Astronomers Surprised by Large Space Rock Less Dense than Water
This is really interesting, much of what we think we know about planet formation maybe wrong.
A planetary scientist has identified the largest-known solid object in the Solar System that could float in a bathtub. The rock-and-ice body, which circles well outside the orbits of the planets, is less dense than water — although a bathtub big enough to hold it would stretch from London to Frankfurt.
The body, dubbed 2002 UX25, lies in the Kuiper belt, a reservoir of dwarf planets, comets and smaller frozen bodies beyond the orbit of Neptune. The object’s low density and size — it is 650 kilometers wide — seem to conflict with a leading model for the formation of large solid bodies in the Kuiper belt and throughout the Solar System. Planetary scientist Michael Brown of the California Institute of Technology in Pasadena reports its density measurement in an upcoming issue of The Astrophysical Journal Letters, with a preprint available on the arXiv online repository.
Because objects in the Kuiper belt are believed to have changed relatively little since the early years of the Solar System, the region “offers our best chance to comprehend how the early stages of planet formation unfold”, says planetary scientist Andrew Youdin of the University of Colorado Boulder.
Update 12:11 pm
edited my little comment above the article I’m quoting to make it clearer as to what I meant.