Closing in on Ultima Thule: New Horizons takes first images of distant KBO

The first views of Ultima Thule from New Horizons. The left image is composed of 48 exposures, taken on Aug. 16, 2018. The right image is a magnified view of the area inside the yellow box in the left image. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

NASA’s New Horizons spacecraft is rapidly closing in on its next target – a small Kuiper Belt Object (KBO) called Ultima Thule (aka 2014 MU69), and has now obtained its first actual images of the distant object. New Horizons will conduct a close flyby of Ultima Thule on Jan. 1, 2019, similar to its flyby of Pluto in 2015. Ultima Thule is much farther from the Sun than Pluto, and also much smaller than Pluto, so it is very difficult to see, even with the best telescopes. But that will soon change however, as New Horizons prepares for its encounter with the most distant object in the Solar System to ever be visited by a probe from Earth.

New Horizons is currently still more than 100 million miles away from Ultima Thule, but getting closer every day. The New Horizons mission team was actually a little surprised that the Long Range Reconnaissance Imager (LORRI) camera on the spacecraft was able to see its target already. This first set of 48 images was taken on Aug. 16, 2018. The images are the farthest ever taken from the Sun, breaking the record set by Voyager 1’s “Pale Blue Dot” image of Earth, taken way back in 1990. Ultima Thule still just looks like a bright dot in the new images, but that will change as New Horizons gets closer over the next few months.

“The image field is extremely rich with background stars, which makes it difficult to detect faint objects,” said Hal Weaver, New Horizons project scientist and LORRI principal investigator from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “It really is like finding a needle in a haystack. In these first images, Ultima appears only as a bump on the side of a background star that’s roughly 17 times brighter, but Ultima will be getting brighter – and easier to see – as the spacecraft gets closer.”

Artist’s concept of Ultima Thule, the next flyby target for NASA’s New Horizons mission. The first images still only show it as a bright dot, but in a few months, we will see it up close for the first time ever. Image Credit: NASA/JHUAPL/SwRI/Alex Parker

These first images will help the mission team refine the course that New Horizons is on, in preparation for the flyby next January. Closest approach for New Horizons is scheduled for 12:33 a.m. EST on Jan. 1, 2019. The team determined that UT is still exactly in the position that is was estimated to be previously, based on data from the Hubble Space Telescope.

“Our team worked hard to determine if Ultima was detected by LORRI at such a great distance, and the result is a clear yes,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado. “We now have Ultima in our sights from much farther out than once thought possible. We are on Ultima’s doorstep, and an amazing exploration awaits!”

Ultima Thule will be the most distant object ever explored so far in our Solar System, about 1 billion miles farther out than Pluto!

Last month, astronomers watched Ultima Thule pass in front of a star (a stellar occultation). This data will also help the mission team refine the trajectory of New Horizons ahead of its flyby this coming January.

Ultima Thule orbits the Sun about a billion miles farther out than Pluto. The yellow line shows the trajectory of New Horizons as it continues past Pluto and approaches Ultima Thule. Image Credit: NASA/JHUAPL/SwRI/Alex Parker

“This occultation will give us hints about what to expect at Ultima Thule and help us refine our flyby plans,” said New Horizons occultation event leader Marc Buie of the Southwest Research Institute in Boulder, Colorado.

Ultima Thule is a tiny world, and New Horizons will fly past it at a much closer distance than it did Pluto – about 3,000 kilometres (1,900 miles) from the surface. There is some evidence that it could resemble Comet 67P or be an “extreme prolate spheroid,” like a skinny football, or even a close binary pair – where two bodies are orbiting very close together or even touching, or perhaps a single body with a large chunk taken out of it. Ultima Thule appears to be no more than 30 kilometres (20 miles) long, or, if a binary, each body about 15-20 kilometres (9-12 miles) in diameter.

“This new finding is simply spectacular,” said Alan Stern, mission principal investigator from the Southwest Research Institute (SwRI) in Boulder, Colorado. “The shape of MU69 is truly provocative, and could mean another first for New Horizons going to a binary object in the Kuiper Belt. I could not be happier with the occultation results, which promise a scientific bonanza for the flyby.”

It is also thought that Ultima Thule could have a moon.

New Horizons provided the first close-up views of Pluto and its moons in 2015. In a few months, we will also have the first views of the next target, Ultima Thule. Photo Credit: NASA/JHUAPL/SwRI

New Horizons gave us the first close-up views of Pluto and its moons, revealing incredible worlds like no others in the Solar System. And now, in just a few more months, we will also have the first views of Ultima Thule. Scientists have some idea of what to expect, but as usually happens in planetary exploration, there will likely be some surprises as well.

The first images of Ultima Thule don’t show much, but they are tantalizing, and soon enough we will see this lonely little object up close for the first time ever. Seeing a new world for the first time is one of the most exciting things about planetary exploration.

This article was first published on AmericaSpace.


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