These two signs represent the asteroid Ceres. At the end of the eighteenth
century a German astronomer,
Johann Bode, discovered that it was possible to calculate the
approximate distance of a planet's orbital path from the sun. He
assigned Mercury 0, Venus 3, and then doubled the number assigned for
each new orbit. Thereafter he added 4 and divided with 10. This
calculation yields for Mercury 0.4 and for the outermost planet Pluto
38.8. (The actual mean distances of the orbits of these two planets
from the sun, in astronomical units, i.e. the distance from the earth
to the sun, are 0.39 and 39.52 respectively.)
There are only two remarkable exceptions to Bode's law known today: the first is Neptune, , the mystical planet, which has its own individual orbit, and the second is an "empty" orbit between Mars and Jupiter. In the first day of the year 1801, however, the astronomer Piazzi (probably as a result of Bode's work) discovered Ceres, a planetoid with a diameter of about 1,000 kilometers. Later a large number of asteroids, i.e. small planets or huge space rocks that vary in size from a diameter of over 500 kilometers to a few meters. There are at least 100,000 such asteroids, but their mass nontheless is smaller than one thousandth of the earth's. Ceres is the largest of them. The sign for the asteroid Ceres is or .
Ceres is the name of an ancient Italic-Roman goddess of corn, agriculture and crop, corresponding to the Greek goddess Demeter, a daughter of Chronos and his sister Rhea.
The biggest of the other asteroids is Pallas, drawn , , or ; Juno, drawn , , or ; and Vesta, drawn , , or .
In botany weeds are sometimes symbolized by .