Intellectual Exercise / YouTube Ultima Thule SF Audiobook by Dallas 1545483071.jpg...
Intellectual Exercise / YouTube

Remember New Horizons, the spacecraft that went past Pluto in 2015, and how much fun that was?

(My favorite part is the guy at around 1:00 who sees on his computer that the signal has been received, but he can’t vocalize it so he just pumps his fist.)  I remember watching that with my then-11-year-old daughter and trying not to get choked up as I explained what we were seeing.

Well, as you may know, New Horizons is getting pretty close to a new object in the Kuiper Belt called Ultima Thule.  It’s 10 days away, about 12.5 million km as of tonight.  Flyby is going to be January 1, 12:33 A.M., about 2200 miles from the object.  So the ball will drop, Mariah Carey will lip-sync or have some sort of sonic catastrophe, and then you can just move right on over to NASA TV.

One thing we know about Ultima Thule is that its shape is irregular.  It’s either dumbbell-shaped or actually two separate objects orbiting each other really closely.  They figured that out because when it passed in front of a star it gave a double-dip to the star’s brightness.

Another thing we know is that this is going to be the farthest object ever visited by a spacecraft!  Wooooo!

Sorry — anyway, as New Horizons is approaching Ultima Thule, it’s noticing something strange.  The reflection of light off this thing should be irregular like if you shone a light off a spinning, weird-shaped object, you’d expect the light reflected back to you to go up and down in intensity as different parts of the object were facing you.

But it’s not doing that.  The reflection is staying the same.  Hmmm…..

So there are a few theories (OK, guesses) as to why this might be.  Funnest one: Ultima Thule is surrounded by a bunch of tiny moons that even out the reflection.  That would be pretty awesome, don’t you think?  Could also be a dust cloud of some sort, but the problem with that is that there isn’t much gravity associated with this 19-mile-wide object to hold something like that in place, and it’s also too cold out there for stuff to vaporize around it.  It could also be that New Horizons just happens to be pointed right at the axis of rotation, but the chances of that aren’t very good.  So what’s the deal?

This is one of those astronomical mysteries that luckily is going to be solved in the next few days.  Instant gratification.  But you’ll have to stay tuned to the mission to find out the answer.

Whatever is going on, I’ll tell you this: we are going to get some seriously interesting imagery starting about 6 hours after the flyby.  (That thing is 6 light-hours away from Earth.)  One of the many reasons astronomy is so much fun, even for non-astronomers like me.

What’s it’s shape?  Is it geologically active?  What’s it made out of?  Why is it reddish?

“The spacecraft is now targeted for the optimal flyby, over three times closer than we flew to Pluto,” said New Horizons’ principal investigator Alan Stern. “Ultima, here we come!”

I like that guy!


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This is a Creative Commons article. The original version of this article appeared here.



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