Why is the sun a dwarf planet

Solar system: dwarf planet under a magnifying glass

  1. The dwarf planet Ceres has a diameter of 963 kilometers, making it the largest body in the asteroid belt.

  2. The Dawn space probe spent three years studying Ceres at close range and discovered traces of water that is believed to be part of an extensive layer of brine underground.

  3. Presumably the liquid mass penetrates to the surface after meteorite impacts and leaves visible salt deposits there.

On New Year's Eve of 1801, the Catholic priest and astronomer Giuseppe Piazzi (1746-1826) discovered something special in the sky: a weakly shining object that seemed to move a little night after night. Piazzi, then director of the observatory in Palermo, gave the "wandering star" a name: Ceres, like the Roman goddess of fertility and agriculture.

At first he thought Ceres was a comet, other astronomers believed in a planet. In the middle of the 19th century it became clear that neither was true: The newcomer belonged to a class of its own, the asteroids. As we know today, most of them move between the orbits of Mars and Jupiter around the sun, in the asteroid belt.

This article is included in Spectrum of Science 5/2021

With an equatorial diameter of 963 kilometers, Ceres is by far the largest celestial body and combines 90 percent of the mass of all asteroids. And as the only representative, Ceres has enough of its own gravity for an approximately round shape. In 2006, the International Astronomical Union (IAU) therefore raised the object to the newly created category of dwarf planets, to which Pluto also belongs ...