Asteroid Evolution

[mishalak]

I read an interesting report in the BBC about light causing asteroids to spin faster. I wonder if this might mean there is a lower stable limit for asteroids.

My thought experiment runs thus: The Yorp effect spins objects faster and faster with the upper limit being their structural integrity. A large mass object probably would not be imparted much spin as their mass to surface area ratio would be higher. If a 114 meter across asteroid is only spun up at about 1 millisecond a year then for a asteroid of double the diameter would probably be only spun about one quarter that value, all else being equal. The asteroid observed will probably spin apart in 15-40 million years. So at least double that for a much larger asteroid. Call one billion years essentially stable and my black of the envelope guesses would lead me to believe that anything under about 2.5 km would be unstable over the life of the solar system. With a very, very large error bar on my calculations since I'm doing them in my head without taking into account everything these scientists know.

Rather too bad that it doesn't do more about larger objects. If so the potential impactors of earth problem would be slowly taking care of itself. And now to bed as I am still very tired from the whole sickness thing I've just been getting over.

Comments

[major-clanger.livejournal.com]

The Wikipedia entry on the YORP effect (http://en.wikipedia.org/wiki/Yorp) notes that the changes to an asteroid's spin can be complex and in some cases cyclic rather than progressive. But yes, apparently there is an excess of small asteroids with hgh spin rates.

I'd be interested to know what the distribution of spin rates is against the overall population of asteroids. At any given time there must be a number of asteroids spinning at just below the point where they fragment, and for small but monolithic ones this will be limited by the tensile strength of the rock or metal they're made of.

[mishalak.livejournal.com]

I would guess from the (very large) population of asteroids of small sizes that there ought to be at least one fragmenting into a binary (or more) asteroid in any given year. If there are larger numbers of binary asteroids than can be accounted for by gravitational binding then it might be a proof that asteroids are flying apart due to Yorp.