Ultima Thule — A Little Closer Now

This image, taken by NASA’s New Horizons spacecraft during the historic Jan. 1 flyby reveals small and large depressions in twin-lobed Ultima Thule. The icy object is about 19 miles long (31 km) and located a billion miles beyond Pluto in the icy asteroid belt called the Kuiper Belt. NASA/JHUAPL/SwRI

Clearer and clearer, bit by bit. This latest photo of 2014 MU69 , better known by its informal name, Ultima Thule, is the clearest view yet of the icy asteroid. New Horizons took the photo from a distance of 4,200 miles (6,700 km) just 7 minutes before closest approach on Jan. 1. Earlier photos of the asteroid were taken with the sun at the spacecraft’s back, so the asteroid was lit like a full moon without shadow detail. The lighting here is more oblique so we can start to see details along the day-night boundary called the terminator, located near the top.

Want to see a terminator? Just look at the moon. The terminator divides the day-lit part of the moon from the night. Because the sun is rising or setting at the terminator, features cast long shadows and reveal lots of fine details compared to fully-lit parts of the moon, like what you see along its right side in this photo. Bob King

New details have emerged including lots of small pits up to 0.4 miles (0.7 km) in diameter. The large circular feature on the smaller lobe is about 4 miles (7 km) wide and also appears to be a deep depression. It’s tempting to call them craters since that’s what they look like, but they may also be collapse pits, similar to what Europe’s Rosetta spacecraft found at comet 67P/Churyumov-Gerasimenko. Pits form when ices below the surface vaporize and vent to the surface, creating sinkholes.

This is a collapse pit on comet 67P/Churyumov-Gerasimenko photographed by the Rosetta probe. The contrast has been stretched to show the dusty streams of material rising from the fractured wall of the pit. This photo was taken on Oct. 20, 2014 from a distance of 4.3 miles (7 km). “Sublimation” means that the comet’s ice goes directly from solid to gas, skipping the liquid phase. ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Both lobes also show fascinating light and dark patterns that hint at how it was assembled from smaller objects at the dawn of the solar system 4.5 billion years ago. Perhaps the most striking feature is the bright collar connecting both lobes, which might be icy materials that tumbled down the slopes of both objects when they met and “melded” together long ago. Better photos are still are on their way, and I’ll share them as they arrive.

In this step-by-step view we see how Ultima Thule probably formed — from much smaller chunks that ended up as two objects, which spiraled in toward one another, met gently and joined together in a beautiful “marriage.” NASA / JHUAPL / SwRI

New Horizons is approximately 4.13 billion miles (6.64 billion km) from Earth, operating normally and speeding away from the Sun (and Ultima Thule) at more than 31,500 mph (50,700 kph). At that distance, a radio signal reaches Earth six hours and nine minutes after leaving the spacecraft.

11 Responses

  1. Norman Sanker

    Two questions, Bob. Does NASA have a tentative next target for New Horizons? And, what is an approximate analogy for the level of illumination at this distance from the Sun? Is it like a cloudy night with a full moon? A clear night with no moon? A 40 watt bulb in the Astrodome? Any clue would help. Thanks for everything. Norman Sanker

    1. astrobob

      Hi Norman,
      They’re just starting to work up a target list. Nothing definite or published yet. I know that the light on the surface of Ultima Thule is 0.05% that of Earth. From Pluto, the sun ranges from 150 to 450 times as bright as the full moon since Pluto’s distance from the sun varies by nearly 3 billion km. The sun both from Pluto and Ultima Thule would be tiny and not resolvable as disk with the naked eye but stillintensely bright. Given Pluto’s current distance, sunlight equals about 400 full moons, so it would probably look something like early, bright twilight there. Right now, the sun from Ultima Thule would equal about 200-250 full moons, so darker than Pluto but enough light to find your way around the asteroid.

    2. Troy

      Alan Stern is pretty clear he thinks there will be another encounter. There were two other potential targets besides Ultima Thule, and those can’t be targets at this point. So it will have to be some as yet undiscovered object. I’m wondering if they NH team is waiting for the James Webb scope to launch to scan for possible targets. After all even Hubble had a hard time finding targets, and was employed only after ground based searches came up with nothing. (It is always possible that other targets were already found and kept under wraps.)

  2. kevan hubbard

    If it’s 400x the full moon I’m guessing that it’s bright enough to damage your eyes if you where to look at the sun with binoculars from Pluto?not that there are any binoculars on Pluto …. Or anyone to look through them!

    1. astrobob

      Hi Kevan,
      I think you’re right. It still is producing UV and IR light and Pluto’s thin atmosphere would filter next to none of that out.

  3. Edward M Boll

    The wife and I went to see Stan and Ollie yesterday afternoon, new movie about Laurel and Hardy, well done. Laurel and Hardy have a reference to comets in the 1931 movie Pardon Us. As bootleggers during prohibition, they end up in prison. Their prison teacher is the very funny Jimmy Finlayson. He asks what is a comet. One prison student says that a comet is a star with a tail on it. Jimmy says Right, name one. Laurel said Rin Tin Tin. Not knowing the historical year of this film, years ago, my younger sister asked, Why didn’t he say Lassie?

    1. astrobob

      Hey, that’s great, Edward. I’ve always been a Laurel and Hardy fan. My wife and I are planning on seeing the movie this week. Thanks for the comet joke reference!

  4. Edward M Boll

    Not as good a day. Winter storm last night. My wife called into work got stuck just east of the driveway this morning. We finally got the car out but still had a 3 foot high drift on the road just west of the driveway. We finally got plowed out this evening. I thought about driving into the country to look at Wirtanen, but the last thing that I wanted to do was to possibly get the car stuck tonight. We probably will not go too far the next couple days. Wind chills so bitter, that the students are off school from this past Friday afternoon to this Thursday morning.

  5. Patrick

    Hi Bob. This is Ian’s dad from your astronomy class. Thanks again for your help with the Fireball’s LEGO Robotics team. They would like to send you a thank you card but now that you are retired and the email address I had for you doesn’t work, I can’t find a better way to contact you than through this blog. Not sure if you still have my email address, but I’m wondering if I can get your address so I can send the card to you.

    Thanks again for all you do.

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