Ceres at Opposition
Posted by Brian Ventrudo
Ceres, the largest asteroid and the brightest of the five dwarf planets of our solar system reaches opposition and maximum brightness this year on December 18. Ceres is nearly as high as it gets for observers in the northern hemisphere, and remains visible in the south well above the northern horizon in the constellation Taurus. Here’s how to spot Ceres in binoculars or small telescope this week, along with a few particulars about this mysterious mini-world…
Ceres was discovered in 1801 by Giuseppe Piazzi. It was first classified as a planet, but as more asteroids were found, Ceres was demoted to rank as the largest asteroid, one of the millions of small bodies orbiting between Mars and Jupiter. Today, Ceres also ranks as a one of five dwarf planets in our solar system along with Pluto, Eris, Makemake, and Haumea. But Ceres is the only dwarf planet in the inner solar system, so it’s by far the closest to Earth and the easiest to observe with small optics.
For the record, the term “dwarf planet” was officially adopted by astronomers in 2006 to describe bodies large enough to pull themselves into a spherical shape through their own gravity, but which is not large enough to clear its orbital paths of other bodies.
The Hubble Space Telescope has taken the best image to date of Ceres (see image at top). You can clearly see the spheroidal shape of this little world along with some tantalizing surface markings. NASA’s Dawn spacecraft, which already examined Vesta in 2011-2012, will enter orbit around Ceres just 6,000 km above its surface in 2015.
Ceres reaches opposition on December 18, 2012 and makes its closest approach to Earth two days later when it comes within 1.68 A.U. (astronomical units). Tangled in the horns of the celestial bull, Ceres will reach magnitude 6.7 on the 18th. That makes it easily visible in any pair of binoculars. Have a look at the images below to show you where to find Ceres. For the next week or so, it makes a squat isosceles triangle with the bright stars Alnath and ζ (zeta) Tauri.
Both Vesta and Ceres linger in this part of the sky for the next few months and remain respectably bright. Here’s a link to finder chart from Sky and Telescope magazine to help you find these objects as they slowly wander across the northern sky…