- A brilliant flash and earthshaking boom
noticed by thousands of Alaskans late Friday were likely a meteor exploding
in Earth's atmosphere, scientists said Saturday.
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- Donald Martins, an astronomy professor
at the University of Alaska Anchorage, wasn't lucky enough to see the object
that streaked blue, green and red across the Southcentral Alaska sky. But
based on witness accounts, Martins and other scientists believe the flash
came from a meteor or comet fragment - probably the size of a pumpkin -
that exploded about 50 miles above Earth's surface.
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- "That's almost certainly what it
was," Martins said. "They aren't uncommon. But it is very rare
to have one explode and hear it."
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- Dozens of people phoned authorities late
Friday to report the event, which happened about 10:25 p.m. Most eyewitnesses
described a brilliant and colorful flash, followed several minutes later
by a boom. The boom was so loud it shook houses in Palmer and Wasilla and
was heard from South Anchorage to Sutton and beyond.
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- "I wish I could describe it,"
said Gina Gilmore, who watched the fireball from a hot tub near Palmer.
"It was an eerie blue and green color and lit up the whole area. Then
we heard an explosion, and it stilled our conversations."
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- Gilmore said she thought at first that
the object was a shooting star or meteor, but its intensity made the group
in the hot tub wonder: Could it have been a missile, an electrical explosion
or something from the "X-Files"?
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- "It was greenish, and it was loud,"
said Rachael Wagner, 16, another observer from Wasilla. She was inside
her home and noticed the flash through the window.
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- Assuming the object was a meteor, Martins
said, it's possible that the fireball was part of the Quandrantid meteor
shower, which was expected to be active from Dec. 28 through Thursday.
On Tuesday, Anchorage residents reported an object streaking low in the
sky across the backdrop of the Chugach Mountains.
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- The Quandrantids are one of the year's
most intense meteor showers but are among the least observed because of
their location high in the Northern sky. The meteors appear to emanate
from the obsolete constellation Quadrans Muralis, hence the name Quandrantids.
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- Though the origin of the Quandrantids
is unknown, most meteor showers are caused by fragments of comets - dust
and ice debris - that boil away from a comet's nucleus when it passes close
to the sun. A meteor shower results when Earth passes through a comet's
debris stream.
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- Martins said most meteors burn up from
friction as they enter Earth's atmosphere. When the chunks are large enough,
they sometimes explode because the core of the object is much cooler than
the outside.
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- "Imagine a cold rock coming in and
getting very hot," said Greg Durocher, a scientist with the U.S. Geological
Survey. "It's under tremendous stress."
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- Durocher and other observers of the fireball
said they heard the boom about three or four minutes after they saw the
flash. Based on that information, Martins estimated that the object was
about 50 miles away at the time of the explosion.
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- The noise people reported may have been
a sonic boom. However, a single noise heard at the same time by everyone
would indicate an explosion, he said.
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- Martins said he once heard of a fireball
so loud it almost deafened several fishermen in the South Pacific.
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- Although the object may have been fairly
large for a meteor, Martins said, it is unlikely that anyone will find
a meteorite, which is a fragment of a meteor that falls to Earth.
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- There were rumors Friday of objects striking
the Parks Highway at Mile 141 and reports by pilots of debris falling,
but meteorites are extremely hard to find, Martins said.
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- "Unless you can actually determine
where the impact occurred, you're worse off than finding a needle in a
haystack," he said.
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- And if the object was part of a comet,
Martins said, most of the fireball was probably composed of ice, which
would have melted before hitting the ground. Martins said the colors people
described suggest that the fragment was part of a comet.
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- "It had a good tail on it,"
Gilmore said. "And it was amazing to watch it going across the sky.
I probably won't ever see that again."
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