Wednesday, August 08, 2007

[FOTHP] The Perseid Meteor Shower

Friends of the Hudnall Planetarium,


The Perseid Meteor Shower: Of Comets and Meteors

This coming Sunday night and early Monday morning, August 12-13, 2007,
marks the peak of one of the most reliable meteor showers known * the
Perseids. The shower is named after the constellation Perseus from
which the meteors appear to radiate. Estimates are that the Perseids
should produce anywhere from 60 to 100 meteors per hour. Whether the
meteors are observable will depend upon your local weather and lighting
conditions. Meteors are best observed away from city lights under dark
skies. The moon is new and will not brighten the sky, making this an
excellent year to observe the shower. While the shower's peak is
early in the pre-dawn hours of Monday morning, observers should be able
to spot a few meteor streaks as early as late Saturday night. Look to
the northeast starting after 9:00 PM, and then be patient. You should
see one every few minutes. No special equipment is necessary, except
maybe a comfortable chair and mosquito spray. The next night, as Sunday
turns into Monday morning, the number of meteors observable should
increase.

So what makes a meteor shower? To understand this you first need to
know a bit about comets. Comets, which can be thought of as giant muddy
icebergs, orbit the Sun just like the planets, asteroids, and dwarf
planets. However, unlike most members of the solar system, comets tend
to obit the Sun in very elongated elliptical orbits. As these muddy
icebergs move close to the Sun they lose part of their dirty mass along
the way. Loosened grains of dust and gas escape the comet and spread
out along in the same general orbit as the comet. Technically speaking,
these freed dust particles are now called meteoroids.

One particular comet, Swift-Tuttle, passes very near the orbit of the
earth leaving behind tiny bits of itself all along the path. Then, once
per year, as the Earth passes through the dusty trail, the left-behind
meteoroids slam into the Earth. Relative to the Earth, these meteoroids
are moving at incredible speeds, on the order of 140,000 miles per hour.
Anything traveling at these speeds, even tiny dust particles, will
release a lot of energy when they hit something, even if the something
they hit is as soft as the Earth's atmosphere. From the point of view
of an Earth-bound observer, the impact of meteoroids on the atmosphere
leaves behind bright streaks as the surrounding air heats up and the
particles disintegrate. Again, technically speaker, the bright streaks
are called meteors. Because the stream of meteoroid particles all hit
the atmosphere in roughly the same spot each year, it can appear as if
the meteors are radiating from one point in the sky * in this case the
constellation Perseus.

Enjoy your universe. Get out and observe the Perseids this year.


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