[meteorite-list] Stardust SRC Hot to the touch?

[Chris Peterson]

Dave-

The interior temperature of the parent body will likely not be extreme. From 
a practical standpoint, space has no temperature. A body absorbs energy from 
the Sun, and radiates it to space (with a background temperature of a few 
kelvins).

An iron body will probably have a warm temperature when it encounters the 
Earth. Iron is a very efficient absorber of long wavelengths, which make up 
about half of the output of the Sun. It is a much less efficient radiator. 
An object that hits the Earth will likely have spent a reasonable time at a 
distance of 1 AU from the Sun. Think how hot a piece of iron gets sitting in 
the Sun.

A stony body will be cooler, because it doesn't absorb radiation as 
efficiently. Its interior will probably be somewhat colder than freezing- 
but still not extreme from the standpoint of human touch.

None of this matters much for typical small meteorites (up to a few tens of 
centimeters). At that size, the convective cooling experienced while falling 
through cold air at ~100 m/s will largely determine the final temperature.

You might want to search back a year or so in the archives. This was 
discussed in detail, complete with various solutions to the Stefan-Boltzmann 
equation.

Chris

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


----- Original Message ----- 
From: <dfpens at comcast.net>
To: "Chris Peterson" <clp at alumni.caltech.edu>; "Meteorite Mailing List" 
<meteorite-list at meteoritecentral.com>
Sent: Wednesday, January 18, 2006 12:55 PM
Subject: Re: [meteorite-list] Stardust SRC Hot to the touch?


> Has anyone considered that a very cold object will also "burn" your hands 
> and thus feel hot.  Try picking up something that has been in a tank of 
> liquid nitrogen and try to tell if it is hot or cold.
>
> A meteorite travelling for eons in near absolute zero should have an 
> interior temperature very very cold.  Afterall, it only spends a few 
> seconds going through an atmosphere where friction can supply any energy.
>
> Any thermodynamicists out there?
>
> Dave