system maps, scale, and such

[Puke]

i have been working on tweaking the system types for a mod i am putting together, and got to wondering what real asteroid fields look like. I honestly had no idea of the scale of what our asteroid belt was, and just had this vague imagining of what it might be like.

i only knew a few things, like all the probes we have sent past the asteroid belt have needed no guidance or collision avoidance programming, and that its not dense enough to require any sort of worry for most things passing through. I also knew that it accounts for a large amount of mass, and that many (most) of the objects are still uncharted.

today, i found this great plot of objects in the inner solar system (inside jupiter) linked to on slashdot. the asteroid belt is alot bigger than i thought, as far as the distance it covers. it looks like larger chunks extend into the orbits of venus and mercury, while smaller objects spread out from just outside of the martian orbit and extend half way to the jovian orbit.

I had also never heard of jovian trojans before (and no, they are not a new kind of contraceptive), although they are probably well known to anyone who is familiar with astronomy.

check it out:
http://cfa-www.harvard.edu/iau/lists/InnerPlot.html

[Elowan]

Trojans either lead or trail a planet at a specific distance called - oddly enough - the Trojan Point. This point (actually a 'smear') is similar to a LaGrange point except that the Trojans are not orbiting.

A LaGrange point is that position in space between a planet and its moon wherein the gravitational pull of either is in balance.

I think I have this right but I'm ducking just in case one of my professors reads this.

As for the asteroid belt, in 1772 Johannes Bode publicized a connection between the spacing of planets, now known as Bode's Law. He had found out that the distance from the planets in our solar system to the sun followed the following sequence surprisingly well:

4, 4+(3*2^0), 4+(3*2^1), 4+(3*2^2), 4+(3*2^3),.....
....divided each result by 10,
so arrive at the sequence.....
0.4, 0.7, 1.0, 1.6, 2.8, 5.2, 10.0, 19.6, 38.8, 77.2,.....

0.39, 0.72, 1.00, 1.52,....., 5.20, 9.54, 19.2, 30.1, 39.5 is the real spacing of the planets.

By taking into account that the asteroid belt lies at a distance between 2.3 and 3.3 AU and that the two most distant planets (Neptune and Pluto) do not follow the sequence, this law works surprisingly well for the other planets. Since it works so well for our planetary system - it probably holds for other systems as well - scaled for solar mass.

It implies the presence (at one time) of a aborted concretion of 'dust' into a planet.

From Bode's Law follows that the difference of the logarithm of the distances is of the same order of magnitude for every two neighbouring planets (so if you plot the distances from the planets to the sun on a one dimensional logarithmic axis, the space in cm between two successive points is about the same every time.

[ July 31, 2002, 19:21: Message edited by: Elowan ]

[geoschmo]

From this plot chart it appears the asteroid belt is a solid sheet of green, but that obviously is a trick of the scale of the image. There is an absolute minimum pixel size that can be displayed on a computer monitor, and a somewhat smaller absulute minimum size dot that is visible to the human eye. A chart with scale size dots representing the asteroids would have to be tremendously larger than what will fit on a computer screen, and would make obvious how much empty space there is between the asteroids.

There is a representation of the solar system at my local natural history museum, as there probably is one at yours. The earth in it is about the size of an avegage frozen pea. Even at this scale it is not possible to fit the entire system into the building, but they have a map of the county that shows the location of where the outer planets would have to be positioned to be to scale. At that scale most of the asteroids would be invisible without a microscope.

That being said the area the asteroids cover is a tremendous one, and the toal mass of the rocks is quite large. I am sure it would make a quite decent size planet if it were collected into one body the way the rest of the planets did.

Geoschmo

[capnq]

I am sure it would make a quite decent size planet if it were collected into one body the way the rest of the planets did.

Actually, I've heard that the combined mass of all the asteroids is less than Pluto.

There's a reference in the novel 2001: A Space Oddyssey that on average, the asteroid "belt" has one rock per 1000000 mile cube of space (10^18 cubic miles).

[henk brouwer]

Originally posted by geoschmo:


That being said the area the asteroids cover is a tremendous one, and the toal mass of the rocks is quite large. I am sure it would make a quite decent size planet if it were collected into one body the way the rest of the planets did.

Geoschmo

Actually it wouldn't. The total mass isn't very impressive, all the asteroids together would make an object that's smaller than the earths moon ( http://www.seds.org/billa/tnp/asteroids.html ) The earths moon is quite large though, for a moon at least (larger than Pluto for example).

Edit: aaaaargh I'm typing to slow, Capnq beat me with his post...

[ July 31, 2002, 19:59: Message edited by: henk brouwer ]

[Puke]

right, i didnt mean to suggest that there was a solid sheet of rock out there. if you zoom in on the image, you can see the individual objects.

i recal a bit from an old astronomy class that if the sun was the size of a basketball, the earth would be about the size of the head of a pin. the professor then explained that if the sun was "here" that the earth would be (pointing out the window and across the football field) "over there"

indeed, if you look at the orbital distances as Elowan suggests, it is clear that there is a vast amount of empty space out there. which reminds me of another slashdot story a while back. we have known for quite some time that well over 99.9% of matter is empty space, or 'nothing'

now recent discoveries about sub atomic particles has revealed that most of the Last .1 percent of matter is nothing as well. i suspect we will keep on going indefinitly, untill we realize that this whole universe and reality business is all made up. imaginary, that is. a work of fiction, as it were.

[capnq]

aaaaargh I'm typing to slow, Capnq beat me with his post

<does victory dance>

That has happened to me so many times, it's hard to believe someone can type slower than I do.

[ July 31, 2002, 20:51: Message edited by: capnq ]

[geoschmo]

I stand corrected on the total mass of the asteroids. Although as with everything else it is relative. Even a planet the size of Pluto would fit a loose definition of "decently sized" when compared to even a large asteroid.

Geo

[Baron Munchausen]

I think the speculation at this time is that Jupiter actually disrupted the formation of the planet in the region of the asteroid belt because if its sheer size. A lot of the asteroids from the belt were 'redirected' to the two 'Trojan' Groups, for example. Many of the early asteroids were apparently ejected from the Solar system completely. But this effect of Jupiter is probably what made life possible on earth. By ejecting so many asteroids from the Solar system it has reduced the number of hits we have had to suffer here and made relatively stable evolution possible.

[ July 31, 2002, 21:25: Message edited by: Baron Munchausen ]