Ok, time to put this to bed. Darkstar you quoted a particular piece of information regarding our asteroid belt and have chosen to use it and the information from another website (
http://aa.usno.navy.mil/hilton/asteroid_masses.htm) as evidence that the asteroids of the Hoth asteroid belt are less dense than some claim. I have reviewed this website and found that your justification for using the data found therein is without merit since this web site is clearly talking about the largest of the asteroids in OUR asteroid belt. As to the quote you used
"Not long ago, astronomers thought of asteroids as rocks, perhaps rubble covered, but still mainly single bodies. But evidence has accumulated that asteroids are rubble piles all the way through, loosely bound together by what is generously called "gravity" (escape velocity is 11,000 meters per second on Earth but less than 1 meter per second on a typical small asteroid)." . . . "Crater chains on the moons of Jupiter, on Earth's moon, and on Earth itself also point to the gravity-induced disintegration of many asteroids prior to impact. Asteroids which rotate fast enough to fling pieces clear are extremely rare -- only two are known -- which suggests that these are the rare single-rock objects."
There is an interesting point about this statement for OUR asteroid belt. The escape velocity of the small rocks is listed as less then a meter per second. The largest asteroids (Ceres, etc) would have escape velocities on the order of 350 m/s. In ESB, we see asteroids with velocities in excess of 350 m/s as shown on screen, even you agree this is the case. What does this mean? Since we do not see pieces of the asteroids being flung off into space due to it transnational and rotational velocities we can conclude that the Hoth asteroids are not the low bulk density rubble piles OUR asteroid belt seem to exhibit. Therefore they are solid chunks of rock and/or nickel-iron. Or, the asteroids in the Hoth asteroid belt are much more dense and therefore much more massive so that the corresponding escape velocities are higher to keep pieces of the asteroids from being flung off due to their transnational and rotational velocities. If I were to use Darkstars numbers for the diameter and density if the asteroid that hit the ISD in the ESB, I get an escape velocity of 0.04m/s. Since we do not see any pieces of the asteroid trailing behind we therefore have to assume that the asteroid is much more massive than Darkstar gives it credit for. Since we see no pieces of the asteroid being flung into space just before impact with the ISD, and using Darkstars velocity of 650m/s as a lower limit we can calculate the mass of the object. Doing a little algebra and math, I calculate a mass for the asteroid of 9.5E16kg. Using this mass to calculate the KE of the impactor yields a number on the order of 3 million megatons. This is again using Darkstars own information.
Finally, I will address some points Darkstar made regarding my post.
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Originally posted by Captain Hornblower:
As to the density issue, iron-nickel asteroids (S-type and M-type) have densities closer to 8000kg/cu.m.
That is simply false. There are no S-type asteroids I am aware of with densities in that range, and though we have very little info on the densities of rarer M-types, the ones we know of also don't fit that range.
The only thing I can think of that might be the origin of your false information (thus leaving you innocent) would be that you're getting info about meteors that have come down. Those have already had most of their material burned off, though, so they usually have better densities by the time they get to our hands.
As to the density of S-type I stand corrected, density ranges are for these are in the 3k-4k kg/cu.m. M-type asteroids are suspected to have densities in the range of 7800 kg/cu.m. Though this info is sketchy due to the lack of data. More to the point, I do not think a direct comparison between out asteroid belt and the Hoth asteroid belt is justifiable due to their completely different ways they each belt was formed. Two different dynamics are involved here. When the asteroid belt in our solar system formed, most if the heavier elements had already been pulled toward the inner terrestrial planets and the sun. Leaving very little of the metals left in the region of the asteroid belt. On the other hand, the Hoth asteroid belt was formed from the recent (at least recently relative to the formation of the Hoth system) collision of 2 terrestrial type planets. Therefore there will be much more of the heavier metals remaining within this type of asteroid belt.
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Your numbers are purely for stony asteroids and porous ones at that. Stony asteroids (C-type) make up about 75% of OUR asteroid belt. If you want to claim that the Hoth asteroid belt has a similar composition to ours then show us your justification.
Wong gave it with the claim of two planets colliding. If these were planets like Earth and Venus, the average density of the material would be ~5500kg/m^3. If it were two planets like Mars and a body like the moon, the average density would be ~3500kg/m^3.
Which still has nothing to do with your assumption that the asteroids in the Hoth belt are similar to those in our asteroid belt. Since the Hoth belt is a result of 2 planets colliding and not the left over remnants of a solar system formation, you are not justified in using the lower densities.
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However, you might want to be careful in that regard because an asteroid belt as dense as Hoths would quickly pulverize the lower density asteroids to dust with the frequent collisions that occur as shown in the movie.
And these fragments would get picked up by the slower moving asteroids. The main problem with your idea, though, is that a belt as hostile as that would phase itself out without something maintaining it, like a strong gravity source nearby.
Again you are using our asteroid belt as analogous to the Hoth asteroid belt, which I don’t think you can do since, as I have said before, the two systems formed through different mechanisms. The dynamic difference between our asteroid belt and Hoths is that Hoths is not a naturally occurring belt, but the result of 2 planets colliding. Since there was a planet there in the first place we have to assume that a gravity source does not exist, because if it had, than a planet would not have been able to form in the first place when the Hoth system was initially created. Additionally, when two planets collide and pulverize themselves, they expose the cores, which contain the heaviest of its elements. Fluid mechanics dictates that the molten cores will eventually cool and solidify, forming roughly spheroid shapes that are seen on the screen. These more massive bits of the planets will tend to coalesce in the center of what is now called the Hoth asteroid belt. The lighter silicates will remain at the outer fringes of the belt since those silicate bodies that remain within the nickel-iron zone will completely pulverize into dust those silicate bodies that remain and due to the observed velocities of the asteroids within the Hoth belt, that pulverization process will continue until the energy of the system has reached a steady state. However, I do not think that that is likely to occur since there was a planet there to begin with; steady state for that particular orbital position is a planet. So, eventually the Hoth belt will re-coalesce back into a planet as time progresses. Also, since we have no idea as to how long ago the 2 planets collided its would be difficult to determine the energy state of the Hoth asteroid belt at time t = TESB. What we do know we can glean from the on screen evidence. The energy state of the asteroid belt is still relatively high because of the observed velocities (rotational and translational) and the frequency of impactors on the rebel planet. Hell, maybe it’s the result of a very large impactor that gave rise to Hoth’s icy condition.
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So, if I were to use your number for the 60-meter rock, my number for the density and split the difference for the velocity between your number and Mikes the calcs would come out something like this….
V = volume = 4/3*pi*R^3 = 4/3*3.1416*30^3 = 113,100 m^3
”You used a sphere. The asteroid is not a sphere.”
Fine, you say its not a sphere, I say it’s close enough for the purposes of my calculations. If you have a problem with that, do some cut-and-paste and show your evidence. I will look it over.
