Ring in the New Year With NASA’s Most Distant Planetary Encounter in History

At 12:33 a.m. EST on January 1, 2019, more than four billion miles from Earth, a NASA spacecraft launched in January 2006 will fly within 2,200 miles of an ancient planetary body, orbiting more than 40 times the distance from the Earth to the sun and undisturbed for perhaps billions of years. The New Horizons flyby of 2014 MU69, aptly nicknamed Ultima Thule for a Latin phrase meaning beyond the known world, will not only be the most distant planetary encounter in human history, but the object will also be the most primitive world ever visited by spacecraft.

As the clock strikes midnight on the east coast of the United States, you can tune in to NASA TV to join the space agency at mission control in the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, as the world celebrates the arrival of New Horizons at Ultima Thule. Talks and presentations by members of the mission team will begin today at 2:00 p.m. EST.

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The New Horizons spacecraft accomplished its primary mission on July 14, 2015, when it performed the first close encounter of Pluto. That flyby revealed that even little Pluto, more than three billion miles from the sun, is an active world with shifting plains, glaciers and mountains that reach up to about 15,000 feet. Hard water ice forms the bedrock on Pluto with softer ices on top, such as nitrogen, carbon monoxide and methane.

The spacecraft’s next target, Ultima Thule, could contain even more surprises. “We hardly know anything about it,” says Alan Stern, principal investigator of the New Horizons mission, at APL.

Ultima Thule was only discovered in June 2014 by the Hubble Space Telescope in an effort to find an additional target for New Horizons in the distant family of bodies beyond Neptune known as the Kuiper Belt, the third region of the solar system. “Beyond the terrestrial planets lie the giant planets, and beyond the giant planets lies the Kuiper Belt,” Stern says.

After discovery by the Hubble Space Telescope, a series of ground observations were carried out to measure Ultima Thule during an occultation—as it passed in front of a background star and blocked out some of the starlight. The object appears to be irregularly shaped, about 20 to 30 kilometers in diameter, and tinted red. What types of ices and rocks constitute the object will provide planetary scientists with the first example of a primordial planetary body orbiting in this distant realm. The instruments on New Horizons will create geologic and compositional maps of Ultima Thule, as well as searching for any rings, debris, or even small satellites orbiting the object.

It may be that Ultima Thule is similar to comets that follow elliptical paths taking them close to the sun, only Ultima was never perturbed and flung inward by a gravitational encounter with Neptune or Uranus. The small body continues to orbit undisturbed on a more circular path than comets, never getting closer than 42 Astronomical Units, or 42 times the average distance between the Earth and the sun.

At the moment, Ultima Thule is little more than a pixel of light on New Horizon’s imaging instruments. Images of the object taken just before the encounter will grow to a few more pixels, transmitted back to Earth at the speed of light in about six hours. The high-resolution images of Ultima Thule are scheduled to be received and released back on Earth on Wednesday, January 2, truly revealing this distant body to the world for the first time.

“Being on the first mission of discovery when points of light become real places almost overnight is an incredibly humbling experience to be a part of,” Stern told Smithsonian.com. “It’s scientifically indescribable. … To have the chance to lead this from the inception through design and build and flight across the solar system, and now to our capstone in the Kuiper Belt, is the product of a lifetime, and it’s something that dreams are made of.”

Jay Bennett | | READ MORE

Jay Bennett was the associate web editor, science, for Smithsonian.