A Deluge of Draconids?

Everyone enjoys a great meteor shower, those special times each year when a profusion of shooting stars zip across the sky. So here's a head's up: all of you should circle October 8th on next year's calendar.

This is the yearly date when Earth plows through a tenuous band of space dust created by Comet Giacobini-Zinner along its orbit. Ordinarily, the Draconid shower (formerly called the Giacobinids) puts on a so-so celestial show, delivering about 20 meteors per hour if you can view them under a moonless, pitch-black sky. That's hardly worth staying up for: after all, from a similarly clear, dark site you'll see six or seven random ("sporadic") meteors per hour.

However, this shower has a Jekyll-and-Hyde personality. In 1933 and 1946 the Draconids dazzled skywatchers with astounding meteor "storms" — delivering shooting stars at rates that briefly topped 10,000 per hour! — because Earth crossed through a particularly dense ribbon of debris shed by the comet in 1900. The shower hasn't put on that kind of performance in the years since, though in 2005 it surged unexpectedly to double or triple the usual rate.

If celestial prognosticators are right, we're in for a treat next year, when Draconid rates could top 600 per hour — that's 10 per minute — under ideal viewing conditions. That surge is in the cards because we'll likely clip the stream of particles ejected in 1900. Odds are that it's still largely intact, even though the comet's 6½-year-long orbit periodically puts it in Jupiter's disruptive vicinity.

Earth's path through 2011 Draconid meteors
On October 8, 2011, Earth will pass through several streams of particles ejected over the past 200 years by Comet Giacobini-Zinner.
J. Vaubaillon & others
At a meeting of planetary scientists now under way in Pasadena, California, meteor dynamicist Jérémie Vaubaillon (IMCEE, France) put forth predictions that he'd calculated with colleagues Mikiya Sato and Jun-ichi Watanabe (NAOJ, Japan). If they're right, next October 8th Earth crosses some cometary debris shed by Comet G-Z between 1873 and 1894, peaking at perhaps 60 meteors per hour centered at 17:09 Universal Time, followed at 19:57 UT by a much stronger, 600-per-hour pulse from the 1900 stream.

The rate is very uncertain, Vaubaillon admits, because there's no way to know whether those earlier streams are still densely packed or have been spread thin. Meteor observing wasn't as rigorous back then as it is now. But next year's results should help disentangle which streams are still contributing to the overall rates.

Other meteor specialists are also struggling to come up with firm rates. In 2008 Sato and Watanabe independently estimated a maximum of 500 per hour (at 20:36 UT), whereas NASA researchers Danielle Moser and William Cooke have offered a more optimistic 800 per hour (at 19:11).

These times favor observers in Europe, but don't rush out to book a plane just yet. First, the Draconid shower tends to produce many faint meteors that'll be obliterated by a nearly full Moon that night.

Cloud cover during 2011 Draconids
Although Europe is favored for watching the 2011 Draconid meteor shower, this map of average cloud cover during October suggests finding clear skies might prove challenging. (Bluer hues denote more frequent clouds.) Click on the image for a larger view.
Jay Anderson
Second, because the shower's radiant is way up near the head of Draco (declination +54°), the best observing sites would likewise be geographically north. But there's a reason that so few people book vacations to Scandinavia in October: "Weather in Northern Europe is not very pretty," notes Canadian meteorologist Jay Anderson. "October can be very nice, but usually it is the time when the winter cloudiness begins to encroach on the daily weather."

Instead, Anderson's cloud-cover map (at right) suggests that the northernmost "good weather" spot is in the Greek Islands. "Santorini — a favorite place of mine — has clear/few/scattered cloud cover 74% of the time. I know where I'd go."

Great advice, Jay! Now, can you do something about that bright Moon?

3 thoughts on “A Deluge of Draconids?

  1. MopMop

    Mark, Canada should be able to see it easily.

    I wonder if the 1900 comet passage had some kind of disconnection event? It seems that the 1900 stream has a dense pack of meteoroids in it’s path.
    Is there any information on the comet passage at that time, that might tell us more?

  2. MopMop

    Mark, Canada should be able to see it easily.

    I wonder if the 1900 comet passage had some kind of disconnection event? It seems that the 1900 stream has a dense pack of meteoroids in it’s path.
    Is there any information on the comet passage at that time, that might tell us more?

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