Fantastic Year for Geminid Meteor Shower

Mark the date: December 13th. That's the night the Geminid meteor shower peaks. Highlighted by the return of its parent asteroid 3200 Phaethon, this year's show promises to be one of the best ever.

Evening viewing, too!

This should be a good year for the Geminids. There’s almost no moonlight to interfere with observing, and the shower reliably produces a high meteor count.

This is it, the shower we've been waiting for. Set aside some time Wednesday night December 13–14 for the Geminids. Not only is it the year's most prolific, with up to 120 meteors per hour visible from rural skies, the Moon is essentially out of the picture. Rising around 4:30 a.m. on the 14th, the waning crescent will shine just 3.5° north of the planet Jupiter in a frosting-on-the-cake conjunction to top off the big event.

The Geminid maximum also coincides with a bright return of its parent asteroid, 3200 Phaethon. On the night of maximum, Phaethon won't be very far away, clipping across neighboring Perseus at about 30″ a minute at its peak predicted magnitude of 10.7.

Set up the scope, spot papa, and then stretch out on the ground, suitably insulated from the cold with a blanket or sleeping bag, and witness his progeny put on a spectacular light show. For detailed maps of the asteroid's path, click here.

A word about that 120 per hour rate. That's the zenithal hourly rate, or ZHR, an idealized number based on observing under a pristine, moonless sky with the radiant at the zenith. Depending on the time you observe and local light pollution, counts will vary. At my observing site, which is handicapped by minor to moderate skyglow, I cut the rate in half to keep expectations realistic. A meteor a minute is certainly nothing to complain about.

Geminid Meteor Crosses Orion

During the 2004 Geminid meteor shower, Alan Dyer caught a bright fireball to the left of Orion with a tripod-mounted digital camera. He used a wide-field, 16-mm lens for a 1-minute exposure at f/2.8 at ISO 800. Give it a try with your digital camera. 30 seconds at ISO 1600 also works and makes for more pinpoint stars. First, focus on a bright star using the "Live View" feature located near your back display screen, then compose the scene and shoot one photo after another. An intervalometer makes taking continuous time exposures easy by activating the shutter automatically. You can find one at most online camera supply stores.

Most major showers peak in the early morning hours. While that's also true of the Geminids, the shower offers something others don't: an evening matinee. You can spot a modest number of meteors visible starting as early as 9 p.m. because the radiant already stands some 30° high in the eastern sky. True, a fair number of shower members are cut off by the horizon at that time, but more of us are likely to go out and share it with our children in the evening as opposed to waking before dawn. Since Geminids travel at moderate to slow speeds and approach us from a low angle at that hour, they can produce brilliant and long-lasting fireballs.

Zenithal view

The view shown here is for 2 a.m. Thursday morning, Dec.ember 14th, when the radiant will be high in the southwestern sky near the zenith. Shower maximum is expected around 6h UT (1 a.m. EST) Dec. 14.

If you want to experience the full power of the shower, set your clock for 2 a.m., when the radiant will be practically overhead. Shower members appear to originate or radiate from near Castor and Pollux in Gemini, the Twins. It may seem weird that the radiant is a point in sky until you realize you're staring down the shower's vanishing point, where the incoming meteoroids appear to converge in the distance, exactly the way railroad tracks appear to meet at the horizon.

As Earth plunges headlong into the debris left by the asteroid, each crumb leaves a hot streak of ionized air in its wake we see as a meteor. Though they may appear anywhere in the sky, every fragment flies in parallel, like a squadron of B-52s on a bombing run. Only a skosh faster — about 35 kilometers a second.

Convergence makes it easy to distinguish a Geminid from a random or sporadic meteor. If you can trace the bright streak back to the Twins, you can confidently say you've witnessed a millimeter fragment of an asteroid burn up in the atmosphere. Farewell, spawn of Phaethon.

After getting washed out by last year's supermoon, we look forward with anticipation to a truly excellent show this year. Although northern hemisphere skywatchers are favored, the Geminids are also visible with reduced numbers from Down Under, where the radiant stands some 40° high from northern Australia around 2 a.m. local time. With near-peak numbers lasting about a day, the entire planet except for Antarctica, where the Sun now shines 24/7, will get a crack at the shower.

Geminid Snow

This montage shows multiple Geminids flashing across the sky during the 2012 maximum. This year's shower won't be compromised by moonlight as were last year's Geminids and this year's Perseids.
Catalin Padraru

To summarize: If you're meteor-watching in the evening, head out around 9 p.m. local time or later and observe from a place as far from city lights as possible. Bring warm clothing and a blanket or sleeping bag for huddling and cuddling and face east. Then, just lie back and wait for the meteors to flare. Even 30 minutes of watching should net a few celestial sparks. If you want to catch the peak, plan on watching from about 1–3 a.m. facing south on Thursday morning the 14th. Even 3–5 a.m. works if you're keen on that conjunction.

Prospects for this year's Geminids are so good, only cloudy skies could muck it up. But that won't happen, right? If bad weather prevails, you can still watch the shower at Gianluca Masi's Virtual Telescope Project site live from Italy starting at 22:00 UT (5 p.m. EST) Dec. 13 and from Arizona at 10:00 UT (5 a.m. EST) on the 14th.

15 thoughts on “Fantastic Year for Geminid Meteor Shower

  1. Tom-Reiland

    Bob, Thanks for guaranteeing cloudy weather for Western Pa next week. Our weather in December is usually poor, but this makes it almost a certainty that we won’t see the night sky all of next week. Hope you have better luck. As a friend of my says, it’s always clear ten miles from us, straight above us.

    1. rocksnstarsrocksnstars

      Hoffelder’s corollary (to Murphy’s Law), rev 2: The probability of cloud cover at night is a) inversely proportional to the amount of moonlight in the sky, and b) directly proportional to the observer’s level of interest in any celestial event, with the latter taking precedence when applicable.

  2. StardocJGStardocJG

    Great article, Bob! Forwarding to attendees at Geminids Watch at Howard County Conservancy here in MD. Always our best, as well as coldest, meteors watch of the year.

    1. Bob KingBob King Post author

      Hi bclose,
      The maximum and good activity is spread over about two days but drops off quickly after that. Since you’ll watching one day after the maximum, you’ll still see some Geminids.

  3. rocksnstarsrocksnstars

    So nice to see words about ZHR! Most mainstream media articles simply say “expect to see as many as 120/hr,” disregarding the fact that that is the ZHR number, and the fact that it makes a difference when you look. I saw some articles for the Leonids last month saying look as soon as it gets dark, totally ignoring the fact that the radiant doesn’t rise until at least 11 PM. As far as what could go wrong, see my corollary reply to Mr. Reiland above. Perhaps you know that he and I were the first observers, as far as we know, to see more than 100 M objects in one night.

  4. Anthony BarreiroAnthony Barreiro

    It’s been fairly clear here in SF (good for skywatching, not so good for taking showers next year!). I saw a few Geminids from my light-polluted back yard, including a couple of really bright ones, magnitude -1 or -2 — one about 0500 PST yesterday morning 13 December, and one about 2200 PST last night, 13 December. I am grateful to all my immediate neighbors for getting into the habit of turning off their outside lights when they’re not using them.

  5. Graham-Wolf

    Hi Bob

    Call it the “dastardly Digit of Destiny” or the “Fickle Finger of Fate”, but I was murphied out by overcast skies BOTH nights. Might have to call this effect the “Occultids”!

    Did manage to briefly sight Paethon a few days ago, near it’s peak. Rather faint in my 12cm f8.3 Newtonian.

    Graham W. Wolf at 46 South, Dunedin, NZ.

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