At 12:33 a.m. EST on New Year’s Day, NASA’s New Horizons spacecraft made its closest approach to the most distant object humankind has ever explored : Kuiper Belt Object 2014 MU69, better known by its nickname Ultima Thule—Latin for “beyond the known world.”

As the clocks stroked midnight, a resounding cheer echoed throughout the room. But in the afterglow, the room still buzzed with anticipation. The biggest countdown was yet to come—just shy of 33 minutes past the hour: For this crowd, ushering in the year 2019 had taken a backseat to a far more singular event. At the Johns Hopkins University Applied Physics Laboratory, history was being made.

Four billion miles away, the piano-sized spacecraft celebrated alone. Then, in the early hours of the morning, it peeked briefly homeward to signal that it was safe. But the moment of closest approach was commemorated here on Earth with tears, shouts, and laughter. After 13 years abroad, New Horizons has put Ultima Thule in its rearview mirror.

“It’s definitely sunk in now, and I’m excited,” says New Horizons Deputy Project Scientist Cathy Olkin. “I was getting nervous, waiting for that signal… but the minute I heard the data recorder was as full as we expected to be... that was the key to everything. That means we got the data on the spacecraft.”

The mysterious object, thought to be a frozen fossil that’s been pristinely preserved in outer space since the birth of our solar system, has so far played it close to the vest: At a press briefing on Sunday, less than two days prior to closest approach, Principal Investigator Alan Stern said he couldn’t definitely produce five facts about Ultima Thule.

“We’ve never, in the history of spaceflight, gone to an object we’ve known less about,” Stern said. “We know its orbit, we know its color, we know a little bit about its shape, and its reflectivity. We can’t even get the rotational period. I thought we’d have that 10 weeks ago.”

Ultima Thule wasn’t even discovered at the time of New Horizons’ launch in 2006. The mission, originally billed as an exploration of the then-planet Pluto, was extended after Ultima Thule, a teeny, wonky-shaped object estimated at less than 20 miles long, was first identified with the Hubble Telescope in the summer of 2014. And it has remained stalwartly enigmatic ever since.

But this oblong orb probably has a lot to say. Researchers believe that objects like Ultima Thule are the Solar System’s version of primordial soup: A time capsule from the pre-planet era that’s been orbiting the Sun undisturbed for the past 4.6 billion years. Which means getting up close and personal with Ultima could yield some critical insights into what the building blocks of our solar system looked like at their inception.

In the days leading up to the flyby, the Applied Physics Laboratory was abuzz with the fervor of sleep-deprived scientists, engineers, and staffers eager for their long-awaited moment of truth. On Sunday, Project Scientist Hal Weaver cheerily predicted that most of his team would be running on pure adrenaline for the entirety of New Year’s week.

Last minute meetings turned into all-nighters; scientists signed up to work in shifts. Some personnel even began toting sleeping bags, pillows, and air mattresses onto the premises. But it was probably Mark Holdridge, New Horizons’ Encounter Mission Manager, who took the cake—by pitching a full tent in his office.

Mark Holdridge, New Horizons’ encounter mission manager, pitched a tent in his office in the days leading up to the flyby in preparation for the long nights at the Applied Physics Laboratory. Image Credit: Hong Kang, Johns Hopkins University Applied Physics Laboratory

“We’re here for the exploration,” Alice Bowman, Mission Operations Manager, or MOM, of New Horizons’ Mission Operations Center, said at Sunday’s press briefing. “We’re happy to spend the night if that’s what it takes.”

On New Year’s Eve, scores of scientists, reporters, and space enthusiasts from around the country congregated at the Applied Physics Laboratory’s Kossiakoff Center. In the moments before midnight, a sea of scientists sipped champagne from plastic cups; wide-eyed children in space-themed t-shirts flitted in and out of the room waving American flags. As the first minutes of 2019 ticked onto the clock, rock and roll legend Brian May took the stage, debuting an anthem celebrating New Horizons’ historic journey. But for once, the lead guitarist of Queen was only the opening act.

Thirty-three minutes after the crowd rang in the new year, the New Horizons spacecraft came within 2,200 miles of Ultima Thule’s surface, capturing humankind’s first bits of data on the most primitive and most distant object ever explored.