Astronomy

What causes Shooting Stars



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A shooting star can be anything that enters the earth’s atmosphere, from comets, to meteors, to old satellites, amongst a host of other things.  Any bit of old metal debris, or cosmic detritus that happens to fall out of its orbit, and collides with the atmosphere creates friction.  This friction then produces heat, which causes the bright streak of light we call a shooting star.

Meteorites, usually no larger than a grain of sand, cause the vast majority of the shooting stars we see.  These little motes of space dust usually appear sporadically and in isolation.  All of this usually takes place at an altitude of 80 to 120 kilometres. 

There are spectacular shows of meteorite showers where the amounts of shooting stars to be seen are in the range of a 100 per hour.  The meteors in this case are dust from a comet whose orbit has taken it too near the Sun.  Some of the ice of the comet evaporates, releasing a cloud of dust.  The dust cloud detaches itself from the comet, and when the comet passes the earth, the dust collides with the Earth’s atmosphere.  The resultant display can be quite spectacular.

Comets follow regular orbits, so the resultant meteor shower or show of shooting stars can be accurately predicted.  This allows for a well-planned night of star watching the meteor showers.  Among these regular visitors are the Perseids, which can be viewed around the 12th of August.  The Perseids consist of dust from the comet Swift-Tuttle.  Another grand shower are the Leonids, which can be seen about the 17th of November.  The Tempel-Tuttle comet is responsible for these showers.

As with many regular meteor showers, they always appear to originate from a specific area.  An example is the Leonids, which always appear to originate from within the constellation of Leo.  They don’t actually originate from the constellation; the comet dust just intercepts the Earth’s atmosphere at that point.  Astronomers name the meteorite showers after the nearby constellations to make finding them in the night sky easier.

The perceived point of origin of a meteor shower is all to do with perspective.  A shower of meteorites seems to radiate from the same point in the sky.  If you can find this radiating point, and settle down during a meteor shower with a good cloud free night, you may be lucky to see a spectacular show.  A show which is increased if the shower peaks when its radiant is at the highest point in the sky, combined with the early hours of the morning.

The biggest meteor shower ever recorded was in 1833 when 60,000 shooting stars an hour was recorded.  This astounding sight was the spur to a new study of meteorite astronomy.  Up until then, these showers were considered interesting, but no one took the time to study this phenomena.  That is definitely not the case now, where professional and amateur astronomers alike enjoy studying such phenomena.


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