Fireball: a meteor brighter than the evening or morning star, Venus (technically, brighter than magnitude -4).
Bolide: a fireball that explodes in a bright flash often with visible fragmentation. Also the generic name for a large crater-forming projectile (comet, asteroid or UFO).
Meteor Trail: the trail of ionized dust and gas that remains along the path of a meteor.
Meteor Stream: a group of meteoroids in a given orbit as they travel around the sun. These meteoroids are usually the by-product of comets, so it is possible for the parent comet to be traveling in the same orbit--if it still exists.
Meteor Shower: the occurrence of meteors as Earth's orbit intersects a meteor stream. The meteors in a shower appear to emanate from a point in the sky known as the radiant. A meteor shower is named after the constellation in which its radiant is located.
Meteor Storm: an intense meteor shower that exceeds 1000 meteors per hour which occurs when Earth encounters a dense group of meteoroids within a meteor stream.
Minor Meteor Showers: meteor showers that produce less than 10 meteors per hour at the time of maximum activity.
Sporadic Meteor: a meteor that occurs randomly, instead of being associated with a meteor shower. There are about 5 per hour in the night sky (peak viewing time is in the autumn before morning twilight).
When a meteoroid plunges into the atmosphere at a velocity of between 25,000 mph and 160,000 mph (11 and 72 km/sec), the air does not have time to flow around the meteoroid. The result is that friction produces enough heat to ablate (vaporize) the meteoroid and to ionize air molecules, producing a highly charged plasma. The ions quickly recombine and energy is released as light. The whole process usually takes a few tenths of a second and so a meteor appears as a moving streak of light. (The light streak is not just the glowing hot meteoroid itself.)
The wide range in meteoroid speeds is caused partly by the fact that the Earth itself is traveling at about 67,000 mph (30 km/sec) as it revolves around the sun. On the evening side, or trailing edge of the Earth, meteoroids must catch up to the earth's atmosphere to cause a meteor, and tend to be slow. On the morning side, or leading edge of the earth, meteoroids can collide head-on with the atmosphere and tend to be fast.
|Date of Peak Display||Name of Shower|
|Apr 21-22||April Lyrids|
|May 4-5||Eta Aquarids|
|Jul 28-29||Delta Aquarids|
|Dec 13-14||Geminids *|