A NASA probe more than 6 billion kilometres from Earth has photographed the most distant object any human-made craft has ever visited.
Ultima Thule is a small object in the Kuiper Belt, beyond the orbit of Pluto.
NASA's New Horizons craft, launched in 2006, flew by the distant ex-planet in 2015.
When the space agency realised New Horizons had fuel left over, they set its sights on Ultima Thule. At that point, Ultima Thule's existence was only known of because it had been detected by the Hubble Space Telescope. It was only discovered in 2014 when it blocked the light of distant stars, and little about it has been known - until now.
"We know it's not round," said John Spencer, a scientist on the New Horizons project, when the first close-up image came in.
The images are pixelated, with each block representing about 10km - Ultima Thule itself is only estimated to be about 30km long.
"I've never seen so many people so excited about two pixels," added Alan Stern, lead scientist on the New Horizons mission.
The photo was taken from about 2 million kilometres away.
Combining several images and using sharpening techniques revealed the object to be elongated, looking somewhat like a bean or peanut.
"We just don't have the details to see it yet," said Dr Spencer. "There's a lot of chatter in the science team room… We're doing everything we can with so little information."
He declined to speculate on what Ultima Thule might be made of, since more images are due over the coming days.
"We know that anything we say is going to be wrong tomorrow."
It takes more than six hours for a signal from New Horizons to reach Earth.
Brian May, guitarist of rock band Queen and a qualified astrophysicist, will release a soundtrack song to mark the mission on Tuesday afternoon (NZ time).