The Astronomy Book

82

I

n the space of 75 years across

the 18th and 19th centuries,

two new planets were

discovered, bringing the number

of known major planets to eight

(including Earth). However, the

circumstances under which

Neptune was found in 1846

were very different from those

that resulted in the accidental

identification of Uranus in 1781.

In between these two discoveries,

many other bodies were found in

the solar system, showing that

it contains a far greater number

and variety of objects than had

previously been imagined.

Powers of observation

Briton William Herschel is

considered by many to have been

the greatest visual astronomer of

all time. He built better telescopes

than any of his contemporaries

and was an obsessive observer

of apparently boundless stamina

and enthusiasm. In addition, he

persuaded members of his family

to help his enterprises, notably

his sister Caroline, who gained

recognition as an astronomer

in her own right.

William was not looking for a

planet when he noticed Uranus, but

his discovery was a consequence

of his skill at telescope-making and

systematic approach to observing,

which enabled him to spot the

movement of the planet over time.

Herschel also studied double and

multiple stars, cataloged nebulae

and star clusters, and attempted to

map the structure of the Milky Way.

Always alert to the unexpected,

he discovered infrared radiation

by accident when studying the

spectrum of the sun in 1800.

Better telescopes led to far more

detailed surveys of the sky. William’s

son, John Herschel, inherited his

father’s aptitude for astronomy and

spent five years in South Africa

completing his father’s surveys.

INTRODUCTION

1771

1781

1794

1801

1783

1786

Ernst Chladni studies

reports of rock falls and

concludes that chunks

of rock and metal

fall from space.

William Herschel

discovers Uranus,

believing at first that he

has found a new comet.

English clergyman

John Michell first

proposes the concept

of black holes, which

he calls “dark stars.”

Pierre-Simon Laplace

puts forward the theory

that the solar system

formed from a rotating

mass of gas.

French astronomer
Charles Messier
compiles a list of
103 known nebulae.

Giuseppe Piazzi

discovers Ceres, the

biggest asteroid in

the asteroid belt.

All the effects of Nature

are only the mathematical

consequences of a small

number of immutable laws.

Pierre-Simon Laplace