Ceres (dwarf planet)
Ceres is the largest object in the asteroid belt.
It is sometimes assumed that Ceres has been "re"classified as a dwarf planet, and that it is therefore no longer considered an asteroid. For example, a news update at Space.com spoke of "Pallas, the largest asteroid, and Ceres, the dwarf planet formerly classified as an asteroid", whereas an IAU question-and-answer posting states, "Ceres is (or now we can say it was) the largest asteroid", though it then speaks of "other asteroids" crossing Ceres' path and otherwise implies that Ceres is still considered an asteroid. The Minor Planet Center notes that such bodies may have dual designations. The 2006 IAU decision that classified Ceres as a dwarf planet never addressed whether it is or is not an asteroid. Indeed, the IAU has never defined the word 'asteroid' at all, having preferred the term 'minor planet' until 2006, and preferring the terms 'small Solar System body' and 'dwarf planet' after 2006. Lang (2011) comments "the [IAU has] added a new designation to Ceres, classifying it as a dwarf planet. ... By [its] definition, Eris, Haumea, Makemake and Pluto, as well as the largest asteroid, 1 Ceres, are all dwarf planets", and describes it elsewhere as "the dwarf planet–asteroid 1 Ceres". NASA continues to refer to Ceres as an asteroid, as do various academic textbooks.
Extraterrestrial skies
The asteroid 87 Sylvia is one of the largest main-belt asteroids and the first asteroid observed to have two moons. These moons, Romulus and Remus, would appear roughly the same size. Romulus, the farther one, would be about 0.89° across, slightly bigger than the closer but smaller Remus, which would be about 0.78° across. Because Sylvia is far from spherical, these values can vary by about a little more than 10%, depending on where the observer is on Sylvia's surface. Since the two asteroidal moons appear to orbit (as best we can tell) in the same plane, they would occult each other once every 2.2 days. When the season is right, twice during Sylvia's 6.52 year orbital period, they would eclipse the Sun, which, at 0.15° across, is much smaller than when seen from Earth (0.53°). From Remus, the inner moon, Sylvia is huge, roughly 30°×18° across, while its view of Romulus varies between 1.59 and 0.50° across. From Romulus, Sylvia measures 16°×10° across, while Remus varies between 0.62° and 0.19°.