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'Something Weird Is Going On' as New Horizons Approaches Distant Asteroid (popularmechanics.com)

NASA's New Horizons spacecraft passed Pluto in 2015. But now it's getting strange readings while approaching its next destination, the Ultima Thule asteroid.

Popular Mechanics reports: Ultima Thule appears to not have a light curve, which is perplexing scientists... Asteroids like Ultima Thule reflect sunlight -- that's why they're bright spots instead of dark spots -- but the amount of light they reflect depends on how much of their surface is facing the Sun. The bigger their surface area, the brighter they become. Small asteroids like Ultima Thule aren't perfectly round, which means how much of their surface is facing the Sun changes as they rotate....

Ultima Thule isn't changing its brightness at all. New Horizons has been watching Ultima Thule for three months and hasn't spotted any brightness change, which is really odd. Ultima Thule is definitely not spherical -- astronomers determined that a year ago -- so why doesn't its brightness change?

One theory is that the New Horizon's probe is perfectly aligned with the asteroid's axis of rotation, so it's only seeing Ultima Thule's north (or south) pole. Another is that the asteroid is surrounded by dust clouds that "even out" its light curve. But that usually only happens when asteroids are near the sun and heating up, whereas Ultima Thule "is cold and dark and shouldn't have any dust...."

"Fortunately, we might not have to wait long for an answer to this problem. New Horizons will fly by Ultima Thule on January 1, and should give us high-resolution photos of the entire system," the article concludes. "With any luck, those photos will solve the mystery."

9 of 83 comments (clear)

  1. And Cue by maroberts · · Score: 2

    ,,,alien spaceship theories.

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    1. Re:And Cue by pslytely+psycho · · Score: 5, Funny

      That's no moon...

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      Donald Trump, on a crusade to make Nixon look respectable
    2. Re:And Cue by Paul+Johnson · · Score: 4, Interesting

      "First, there was the problem of Rama's light curve. It didn't have one." From "Rendevous with Rama" by Arthur C. Clarke.

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      You are lost in a twisty maze of little standards, all different.
  2. "Something weird is going on" is good for science by Anonymous Coward · · Score: 5, Insightful

    As the apocryphal quotation goes, "The most exciting phrase in science is not ‘Eureka!’ but ‘That’s funny ’."

  3. Not rotating ? by Alain+Williams · · Score: 3, Interesting

    But it is a bit far out to be gravitationally locked to the sun.

    It can't be covered by an ocean as it is not perfectly round, so there would be islands/continents that would have a different albedo. What would be liquid that far out (ie cold) ?

    1. Re:Not rotating ? by RockDoctor · · Score: 3, Interesting
      When a satellite and it's primary are gravitationally (tidally) locked, the locked component rotates at the same period as the rotation of the secondary around the primary. That's the situation we have between Earth and Moon - the Moon goes around the Earth every 29.x days (x varies on which version of "around" you want) and the Moon rotates on it's axis every 29.x days (same caveat). It is also possible for the primary to become tidally locked to the secondary, which is the situation between Pluto and Charon.

      What would be liquid that far out (ie cold)

      H2, He (miscible above 3.x K, IIRC), Ne. Nitrogen is close to it's triple point on Pluto, so it can slip in and out of fluidity.

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    2. Re:Not rotating ? by war4peace · · Score: 3, Interesting

      The moon isn't perfectly tidally locked to the Earth, see Lunar Libration.
      https://en.wikipedia.org/wiki/...

      Therefore it does have a light curve.

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      ...gis sdrawkcab (usually not responding to ACs; don't bother posting as AC)
  4. Re:"Something weird is going on" is good for scien by DCFusor · · Score: 4, Insightful

    And all real scientists live to hear, or better, speak just that phrase. It's the payoff for all that work.

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    Why guess when you can know? Measure!
  5. Re:"Something weird is going on" is good for scien by jythie · · Score: 3, Insightful

    Yeah.. any time I hear people complaining that scientists are dogmatic and hate anything new or novel, I wonder if they have ever actually met a scientist outside having their ideas debunked.