Ceres
Ceres was discovered on 1 January 1801 and announced as a new planet. Today it is classified as a dwarf planet in the main asteroid belt between Mars and Jupiter.
Briefing
Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the main asteroid belt between the orbits of Mars and Jupiter. It was the first known asteroid, later reclassified as an asteroid, and more recently described as the only confirmed dwarf planet within the orbit of Neptune and the largest without a moon.
How we know
For much of its history, Ceres was an object mostly inferred rather than closely inspected: its surface features were described as barely visible even with the most powerful telescopes, and little was known about it. That changed when the robotic NASA spacecraft Dawn approached Ceres for its orbital mission in 2015, observing the surface directly and finding it to be a mixture of water, ice, and hydrated minerals such as carbonates and clay. Dawn also returned gravity data, which suggest Ceres to be partially differentiated into a muddy (ice–rock) mantle/core and a less dense layer above.
- Field conditions
- Even at its brightest, Ceres is too dim to be seen by the naked eye except under extremely dark skies. Its apparent magnitude ranges from 6.7 to 9.3, peaking at opposition once every 15- to 16-month synodic period.
