Reply to : Bill Gray

>> I cannibalized a private e-mail I sent about three years ago on the

subject of projections for star charts, added some comments about lunar
cartography, "sort of" HTML-ized it, and posted it at
http://www.projectpluto.com/project.htm <<

Thanks Bill, I will have some studying to do :-)

>> The "Yarkovsky effect" is one in which an asteroid heats up in

sunlight, rotates a bit, and emits thermal radiation preferentially in
that direction (by the time it rotates around a bit further, it's cooled
somewhat and radiates less). The result can speed it up or slow it down
enough, over millions of years, to do things such as bring main belt
objects into the inner solar system. An absurdly small effect, but over
enough time, it accumulates and you have to take it into account. (It
matters most for smaller objects, which is a Good Thing; there is no risk
that this will cause the major planets to fall into the sun, or spiral
outward toward interstellar space.) <<

Thanks again, I won't lose sleep worrying about the effect on the Earth :-)

Richard.


E-mail from: Richard Mallett, 14-Apr-2002