Image Credit: NASA/JSC/ARES
Canadian astronomer Paul Wiegert announced at a meeting of professional astronomers in Canada that the annual Draconid meteor shower might produce unusually high peak meteor rates of 1,000 per hour on October 8, 2011.
Wiegert is an astronomer at University of Western Ontario. His specialty is solar system dynamics. In other words, he conducts numerical analyses of the way objects in our solar system move. He says he likes working with smaller bodies particularly: asteroids, comets and meteoroid streams.
Like most meteors in annual showers, any fiery Draconid meteors we see streaking across a dark night sky actually started out in a meteoroid stream in space – a river of icy, rocky debris – left behind in the orbit of a comet. The comet that spawns the Draconid shower is named Giacobini-Zinner. Known for over 100 years, this comet takes about 6.6 years to orbit our sun once. Astronomer Paul Wiegert – in his analysis of the movement of Giacobini-Zinner and its attendant meteoroid stream of icy bits – has determined that conditions will line up just right in 2011 for us to see a spectacular Draconid meteor shower. A shower of 1,000 meteors per hour would be spectacular indeed.
Not yet. The peak of the shower is very narrow (lasting only one hour), and it so happens that narrow peak of the Draconids will come during daylight on October 8, 2011 for us in North America. The 2011 Draconid outburst is expected to occur between 17 and 18 Universal Time on October 8 – translating to between 1 and 2 p.m. Eastern Daylight Time on that day. In other words, pretty darn close to high noon for us in the continental U.S.
Can you see meteors in daylight? No. So Wiegert says the best locations from which to view the shower – which is primarily a northern hemisphere event, since the meteors radiate from a point that’s far to the north on the celestial sphere – will be Europe, North Africa, and the Middle East.
But there is yet another factor. The moon will be in a waxing gibbous phase on October 8. And as all meteor-watchers know, a large bright moon can drown out a meteor shower.
A typically strong meteor shower like the Perseid shower, which occurs every summer in mid-August, might produce up to 100 meteors per hour under favorable skies. Normally, the Draconids (so-named because its meteors appear to radiate from the northern constellation Draco) are a weak shower producing perhaps 10 meteors per hour. However, this shower has proved strongly variable in the past. In 1933 and 1946, the Draconids produced “meteor storms” where shooting stars were produced at rates of 10,000 per hour or even more. Other less dramatic outbursts — where the meteor counts nonetheless ran into the hundreds per hour — occurred in 1952, 1985, and 1998.
Though the peak of the outburst is predicted to occur during daylight hours in North America, the shower is expected to continue to produce meteors, albeit at a reduced level, into the evening of October 8. So North Americans will still have a chance to see a stronger-than-usual Draconid meteor shower.
Paul Wiegert, an astronomer at University of Western Ontario, who is presenting his results at this week’s CASCA 2011 meeting in Ontario, Canada, said:
And you never know. Meteor showers are as difficult to predict as rain showers. The Draconids have surprised us before, and they may do so again. I’d encourage anyone outside on the night of October the 8 to look to the northern skies, just in case.
How to view the Draconid shower
This meteor shower really favors the northerly latitudes, but that’s not to say the Draconid meteors can’t be seen from the northern tropics. Predicting the intensity and the peak (or multiple peaks) of a meteor shower is a very tricky business, and represents a best guess – not an ironclad guarantee. You’ll never know for sure what a meteor shower has to offer unless you watch.
Wherever you may reside worldwide, the best viewing of these meteors will probably be at nightfall and early evening on October 8. That’s when the radiant point for the shower will be highest in the sky for the night. All other things being equal, the most meteors tend to fall when the the radiant point is highest in the sky. North of about 35 degrees north latitude – the latitude of Memphis, Tenessee – the radiant is actually circumpolar. Circumpolar means that the radaint stays above the horizon all night long.
Even so, the radiant will fall downward during the night and reach its low point around 5:00 a.m. local time (6:00 a.m. local daylight saving time). Generally, you see few – if any – meteors when the radiant of the shower falls close to the horizon. However, if the Draconids should burst into storm during the predawn hours (that’ll be in Asia and possibly Alaska on October 9, if the prediction holds), you might not see an abundance of meteors but you may see some earthgrazers – unusually bright and long meteors that go horizontally across the sky.
However, nightfall and early evening (on October 8, 2011) will probably provide the greatest number of meteors. At this time, the waxing gibbous moon will be rather low in your east to southeast sky and casting long shadows. Sit in the shadow of a barn or hedgerow of trees, though with an otherwise open view of sky. This should help darken the night for meteor watching.
Source of the Draconid meteor shower
Comet Giacobini-Zinner is the source of the Draconid meteor shower and was the first comet to be examined by a spacecraft, when in 1985 the International Cometary Explorer flew through its tail, passing approximately 4,847 miles (7,800 km) from its nucleus.
A comet’s tail may extend for millions of km, but that spectacular display all originates from the much-smaller nucleus at its head. Essentially an ice asteroid, the frozen nucleus partly evaporates when its orbit brings it close to the sun. At this time the comet’s tail, which is composed largely of water vapor and chemically related species, grows in size and may achieve naked-eye visibility from Earth. The vaporization process also releases copious quantities of small rocks and dust because the nucleus is far from pristine ice: it is more like a dirty city snow-bank after a long winter.
The solid rocky material produced by a comet continues to orbit the sun after its release. If that orbit brings it into collision with the Earth, its high speed — which may exceed 155,342 mph (250,000 kph) — causes it to burn up in the upper atmosphere and produce a bright flash we call a meteor, shooting star or falling star. Particles no larger than a pea and which burn up at altitudes of 62 miles (100 km) are easily noticeable from the ground; in fact, this describes most meteors visible to the human eye. When these particles arrive in large numbers, they produce a beautiful display called a meteor shower.