During a press conference this morning, the New Horizons team unveiled a new photo of the Kuiper Belt object Ultima Thule (ull-tee-muh THOO-lee) that clearly shows the Kuiper Belt object’s shape, described as bi-lobate or having two lobes like a peanut in its shell. Given the low resolution of the photo there’s a small chance the asteroid may be two separate objects in close orbit around their center of gravity.
Assuming Ultima is single object, the shape is becoming familiar to anyone who’s been keeping tabs of the various asteroid and comet flybys. There seem to be lots of bi-lobate small bodies in the solar system. Of the tiny number we’ve seen up close, there are the comets 103P/Hartley, 67P/Churyumov-Gerasimenko (the target of the European Rosetta Mission) and 19P/Borrelly, along with asteroids Kleopatra and Toutatis and even Pluto’s moon Kerberos, to name a few.
Why does this appear to bbbe a common shape? First, all of these objects are too small to crunch themselves into spheres through self-gravity, and second, they likely formed through collisions with or proximity to other small objects. Everything in the solar system started from the ground up to speak, with smaller objects forming first that later coalesced into planets, where there was enough material available. When the material was sparse or disturbed by the gravity of the growing planets, body-building never got beyond the bits-and -pieces stage.
New Horizons is now speeding past Ultima at 32,000 mph never to return, but the data is downloading across space and time — 4 billion miles and more than 6 light-hours — as you read this. Tomorrow, we’ll see the first detailed black-and-white images with low resolution color pictures later this week. The highest resolution color photos will have to wait until sometime in February.