It's getting bigger.
Last week, NASA released photos of the New Horizons space exploration ship gradually approaching an ancient little-known object in deep space called Ultima Thule.
Ultima orbits the sun 1 billion miles from Pluto, and Nasa hopes to approach the distant object just after midnight on January 1, 2019.
It will be humanity's furthest encounter with another world.
"What will Ultima reveal? No one knows," wrote Alan Stern, NASA's planetary scientist who heads the deep space mission last week.
NASA Ultima suspects is a type of icy mass formed about 4.5 billion years ago during the early solar system.
But since then, hovering in the deep cold regions of the solar system, Ultima has been presumed to have largely been preserved in its primitive and primitive state – allowing scientists to see the distant past.
"In fact, Ultima should be a valuable window into the early stages of planet formation and into what the solar system was for over 4.5 billion years," Stern said.
Ultima is formally classified as a "Kuiper Belt Object," which is a ring of icy worlds that surrounds the solar system beyond the last great planet, Neptune. It is a "leftover region early in the history of the solar system," NASA says.
Ultima has already proven to be a bit mysterious.
From previous images, scientists have discovered that Ultima probably has a strange, non-spherical shape. But as the New Horizons approaches, the Ultima light pattern, or its light curve, is inconsistent. With most other objects, these patterns of light are repeated when objects rotate.
"It's really a puzzle," Stern said in a statement.
Other New Horizons scientists have said that a cloud of dust or moons "falling" around Ultima may be producing the strange curve of light.
But there is one thing that is almost certain.
On December 15, Stern's team concluded that there were no obstructions between the New Horizons – a triangular spacecraft 7 feet long and 9 feet high – and Ultima Thule.
Stern told NASA that the space probe is now "Go" to approach Ultima.
In the summer of 2015, New Horizons flew by Pluto. It captured unprecedented details of the dwarf planet, its mountains, cliffs, and icy plains. The exploration vessel flew 7,000 miles from the surface of Pluto.
But it will get much closer to Ultima Thule, 2,200 miles above the little-known object.
The first images are expected on New Year's Day, about 30 minutes after the ball falls in Times Square.
"Ultima Thule's flight will be fast, challenging and will bring new insights," Stern said.
"To be the farthest exploration of anything in history, will also be historical."
We'll be watching.
To watch the images arrive during the approach of the Ultima, tune in to a livestream of NASA TV begins around 12:15 AM on January 1, 2019.