No rotational light curve from Ultima Thule?


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Data from New Horizons as it is quickly approaching Ultima Thule has found that even though the object is expected to be oblong or even two objects it has shown absolutely no variation in light as it rotates.

Even though scientists determined in 2017 that the Kuiper Belt object isn’t shaped like a sphere – that it is probably elongated or maybe even two objects – they haven’t seen the repeated pulsations in brightness that they’d expect from a rotating object of that shape. The periodic variation in brightness during every rotation produces what scientists refer to as a light curve.

“It’s really a puzzle,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “I call this Ultima’s first puzzle – why does it have such a tiny light curve that we can’t even detect it? I expect the detailed flyby images coming soon to give us many more mysteries, but I did not expect this, and so soon.”

They have several theories, all implausible, to explain this. It could be they are looking at the object’s pole. Or maybe a dust cloud or numerous tumbling moons surround the object and hide the light variation.

Fortunately, we shall have an answer to this mystery in less than two weeks, when New Horizons zips past.

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12 comments

  • Col Beausabre

    Let’s shave with the Razor of Willian of Occam.

    There’s no light curve because it’s not rotating.

    “When you have eliminated the impossible, whatever remains, however improbable, must be the truth. “– Sir Arthur Conan Doyle, stated by Sherlock Holmes”

  • Diane

    I think William of Occam might nick himself on that one. “No rotation” would be extraordinary.

    I will bet ten quatloos that New Horizons is looking down at a pole. Ultima Thule is looking at the same view, even with rotation taken into account.

  • Matt in AZ

    Perhaps the large spacecraft parked next to it during the occultations is no longer there :-)

  • Andrew_W

    From what I can judge the Sun is right behind New Horizons, so I’m betting on the polar view.

  • Col Beausabre

    “Extraordinary” is not “impossible.” If one theme runs through BtB, it’s that every time we say, “That’s it, it can’t get any weirder than this”, nature grins and tops itself.

    “I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose”. JBS Haldane Possible Worlds and Other Papers (1927), p. 286

    As Bob says, it necessary to have an open mind, although one should make sure it is not an empty one. (Zimmerman’s Law)

  • Diane

    Yes, there’s a difference between having an open mind and having a hole in your head. I’m fine with staying on the “open mind” side.

    However, Occam’s Razor says that the simplest explanation is likely to be the correct explanation. “No rotation” opens up a host of other questions, given that we’ve never seen anything like that. (Always a possibility for firsts, though.) The closest we’ve seen has been tidal locks (e.g., our moon). Ultima Thule may be tidally locked to its companion, if it has one, but that’s not the explanation we would want here.

    Second guess, it’s aliens.

  • Steve Earle

    Diane, if we accept your bet, do we also have to be dressed as Triskellion Gamesters? (Did I spell that right? Lol )

    Wayne, where is your usual timely Star Trek video clip?

  • wayne

    Steve Earle-
    (You sir, are a great American!)
    The one that comes to mind is (original series) “For the World is Hollow and I have touched the sky,” –where they encounter an asteroid that is really a spaceship, but nobody on board is aware of it. And the ‘oracle’/computer running it, has the cure to Dr. McCoy’s terminal illness. Conflict ensues. (the relevant clip isn’t uploaded to YouTube.)

    Diane–
    (“1,500 quatloos on the newcomers”)
    Tend to believe you are correct—I’m under the impression very few (if any) objects in Space, have zero inherent rotation/movement.
    (let me see if I can mangle this; “it’s never Aliens, it is however, always a mole-hunt.”)

    Col Beausabre-
    Good stuff. (spent 30 years dealing with [terrestrial] craziness and every time I had the urge to tell myself ‘now, I’ve finally seen it all,’ somebody unique walks in the door.

  • wayne

    “For the world is hollow and I have touched the sky”
    ST original: season 3, episode 8
    https://youtu.be/JEB7O1K1ZXI
    (0:37)

  • Col Beausabre

    “an asteroid that’s really a space ship”

    Rendezvous with Rama by Arthur C Clarke

    “The “Rama” of the title is an alien starship, initially mistaken for an asteroid”

    https://en.wikipedia.org/wiki/Rendezvous_with_Rama

  • Diane Wilson

    ‘Omuamua was a good bet for Rama-type path through the solar system. On the other hand, Ultima Thule seems to be a better spot for a Sentinel or gateway than Iapetus.

    If New Horizons’ last message is a voice saying, “My God, it’s full of stars!”, then we’ll know.

    Triskelion dress codes have been relaxed.

  • Edward

    Diane wrote: “‘No rotation’ opens up a host of other questions, given that we’ve never seen anything like that. (Always a possibility for firsts, though.) The closest we’ve seen has been tidal locks (e.g., our moon).

    One question that it opens up is: what is the definition of “no rotation?” Just how slow can an asteroid go and still be considered as rotating. If an asteroid rotates once every 100,000 years, with respect to the universe as opposed to the sun, is that slow enough to be considered no rotation? However, the Milky Way galaxy rotates at a much slower rate, but we still consider it as rotating.

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