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(meteorobs) Re: Meteor Velocities

Mark and All,

You should not really say that showers have their own characteristic 
speed as velocity alone is a poor indicator of shower association. ANY 
shower can produce slow meteors. Leonids seen near the radiant or low in 
the sky will appear to travel slowly.

To clear up another misconception, during the evening hours all activity 
  will be slow since the earth and any meteoroids that happen to strike 
the earth will be orbiting in the same general direction. The earth is 
not moving away from the meteoroid or it would never collide with earth.

Meteors of a given shower that is active above the horizon from evening 
to dusk would not show any significant increase in speed because they 
are striking the earth at the same angle no matter what time it is. 
Picture a swarm of meteors striking the earth from a direction directly 
opposite the sun. At dusk these meteors would radiate from a location 
near the eastern horizon. The observed velocities would be medium to 
slow depending on where the meteors appeared in the sky. At midnight the 
radiant would appear on the meridian but the meteors would still be slow 
to medium speed. At dawn the radiant would be near the western horizon 
but the velocity would still be the same. The angle for which the 
meteoroids strike the earth has not changed. What has changed is your 
angle with respect to the radiant.

In order for a shower to change its velocity during the night the 
radiant would have to move about the constellations as the night 
progresses. This is an impossible situation. Radiants do travel but at  
a rate of only 1 degree per day. This motion is not caused by the 
earth's rotation but rather the earth revolving around the sun.

The speeds listed for each shower are certainly averaged for those who 
face away from the radiant at least 45 degrees distant and at least 45 
degrees altitude above the horizon. If you look closer to the radiant 
then the apparent speed will be slower.

I hope this helps.

Clear Skies!

Robert Lunsford



Mark Fox wrote:

> January 22, 2002
> 
> Greetings Meteor Enthusiasts!
> 
> If I am correct, it is stated that many meteor showers
> have more or less their own characteristic speed,
> differing only slightly for each individual shower
> member.  Perseid and Leonid meteors are quoted as 
> being fast, and the Taurids as slow, for instance.
> 
> With that said, it is also realized that most meteors
> observed in the evening will be generally slow due to
> their "catching up" with earth, since the planet at
> that time is moving away from them.  As the night
> progresses, however, the meteors will become faster as
> the same side of earth rotates towards the front that
> is moving through space and plowing into meteoritic
> particles.
> 
> Thus, wouldn't the meteors of a given shower that is
> active above the horizon from evening to dusk show any
> significant increase in speed?   Also, with this in
> mind, are the speeds given for a particular meteor
> shower an average, not only for shower members seen at
> a specific time, but for the whole night as well?     
>  
> My e-mail is unclefireballmtf@yahoo.com.
> 
> Long trains!
> 
> Mark Fox
> Newaygo, MI USA
> Coordinates: 43 deg. 27' N, 85 deg. 49' W
> 
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