Science & Technology

First MU69–Ultima Thule–insights returned by New Horizons probe

Main image: The clearest image of MU69--Ultima Thule--captured by the New Horizons probe (NASA)
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The first data is back from NASA’s New Horizons probe’s encounter with MU69, also known as Ultima Thule–a primordial object that likely formed at the very dawn of the solar system.

On the first day of 2019, NASA’s New Horizons Spacecraft conducted a flyby of MU69 —otherwise known as Ultima Thule– a distant object orbiting in the outer reaches of the Solar System.

In fact, at 6.6 billion kilometres from Earth, the encounter represents the most distant object ever examined up close and personal by any space agency.


An artist’s depiction of MU69, also known as Ultima Thule, a solar system body about to be visited by the New Horizons spacecraft (NASA. John Hopkins. Parker)

Now, less than six months later, Alan Stern and his colleagues present the first results from the probe’s investigation, showing that MU69–
a 35-kilometre-wide object some 6.6 billion kilometres away– is an ancient relic that has remained largely untouched — even by the heat of the Sun — since its formation roughly 4.5 billion years ago.

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The New Horizons spacecraft skimmed Pluto back in 2015 on its way to the furthest reaches of the solar system and into the Kuiper Belt — a region of the beyond the orbit of Neptune populated by small icy bodies. 

The Kuiper Belt–where MU69 is located–comprised of icy-bodies- referred to as Kuiper Belt objects (KBOs) or trans-Neptunian objects (TNOs)- lying beyond the orbit of Neptune. These icy-bodies can be loosely defined as the remnants of the early history of the solar system.

Ultima Thule is what is known as a ‘Cold Classical Kuiper Belt Object’ — a class of objects which are thought to be largely undisturbed since the Solar System’s formation as a result of their stable orbit and weak heating from the distant Sun. This means unspoiled objects like MU69 preserve clues about the early history of the Solar System.

The authors describe results from the New Horizons data that was transmitted back to Earth in the first few weeks after the flyby. Their analysis indicates that MU69 has a flattened bi-lobate shape, probably formed by the gentle collision of two smaller objects. 

Discrete geological units were identified on the surface, but there is little in the way of variation in colour and composition. No moons, rings or dust clouds were found orbiting MU69; nor is there any evidence of an atmosphere. 

According to Stern et al., the insights gained in this study are based on only about 10% of the total data collected during the flyby; the full data transmission from the spacecraft to Earth is expected to be complete in 2020.

Main image: The clearest image of MU69–Ultima Thule–captured by the New Horizons probe (NASA)

Original research: https://science.sciencemag.org/cgi/doi/10.1126/science.aaw9771

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