What Is a Meteor Shower?
If it's time for a meteor shower, you won't need a
telescope, binoculars, or a high mountain to have a "star gazing"
party. You might need a warm sleeping bag and an alarm clock to wake you in the
middle of the night. But then just lying down in your own back yard will put
you in the perfect spot to enjoy a great show.
Because meteor shower particles are all traveling in
parallel paths, and at the same velocity, they will all appear to an observer
below to radiate away from a single point in the sky. This radiant point is
caused by the effect of perspective, similar to parallel railroad tracks
converging at a single vanishing point on the horizon when viewed from the
middle of the tracks. Meteor showers are almost always named after the
constellation from which the meteors appear to originate. This "fixed
point" slowly moves across the sky during the night due to the Earth
turning on its axis, the same reason the stars appear to slowly march across
the sky. The radiant also moves slightly from night to night against the
background stars (radiant drift) due to the Earth moving in its orbit around
the Sun. See IMO Meteor Shower Calendar 2017 (International Meteor
Organization) for maps of drifting "fixed points."
When the moving radiant is at the highest point it
will reach in the observer's sky that night, the Sun will be just clearing the
eastern horizon. For this reason, the best viewing time for a meteor shower is
generally slightly before dawn — a compromise between the maximum number of
meteors available for viewing, and the lightening sky which makes them harder
to see.
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