We’d never flown past or imaged a small, isolated Kuiper belt object before. Here’s what we know so far.
As 2018 ended and 2019 began, NASA’s New Horizons flew past its first target after Pluto: 2014 MU69.
Nicknamed Ultima Thule, it’s transformed from a single pixel in our detectors to a red-hued, mottled snowman.
The first three weeks of data have revealed spectacular details concerning this distant world.
Aside from its inactivity, it conforms perfectly to our expectations of cometary nuclei.
In 1986, Halley’s comet was imaged by the ESA’s Giotto mission, revealing a two-lobed core.
Similarly, Deep Impact’s 2010 pictures of comet Hartley 2 revealed volatile-laden lobes connected by a smooth neck.
But the ESA’s Rosetta mission set a new standard in cometary imaging.
Its now-legendary snapshots and movies of comet 67P/Churyumov-Gerasimenko show offgassing, plumes, and even snow.
Volatile, icy materials are abundant on these comets, and change phase rapidly when they’re exposed to sunlight.
Ultima Thule is currently rotating and tumbling in a similar fashion to these known, close-in comets.
The only difference? It’s still incredibly distant from the Sun, causing its ices to remain intact.
Ultima Thule looks just like a typical cometary nucleus, marking the first time we’ve imaged one in its place of origin: the Kuiper belt.
Mostly Mute Monday tells the scientific story of an astronomical phenomenon or object in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.