Objective Describe the characteristics of comets, asteroids, and meteors. Comet Facts, Myths, and Legends

Objective

Describe the characteristics of comets, asteroids, and meteors.

Comet Facts, Myths, and Legends

(from NASA - Space Science: Adventure Is Waiting/Hubble – Amazing Space)

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.

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, when Halley’s Comet returned, 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!

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 successfully predict 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! Here’s a good picture of the comet.

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.

Did comets kill the dinosaurs? Sixty-five million years ago, 70 percent of all species then living on Earth disappeared within a very short time. This included the last of the great dinosaurs. One possibility is that a comet about 10 kilometers in size struck the Earth. Scientists think that the impact disrupted the environment by displacing great amounts of dirt and rocks into the air.

The explosion that this object must have caused was similar to the explosion a rock the size of Mount Everest, traveling 10 times faster than the fastest bullet, would cause if it hit the Earth. There is a 65-million-year-old crater from an impact of similar magnitude just off the coast of Mexico in the Yucatan Peninsula.
NASA knows of no asteroid or comet currently on a collision course with Earth. The probability of such a collision is quite small. In fact, as far as we can tell, no large object is likely to strike Earth any time in the next several hundred years.


Comet Hale-Bopp
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 for another 2,400 years
Comet Swift-Tuttle 1992

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.

Comet Hyakutake
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 for about 14,000 years.
Comet Halley

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 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

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.

Myths vs. Fact - Comets
Myth
Comets come from regions outside the Solar System.
Fact
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.
Fact
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.
Fact
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.
Fact
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.
Fact
Beyond Pluto's orbit is a group of icy objects known as the Kuiper Belt, from which short- period 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.
Fact
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.

Identifying Comets
1. The word for comet comes from the Greek word for…
a. beard. c. hair.

b. fleece. d. moustache.

2. Who was the first astronomer to show comets travel beyond the Moon?
a. Sir Isaac Newton c. Edmund Halley

b. Tycho Brahe d. Johannes Kepler

3. At one time, astronomers believed comets came once and were never seen again.
a. True b. False
4. When Halley’s Comet returned in 1910, people sold…
a. comet protecting umbrellas. c. gas masks.

b. anti-comet pills. d. all of the above.

5. The Chinese recorded a visit from Halley’s Comet as far back as…
a. 1,000 B.C. c. 1,000 A.D.

b. 240 A.D. d. 240 B.C.

6. The Bayeux (bye-you) Tapestry shows Halley’s Comet. Some people thought their king would lose his throne. Who was that King?
a. King William c. King Henry

b. King Phillip d. King Harold

7. Halley’s Comet returns every ______ years.
a. 7.6 c. 760

b. 76 d. 7,600

8. When the Earth travels through a trail of debris left by a comet, this occurs.
a. Asteroid shower c. Meteorite shower

b. Meteor shower d. Rain shower

9. When the Earth passes through the debris left by Comet Swift-Tuttle, we see this meteor shower.
a. Aquarids c. Orionids

b. Leonids d. Perseids

10. There is no possibility that a comet struck Earth and was responsible for killing the dinosaurs.
a. True b. False
11. The comet that may have struck the Earth was the size of which mountain?
a. Mount Everest c. Mount Olympus

b. Mount McKinley d. Mount Rainer

Match the famous comet with the year it appeared, last appeared, or will return.

_____ 12. Comet Hale-Bopp _____ 13. Comet Halley _____ 14. Comet Hyakutake _____ 15. Comet Shoemaker Levy 9 _____ 16. Comet Swift-Tuttle

A. 1992 B. 1995 C. 1996 D. Will return again in 2061 E. This come struck Jupiter in 1994.

Identify whether the statement is fact or myth.

_____ 17. Comets come from outside of the Solar System. _____ 18. Comets are composed of the same material as asteroids. _____ 19. Comets do not always have tails. _____ 20. Comets do not change their appearance. _____ 21. Pluto is the most distant object in our Solar System.

A. Fact B. Myth

Identifying Comets - Key
1. The word for comet comes from the Greek word for…
c. hair
2. Who was the first astronomer to show comets travel beyond the Moon?
b. Tycho Brahe
3. At one time, astronomers believed comets came once and were never seen again.
a. True
4. When Halley’s Comet returned in 1910, people sold…
d. all of the above
5. The Chinese recorded a visit from Halley’s Comet as far back as…
d. 240 B.C.
6. The Bayeux (bye-you) Tapestry shows Halley’s Comet. Some people thought their king would lose his throne. Who was that King?
d. King Harold
7. Halley’s Comet returns every ______ years.
b. 76
8. When the Earth travels through a trail of debris left by a comet, this occurs.
b. Meteor shower
9. When the Earth passes through the debris left by Comet Swift-Tuttle, we see this meteor shower.
d. Perseids
10. There is no possibility that a comet struck Earth and was responsible for killing the dinosaurs.
b. False
11. The comet that may have struck the Earth was the size of which mountain?
a. Mount Everest
B 12. Comet Hale-Bopp (5 choices)
D 13. Comet Halley (5 choices)
C 14. Comet Hyakutake (5 choices)
E 15. Comet Shoemaker Levy 9 (5 choices)
A 16. Comet Swift-Tuttle (5 choices)
B 17. Comets come from outside of the Solar System. (5 choices)
B 18. Comets are composed of the same material as asteroids. (5 choices)
A 19. Comets do not always have tails. (5 choices)
B 20. Comets do not change their appearance. (5 choices)
A 21. Pluto is not the most distant object in our Solar System. (5 choices)

Identifying Comets

1. c 2. b 3. a (2 choices) 4. d 5. d 6. d 7. b 8. b 9. d 10. b (2 choices) 11. a 12. B (5 choices) 13. D (5 choices) 14. C (5 choices) 15. E (5 choices) 16. A (5 choices) 17. B (2 choices) 18. B (2 choices) 19. A (2 choices) 20. B (2 choices) 21. A (2 choices)

Scoring Guide 19-21 – 3 17-18 – 2.5 13-16 – 2 8-12 – 1.5 4-6 – 1 1-3 – .5 0 – 0