Data Fit Model for B Ring
A couple of weeks ago I posted this prediction based on our self-gravity wake model for Saturn’s B ring. Basically, depending on the angle that we look at Saturn’s rings, we see a different amount of starlight shining through. That amount depends on the size, shape, spacing, and orientation of clumps of particles in the rings that, in the case of the B ring, are about as wide as a football field, and perhaps much longer. Using our first set of measurements we calculated the size, shape, spacing, and orientation of the B ring clumps, and I used that to predict our next B ring measurement. Well, now we have that measurement, and I’m happy to report the agreement is pretty good. In the images below, the red diamonds are the predicted values and the blue curve is the measurement. The green curve is an earlier measurement that gives an indication of the range of values between different measurements. These results are preliminary, but the agreement here, like that for the A ring, shows that the self-gravity wake model is working well to explain our measurements of the rings. We still need to understand all the structure in the rings responsible for the bumps and wiggles in the blue and green curves. And future measurements will certainly allow us to improve this initial self-gravity wake model.
September 14th, 2006 at 7:48 pm
Are the earlier measurements done with the same instrument? A least some of the difference between the green and blue lines looks like a systematic offset.
September 14th, 2006 at 11:22 pm
All measurements are with the same instrument. While the star brightnesses are different so that the signal to noise ratio varies between different observations, the offsets are in fact due to the ring structure and not to instrumental effects. This is how we were able to construct a predicted curve (the red diamonds) from the previous measurements. Basically it’s like looking at headlights flickering behind a picket fence as a car drives by: if you look straight at the picket fence you will see a different amount of light than if you stand next to it and look along it. The differences tell you about the spacing of the pickets. Saturn’s ring particles clump together into these pickets.