[meteorite-list] ANOTHER QUESTION

[Chris Peterson]

My understanding is that the IAU Commission 22 formally defined 
"fireball" back in the 1960s as any meteor equal or greater in 
luminosity to the brightest planet, without assigning an actual value. 
The brightest planet is Venus, and its magnitude at peak brightness 
is -4, which is why most researchers (including myself) use that value 
for fireballs. From a purely technical standpoint, the term isn't really 
all that useful anyway. The magnitude is apparent, so the same event may 
be a fireball to one person and an ordinary meteor to another who is 
farther away. One of the first things that gets done in analyzing a 
bright meteor is to convert to absolute magnitude, since it's possible 
to do something with that.

It isn't always easy tracking down IAU definitions. If somebody is aware 
of a later definition, or an online reference to the Commission 22 
definitions, I'd appreciate knowing about it.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "mark ford" <markf at ssl.gb.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, November 20, 2006 9:53 AM
Subject: Re: [meteorite-list] ANOTHER QUESTION

> The 'rule of thumb' used in a lot meteor observation/astronomy is a
> fireball is taken to be any meteor/event with a magnitude at or above
> that of the planet venus. (This way you have a quick guide (although
> venus varies a bit in brightness)