The spacecraft was approximately 1.2 million miles (1.9 million km) from Ultima Thule when this image was taken on December 30, 2018. Instead, hundreds of team members and their guests gathered nearby on campus for back-to-back countdowns.
Now it hopes to solve the mystery surrounding Ultima Thule, which is believed to be a binary system but could be something much stranger.
"We set a record".
"Think about it - we're a billion miles further than Pluto".
Stern called it an auspicious beginning to 2019, which will mark the 50th anniversary of Neil Armstrong and Buzz Aldrin's footsteps on the moon in July 1969. After the quick flyby, New Horizons will continue on through the Kuiper Belt with other planned observations of more objects, but the mission scientists said this is the highlight. This configuration limits the spacecraft's communication with Earth, commanding it to quickly address any technical issues on its own, then get back to science.
This artist's impression of Ultima Thule depicts it as a contact binary, two smaller objects that orbit each other and are so close that they touch. The close encounter comes 3½ years after the spacecraft swung past Pluto.
"I can't promise you success".
"We're rendezvousing with something that's a mountain draped in black velvet in nearly pitch dark conditions and we're screaming up to it ... within 2 seconds of perfection", Stern said. "So stay tuned. There are no second chances for New Horizons".
The risk added to the excitement.
"This is completely unknown territory, which is what makes us all so excited at this moment."
NASA's live stream of the event was very informative, providing details about the mission and animations to show where the spacecraft was in relation to Ultima Thule.
But the new target is so far away and so faint that NASA's Hubble Space Telescope was the only instrument that could see it.
This composite image made available by NASA shows the Kuiper Belt object nicknamed "Ultima Thule," indicated by the crosshairs at centre, with stars surrounding it on August 16, 2018, made by the New Horizons spacecraft.
"We're already learning about Ultima from up close", Stern said. The object is 20 miles long by 10 miles wide. "This science will help us understand the origins of our solar system".
Ultima Thule was named for a mythical, far-northern island in medieval literature and cartography, according to Nasa. Ultima Thule was discovered only four years ago, and its orbit and surroundings still aren't well known. 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 have a healthy spacecraft", Alice Bowman, mission operations manager for New Horizons, said after signal notification.
"This really just starts with the downlink and transmissions that begin tomorrow, and will last for a year-and-a-half", he said.
"Who knows what we might find?".
"This is just raw exploration", said Alan Stern, a scientist at the Southwest Research Institute and the principal investigator for the mission.