Thursday, April 14, 2011

Meteors

After midnight, the only meteoroids escaping collision are those ahead of the Earth and moving in the same direction with velocities exceeding 18.5 miles per second (30 kilometers per second). All others we will either overtake or meet head-on.
But before midnight, when we are on the back side, the only meteoroids we encounter are those with velocities high enough to overtake the Earth. Therefore, on average, morning meteors appear brighter and faster than those we see in the evening.
And because the Leonids are moving along in their orbit around the sun in a direction opposite to that of Earth, they slam into our atmosphere nearly head-on, resulting in the fastest meteor velocities possible: 45 miles per second (72 kms).  Such speeds tend to produce bright meteors, which leave those aforementioned long-lasting streaks or trains in their wake.
Also, as Leo is beginning to climb the eastern sky near and before midnight, there is a small chance of perhaps catching sight of an "Earth-grazing" meteor.
Earth-grazers are long, bright shooting stars that streak overhead from near to even just below the horizon. Earth-grazers are distinctive because they follow a path nearly parallel to our atmosphere. 

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