted with the winter stars. Orion and his entourage are absolutely gorgeous, and if you spend an hour outside you’ll be able to see them slowly climb the sky, proof the planet you live on spins.
Most meteor showers are dust particles and small crumbs dropped by comets along their orbital paths. Each time a comet nears the sun, solar heating vaporizes dust-laden comet ice. The ices dissipate, but the dust trails behind like the Peanuts character Pigpen who’s always surrounded by his personal debris cloud. When the orbiting Earth intersects the comet’s orbit we slam head on into the material. Each drib and drab strikes the upper atmosphere and creates a sudden, brief streak of light called a meteor. As the shards incinerate from friction, they excite the air molecules around them to create glowing tubes of light. That’s what a meteor is in truth — a tube of excited or ionized air that gives off light for a brief second or two.
One after another the particles slam into the air some 60-70 miles overhead and etch glowing streaks that make us shout “Oooooh!” aloud.
The Geminids are a little different. Instead of comet dust the Earth plows through debris left by the asteroid 3200 Phaethon. Phaethon (FAY-eh-thon) is an exceptional object. It’s 3.6 miles (5.1 km) across, spins once every 3.6 hours (whew!) and swings only 13 million miles (20.9 million km) to the sun during its 1.4-year-long orbit. That’s less than half Mercury’s distance, so guess what? It gets HOT!
Astronomers have twice seen the asteroid grow a dusty comet tail, the reason why Phaethon is sometimes called a “rock comet.” It’s made of rock and looks like an asteroid most of the time but every so often the intense heat from the sun causes its surface to expand, contract and crack, releasing bits and pieces into space. Those flakes of dust and tiny fragments, that weigh no more than an almond or two, make the Geminids.
How to Watch
You can start early around 9 o’clock local time on Friday. Set your chair up and face away from the glare of the moon. That way you’ll preserve your night vision. Allow at least 15 minutes for your eyes to dark-adapt. I suggest facing south or north. Geminids can appear anywhere in the sky, but they all point back to the radiant near the bright stars Pollux and Castor in Gemini. You can also get up and watch between 1-3 a.m. during the peak of the shower.
Kick back and spent an hour with the shower. That should be enough time to bag a bunch of meteors — 10, 20 maybe? Sometimes there are gaps of 5 minutes or more when no meteors are visible. Just hang in there. More are on the way. The only hard thing about meteor watching is deciding when to quit. I always think there’s just one more around the corner.
You can stay up as late you like. The later the better because the radiant gets higher and higher. Shower peak is forecast around 12:00 Greenwich Time (6 a.m. CST Dec. 14). I hope this Friday the 13th will be a lucky one for you. Clear skies!