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New Horizons’ first hi-res imagery of Ultima Thule

pluto.jhuapl.edu

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Re: New Horizons’ first hi-res imagery of Ultima Thule

#71

Post by prewett »

robotrout wrote: post #19
quakeguy wrote: post #15

"The team says that the two spheres likely joined as early as 99 percent of the way back to the formation of the solar system, colliding no faster than two cars in a fender-bender." Welded together by gravity, i'm really in awe seeing the, by far, weakest power so lovely at work.

So, two masses were close enough in relative velocity and vector, that one of them didn't careen off the other one, and instead, allowed the weakest of all known forces to bond them together as they hurtled at high velocity through space. This object(s) seem statistically unlikely to me. I'm not saying it's artificial. That would be even more unlikely, by orders of magnitude. Just saying "Wow!".

Given the slower speeds in the outer solar system, especially since they will be rotating in the same direction, so the relative speed will be less, I would imagine that contact binaries would be fairly common. And since they are primarily made of ices, the actual contact event should melt the ice, which will then re-solidify since the impact speed is so little.

I don't know if this is how it actually happens, but it gives a mechanism for this being fairly common. The only information I could find was a short wikipedia article:

https://en.wikipedia.org/wiki/Contact_binary_(small_Solar_Sy...

Re: New Horizons’ first hi-res imagery of Ultima Thule

#72

Post by deeths »

robotrout wrote: post #19
quakeguy wrote: post #15

"The team says that the two spheres likely joined as early as 99 percent of the way back to the formation of the solar system, colliding no faster than two cars in a fender-bender." Welded together by gravity, i'm really in awe seeing the, by far, weakest power so lovely at work.

So, two masses were close enough in relative velocity and vector, that one of them didn't careen off the other one, and instead, allowed the weakest of all known forces to bond them together as they hurtled at high velocity through space. This object(s) seem statistically unlikely to me. I'm not saying it's artificial. That would be even more unlikely, by orders of magnitude. Just saying "Wow!".

If a center of mass begins to aggregate in an area of space, smaller objects may get captured and will move in an elliptical orbit with the forming object at one of the foci of an ellipse. Because the other foci of the ellipse is also fairly stable, it is also a likely point for smaller objects to aggregate into another larger object. Objects forming in pairs can reinforce each other. Over time when the small objects around the two foci have all aggregated, the objects at the foci will fall together due to gravity.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#73

Post by alejohausner »

theobon wrote: post #30
robotrout wrote: post #19

Earlier quoted context omitted.

So, two masses were close enough in relative velocity and vector, that one of them didn't careen off the other one, and instead, allowed the weakest of all known forces to bond them together as they hurtled at high velocity through space. This object(s) seem statistically unlikely to me. I'm not saying it's artificial. That would be even more unlikely, by orders of magnitude. Just saying "Wow!".

Contact binaries are fairly common. Expected to make up about 10-15% of NEOs. My layman's understanding of how Kuiper object contact binaries develop is mutual capture during the early life of the solar system and angular momentum decay until they come into contact.

Can you say more about how angular momentum decays in orbital mechanics? I understand that, because the Earth rotates faster than the moon orbits, our tidal bulge will be ahead of the sublunar point, and will accelerate the moon in its orbit. Are there any other ways to get rid of angular momentum?

Re: New Horizons’ first hi-res imagery of Ultima Thule

#75

Post by gshubert17 »

11thEarlOfMar wrote: post #67

Can a human jump off of Ultima Thule? https://xkcd.com/681_large/

Modeling it as two spheres, one 16 km across the other 12 km, with a density the same as water, its total mass would be about 3*10^15 kg. At a distance of 8 km from the center of mass, the escape velocity [0] would be about 7 meters/second or 16 miles/hour.

But the asymmetry of Ultima Thule means that its gravitational field would be weird. Not like a sphere at all. So the acceleration of gravity and escape velocity would vary a lot from place to place.

[0] https://en.wikipedia.org/wiki/Escape_velocity

Re: New Horizons’ first hi-res imagery of Ultima Thule

#76

Post by InclinedPlane »

ilamont wrote: post #21

The new images — taken from as close as 17,000 miles (27,000 kilometers) on approach — revealed Ultima Thule as a "contact binary," consisting of two connected spheres. Are these common in the asteroid belt or as smaller moons of the outer planets?

As far as we can tell, they are pretty common. But we haven't visited enough objects to have firm statistics.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#77

Post by dmurray »

zabzonk wrote: post #46
hughes wrote: post #22

Earlier quoted context omitted.

As this is the first Kuiper Belt Object we've visited, it's hard to draw much about the statistics of the thing.

The second, actually - Pluto is generally recgnised a Kuiper Belt object.

Or the seventh, since New Horizons imaged several satellites in the Pluto system, some at similar resolutions to the latest pictures.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#78

Post by theon144 »

brianpgordon wrote: post #60
TeMPOraL wrote: post #56

Earlier quoted context omitted.

Yup. And if you've ever done maneuvers manually in KSP, you know that a tiny error in your nudge early on - e.g. hamfisting the throttle, or being a little too late in mid-maneuver staging - leads to a huge difference farther out, which you then have to correct, wasting precious ∆v :). I'm very much impressed by the control precision of real-life space probes.

Check out the crazy journey Rosetta took on the way to 67P/Churyumov–Gerasimenko: https://commons.wikimedia.org/wiki/File:Animation_of_Rosetta...

Wow, I actually had no idea; how is this all pre-planned, does somebody at NASA just put "67-P/Churyumov" into a "Orbital Maneuver Planner" and let some computers crunch the possible paths out? Or does someone actually sit down and come up with the possible sequence of orbital assits (to later verify with a computer) with a pencil and paper?

Re: New Horizons’ first hi-res imagery of Ultima Thule

#80

Post by mhh__ »

wallace_f wrote: post #24
samstave wrote: post #16

I personally find it amusing and interesting that the physical object, Ultima Thule, looks similar to the Virtual Game logo "Ultima" https://upload.wikimedia.org/wikipedia/en/6/6a/Ultima_Online...

The nostalgia and innocence and discovry of childhood hit me so hard when I saw that logo

Quite interested as to by whom/why this was downvoted
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