A NASA probe goes full speed to fly over the most distant celestial object ever studied, an icy relic of the early days of the solar system called Ultima Thule, on a journey that should culminate on New Year's Day.
The unmanned probe called New Horizons is on its way to its destination, about 6.4 billion kilometers from Earth, where it is expected to arrive on January 1 to fly over this space object at a distance of 3,500 kilometers.
That is more than three times closer than the distance that this same probe approached Pluto in 2015. "This is actually the most primitive object a probe encountered," says Hal Weaver, a scientist at the UK Applied Physics Laboratory. Johns Hopkins University. Scientists are not sure of its exact size, but believe it to be about 100 times smaller than Pluto, which measures about 1,500 km in diameter.
The Ultima Thule is located in an icy area of space, suggesting that it is well preserved. "It's really a remnant of the formation of the solar system," says Weaver.
Ultima Thule is located in the Kuiper Belt, a vast disk that results from the time of the formation of the planets that astronomers sometimes call. the "attic" of the solar system. Scientists did not know that this Kuiper belt existed until the 90s.
It is about 4.8 billion kilometers from the Sun, even further than the orbit of Neptune, the planet farthest from the star. This belt "is literally replete with billions of comets, millions of objects like Ultima Thule – called planetesimals, the elements from which the planets were formed – and a handful of continent-sized dwarf planets like Pluto," explains Alan Stern, researcher at New Horizons.
"This is important to us in the science of the planets because this region of the solar system, far from the Sun, preserves the original conditions of 4,500 million years ago"he adds. So when we fly over Ultima, we can see how things were at the beginning. "
The New Horizons spacecraft travels through the universe at a speed of 51,500 kilometers per hour, or about 1.6 million kilometers per day.
At this speed, if you hit an object as small as a grain of rice, the probe can be destroyed instantly.
But if he survives the voyage, the ship will take hundreds of photos of Ultima Thule, with the hope of revealing its form and its geology. New Horizons sent impressive images of Pluto in 2015, some of which showed a heart shape on the surface of the planet never seen before.
This time around, "we're going to try to take pictures with a resolution three times larger than we had for Pluto," says Stern. But overflight "requires extremely accurate navigation, much more than we've ever experienced before, maybe we'll get there, maybe not."
Ultima Thule was discovered by the Hubble Space Telescope in 2014. Scientists noticed in 2017 that Ultima Thule is not spherical, but possibly elongated. It may even be two objects.
And that does not project the light that scientists expect to see on a rotating object, which raises many questions. It may be that it is surrounded by cosmic dust. Little moons? Oriented in such a way that its poles face the approaching ship?
The US space agency hopes the mission will provide answers. The first images should arrive the afternoon of January 1 and be published the next day.
Although it is not possible to transmit live images at this distance, NASA plans to broadcast live during the fly-over with the soundtrack to Brian May's Ph.D. in astrophysics. "Gathering these two aspects of my life, astronomy and music, was an interesting challenge," said former singer Freddie Mercury's partner at Queen.