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Transcript
Objective
Describe the characteristics of comets, asteroids, and meteors.
Introduction to Comets
(from NASA: Amazing Space Online Exploration website)
The word "comet" comes from the Greek word for "hair." Our
ancestors thought comets were stars with what looked like flowing
hair trailing behind.
For centuries, scientists thought comets traveled in the Earth's
atmosphere. In 1577, observations by Danish astronomer Tycho Brahe
showed that they actually traveled far beyond the moon.
Sir Isaac Newton (1642-1727), the great English scientist,
discovered that comets move in elliptical (egg-shaped) orbits
around the Sun. He also thought that comets were members of
the Solar System, just like planets, and that they could return
over and over again. He was right!
As early as the 1700's, scientists began developing
mathematical formulas that could predict the orbit of a
particular comet around the Sun. At that time, calculators and
computers didn’t exist, so everyone had to do the calculations
by hand!
Most astronomers in the 1500's and early 1600's thought that a
comet came once and was never seen again. They believed that a comet approached the Sun in a
straight line, spun around it, and then disappeared into space in a straight path.
Objective
Describe the characteristics of comets, asteroids, and meteors.
People did not always know what comets were. In
ancient times, people thought comets were "power
rays" of supernatural beings. They thought comets
contained fire because they were so bright in the
sky.
Some people in ancient times thought that a comet was a curse. To save himself from the "curse
of the comet," Emperor Nero of Rome had all possible successors to his throne executed.
In 1910, people panicked when a comet passed through Earth’s path
around the Sun. In Chicago, people sealed their windows to protect
themselves from the comet’s poisonous tail. Others committed
suicide. Special "Comet Protecting Umbrellas," gas masks, and
"anti-comet pills" were sold.
Not everyone saw comets as bad luck.
Some thought they brought good luck.
They also believed that comets carried
angels through the heavens.
People have known about comets, unlike other small bodies in the Solar
System, since ancient times. The Chinese recorded visits by Halley's
Comet as far back as 240 B.C.
The famous Bayeux Tapestry, which commemorates the Norman
Conquest of England in 1066, depicts an image of Halley's Comet bright
in the sky before the Battle of Hastings.
Some people thought this meant that King Harold would lose his throne
to William, the Duke of Normandy. He did!
Objective
Describe the characteristics of comets, asteroids, and meteors.
Edmund Halley of England studied comets and developed a theory suggesting
that those sighted in 1531, 1607 and 1682 were actually the same object. He
was the first to predict successfully the comet’s next appearance in 1758,
but he died 16 years before the comet returned.
Halley’s Comet reappears every 76 years. Its next appearance is in 2061.
Maybe you will see it return!
Comets leave a trail of debris behind them. If their path crosses Earth's
path, then at that point, every year for a long time, there will be meteor
showers as the long-gone comet's debris strikes our atmosphere.
Some of these meteor showers occur every year
when the Earth passes the place where the comet
had been long ago.
The Perseid meteor shower occurs every year
between August 9 and 13 when the Earth passes
through the orbit of the Swift-Tuttle comet. Halley's Comet is the
source of the Orionid shower in October.
Comets are brightest when they are near the Sun.
Comet Hale-Bopp 1995
On July 23, 1995, an unusually large and bright comet was seen
outside of Jupiter's orbit by Alan Hale of New Mexico and
Thomas Bopp of Arizona. Careful analysis of Hubble Space
Telescope images suggested that its intense brightness was due
to its exceptionally large size. While the nuclei of most comets
are about 1.6 to 3.2 km (1 to 2 miles) across, Hale-Bopp's was
estimated to be 40 km (25 miles) across. It was visible even
through bright city skies, and may have been the most viewed
comet in recorded history. Comet Hale-Bopp holds the record for
the longest period of naked-eye visibility: an astonishing 19
months. It will not appear again until around 4400.
Objective
Describe the characteristics of comets, asteroids, and meteors.
Comet Swift-Tuttle 1982
This comet was first seen in July 1862 by American
astronomers Lewis Swift and Horace Tuttle. As Comet
Swift-Tuttle moves closer to the Sun every 120 years, it
leaves behind a trail of dust debris that provides the
ingredients for a spectacular fireworks display seen in
July and August. As Earth passes through the remnants of
this dust tail, we can see on a clear night the Perseid
meteor shower. Comet Swift-Tuttle is noted as the comet
some scientists predicted could one day collide with Earth
because the two orbits closely intercept each other. The latest calculations show that it will
pass a comfortable 24 million km (15 million miles) from Earth on its next trip to the inner Solar
System (2102).
Comet Hyakutake 1996
On January 30, 1996, Yuji Hyakutake (pronounced
"hyah-koo-tah-kay"), an amateur astronomer from
southern Japan, discovered a new comet using a pair of
binoculars. In the spring of that year, this small bright
comet with a nucleus of 1.6 to 3.2 km (1 to 2 miles)
made a close flyby of Earth — sporting one of the
longest tails ever observed. The Hubble Space
Telescope studied the nucleus of this comet in great
detail. This is not Comet Hyakutake's first visit to the
inner Solar System. Astronomers have calculated its
orbit and believe it was here about 8,000 years ago. Its orbit will not bring it near the Sun
again until the year 16,000.
Comet Halley 1985
Comet Halley is perhaps the most famous comet in history. It was
named after British astronomer Edmund Halley, who calculated its
orbit. He determined that the comets seen in 1531 and 1607 were
the same objects that followed a 76-year orbit. Unfortunately,
Halley died in 1742, never living to see his prediction come true
when the comet returned on Christmas Eve in 1758. Each time this
Objective
Describe the characteristics of comets, asteroids, and meteors.
comet's orbit approaches the Sun, its 15-km (9-mile) nucleus sheds about 6 m (7 yards) of ice
and rock into space. This debris forms an orbiting trail that, when falling to Earth, is called the
Orionids meteor shower. Comet Halley will return to the inner Solar System in the year 2061.
Comet Shoemaker-Levy 9 1993
Between July 16 and July 22, 1994, more than 20 fragments of Comet Shoemaker-Levy 9
collided with the planet Jupiter. Astronomers Carolyn and Eugene Shoemaker and David Levy
discovered the comet in 1993. The Hubble Space Telescope took many spectacular pictures of
this event as the comet's pieces crashed into Jupiter's southern hemisphere. It was the first
collision of two Solar System bodies ever to be recorded. The impacts created atmospheric
plumes many thousands of kilometers high that showed hot "bubbles" of gas with large dark
"scars" covering the planet's sky.
(source: hubblesite.org)
Myths vs. Reality - Comets
(from NASA: Amazing Space)
Myth
Comets come from regions outside the Solar System.
Objective
Describe the characteristics of comets, asteroids, and meteors.
Reality
Comets are part of the Solar System. Scientists believe they come from one of two locations
within the Solar System: the Kuiper belt and the Oort cloud. The comets that we see often –
every 100 years – come from the Kuiper belt, and comets that we see rarely – every few
thousand years – come from the Oort cloud.
Myth
Comets are composed of the same material as asteroids.
Reality
Although comets and asteroids are both tiny bodies that orbit in the Solar System, their
composition is different. Asteroids are mostly rock with some ice, while comets are mostly ice
with some rock.
Myth
Comets always have tails.
Reality
Comets do not always have tails. They develop a fuzzy, shell-like cloud called a coma, and one,
two, or three tails when near the Sun. Comets have no coma or tail when far away from the Sun.
Myth
All comets look the same and don't change their appearance.
Reality
Comets have a coma and one, two, or three tails when near the Sun, and no coma or tail when far
away from the Sun. (A coma is a cloud of gaseous material surrounding the nucleus.)
Myth
Pluto is the most distant and last object in the Solar System.
Objective
Describe the characteristics of comets, asteroids, and meteors.
Reality
Beyond Pluto's orbit is a group of icy objects known as the Kuiper Belt, from which shortperiod comets emerge. Farther still is a sphere of icy bodies, called the Oort Cloud, from which
long-period comets emerge. Short-period comets visit the inner Solar System frequently, while
the long-period comets visit infrequently.
Myth
There is empty space between the planets.
Reality
There is gas and dust, also known as the interplanetary medium, between the planets. Comets
are responsible for depositing some of the gas and dust found in the inner Solar System.
Vocabulary
Coma — The cloud of gas and dust that forms around a comet's nucleus.
Comet — A “dirty snowball” consisting of ices, rocks, and dirt.
Dust Tail — Forms when the solar wind separates dust from the coma, pushing it outward away
from the Sun.
Gas-Ion Tail — Forms when the solar wind separates gases from the coma, pushing them
outward away from the Sun.
Inner Solar System — The path of the Solar System between the Sun and the orbit of Jupiter
Meteor Shower —Many meteors are seen in the night sky as a result of the Earth passing
through the former path of a comet. The debris released by the comet causes the meteor
shower.
Naked-eye Visibility —Being able to see a celestial object, such as a comet, without the aid of
telescopes, binoculars or other astronomical devices.
Comet Nucleus —The solid icy/rocky part of a comet.
Orbit —The path followed by body around another, such as Earth’s path around the Sun or the
Moon’s path around Earth.
Period —The time needed for one complete trip or cycle. For example, the period for the Earth
to travel around the Sun is 365 days.
Solar Wind —A stream of charged particles ejected from the surface of the Sun.
Objective
Describe the characteristics of comets, asteroids, and meteors.
Name _________________________________________________________________
Comet Review Worksheet
1. The work comet comes from a Greek word meaning…
a. beard.
b. hair.
c. mane.
d. ponytail.
2. Who was the scientist who proved that comets traveled far beyond the Moon?
a. Tycho Brahe
b. Galileo
c. Edmund Halley
d. Sir Isaac Newton
3. From ancient times, people knew what comets were.
a. True
b. False
4. To save himself from the comet’s curse, Emperor Nero did what?
a. Left Rome for his safety.
b. Killed all his possible successors.
c. Sent his sons to convents.
d. Did nothing because he didn’t believe in comet curses.
5. In 1910, people bought which of the following item(s) to protect themselves from Comet
Halley?
a. Comet protecting umbrellas
b. Anti-comet pills.
c. Gas mask
d. All of the above
6. Some people thought comets brought good luck because they carried angels across the
heavens.
a. True
b. False
7. When did the Chinese first record visits by Comet Halley?
a. 440 B.C.
c. 240 A.D.
Objective
Describe the characteristics of comets, asteroids, and meteors.
b. 240 B.C.
d. 440 A.D.
8. The Bayeux Tapestry showed Comet Halley in the sky during the Battle of Hastings in 1066
A.D. People thought this meant King ___________ would lose the throne.
a. Charles
b. George
c. Harold
d. Richard
9. Edmund Halley proposed a hypothesis that the comets seen in 1531, 1607, and 1682 were the
same comets. He predicted the comet would return again in 1758. Edmund Halley was…
a. correct.
b. incorrect.
Match the Comet with the year it will return.
_____ 10. Comet Hale-Bopp
A. Never
_____ 11. Comet Halley
B. 2061
_____ 12. Comet Hyakutake
C. 2102
_____ 13. Comet Shoemaker-Levy 9
D. 4400
_____ 14. Comet Swift-Tuttle
E. 16,000
Match the term with its definition.
_____ 15. Coma
A. A “dirty snowball” consisting of ices, rocks, and dirt.
_____ 16. Comet
B. A stream of charged particles ejected from the surface
of the Sun.
_____ 17. Dust tail
_____ 18. Nucleus
_____ 19. Solar wind
C. Forms when the solar wind separates dust from the coma,
pushing it outward away from the Sun.
D. The cloud of gas and dust that forms around a comet's
nucleus.
E. The solid icy/rocky part of a comet.
Objective
Describe the characteristics of comets, asteroids, and meteors.
Identify which statement is “reality” or a “myth.”
_____ 20. Comets come from regions outside the Solar System.
A. Myth
_____ 21. Asteroids are mostly rock; comets are mostly ice with some
rock.
B. Reality
_____ 22. Comets do not always have a tail.
_____ 23. All comets look the same and don't change their
appearance.
_____ 24. Comets are found beyond the orbit of Pluto.
_____ 25. There is empty space between the planets.
Statement
True
False
26.
Only a professional astronomer with a powerful telescope can
discover a new comet.
A
B
27.
About 100 years ago, some people bought comet-protecting
umbrellas and anti-comet pills to protect themselves.
A
B
28.
The closer a comet is to the Sun, the brighter it will appear.
A
B
29.
The ancients thought comets were the power rays of
supernatural beings.
A
B
30.
A meteor shower occurs when many comets at once pass over
the Earth.
A
B
Objective
Describe the characteristics of comets, asteroids, and meteors.
Comet Review
1. The work comet comes from a Greek word meaning…
b. hair
2. Who was the scientist who proved that comets traveled far beyond
the Moon?
a. Tycho Brahe
3. From ancient times, people knew what comets were.
b. False (2 choices)
4. To save himself from the comet’s curse, Emperor Nero did what?
b. Killed all his possible successors.
5. In 1910, people bought which of the following item(s) to protect
themselves from Comet Halley?
d. All of the above
6. Some people thought comets brought good luck because they carried
angels across the heavens.
a. True (2 choices)
Objective
Describe the characteristics of comets, asteroids, and meteors.
7. When did the Chinese first record visits by Comet Halley?
b. 240 B.C.
8. The Bayeux Tapestry showed Comet Halley in the sky during the
Battle of Hastings in 1066 A.D. People thought this meant King
___________ would lose the throne.
8. c. Harold
9. Edmund Halley proposed a hypothesis that the comets seen in 1531,
1607, and 1682 were the same comets. He predicted the comet would
return again in 1758. Edmund Halley was…
a. correct (2 choices)
D 10. Comet Hale-Bopp (5 choices)
B 11. Comet Halley (5 choices)
E 12. Comet Hyakutake (5 choices)
A 13. Comet Shoemaker-Levy 9 (5 choices)
C 14. Comet Swift-Tuttle (5 choices)
D 15. Coma (5 choices)
A 16. Comet (5 choices)
Objective
Describe the characteristics of comets, asteroids, and meteors.
C 17. Dust tail (5 choices)
E 18. Nucleus (5 choices)
B 19. Solar wind (5 choices)
A 20. Comets come from regions outside the Solar System. (6 choices)
B 21. Asteroids are mostly rock; comets are mostly ice with some rock.
(6 choices)
B 22. Comets do not always have a tail. (6 choices)
A 23. All comets look the same and don't change their appearance. (6
choices)
B 24. Comets are found beyond the orbit of Pluto. (6 choices)
A 25. There is empty space between the planets. (6 choices)
B 26. Only a professional astronomer with a powerful telescope can
discover a new comet.
A 27. About 100 years ago, some people bought comet-protecting
umbrellas and anti-comet pills to protect themselves.
A 28. The closer a comet is to the Sun, the brighter it will appear.
A 29. The ancients thought comets were the power rays of
supernatural beings.
Objective
Describe the characteristics of comets, asteroids, and meteors.
B 30. A meteor shower occurs when many comets at once pass over the
Earth.