APOD: Abell 2218: A Galaxy Cluster Lens (2010 Jun 20)

Comments and questions about the APOD on the main view screen.
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rstevenson
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Re: APOD: Abell 2218: A Galaxy Cluster Lens (2010 Jun 20)

Post by rstevenson » Thu Oct 07, 2010 1:00 pm

neufer wrote:... It's like a spacecraft doing a flyby of the planet Jupiter:

1) So far as Jupiter is concerned the spacecraft exits with exactly the same speed |Vx| as it entered with |Ve|.

2) However, since Jupiter is moving with velocity vector VJ vis-a-vis the solar system the dynamical exit speed |Vx+VJ| does not necessarily equal the entrance speed |Ve+VJ|. This fact has been used extensively to boast the speed of all spacecraft passing beyond Jupiter (by intentionally flying behind Jupiter).
Thank you Art. I've been reading about sling-shot maneuvers for decades but never grasped that fine distinction. Very nice.

The things you don't know you don't know!

Rob

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