Welcome to our solar system, Ammonite!

Ammonite, captured over several hours. Image credit: NAOJ, ASIAA

I imagine many of you have already heard this but just in case you might think I need to be notified by email or social media, yes, I know. And, yes, it’s very cool!

The Subaru telescope located at the Mauna Kea Observatory on Hawai’i has “found a new world within our Solar System,” affectionately (I hope) nicknamed ‘Ammonite‘ (more officially listed as ‘2023 KQ14’) by the team who spotted it. While they call it a ‘world’, it’s not a planet; technically, Ammonite is a sednoid, that is, a trans-Neptunian object with a large, semi-major axis and highly-eccentric orbit. And this one is pretty eccentric, with its perihelion between 50 and 75 AU and aphelion about 252 AU.1

I’m guessing this tiny new world (its diameter is calculated at somewhere between 220 and 380 kilometers) was dubbed Ammonite because, well, what else are you going to call a rock discovered by the FOSSIL (Formation of the Outer Solar System: An Icy Legacy) project? But I think it’s an excellent name, and will amuse myself by believing in my heart of hearts that really it’s named in honour of a certain novel. After all, NASA/JPL have already named a crater on Europa ‘Uaithne’…

Fir the geeks among us, there’s lots more info in this Nature article.

One AU (astronomical unit) is the distance between the earth and sun ︎