Orbit determination through transit timing?

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Orbit determination through transit timing?

Post by Sirius_Alpha on 19th December 2008, 9:13 pm

I had an idea, and I'm sure it may sound crazy but hear me out. I think that careful transit timing might enable one to determine the orientation of the orbit without the use of polarized light (as has been done at HD 189733).

As a planet is transiting it's star, the planet casts a shadow that sweeps out into space, every few days aligning with Earth. This shadow always exists, as the planet can alway observed to be transiting from somewhere. As the shadow is moving, the time that one location can observe an eclipse would be different than the time another location could observe it. Doing some cheap modeling in Celestia I found the speed of shadows of transiting planets at their distance from Sol. (The farther the star is from Earth, the faster the shadow moves at our distance).

Speeds of transit shadows

Gliese 436 b --> ~59 AU/sec
HD 209458 b --> ~160 AU/sec
WASP-1 b --> ~1200 AU/sec?


With extremely precise photometry, could multiple spacecraft across the solar system unite to observe, say, Gliese 436 b, and would there be enough sensitivity to determine if a transit occurs at 1/10 of a second later for one of the spacecraft (for example)?

The detection of a transit at different times could tell us which direction the transit shadow is moving, thus giving a determination of which direction the planet itself is actually moving. I don't know if stellar jitter would affect things, as the same jitter would be observed by both spacecraft. Very precise photometry would be needed, else the difference inbetween light curve starts might no be noticeable.

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