Re: [guide-user] Re: Comets data update failed

Bill J Gray Sep 26, 2012

Hi Claudio,

I think I may have mentioned this before, but... I've figured out the corruption
issue in 'comets.dat' (it has to do with some recent files having _many_ more objects
than were expected) and will be posting a fix. The process is causing me to re-think
how downloaded comets and asteroids are handled, though.

Don't put too much faith in the magnitude estimates for C/2012 S1 (ISON). I hope
they're right. But comets do really weird things. It could fizzle; it could be
truly stupendous. A complicating factor is that this object is currently out beyond
Jupiter. I don't think there is very much data on how incoming parabolic-orbit comets
brighten when you get this far out.

On a more optimistic note: shortly after Rob McNaught found C/2006 P1, he pointed
out that comets tend to brighten up a lot as they get within about 2.5 AU. (I assume
this is the point where the ice begins to sublimate. Or sublime, or whatever the
proper verb is... turn from solid to a gas, anyway.) So the brightness estimates
based on data from beyond that point, he suggested, would probably be low. And
as it turned out, he was very much right; the object got a _lot_ brighter at
perihelion than originally predicted. With luck, C/2012 S1 will follow the
same path.

-- Bill