|Understanding of cosmic motion in 1700
A comet heading towards Earth: the first NEO
by Giovanni Valsecchi
The comet was
then observed until the first days of October. A serious
problem soon became clear to astronomers: although the
ephemeris by Pingre' had allowed the recovery of the
comet in August, it was clearly incapable of accounting
for the entire set of observations. Prosperin tried to
use three parabolas to fit separately the observations of
June, August, and September, but this was evidently
unsatisfactory, and unjustifiable from the point of view
of celestial mechanics.
|Who is Messier and what is the Messier
Charles Messier was a French astronomer, born on June 26, 1760 (1760-1817). He became an astronomer, inspired by childhood sightings of comets and a by a solar eclipse visible from his home town of Badonvillier. Messier is one of the most famous comet hunters. He baecame famous for having kept careful records of his observations: while hunting for comets, during the years from 1758 to 1782, Messier compiled a detailed list of approximately 100 diffuse objects that were difficult to distinguish from comets but that couldn't possibly be comets (since they did not move with respect to the background stars). This list became famous as the Messier Catalog , and is today well known as a collection of the most beautiful objects in the sky including nebulae, star clusters and galaxies. In fact, it was the first reliable list of this kind and today's versions of the catalog usually include also later additions of objects observed by Messier. The objects that are catalogued on Messier list are still referred to by their Messier Number, as for example the first object in his catalog, the Crab Nebula M1.
|Who is Lexell?
(sometimes known by the Russian version of his name,
Andrei Ivanovich Lexell) was born on 24, December 1740 in
Sweden and died on 11 December 1784. He studied and
graduated in Sweden, where he first became appointed
professor of mathematics. He was then invited to the St
Petersburg Academy of Science, where he started working
from 1769 with Euler and other high quality scientists,
becoming appointed professor of astronomy in 1771.
|What are comets made of?
Comets: these strange snowballs! by Livia Giacomini
But exactly, what is a comet? Nowadays, comets are seen as dirty snowballs (or icy mudballs). In fact, comets are thought to be made of a mixture of ices and dust that wasn't incorporated into the planets when the solar system was formed. This is the main reason why they are believed to share the same composition of the primordial solar system, having formed essentially form the same material. Click here to know more about comets' composition