THE "CELESTIAL POLICE" WHO DISCOVERED CERES.

 In 1772 two German astronomers, Titius and Bode, published an empirical law that described with good approximation the distribution of distances from the Sun of planets that became known as the Titius-Bode Law. 

This extremely simple law was formulated as d=0.4+0.3*2^n, where n was the number of a planet in order of its distance from the Sun.

So for n=-infinity you find d=0.4 AU, which corresponds to the semi-major axis of Mercury, for n=0 you find d=0.7 AU, which corresponds to the distance of Venus, for n=1 you find d=1 UA, corresponding to Earth, and so on for Mars, Jupiter and Saturn. The distances found were in very good approximation to the observed values, and so the formula was a great success. The only oddity was that at n=3 no planet was found.

Just nine years after the publication of this law, in 1781, William Herschel discovered by pure chance the seventh planet in the Solar System: Uranus. Observations then incredibly showed that Uranus also obeyed the Titius-Bode law for n=6.

Some astronomers, now convinced of the validity of the law, then set out to find the missing planet between Mars and Jupiter corresponding to n=3. A network of observatories and telescopes scattered throughout Europe was thus organized with the sole aim of discovering this missing planet. These astronomers jokingly dubbed themselves the Celestial Police.

Just a few years later, in 1801, Giuseppe Piazzi from the Palermo Observatory discovered the missing body, which he named Ceres. Such an object, however, turned out to be strange from the start, as it appeared to be too small to be a planet. Moreover, within a few years, other objects smaller than Ceres were discovered almost on its own orbit. Thus the Main Asteroid Belt was gradually identified, what was left of a planet that could never be aggregated because of the intense gravitational influence due to Jupiter.

Titius-Bode's Law has no scientific rationale behind it, and over the years it has been proven to be pure coincidence, since neither Neptune nor Pluto respects its constraints.

Although it has been shown to be invalid, it is undeniable to recognize the importance that this law had for the discovery of the Main Asteroid Belt.

Credit: NASA, JPL.