85
See also: Shifting stars 22 ■ Gravitational theory 66–73 ■ The discovery of Neptune 106–07
URANUS TO NEPTUNE
he noticed that its position had
changed in relation to the stars
around it. He also noted that if
he increased the power of the
telescope he was using the new
object increased in size more
than the fixed stars. These two
observations indicated that it was
not a star, and when he presented
his discovery to the Royal Society
he announced that he had found
a new comet. The Astronomer
Royal, Nevil Maskelyne, looked
at Herschel’s discovery and decided
that the new object was as likely
to be a planet as a comet. Swedish-
Russian Anders Johan Lexell
and German Johann Elert Bode
independently computed the
orbit of Herschel’s object and
concluded that this was a planet
in a near-circular orbit, roughly
twice as far away as Saturn.Naming the planet
Herschel’s discovery was praised
by King George III, who appointed
Herschel “The King’s Astronomer.”
Maskelyne asked Herschel to name
the new planet, and he chose
Georgium Sidus (George’s Star) in
honor of his patron. Other names,
including Neptune, were proposed,
and Bode suggested Uranus. His
suggestion became universal in
1850, when the UK’s Greenwich
Observatory finally abandoned
the name Georgium Sidus.
The detailed study of the
orbit of Uranus by subsequent
astronomers showed that there
were discrepancies between
its observed orbit and the orbitpredicted according to Newton’s
laws—irregularities that could only
be explained by the gravitational
influence of an eighth, even more
distant planet. This led to the
discovery of Neptune by Urbain
Le Verrier in 1846. ■William Herschel Born in Hanover, Germany,
Frederick William Herschel
emigrated to Britain at the age
of 19 to make a career in music.
His studies of harmonics and
mathematics led to an interest in
optics and astronomy, and he set
out to make his own telescopes.
Following his discovery of
Uranus, Herschel detected two
new moons of Saturn and the
largest two moons of Uranus.
He also showed that the solar
system is in motion relative
to the rest of the galaxy and
identified numerous nebulae.
While studying the sun in 1800,Herschel discovered a new
form of radiation, now known
as infrared radiation.
Herschel’s sister Caroline
(1750–1848) acted as his
assistant, polishing mirrors
and recording and organizing
his observations. She began
to make observations of her
own in 1782, and went on to
discover a number of comets.Key works1781 Account of a Comet
1786 Catalogue of 1,000 New
Nebulae and Clusters of StarsHerschel observed Uranus using a
7-ft (2.1-m) reflector telescope. He would
later construct a 40-ft (12-m) telescope,
which was the largest telescope in the
world for half a century.I compared it to H. Geminorum
and the small star in the
quartile between Auriga and
Gemini, finding it so much
larger than either of them.
William Herschel