Right on cue, more images have returned to Earth from New Horizons, bringing Ultima Thule into sharper focus. Where yesterday's images showed just a few blurry pixels that looked like a bowling pin, the new photos reveal the rocky world to be more of a "snowman" shape, confirming its identity as a contact binary consisting of two large spheres.
These new images were taken from a distance of 17,000 miles (27,000 km), about 30 minutes before New Horizons made its closest approach to the object. From this vantage point, the science team was able to confirm that Ultima Thule isn't two separate objects in an extremely close orbit, but one object formed when two smaller pieces smashed into each other billions of years ago.
The spacecraft is kitted out with various instruments to examine Ultima Thule in more detail. The Long-Range Reconnaissance Imager (LORRI) is responsible for the relatively high-resolution images, while the Multispectral Visible Imaging Camera (MVIC) is able to get a sense of the object's color. By combining red, blue and near infrared light, the instrument shows Ultima Thule as a reddish-brown color, confirming long-standing data collected through other methods.
The New Horizons team was also able to pin down Ultima Thule's size more accurately. As a whole, the little world measures 19 miles (30.5 km) long. The larger sphere, which the team has now dubbed "Ultima," is 12 miles (19 km) wide, while the smaller one, "Thule," measures 9 miles (14.5 km) across. That means the object is slightly shorter but a bit wider than was believed just yesterday.
According to the researchers, Ultima Thule's two pieces would have come together in the early days of the solar system, around four and a half billion years ago. From its cold, quiet position some 4 billion miles (6.4 billion km) from the Sun, Ultima Thule is basically a time capsule for that period.
"New Horizons is like a time machine, taking us back to the birth of the solar system," says Jeff Moore, team lead of New Horizons Geology and Geophysics. "We are seeing a physical representation of the beginning of planetary formation, frozen in time. Studying Ultima Thule is helping us understand how planets form – both those in our own solar system and those orbiting other stars in our galaxy."
These new images are a huge improvement over earlier snaps, but New Horizons is far from finished. Much higher resolution images are still incoming over the next few days and weeks – after all, these photos were taken when the craft was almost 10 times further from the object than it got at its closest pass. Other data will continue streaming in for another 20 months, so for now we just have to be patient – it takes a while to download photos from the fringes of the solar system.