Most distant world ever visited is shaped like a peanut

Latest images snapped by NASA’s New Horizons spacecraft reveal the contours of ‘Ultima Thule’ — the space rock 2014 MU69.

The peanut-like shape of MU69 is revealed in the latest images from NASA's New Horizons mission.NASA/JHUAPL/SwRI; sketch courtesy of James Tuttle Keane

NASA’s New Horizons spacecraft zipped past the space rock 2014 MU69 on 1 January — making the rock, nearly 6.5 billion kilometres from Earth, the most distant object ever visited. Images taken before the spacecraft’s closest approach at 12:33 a.m. US Eastern time show an elongated blob that resembles a spinning bowling pin.

MU69 is roughly 32 kilometres long and 16 kilometres wide. The two lobes shown in the images could represent a peanut-shaped object or two smaller objects orbiting one another. The rock appears to be spinning almost directly face on to Earth, either once every 15 hours or once every 30 hours.

Three images taken on 31 December by New Horizons show the rotation of MU69.NASA/JHUAPL/SwRI

“It’s almost like a propeller blade,” said team member Hal Weaver, a planetary scientist with the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, where mission control is based.

Snapshots from the outer Solar System

The New Horizons spacecraft is now sending bursts of data and photographs back to Earth. The probe is safe and seems to have gathered all the data it was expected to as it whizzed 3,500 kilometres above the surface of MU69. Mission scientists plan to release higher-resolution images on 2 January.

“Tomorrow we’ll have a world with geology,” says Heidi Hammel, a planetary astronomer and executive vice-president of the Association of Universities for Research in Astronomy in Washington DC. “That’s a really exciting thing.”

Scientists will be looking for features such as craters or fractures on the surface of MU69, which they have nicknamed Ultima Thule.

“We’re going to start writing our first scientific paper next week,” said Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, and the mission’s principal investigator.

New Horizons flew by Pluto in July 2015. Its visit to MU69 is the first to explore an object from the ‘cold classical Kuiper belt’, a collection of distant space rocks that have been essentially undisturbed since the Solar System formed more than 4.5 billion years ago. They lie beyond Pluto’s orbit and represent some of the most primordial material in the Solar System. “This could very well be the pristine sample we’ve been waiting for,” says Hammel.

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