Space and Physics

Ultima Thule Has Neither A Moon Nor Rings So New Horizons Will Fly As Close As Possible


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockDec 19 2018, 17:26 UTC

Artist’s impression of New Horizons encountering Ultima Thule.  NASA / JHUAPL / SwRI / Alex Parker

UPDATE: 2014 MU69 is now officially named Arrokoth


In less than two weeks, humanity will explore a tiny world at the edge of the Solar System. 2014 MU69, or Ultima Thule, is a tiny Kuiper Belt Object (KBO) that will have a close encounter with NASA’s New Horizons spacecraft on January 1.

The team has now confirmed that Ultima Thule hasn’t got a moon, rings, or other hazards. In images taken between August and now, they didn't see any moons larger than 3 kilometers (2 miles) across or any dusty rings, not even those that reflect just five 10-millionths of the sunlight they receive. Given these observations, they decided to keep the spacecraft on its primary and closest trajectory. New Horizons will fly just 3,500 kilometers (2,200 miles) from the small world. The spacecraft is moving at 50,700 kilometers (31,500 miles) per hour so even a small grain of ice or dust could lead to severe damage.

"Our team feels like we have been riding along with the spacecraft, as if we were mariners perched on the crow's nest of a ship, looking out for dangers ahead," hazards team lead Mark Showalter, of the SETI Institute, said in a statement. "The team was in complete consensus that the spacecraft should remain on the closer trajectory, and mission leadership adopted our recommendation."

New Horizons continues to be a probe that sets records. It was the first mission to Pluto when it flew by the dwarf planet in 2015, and it will now be the first one to observe a KBO. Ultima Thule is roughly 30 kilometers (19 miles) in diameter and New Horizons will pass over it at a distance three times closer than it was to Pluto. Images will have a resolution of between 30 and 70 meters (98 and 230 feet).


The spacecraft also performed its last trajectory correction burn and New Horizons Principal Investigator Alan Stern took to Twitter to state that it was “spot on”. Humanity’s rendezvous with its first KBO is now mere days away.

"The spacecraft is now targeted for the optimal flyby, over three times closer than we flew to Pluto," added Stern. "Ultima, here we come!"

New Horizons will make its historic close approach of Ultima Thule at 12.33am EST (5.33am GMT) on January 1, 2019. Given that the object is 6.4 billion kilometers (4 billion miles) from us it will take roughly six hours for us to receive confirmation of a successful flyby.

Space and Physics
  • New Horizons,

  • flyby,

  • Ultima Thule