Ten hours after the middle-of-the-night encounter 4 billion miles (6.4 billion kilometres ) away, flight controllers in Laurel, Maryland, received word from the spacecraft late Tuesday morning.
"We have a healthy spacecraft", mission operations manager Alice Bowman announced here at Johns Hopkins University's Applied Physics Laboratory.
A huge spill-over crowd in a nearby auditorium joined in the loud celebration, cheering each green, or good, status update.
"This is Brian's personal tribute to the on-going NASA New Horizons mission, which on New Years Day 2019 will achieve the most distant spacecraft flyby in history".
New Horizons acquired gigabytes of photos and other observations during the pass, however, because of the vast distance between the spacecraft and Earth, it will take until September 2020 to retrieve all of the data stored on the probe. Unlike every other object previously visited by NASA, including Pluto, MU69 is believed to be unchanged since it formed in its current orbit billions of years ago, granting a window to the solar system's earliest days.
Although the flyby occurred at 12:33 a.m. ET on Tuesday, the spacecraft is so far from Earth that the "phone-home" signal didn't reach us until about 10:30 a.m. ET.
Ultima Thule - an uncharted world over 4 billion miles away - is coming into view.
The last blobby picture sent back before the flyby - the best available so far - showed that Ultima Thule is 35 by 15 kilometer, with a blurry peanut shape, so it is either "bi-lobate", with a different size for each lobe, or it could be two objects whose images blurred together.
The answer is one that scientists already suspected: Ultima Thule's spin axis is roughly pointed toward Earth, so that it appears somewhat like a turning propeller with the illuminated side constantly facing earthbound telescopes.
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"We set a record!"
A tiny, icy world a billion miles beyond Pluto is getting a New Year's Day visitor.
This is the best look scientists have ever had at Ultima. "The New Horizons team makes it look easy". Traveling at 31,500 miles per hour (50,700 kph), the spacecraft could easily be knocked out by a rice-size particle. At a speed of 31,500 miles per hour (50,700 kph), New Horizons could easily be knocked out by a rice-sized particle.
The risk added to the excitement. "This is completely unknown territory".
And even the USA government shutdown couldn't stop NASA from celebrating such an extraordinary feat.
The object Ultima Thule, the nickname for 2014 MU69, was discovered by Marc Buie of Southwest Research Institute in 2014, in an extraordinary search among millions of stars imaged for the goal with the Hubble Space Telescope.
For that reason, Stern said he and his colleagues are "on pins and needles to see how this turns out".
The ancient Greeks and Romans used the name Ultima Thule to refer to a distant place lurking just beyond the borders of the known world. It is thought to be potato-shaped and dark-colored with a touch of red, possibly from being zapped by cosmic rays for eons. "We will find out". "This is exploration at its finest", said Adam L. Hamilton, president and CEO of the Southwest Research Institute in San Antonio.