Starship Asterisk*

I'm not so sure working from the mass of the original gas and dust cloud is the way to go. Consider that our Sun contains 99.8% of the total mass of the Solar System, and that Jupiter contains most of the rest. That leaves very little to work with when trying to turn the basic idea into numbers. I think it makes more sense to extrapolate from known planetary systems, few as they are, so far.

Rob

rstevenson wrote:I'm not so sure working from the mass of the original gas and dust cloud is the way to go. Consider that our Sun contains 99.8% of the total mass of the Solar System, and that Jupiter contains most of the rest. That leaves very little to work with when trying to turn the basic idea into numbers. I think it makes more sense to extrapolate from known planetary systems, few as they are, so far.

That is precisely how we approach the problem in the space dust community. The mass of the Sun is irrelevant, the question is how is the rest of the mass distributed. How much is there? What does the population function look like? By what mechanisms is it consumed, and by what mechanisms created? (Space dust includes planets.)

BDanielMayfield wrote:Would a rigorous approach involve finding a mathematical model or function including the total system mass as a summation of the mass contribution of particles and bodies of all sizes? If so that seems like a daunting task, given the infinite configurations that any given gas and dust cloud might collapse into.

No, I don't think it's daunting at all. This approach recognizes that the population is either described by a smooth function, or a stepwise smooth function, and this is determinable on theoretical grounds. Observational verification is tricky at this point, mainly because of technological limitations. But the problem itself isn't particularly intractable.

Chris Peterson wrote:

BDanielMayfield wrote:Would a rigorous approach involve finding a mathematical model or function including the total system mass as a summation of the mass contribution of particles and bodies of all sizes? If so that seems like a daunting task, given the infinite configurations that any given gas and dust cloud might collapse into.

No, I don't think it's daunting at all. This approach recognizes that the population is either described by a smooth function, or a stepwise smooth function, and this is determinable on theoretical grounds. Observational verification is tricky at this point, mainly because of technological limitations. But the problem itself isn't particularly intractable.

Chris Peterson wrote:

rstevenson wrote:I'm not so sure working from the mass of the original gas and dust cloud is the way to go. Consider that our Sun contains 99.8% of the total mass of the Solar System, and that Jupiter contains most of the rest. That leaves very little to work with when trying to turn the basic idea into numbers. I think it makes more sense to extrapolate from known planetary systems, few as they are, so far.

That is precisely how we approach the problem in the space dust community. The mass of the Sun is irrelevant, the question is how is the rest of the mass distributed. How much is there? What does the population function look like? By what mechanisms is it consumed, and by what mechanisms created? (Space dust includes planets.)

Myself, and perhaps Rob and others too are a bit mystified at this point Chris. Can you point out material we might read that can help us understand this bottom up approach?

Bruce

BDanielMayfield wrote:Myself, and perhaps Rob and others too are a bit mystified at this point Chris. Can you point out material we might read that can help us understand this bottom up approach?

Well, within the Solar System, it's fairly straightforward to catalog bodies from planets down to dust, looking for example at zodiacal light, meteors, comet dynamics, and other factors that are within the capabilities of our instruments. Of course, that capability drops off quickly at the inner edge of the scattered disc. We still don't know much about the far outer Solar System.

When it comes to interstellar space, however, it's quite difficult, because we don't really have the instrumental capacity to detect a significant amount of material in many size ranges. Right now, it's probably best approached using theory and modeling. Verifying the models will have to wait a few more years (or decades) for observational instruments to improve.

See the March 31 APOD at http://asterisk.apod.com/viewtopic.php? ... 98#p223098 re the discovery of a new “farthest member of our solar system” and the hints of another large (about 10 earth masses) planet out at around 250 AU.

Bruce

Thousands more exoplanets have been discovered in the more than six years that this thread has been dormant. (But now that I'm retired, it can rumble to life again, like a volcano.)

Has anything been learned in the interim that weighs on the question of planetary counts?

Bruce