NH Arrokoth (formerly Ultima Thule) Encounter Observations & Results, post-flyby discussion as the data arrives |
NH Arrokoth (formerly Ultima Thule) Encounter Observations & Results, post-flyby discussion as the data arrives |
Jan 4 2019, 01:16 AM
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
This will be where we talk about the data as it arrives over the next 20 months or so.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Jan 17 2019, 05:33 AM
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Newbie Group: Members Posts: 2 Joined: 4-March 14 Member No.: 7145 |
Ultima Thule looks like a snowman. A big snowman is a good way to think about formation and properties.
Comets have density about that of handmade snowballs. U-T is probably similar. Calculating gravitation and centrifugal acceleration will show it is gravitationally bound over the entire surface and so was not formed by stretching a sphere. The escape velocity is about that of a human thrown snowball. Fall velocities would be similar. At such velocity, a small snowball acreating under gravity will splat. For a large falling snowball, self gravitation will keep the ball in shape. Higher impact velocity would change things, but without large nearby planets to shift orbits, this is unlikely. The compressive strength ordinary packed snow is sufficient to prevent a 19km and a 14km balls from merging to a much more compact space. It is easy to estimate the contact area. Modelling the gravitational field shows local down is up to about 30 degrees from surface normal near the neck. This is about the angle of repose of lightly packed snow. |
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