Earth is orbiting through a swarm of space debris that may
be producing an unusual number of nighttime fireballs.
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November 3, 2005: "I thought some wise guy was
shining a spotlight at me," says Josh Bowers of New Germany,
Pennsylvania. "Then I realized what it was: a fireball
in the southern sky. I was doing some backyard astronomy around
9 p.m. on Halloween (Oct. 31, 2005), and this meteor was so
bright it made me lose my night vision."
Bowers
wasn't the only one who saw the fireball. Lots of people were
outdoors Trick or Treating. They saw what Bowers saw ... and
more. Before the night was over, reports of meteors "brighter
than a full moon" were streaming in from coast to coast.
Astronomers
have taken to calling these the "Halloween fireballs."
But there's more to it than Halloween. The display has been
going on for days.
Right:
The bright light behind the clouds is a fireball photographed
Nov. 2, 2005, by Mark Vornhusen of Germany. [More]
On
Oct. 30, for example, Bill Plaskon of Jonesport, Maine, was
"observing Mars through a 10-inch telescope at 10:04
p.m. EST when a brilliant fireball lit up the sky and left
a short corkscrew-like smoke trail that lasted about 1 minute."
On
Oct 28, Lance Taylor of Edmonton, Alberta, woke up early to
go fishing with five friends. At about 6 a.m. they "noticed
a nice fireball. Then 20 minutes later there was another,"
he says.
On
Nov. 2 in the Netherlands, "The sky lit up very bright,"
reports Koen Miskotte. "In the corner of my eye I saw
a fireball about as bright [as a crescent moon]."
And
so on….
What's
happening? "People are probably seeing the Taurid meteor
shower," says meteor expert David Asher of the Armagh
Observatory in Northern Ireland.
Every
year in late October and early November, he explains, Earth
passes through a river of space dust associated with Comet
Encke. Tiny grains hit our atmosphere at 65,000 mph. At that
speed, even a tiny smidgen of dust makes a vivid streak of
light--a meteor--when it disintegrates. Because these meteors
shoot out of the constellation Taurus, they're called Taurids.
Above:
a Taurid fireball photographed Oct. 28, 2005, by Hiroyuki
Iida of Toyama, Japan.
Most
years the shower is weak, producing no more than five rather
dim meteors every hour. But occasionally, the Taurids put
on quite a show. Fireballs streak across the sky, ruining
night vision and interrupting fishing trips.
Asher
thinks 2005 could be such a year.
According
to Asher, the fireballs come from a swarm of particles bigger
than the usual dust grains. "They're about the size of
pebbles or small stones," he says. (It may seem unbelievable
that a pebble can produce a fireball as bright as the Moon,
but remember, these things hit the atmosphere at very high
speed.) The rocky swarm moves within the greater Taurid dust
stream, sometimes hitting Earth, sometimes not.
"In
the early 1990s, when Victor Clube was supervising my PhD
work on Taurids," recalls Asher, "we came up with
this model of a swarm within the Taurid stream to explain
enhanced numbers of bright Taurid meteors being observed in
particular years." They listed "swarm years"
in a
1993 paper in the Quarterly Journal of the Royal Astronomical
Society and predicted an encounter in 2005.
It
seems to be happening.
When
should you look? You might see a fireball flitting across
the sky any time Taurus is above the horizon. At this time
of year, the Bull rises in the east at sunset. The odds of
seeing a bright meteor improve as the constellation climbs
higher. By midnight, Taurus is nearly overhead, so that is
a particularly good time.
Right:
Click on the image to view a full-sized sky map. [More]
According
to the International Meteor Organization, the Taurid shower
peaks between Nov. 5th and Nov. 12th (details).
"Earth takes a week or two to traverse the swarm,"
notes Asher. "This comparatively long duration means
you don't get spectacular outbursts like a Leonid meteor storm."
It's more of a slow drizzle--"maybe one every few hours,"
says Asher.
A
drizzle of fireballs, however, is nothing to sneeze
at. So keep an eye on the sky this month for Taurids.
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Author: Dr. Tony
Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
|