[Prev][Next][Index][Thread]

(meteorobs) Excerpt from "CCNet LETTERS TO THE MODERATOR, 16 March 2000"




------- Forwarded Message

From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: LETTERS TO THE MODERATOR, 16 March 2000
Date: Thu, 16 Mar 2000 16:11:35 -0500 (EST)

LETTERS TO THE MODERATOR, 16 March 2000
---------------------------------------

[...]

(3) FASTEST SPINNING ASTEROID?
    Petr Pravec <ppravec@asudot cas.cz> 

[...]

===================
(3) FASTEST SPINNING ASTEROID?

>From Petr Pravec <ppravec@asudot cas.cz> 

Charles F. Peterson <cfp@mcn.org> wrote:   

> In terms of useful information about NEAs, it would seem that the 
> velocity of the surface of the asteroid tells more than the rotational 
> period.  Am I correct? 
> The surface of a 100 meter asteroid with a rotational (day/night) 
> period of 10 minutes is not moving as fast at its equator as the 
> surface of a one kilometer asteroid with a much longer rotational 
> period.  Surface velocity would tell something about origin and impact 
> history, right? Day/night period seems to be an interesting but 
> inconsequential artifact of the relationship of diameter to surface 
> speed.  

Actually, the most important information brought by the detection 
of a fast asteroid spin is the ratio between centrifugal 
acceleration and gravitational acceleration on the asteroid's 
surface. The superfast spins tell us that the asteroids are 
rotating under tension and therefore are monolithic. (I.e., not 
gravitationally bound "strengthless" bodies.)  The information 
about asteroids internal structure is one of the main reasons why 
to study asteroids spins. The fast day/night changes are less 
important scientifically (but interesting for general public to 
remember, thus they were pointed out in the press release so 
widely distributed), but they are still relevant e.g. for 
computation of temperature distribution on the asteroid surface.

Petr Pravec

-----------------
CCNet-LETTERS is the discussion forum of the Cambridge-Conference 
Network. Contributions to the on-going debate about near-Earth objects, 
the cosmic environment of our planet and how to deal with it are welcome. 
The fully indexed archive of the CCNet, from February 1997 on, 
can be found at http://abob.libs.ugadot edu/bobk/cccmenu.html

------- End of Forwarded Message


To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html