Next week – on February 1, 2018 – Earth will come closest to the dwarf planet Ceres for this year, and this small world, in turn, will shine at its brightest best in our sky. However, February 1 is one day after the full supermoon and eclipse, and the waning gibbous moon will still be plenty bright that night. So start looking around January 25 or 26 – or wait until the end of next week, around February 3 or 4, when the moon will have left the early evening sky – to seek for Ceres.
At a distance of 1.6 astronomical units on February 1, this will be Ceres’ closest approach to Earth since February 25, 2009.
Although not visible to the eye alone, Ceres – largest body within the asteroid belt and the first asteroid to be discovered, in 1801 – is a fairly easy binocular object. You just need to know where and how to look.
Ceres is now considered a dwarf planet, and it’s the only one of five recognized dwarf planets to reside within the inner solar system. Ceres accounts for a full one-quarter of the mass in the asteroid belt, which consists of hundreds of thousands (perhaps millions?) of tiny worlds circling the sun in between the planets Mars and Jupiter.
Ceres is now in front of the faint constellation Cancer and will remain there until mid-May 2018. So, your ticket to star-hopping to Ceres necessitates a good familiarity with the constellation Cancer and a detailed sky chart, which you can find here.
Ceres will look like a faint star through binoculars. Unlike the backdrop stars, which appear fixed relative to one another, Ceres will betray itself as it changes its position, moving noticeably westward in front of this constellation after a few to several days.
The best way to see it is to locate the field of which Ceres is part. Perhaps draw or photograph the star the field. Then watch over several nights for the object that moves.
This movement of Ceres enabled Giuseppe Piazzi, an Italian monk, to discover Ceres in January 1801. At that time, Ceres was in front of the constellation Taurus the Bull. He noted over the following nights that Ceres had changed its position relative to the backdrop stars, meaning this object was a solar system object and not a star.
Bottom line: Earth and Ceres will be closest for 2018 on February 1. Ceres hasn’t been this close since 2009. Start looking for this tiny world – largest body in the asteroid belt – now.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.