by Chris Peterson » Wed Feb 04, 2015 3:27 pm
geckzilla wrote:Thanks, I needed some reassurance tonight that I'm not completely nuts. The abstract is fine. I'm not really that interested in comet clumps at this moment.
It's a pretty interesting paper. I've had it sitting on my table for a few days, but hadn't gotten to it yet (or the other ones in this issue of Science, dedicated to the Rosetta mission).
Grains are detected using multiple images aligned on stars, with bound and unbound particles identified by their trajectories (which also has to take into account the spacecraft motion).
Meter-sized particles are not being ejected. At perihelion, activity is high enough that some bodies of this size are released, but with ejection velocities too low to allow most to escape. So they end up in bound orbits. Fortunately for the Rosetta spacecraft, the density of such bodies is very low. Several hundred bound grains were detected, with sizes in the centimeter range. Again, these large particles are ejected at a low enough velocity that they don't escape. Particles up to that same size range were observed escaping, as well.
Most interesting was the observation that the most of the scattered light we're seeing off the dust is coming from particles in the 0.1-1 mm size range, not micrometer sized particles. I think that was somewhat unexpected. Everyone is looking to see how all these numbers change as the comet gets closer to the Sun.
[quote="geckzilla"]Thanks, I needed some reassurance tonight that I'm not completely nuts. The abstract is fine. I'm not really [i]that[/i] interested in comet clumps at this moment.[/quote]
It's a pretty interesting paper. I've had it sitting on my table for a few days, but hadn't gotten to it yet (or the other ones in this issue of Science, dedicated to the Rosetta mission).
Grains are detected using multiple images aligned on stars, with bound and unbound particles identified by their trajectories (which also has to take into account the spacecraft motion).
Meter-sized particles are not being ejected. At perihelion, activity is high enough that some bodies of this size are released, but with ejection velocities too low to allow most to escape. So they end up in bound orbits. Fortunately for the Rosetta spacecraft, the density of such bodies is very low. Several hundred bound grains were detected, with sizes in the centimeter range. Again, these large particles are ejected at a low enough velocity that they don't escape. Particles up to that same size range were observed escaping, as well.
Most interesting was the observation that the most of the scattered light we're seeing off the dust is coming from particles in the 0.1-1 mm size range, not micrometer sized particles. I think that was somewhat unexpected. Everyone is looking to see how all these numbers change as the comet gets closer to the Sun.