Scenario:
Georgium Sidus
(Herschel's Discovery of
Uranus)
On a march evening in
1781, Frederick William Herschel made a discovery that would
raise his stature from that of an obscure musician to famous
astronomer. He stood near his home in Bath England, peering
through a 7-foot long Newtonian telescope of his own making at
the stars within the triangle formed by 1 Gem, Elnath, and Zeta
Tau. One of them seemed different.
He would later record, "In
examining the small stars in the neighborhood of H Geminorum I
perceived one that appeared visibly larger than the rest; being
struck with its uncommon appearance I compared it to H Geminorum
and the small star in the quartile between Auriga and Gemini,
and finding it so much larger than either of them, I suspected
it to be a comet."
In the months that followed it
became apparent that this was no comet, but rather the first
planet discovered in historical times. The planet he discovered,
which he later named Georgium Sidus after the king who appointed
him as royal astronomer, orbited nearly twice as far from the
sun as Saturn. His name didn't catch on, and for a brief time
the planet was known simply as Herschel. Eventually Elert Bode's
suggestion of Uranus was adopted because it was more in line
with the traditional names of the planets.
Herschel's discovery was by no
means an accident. He and his brother Alexander built the
largest telescopes of the day--the first practical application
of the reflecting telescope invented by Newton. Assisted by his
sister Caroline, Herschel set out to observe every star in the
sky. A he put it, "In a regular manner I examined every
star in the heavens and that night it was its turn to be
discovered." Biographies are full of stories that reflect
his great zeal for observing, including slipping out between the
acts of a play.
You too can discover Uranus by
entering the information below into the Scenario screen. Uranus
is often brighter than 6th magnitude, which makes it just barely
visible to the unaided eye. It's a wonder that no one had
discovered it before. Although Uranus had been recorded as a
star, apparently its slow motion through the sky allowed it to
go undetected as a planet.
Herschel also discovered two of
the moons of Uranus, Oberon and Titania, with his 20-foot long
telescope on January 11, 1787. By this night six years later
Uranus had moved up the left "twin" to a position to
the east of Pollux.
If I
close my eyes and listen carefully, I can almost hear the
Herschel family gathered inside the 40-foot tube of his largest
telescope singing, Merrily, merrily let us all sing, And make
the old telescope rattle and ring. Can you?
Scenario: Georgium Sidus
Location: Bath England
West Longitude: 2:22
Latitude: 51:22
Date: March 13, 1781
Local Time: 21:00
Telescope: 8 inch
Precession: Rigorous
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