Far away on the cold, dark edges of the Solar System – past the rocky inner planets, beyond the gas giants, a billion miles farther than Pluto – drives a small, frozen world, scientists still I am not Definitely, whether it is one or two worlds.
Astronomers call it Ultima Thule, an old concept of cartography called "beyond the known world". His name is indicative of his location in the Kuiper belt, the unexplored "third zone" of our solar system, populated by millions of small, icy bodies.
Although numerous, no object of the Kuiper Belt has ever been seen up close. NASA's two Voyager probes, which crossed the third zone decades ago, might have looked at one of these probes if they had been fitted with the right instruments, except that the Kuiper belt had not yet been discovered , On New Year's Eve, NASA will for the first time get a chance with one of those enigmatic space rocks. At 9:33 pm PST, 33 minutes past midnight on the East Coast, the agency's New Horizons probe will briefly pass Ultima Thule, making it the farthest object ever to be visited by a spacecraft.
Astronomers have almost no idea what to expect. "What will it look like? Nobody knows. What is it made of? Nobody knows. Does it have rings? Moons Does it have an atmosphere? Nobody knows. But in a few days, we'll open the gift, look in the box and find out, "says Alan Stern, the mission's lead investigator.
New Horizons has been traveling for 1
The New Horizons trajectory will bring them three times closer to Ultima Thule than it does Pluto did that when it passed in the summer of 2015. The photographs broadcast by New Horizons at that time were the most detailed ever recorded, not only on the former planet, but also on the outer solar system. Because of the proximity, the images captured by the Ultima Thule probe become even more detailed and from a billion miles down in space. "Pluto opened the doors for us," says Stern, "but now it's about something much more poaching and woolier."
Stern and his team discovered the object in 2014 with the Hubble Space Telescope as the sky sought out places that New Horizons could visit after his brief time encounter with Pluto. In these first pictures, Ultima was just a globe of pixels, moving every few minutes against a background of moving stars.
In recent images taken with the New Horizons Long Range Reconnaissance Imager, the object still seems to be a patch in a sea of much brighter patches. "If you look for it, it looks like stars are puking all over the pictures," says planetary scientist Amanda Zangari, who spent most of December collecting Ultima Thule position and brightness measurements. "To see the damned thing in the first place, you have to stack several images that take into account the distortion between them and subtract the stars." With 1/100 of the diameter of Pluto and 1/10 000 of its brightness, Ultima Thule represents an elusive quarry than the ancient planet.
Through their observations, the team found that Thule (whose official name is 2014 MU69)) is either two separate objects orbiting at close range, or a pair of bodies that move toward each other until they unite and the form two rags of something astronomers call Contact Binary. In any case, the data suggest that Ultima is no more than 20 miles across, dark as reddish dirt, and well within reach of New Horizons fuel supplies.
It's probably very, very old too. That's why astronomers are so excited to study it up close.
It is believed that objects of the Kuiper belt, such as Ultima Thule, are remnants of the formation of the Solar System – the cosmic waste left over from the formation of the planets about 4.6 billion years ago. This makes them a tempting target for astronomers: many of these objects are not only ancient, they are also, astronomers think, perfect at temperatures approaching absolute zero. (So far away is Ultima Thule from the sun's warming sunbeams that our parent star would appear on its surface to an observer about the size of Jupiter from here on Earth). NASA's plan to visit one, map its features, study its composition, recognize its atmosphere (if any), and seek satellites and wrestling is more than just a flyby. It is an archaeological expedition of cosmic dimension and consequence.
New Horizons will investigate Ultima with the same instruments she used to test the Pluto system in 2015. A trio of optical devices captures images of the object in color and black-and-white, mapping its composition and topography, and looking for gases emanating from its surface. Two spectrometers are also looking for charged particles around Ultima Thule. a radioscience instrument measures its surface temperature; A dust counter detects stains from interplanetary debris. The piano-sized probe is fully loaded and weighs a hair that weighs over 1,000 pounds, and uses less energy than a pair of 100-watt incandescent bulbs to power its equipment.
After New Year's Eve, New Horizons will continue on their way out of the Kuiper Belt. But the third zone is huge. Even at a speed of almost nine miles per second, the spacecraft needs a decade to cross and enter interstellar space. Stern and his colleagues will use this time to search for another destination – one that is further from the Sun than Ultima Thule, and perhaps even more mysterious. This is a tantalizing prospect for the New Horizons team. "To visit a place you do not know about," says Weaver. "That's exploration at its best."
More about the New Horizons Mission
- In 2015, New Horizons passed Pluto and gave astronomers their best ever view of the former planet and its moons.
- NASA probe traveled about 3 billion kilometers to Pluto. It has taken another billion to reach Ultima Thule.
- How does New Horizons transfer all his observations back to Earth when it is so far away? Very slowly.