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Milli-Newtons :-) The comet[1] that Rosetta is orbiting has a mass of 10^13 kg and an orbit semi-major axis of 518,060,000 km. This gives the comet a Sphere of

Milli-Newtons :-) The comet[1] that Rosetta is orbiting has a mass of 10^13 kg and an orbit semi-major axis of 518,060,000 km. This gives the comet a Sphere of Influence[2] of roughly 62 km. What this means is that within 62 km or so, the comet is the dominant gravitational body, so orbits of 16, 20, and 30 km (in the video) are perfectly reasonable. The orbital period[3] of the larger 30 km orbit is around 40 ksec or 11.1 hours. [1]: http://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko http://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimen... [2]: http://en.wikipedia.org/wiki/Sphere_of_influence_(astrodynamics) http://en.wikipedia.org/wiki/Sphere_of_influence_(astrodynam... [3]: http://en.wikipedia.org/wiki/Orbital_period http://en.wikipedia.org/wiki/Orbital_period

stromgo 12y ago
Your orbital period of 11.1 hours at 30 km looks wrong. The video shows about 7/8 of a 30-km orbit over 14 days (19 Nov - 3 Dec). The orbital period formula gives 14.6 days (2 * 3.14159265 * sqrt(30000^3/(6.67384e-11 * 10^13)) / 3600 / 24).
- clarkmoody 12y ago
  That's absolutely possible -- I did some in-my-head units conversion. Maybe another look at the units: G - 6.67384e-11 [N (m/kg)^2] = [m^3 / (kg s^2)] M - 1.0e13 [kg] a - 30000 [m] sqrt([m^3] / ([m^3 / (kg s^2)] * [kg])) = sqrt([s^2]) = [s] 2*pi*sqrt(30000^3 / (6.67384e-11 * 1.0e13)) = 1,263,787 s = 14.6 days Well, how about that :-)