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NH Ultima Thule Encounter Observations & Results, post-flyby discussion as the data arrives
Marcin600
post Jan 16 2019, 08:38 AM
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QUOTE (Ian R @ Jan 16 2019, 09:19 AM) *
My speculation is that the two lobes were never individual objects in the first place, and that the original fast rotation of MU69 -- back when it was newly formed and more prone to deformation -- caused a 'blob' to begin to separate from the main body due to centripetal forces, which in the end weren't enough for the two components to part completely.

Just a stab in the dark from a layperson!



I think that this is one of many possibilities. In any case, things seem to be more complicated than they originally seemed
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Marcin600
post Jan 16 2019, 09:03 AM
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For example, two bodies could be originally separate and flattened independently as a result of rotation. More data from New Horizons is needed.
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stevesliva
post Jan 16 2019, 03:40 PM
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QUOTE (Marcin600 @ Jan 16 2019, 04:03 AM) *
For example, two bodies could be originally separate and flattened independently as a result of rotation.


Or accretion.

This is definitely real? If I focus on just the neck/isthmus then it does appear real, but I worry it's just an artifact.
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pdalek
post Jan 17 2019, 05:33 AM
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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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Marcin600
post Jan 17 2019, 08:15 AM
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As Stevesilva supposes, the slightly flattened shape of Ultima (and Thule?) - if it is not a low resolution artifact - may be the result of the specificity of the accretion process itself - in one plane, a bit like an accretion disc (?)

I think the wonderful New Horizons team is already working on the interpretations.
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john_s
post Jan 17 2019, 12:00 PM
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QUOTE (Ian R @ Jan 16 2019, 12:19 AM) *
I took one of the GIF animations and made an aligned and 'bouncy' version:

Looks as if the lobes are less spherical than they are hamburger shape!


Hi Ian-

Thanks for that very revealing "de-rotated" animation. We on the science team had been planning to do the same thing, but you beat us to it. When I sent the team a link to your animation, it sparked quite an e-mail storm. UT continues to surprise!

Thanks again,
John
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Explorer1
post Jan 18 2019, 05:13 AM
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New post from Alan: http://pluto.jhuapl.edu/News-Center/PI-Per...tive_01_17_2019

In addition to data downlink from MU69, some distant observations of the unchosen flyby target in March, and some extra fuel for post 2020 maneuver to a more distant object.
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Roman Tkachenko
post Jan 18 2019, 09:28 AM
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I just played around with the sequence

https://www.youtube.com/watch?v=T_HGXKO9kus


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alex_k
post Jan 18 2019, 03:00 PM
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Looking for surface features. Strong Fourier-based processing performed, details are exaggerated if resolved properly.
05:01:47 (better res) vs 6 stacked 04:04

Focused on Ultima:
Attached Image


Focused on Thule:
Attached Image

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Ian R
post Jan 18 2019, 05:37 PM
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QUOTE (john_s @ Jan 17 2019, 12:00 PM) *
Thanks for that very revealing "de-rotated" animation. We on the science team had been planning to do the same thing, but you beat us to it. When I sent the team a link to your animation, it sparked quite an e-mail storm. UT continues to surprise!

Thanks again,
John


Hi John,

That's pretty amazing! Thanks for the feedback: it's an honor to be tangentially involved with the team as new discoveries are being made about UT.

Ian.


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alan
post Jan 18 2019, 07:54 PM
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What would happen when a body the size of one of UT's lobes was spun up if most of its mass was made up of a bunch of spheres a few km's in diameter instead of many smaller pieces? Would it end up hamburger shaped instead of football shaped as it shifted toward equilibrium?
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kenny
post Jan 21 2019, 07:27 PM
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Analysis of Ultima Thule comparing its morphology with those of previously-imaged comets....

Forbes Magazine on UT January 21

...by astrophysicist author Ethan Siegel.
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john_s
post Jan 24 2019, 08:53 PM
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The current best image (a big improvement over the earlier ones, due to lower noise and higher phase angle) has just been posted:

http://pluto.jhuapl.edu/News-Center/News-A...p?page=20190124

John
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Phil Stooke
post Jan 24 2019, 09:48 PM
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Wow, that is a fantastic image - I have just played with it slightly here by brightening the terminator to show faint features a bit better. Just don't ask me to interpret it! - well, OK, maybe the broader depressions near the terminator of the large lobe look a bit like they are bounded by scalloped scarps retreating due to volatile loss.

Phil

Attached Image


--------------------
... because the Solar System ain't gonna map itself.
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Marcin600
post Jan 24 2019, 10:28 PM
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An amazing object!!! And it is becoming more and more fascinating. There are really a lot of these small hollows on almost the entire surface. I can not wait for more detailed pictures. Sadly, we'll never see the reverse side...
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