who came up with the asteroid theory?

Answer 1

The word "asteroid" was coined by Sir William Herschel (the discoverer of the planet Uranus) in 1802 shortly after the discovery of 2 Pallas by H. W. Olbers in Bremen. The word means "star-like" i.e. a point of light (rather than a distinct disk, such as planets present to the eye/telescope),

In 1801 Giovanni Piazzi in Palermo, Sicily had discovered 1 Ceres and it was immediately hailed as a planet (what else could they call it? There was no other term in use.)

I need to explain by way of background that for some 35 years it had been predicted by the Titius-Bode Law (a mathematical hypothesis devised by Johann Titius in 1766 and popularised by Johann Elert Bode in 1772 for the distance between the planets) that there was a "Missing Planet" between Mars and Jupiter and that it would be at approx 2.8 AU from the Sun.

When Uranus was discovered in 1781 and it happened to fit fairly neatly into the series (predicted distance from the Sun 19.6 AU, actual distance 19.2 AU) postulated by the Titius-Bode Law, a tremendous impetus was given to the hunt for the "Missing Planet". Up till then, the Law had been regarded as interesting, but of no great importance.

Based on this discovery, Bode urged a search for a fifth planet. Ceres, the largest object in the asteroid belt, was found at 2.77 AU from the Sun, very close to the Titius-Bode predicted position in 1801. Bode's law was then widely accepted until Neptune was discovered in 1846 and found not to satisfy it.

However Herschel was unhappy. Ceres was disappointimgly small, he felt, to be regarded as a planet alongside Uranus and the 5 planets known since antiquity. It was also smaller than most of the 14 known moons in the solar system, 4 of which Herschel had discovered.

The further discovery of 2 Pallas the following year, which was smaller still, only confirmed him in this pessimistic view and his idea in creating a new category of asteroids was that the new bodies should be so classified, rather than as planets.

However that was just his view, and when 3 Juno and 4 Vesta were discovered in 1804 and 1807, respectively the concensus among astronomers was to regard them all as planets.

They had no idea that there were thousands of such objects in the asteroid belt (we now know of some 342,500) and when no further such planets were discovered for another 38 years (5 Astraea was discovered in 1845 shortly before Neptune in 1846) could be forgiven for thinking they had found all there were to be found.

However the numbers then started to mushroom, reaching 15 by 1851 and 107 by 1867. The new discoveries from 5 Astraea through 15 Eunomia were added to the list of planets which burgeoned to 23 in the process,

Ceres remained a planet till the 1860s but eventually, faced with the prospect of the number of planets escalating out of control, astronomers came round to Herchel's view (he was long since dead by then), and called them all asteroids and demoted them from planetary status,

IN SUMMARY

The idea that there was such a thing as an asteroid (different from a planet) was initially one man's, William Herschel's, but half a century later the astronomical community finally came round to his way of thinking.

Answer 2

The first asteroid to be observed, Ceres, was discovered in 1801 by Joe Piazzi.

If you're thinking about theories of how the asteroids came to be, see http://en.wikipedia.org/wiki/Protoplanetary_disc

Answer 3

What is the asteroid theory ?

Answer 4

There is no such thing as "the asteroid theory".

Answer 5

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Answer 6

YOU DID! congratulations!