84
I FOUND THAT IT IS A
COMET FOR IT HAS
CHANGED ITS PLACE
OBSERVING URANUS
IN CONTEXT
KEY ASTRONOMER
William Herschel (1738–1822)BEFORE
1660s Mirror-based reflecting
telescopes are developed by
Isaac Newton and others.1690 John Flamsteed
observes Uranus, but
believes it to be a star.1774 French astronomer
Charles Messier publishes
his astronomical survey, which
inspires Herschel to begin
work on a survey of his own.AFTER
1846 Unexplained changes
to the orbit of Uranus lead
French mathematician Urbain
Le Verrier to predict the
existence and position of
an eighth planet—Neptune.1930 US astronomer Clyde
Tombaugh discovers Pluto, a
ninth planet. It has since been
reclassified as a dwarf planet,
the brightest member of the
Kuiper belt of small, icy worlds.U
ranus, the seventh planet
from the sun, is visible
to the naked eye, and
it is believed that the ancient Greek
Hipparchus observed it in 128 bce.
The development of telescopes
in the 17th century led to further
sightings, such as one by English
astronomer John Flamsteed in 1690
when it was recorded as 34 Tauri,a star. It was also observed by the
French astronomer Pierre Lemonier
several times between 1750 and- However, none of the observers
figured out that it was a planet.
William Herschel observed
Uranus on March 13, 1781, while
looking for multiple star systems.
He spotted it again four nights
later, and on this second occasion
Uranus has been observed but
not recognized as a planet.Observations a few days apart show that it has moved,
meaning that it might be a comet.Calculations show that its orbit is almost
circular, so it must be a planet.Irregularities in its orbit indicate that there
may be an eighth planet in the solar system.