Objective – Describe the history of asteroid discovery and how technology was used to learn about the asteroids.
It was on a dark and starry night of New Year’s Day, 1801. Giuseppe Piazzi, an Italian monk,
was at work in his observatory on Sicily. He was a member of the Celestial Police. This was a
group of astronomers looking for a missing planet between Jupiter and Mars. That night he was
confirming and cataloging stars in Taurus. While checking other astronomers’ work, he saw a
tiny point of light. He thought it was just a dim star no one had cataloged. He checked for
it the next night, but it had moved! He watched it move on January 3 and 4. What he was
observing was not a star! He wrote to Johan Bode and told him what he had found; Bode was
certain he had found “the missing planet.”
And the Plot Thickens…
Cloudy weather set in. Piazzi was so sick that he could not observe the skies on some January
nights. By January 24, he realized what he had discovered. He wrote a friend: “I have announced
the star as a comet. But the fact that the star is not accompanied by [a coma] and that its
movement is very slow and rather uniform has caused me many times to seriously consider
that perhaps it might be something better than a comet. I would be very careful, however,
about making [this idea] public.”
He wrote to Bode the next day. He did not receive the letter
until March 20. When the letter reached Bode, he studied his
star maps. He convinced Piazzi that he had found the
“missing planet.” Piazzi named the object Ceres. Piazzi’s
friend, Baron von Zach announced the discovery in his
Monthly Correspondence summer of 1801.
Piazzi tried to predict Ceres’ orbit. Astronomers need this information so they could try to find it.
He observed Ceres for six weeks. He did not have enough information to determine Ceres’
orbit. After that, others searched for Ceres in vain. Several astronomers tried to work out Ceres’
orbit from his data. They each came up with different results. Ceres appeared to be lost. No one
could verify Piazzi’s observations.
But Carl Friedrich Gauss, a young German mathematician, came to the rescue! In October
1801, he applied his new method of “determining the path of a celestial body” to Ceres’
orbit. With surprising speed and accuracy, Gauss used Piazzi’s observations to predict where the
new “planet” should be found. Imagine Gauss’s excitement when Baron von Zach found Ceres on
the night of December 7, just where Gauss said it would be!
Objective – Describe the history of asteroid discovery and how technology was used to learn about the asteroids.
Actually, von Zach found four stars at that location, but when the weather cleared again on
December 18, one of the stars was gone. Von Zach finally confirmed that he had recovered the
missing object on January 1, 1802, exactly one year after Piazzi’s first sighting. Using Gauss’
results, Wilhelm Olbers, an amateur astronomer in Bremen, also found Ceres with his telescope.
Piazzi received a letter sent by the secretary of state on behalf of the
king of Sicily commending him on the discovery of Ceres. Instead of
giving Piazzi a medal, the king agreed to buy the Palermo
Observatory a new telescope.
Von Zach had two roles in this exciting event. He not only
found the missing Ceres, but also, his publication, Monthly
Correspondence, played a vital communication role in the recovery.
By 1809, Gauss had refined the mathematical procedure he used to determine Ceres’ orbit, and it
became the standard procedure for orbital calculations.
The “missing planet” was found, lost, and found again. All’s well that ends well…except this was
not the end! This was only the beginning! Many more asteroids had yet to be discovered. The
NASA Dawn mission will travel to Ceres but first will study another asteroid named Vesta
Worksheet
1. When and where did Giuseppe Piazzi live and work?
a. Sardinia
b. Madagascar
c. Sicily
d. Ceylon
2. What was Piazzi doing when he saw a new point of light?
a. Casually looking at the stars.
b. Looking for galaxies.
c. Observing the Moon.
d. Confirming and cataloging stars in Taurus.
3. What was different about the point of light that he discovered on New Year’s Night, 1801?
a. It looked like a comet.
b. It had moved.
c. He saw three stars.
d. Nothing.
4. What did Johann Bode think that Piazzi had discovered?
a. The missing planet.
b. A missing comet.
c. A missing galaxy.
d. A new planetary nebula.
5. Piazzi did not think that the moving point of light he had discovered was a comet. It didn’t have
anything that looked like gas and dust surrounding it.
a. True
b. False
Objective – Describe the history of asteroid discovery and how technology was used to learn about the asteroids.
6. What did Piazzi name the new object?
a. Ceres
b. Juno
c. Pallas
d. Vesta
7. Piazzi had enough information to calculate an orbit for Ceres.
a. True
b. False
8. Who finally announced that Piazzi had discovered the “missing planet”?
a. Johan Bode
b. Carl Friedrich Gauss
c. Baron von Zach
d. Sir William Herschel
9. How much time elapsed between Ceres’ first discovery and its rediscovery?
a. 6 months
b. 1 year
c. 18 months
d. 2 years
Objective – Describe the history of asteroid discovery and how technology was used to learn about the asteroids.
It Was a Dark and Starry Night - Key
1. When and where did Giuseppe Piazzi live and work?
c. Sicily
2. What was Piazzi doing when he saw a new point of light?
d. Confirming and cataloging stars in Taurus.
3. What was different about the point of light that he discovered on New Year’s Night, 1801?
b. It had moved.
4. What did Johann Bode think that Piazzi had discovered?
a. The missing planet.
5. Piazzi did not think that the moving point of light he had discovered was a comet. It didn’t have
anything that looked like gas and dust surrounding it.
a. True
6. What did Piazzi name the new object?
a. Ceres
7. Piazzi had enough information to calculate an orbit for Ceres.
b. False
8. Who finally announced that Piazzi had discovered the “missing planet”?
c. Baron von Zach
9. How much time elapsed between Ceres’ first discovery and its rediscovery?
b. 1 year
Objective – Describe the history of asteroid discovery and how technology was used to learn about the asteroids.
It Was a Dark and Starry Night – Scoring Guide
1. c
2. d
3. b
4. a
5. a
6. a
7. b
8. c
9. b
Scoring Guide
9–4
8 – 3.5
7–3
6 – 2.5
5–2
4 – 1.5
3–1
1-2 – .5
0–0