Against a backdrop of blurred stars, the comet 21P/Giacobini-Zinner, source of the Draconids meteor shower, is seen. Photograph courtesy NASA JPL.
Published October 7, 2010
The meteor shower forecast for tonight—the peak of the annual Draconids display—calls for no more than a drizzle, although a new moon will offer ideal viewing conditions.
Next year, though, sky-watchers should be prepared for a Draconids downpour, forecasters say.
A new model presented this week predicts that in 2011, Earth will sweep right through the center of a debris trail left behind by the comet 21P/Giacobini-Zinner, creating a Draconids shower that's closer to a storm.
At peak, the 2011 Draconids might produce up to two meteors a minute, the model suggests.
If the prediction is right, this will be the first major Draconids outburst since 1998 and the last we're going to see until 2032, said Jérémie Vaubaillon of France's Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE).
"I hope that my prediction will underestimate the level we are going to see, because [a Draconids outburst can be] just a fantastic thing," Vaubaillon told National Geographic News on Wednesday during a meeting of the American Astronomical Society's Division of Planetary Sciences in Pasadena, California.
"If you've ever seen the Perseids in August—it's going to be like twice that amount, at least!"
Breath of the Dragon
Annual meteor showers happen when Earth crosses the orbit of a periodic comet—one that flies near the sun at regular intervals. (See asteroid and comet pictures.)
When the comet gets close to the sun's warmth, the icy body releases gases, which in turn carry dust grains. The ejected dust gets distributed along the comet's orbital path, said astronomer Mark Hammergren of the Adler Planetarium in Chicago, who was not part of the new research.
When the tiny pieces of comet dust hit Earth's atmosphere, they disintigrate, creating the bright streaks we see as meteors.
Comet 21P/Giacobini-Zinner, discovered in 1900, returns to Earth's neighborhood about every 6.5 years.
Early 20th-century astronomers predicted that the comet's debris trail would produce a meteor shower in October, which was later confirmed and named the Draconids, because the shower seems to radiate from the constellation Draco, the Dragon. (See a solar system map.)
The annual shower hadn't been noticed before 1900 because the Draconids are normally very weak. This is due in part to the fact that, as the comet and its debris go around the sun, they pass close to some very massive objects in the rest of the solar system, such as Earth and Jupiter, IMCCE's Vaubaillon said.
Gravitational interactions with these objects can cause the orbiting debris to bunch up in certain regions but be almost absent in others, he said: "Without the interactions with the planets, the debris trail would be more or less smooth."
In addition, interactions with planets can nudge the debris into slightly different paths each year, so that in most years Earth only grazes the trail. This leads to relatively minor showers of just ten streaks an hour.
Rare Meteor Shower to Spring to Life
But in certain years, the Draconids have suddenly sprung to life. In 1933, for example, the meteor shower reached a peak rate of a hundred meteors a minute, while in 1998 viewers saw as many as 500 meteors an hour.
According to Vaubaillon's model, those outbursts were due to the comet's trail interacting with Jupiter so that the debris moved directly into Earth's path—"a very rare event," he said. "It's not every day you will be able to observe something like that."
And, based on his calculations, Vaubaillon thinks next year we'll be once again headed directly for the Draconids debris.
In fact, the scientist is now working on plans for a research flight over northern Europe that will be able to track the shower at high altitudes, taking detailed readings of the meteor rate and even the composition of the dust grains.
It's been suggested, based on observations of the comet itself, that 21P/Giacobini-Zinner contains organic material, Vaubaillon noted.
Falling into Earth's atmosphere, comet 21P/Giacobini-Zinner's debris moves relatively slowly for meteors—just 12 miles (20 kilometers) a second—so it should be possible to confirm what's in the comet by recording the light the dust emits as it burns and looking for the signatures of specific chemicals.
2011 Draconids May Pose Satellite Dangers
Unfortunately, even if a Draconids meteor outburst occurs in 2011, a bright full moon next October "will interfere very much with viewing the shower," noted Adler's Hammergren.
But that hasn't stopped some tourist groups from organizing viewing parties in Europe, where the shower will be easiest to watch, he said. A quick Internet search turned up several websites offering meteor-watching cruises across the Mediterranean, for example.
"It looks like people are already taking advantage of these predictions!" Hammergren said.
And forecasting meteor outbursts is crucial for more than just sky-watching: IMCCE's Vaubaillon began his modeling work because the French space agency was worried about the possible damage an abundance of comet debris in 2011 might cause to satellites.
If a given meteor shower might pose a risk, protecting a satellite means shutting it off temporarily, and that "is gonna cost you an arm and a leg—like half a million dollars or something like that—and you can't acquire the satellite for one week," Vaubaillon said.
"But if you don't [shut the satellite down], you take the risk that, if there's an impact, well, you might lose the whole satellite, so it's a tough question.
"We really need some very detailed modeling of meteor showers ... to know where they are, when will the Earth encounter them, and will they be a danger to satellites."
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