New images of the most distant object ever explored have shocked the Nasa researchers who saw them.
The bizarre shape of Ultima Thule – which was once described as being like a snowman, but has been confirmed to be more like two pancakes – could prompt scientists to reconsider our understanding of how planets form, scientists say.
"Nothing quite like this has ever been captured in imagery," said Alan Stern, the principle investigator on the New Horizons mission that explored Ultima Thule. "We've never seen something like this orbiting the Sun."
The new images offer a different perspective on the object, which is floating in the Kuiper Belt on the edge of our solar system. As such, they show that the round object isn't so round at all – when looked at from another view, it is almost flat, which scientists did not expect.
After the first images, scientists nicknamed Ultima Thule the snowman, because it seemed to resembles two spheres stacked on top of each other.
But the new analysis and images change that understanding. In part, that is because they have revealed the outline of part of the object that was initially not visible because it was not lit by the Sun – but could be seen by tracing out the background stars that it had blocked out.
Instead of being a snowman, the two sections are not spherical at all. The bigger part is like a giant pancake and the smaller one is like a dented walnut, the scientists say.
"We had an impression of Ultima Thule based on the limited number of images returned in the days around the flyby, but seeing more data has significantly changed our view," Stern said. "It would be closer to reality to say Ultima Thule's shape is flatter, like a pancake. But more importantly, the new images are creating scientific puzzles about how such an object could even be formed. We've never seen something like this orbiting the Sun."
The images aren't the last to be captured or sent by New Horizons, which began its work on Ultima Thule after exploring Pluto. But they are the last views thatit captured as it raced away after its New Years flyby, travelling past at 31,000 miles per hour.
The images were snapped just 10 minutes after New Horizons passed by its closest approach to the distant object.
"This really is an incredible image sequence, taken by a spacecraft exploring a small world four billion miles away from Earth," said Stern. "Nothing quite like this has ever been captured in imagery."
Much of the scientific data being collected is being used to understand how small planets might have formed in the early solar system. But the shocking and strange shape of Ultima Thule could change that understanding fundamentally, scientists say.
"While the very nature of a fast flyby in some ways limits how well we can determine the true shape of Ultima Thule, the new results clearly show that Ultima and Thule are much flatter than originally believed, and much flatter than expected," added Hal Weaver, New Horizons project scientist from the Johns Hopkins Applied Physics Laboratory. "This will undoubtedly motivate new theories of planetesimal formation in the early solar system."