From: "Schroeppel, Richard" <rschroe@sandia.gov>

Moreover ... galactic escape velocity (in our neck of the woods) is a couple of hundred miles/second. Ordinary planetary encounters (near misses) can change the velocities of the players by at most twice the surface escape velocity of the opponent. [Imagine a parabolic orbit that just skims the surface of the opponent.] For Jupiter as the ejector, that's ~ 70 miles/sec. Our hypothetical ejected planet would still be in a galactic orbit.

Yes, sorry, I didn't mean that the planet would travel twice the diameter of the galaxy in a straight line, or that it would reach that distance from us. Also, by saying "truckin'" I mainly wanted to imply a long strange trip, see.

From: math-fun-bounces@mailman.xmission.com on behalf of Mike Speciner [ms@alum.mit.edu]

Remember that escape velocity is the velocity needed, at a particular distance from the object (the sun in this case) to just make it to "infinity" with zero velocity. The escapee slows down as it escapes.

Yes, I took escape velocity as an order-of-magnitude for the range of left-over velocities "after" escaping.

And that's "affecting", not "effecting".

That's the most embarrassing of all. "I shall effect repair." --NOMAD --Steve

--ms Wikipedia says escape velocity from the Sun's gravity starting at Jupiter's (current) orbit is 18.5 km/s. That's about one light year every sixteen thousand years.

Wikipedia also says the Solar System is 4.6 billion years old. Starting when the Solar System was 600 million years old, and traveling at 18.5 km/s, an object would travel about 244 thousand light years (if the Milky Way weren't effecting its path).

That's about twice the diameter of the Milky Way, or ten times the distance from the Sun to the center of the galaxy. In that same period, the Sun has orbited the center of the Galaxy 16 times.

So I guess this means the ejected planet won't be found loitering between the nearby stars. It's truckin'.

--Steve