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Home / Science / We finally learn more about MU69, the strange, flat rock in the outer solar system

We finally learn more about MU69, the strange, flat rock in the outer solar system



MU69
Image: NASA / Johns Hopkins Applied Physics Laboratory / Southwestern Research Institute, National Optical Astronomy Observator

New Horizons mission scientists have published the first expert-verified results of their 2014 MU69 study shows how "immaculate" this object is.

(486958) 2014 MU69, nicknamed Ultima Thule, appears to be a pair of crumpled stones, each about 16 kilometers in diameter. It orbits the sun at a distance of approximately 4 billion miles (Pluto orbits approximately 3.7 billion miles). It seems to have remained relatively unchanged from the first era of the solar system, and it already showed some surprises when the spaceship New Horizon retransmitted its first images – and now these first results are published and reviewed. But this team is just starting.

"It's still very early," said Alan Stern, chief investigator for the New Horizons mission, to Gizmodo. "We're just getting to the point where we can catch our breath."

Astronomer Marc Buie discovered the pixel-wide MU69 in 2014 with the Hubble Space Telescope, and the New Horizons scientists focused their ship's visor on the object after a successful campaign with images of the dwarf planet Pluto. The object is a cold classic object of the Kuiper Belt, meaning that it orbits the Sun in a relatively circular, undisturbed orbit. Untouched is the theme when it comes to this rock. The authors of the study call it "immaculate". Basically it's like a time capsule from the beginning of the solar system that has not been changed by the influence of the sun or other planets.

New horizons flew past the object and took Detailed Observations on January 1, 2019, and today the mission's scientists have published their first published expert-reviewed results in the journal Science. Their first analysis revealed a few important things: First, the object is a two-lobed contact binary, which means that two stones collided relatively slowly. Surprisingly, these stones are flattened and not spherical. Second, there is no evidence of rings, satellites, dust, gas atmosphere, or interactions with the solar wind. Third, brightness and texture appear to vary across the subject, with pits and lighter areas of bright material, but the composition itself does not seem to vary.

These are just initial results, and scientists will be downlinking data from New Horizons for at least another year. However, the researchers are already trying to understand the history of MU69. The object appears to have formed after two nearby homogeneous pebbles fused under the influence of gravity and then slowly fused together.

Scientists studying planetary formation are excited by the idea of ​​this pristine world. "We see something that looks more or less like the end of planetary formation, where it is right now," said Christa Van Laerhoven, postdoctoral fellow at the University of British Columbia New Horizons team, Gizmodo said. She explained that MU69 exists in a size that is a bit too large for electromagnetism to be the dominant force, and a little too small to handle the effects of gravity in the planetary creation process.

And the flattened shape of the object is especially mysterious. "It's a bit surprising that something so flat exists in the outer solar system," said Kat Volk, Associate Staff Scientist at the University of Arizona, who is not part of the New Horizons team, to Gizmodo. Physicists usually assume that things in space are spherical. To understand how MU69 finally looked like it looks, you have to think twice.

However, this is just an object Kuiper belt. "If only we could see more of them, that would be really great," said Volk. "Especially in this size range, which is hard to see from the ground [on Earth.]"

The New Horizons team hopes to further explore Kuiper Belt objects and the intervening space, and possibly even fly past another object schedule as the spaceship resumes its journey away from the sun, Stern said. But before that, there are certainly more secrets waiting to be found in the data still to be downloaded.


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