Asteroids and Comets and Meteors, Oh My!

Transcription

1 Name Asteroids and Comets and Meteors, Oh My! (source Astronomy Picture of the Day) (source NASA Galileo) (source lxixixl)

2 After completing this workbook, students should be able to do the following: Standard/ Pinnacle Description (Pinnacle) Use precise scientific language in oral and written communication Describe the characteristics of comets, asteroids, and meteors.

3 Falling Stars The sight of a falling star is exciting. Before you can say, Look! the streak is gone. You point to where it was and ask others if they saw it, too. Often, no one else sees the speedy flight of light flash by. You re left trying to describe what you saw and felt. You stare at the dark space, hoping another will streak across the sky. What is a falling star? A falling star is not a star at all. It is not even a piece of a star. Stars are huge balls of burning gas sending off great amounts of energy in the form of light and heat. Stars are much bigger than our planet. Stars do not fall; they stay in their own places in their own galaxies. Our Sun is a star. A falling star is a meteor. Meteors are streaks of light in the sky that we can see when a small speck of dust burns up high in the air above us. Where do these specks of dust come from? Comets! (And, don t forget space dirt!) Astronomers call this dirt and comet dust meteoroids. Meteoroids are different sizes. Some are larger. Most are tiny. Meteoroids hit the Earth s atmosphere at super, high speed. Sometimes it s faster than 90,000 miles per hour. When they are in the atmosphere, they become meteors. The meteor usually burns up. This creates the streak of light we see. It looks like a star falling from the sky. This is why they are called a falling star. Meteors usually last just a second or two. pg. 1

4 Sometimes, there are meteor showers. It s exciting to watch a meteor shower. You usually see four or five meteors in an hour. During a meteor shower, you might see more than 80 meteors in an hour. Scientists also watch these meteors. They record the numbers, the brightness, and the paths of the meteors. Why do we have meteor showers? They happen when the Earth passes through the tail of a comet. Like the dust cloud surrounding Pigpen in the Peanuts comics, a meteoroid stream travels along with the comet on its orbit through the Solar System. Some people are confused by comets and meteors. A comet is different from a meteor. A comet is usually larger and travels slowly across the night sky. A very bright comet only appears once or twice in a century but it remains in the sky for many days or months. Comets appear to be bright balls with fat tails. They do not fall rapidly in the sky; you would have to watch one for hours or days to see its movement. The center of a comet is a ball of frozen gas, dust, and water. Like planets or moons, comets orbit around the Sun. The comet that causes the Leonids is called Tempel-Tuttle. It is named after two scientists who discovered it at the end of 1865.The scientists were not working together; one was in France and one was in America. They were each looking through telescopes. Both astronomers spotted the comet and reported their finding. The comet they found was not a big, bright comet. It is so small that it can only be seen with a telescope. The comet Tempel-Tuttle is about 2 1/2 miles in diameter. When comets get close to the Sun, they begin to warm up and their icy material begins to melt. Tiny grains of dirt that have been riding on the comet for perhaps four and a half billion years fly off into space to join a long stream of orbiting meteoroids. When the Earth hits this stream of comet junk from Tempel-Tuttle, meteors seem to shoot out of the constellation Leo. That s why this meteor shower is called the Leonids. The Leonids are famous. The reason that the Leonids are so famous is that sometimes they cause a meteor storm! In a meteor storm, over 1,000 meteors blaze across the sky every hour. In 1833, people all over America woke up to see hundreds of stars falling every minute! All night, the sky was brightened by meteors that rocketed through the night by the thousands! Since no telescopes or fancy equipment were needed to see the storm, ordinary people were able to see that wonderful and rare sight. Many artists tried to paint pictures of the rain of stars that fell so heavily that night. Newspapers ran many stories about the storm. What they saw was a Leonids meteor storm. This display was so beautiful and amazing that meteors suddenly captured the attention and pg. 2

5 imagination of people everywhere. Scientists were inspired to begin a serious study of meteors and their causes. The best way to watch a meteor storm is with your eyes. Telescopes are not required. Dress warmly. Set up a comfortable lounge chair with blankets and snacks or spread out a blanket. Lie down and look up at the sky. Watch the beautiful flashes of light from tiny sky candles created in the long, ago dawn of our Solar System. Directions Some of the following words and phrases describe comets. Some words and phrases describe meteors. Some words and phrases describe meteoroids. Some describe more than one. Based on what you learned in the article Falling Stars, write comets, meteors, and/or meteoroids by the appropriate words and phrases. Shooting stars Composed of minerals and ice Orbits Sun Has a tail Speedy streak of light Usually the size of a grain of sand Hits the atmosphere faster than 90,000 miles per hour Surface melts into gas and dust when gets close to Sun Visible for a second or two Travels slowly across the night sky May come in showers or storms Remains in the sky for many days or weeks pg. 3

6 What is considered a small body? Asteroids, Comets, Meteor0ids (an activity from spaceday.org) Any object in the sky that is smaller than a planet or a moon, such as an asteroid, a comet, or a meteoroid Materials Ruler Tape Scissors Safety Concerns: Scissors. Use scissors in the appropriate manner. Procedure 1. Get a plain sheet of white paper and turn it sideways. 2. Measure four equal strips of paper, each 2,inches wide. 3. Cut strips (see diagram). 4. Select one of the paper strips; draw tick mark on the strip at ¼,inch. Draw a line across the strip. Cut off the ¼,inch section; this represents the scaled size of a meteoroid; tape the strip to the Data Sheet in the space provided. Cut here! ¼-inch strip pg. 4

7 5. Starting at the end of strip where the cut was made, repeat the process, but this time measure ¾,inch; again, draw a line at ¾,inch and cut off the ¾,inch section; this section represents the scaled size of a comet; tape it to the Data Sheet, too. Cut here! ¾-inch strip 6. Tape all the strips together. Measure a strip that is 40,inches in length. These strips represent the scaled size of an asteroid. 7. Tape the strip to the bottom of the Data Sheet in the space provided; neatly fold remaining strips back and forth over the bottom strip. Data Sheet pg. 5

8 Making Comparisons 1. Based on your scale model, which two small bodies are most similar in size? pg. 6

9 It was on a dark and starry night of New Year s Day, 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 any nebulosity [clouds of dust and gas] 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 conjecture [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 pg. 7

10 the missing planet. Piazzi named the object Ceres. Piazzi s friend, Baron von Zach announced the discovery in his Monthly Correspondence summer of To establish that he really had found a new planet, Piazzi needed to be able to predict his new planet s orbit (or path) in the sky. This was necessary so that other astronomers could find the object when they wished to investigate it more thoroughly. Piazzi had observed Ceres for six weeks, but he did not have enough information to calculate the object s orbit by any mathematical methods available at that time. After that, William Herschel and others searched unsuccessfully for the object, and several astronomers attempted to work out Ceres orbit from Piazzi s limited data, but they each came up with different results. Ceres appeared to be lost. It had passed into the evening s twilight before anyone else could verify Piazzi s observations. 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! 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 (Ceres) 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. pg. 8

11 Von Zach had two roles in this exciting event. First, he found the missing Ceres. Second, his publication, Monthly Correspondence, provided information about Ceres. 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. Questions and Analysis (Hint: Look at bold/italics in the reading for answers.) Early Asteroids Discoveries 1. When and where did Giuseppe Piazzi live and work? 2. What was Piazzi doing when he saw a new point of light? 3. What was different about the point of light that he discovered on New Year s Night, 1801? 4. Johan Bode was certain that Piazzi had discovered The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I have discovered it!) but 'That's funny...',isaac Asimov pg. 9

12 And the Plot Thickens 5. Piazzi announced the star was a comet, but he changed his mind. Why? 6. Baron von Zach announced the discovery of Ceres in his publication. What was the publication s name? 7. Piazzi couldn t find Ceres again over a six, week period. Why did he couldn t he find Ceres? 8. How much time passed between Ceres first discovery and its rediscovery? 9. Baron von Zach played two important roles in the rediscovery of Ceres. What were they? a. b. pg. 10

13 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. pg. 11

14 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 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! 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 "anticomet 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. pg. 12

15 Share two legends about comets. a. b. 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. 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 Maybe you will see it return! Here s a good picture of the comet. pg. 13

16 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 chance of 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. pg. 14

17 Explain how comets may have been responsible for the dinosaurs becoming extinct. Based on your reading of Comet Facts, Myths, and Legends, would you say the following statements are true or false? Statement True False 1. It's possible that a big comet striking the Earth killed off the dinosaurs. 2. Only a professional astronomer with a powerful telescope can discover a new comet. 3. About 100 years ago, some people bought comet-protecting umbrellas and anti-comet pills to protect themselves. 4, The closer a comet is to the Sun, the brighter it will appear. 5. The ancients thought comets were the power rays of supernatural beings. 6. A meteor shower occurs when many comets at once pass over the Earth. Comet Hale-Bopp On July 23, 1995, 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 brightness was due to its large size. While the nuclei of most comets are about 1 to 2 miles across, Hale-Bopp's was estimated to be 25 miles across. It was visible even through pg. 15

18 bright city skies. It may have been the most viewed comet in 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 This comet was first seen in July 1862 by American astronomers Lewis Swift and Horace Tuttle. Comet Swift- Tuttle appears every 120 years. It leaves behind a trail of dust that Earth passes through in August. As Earth passes through the dust, we can see the Perseid meteor shower. Comet Swift-Tuttle could one day collide with Earth because the two orbits closely intercept each Earth. The latest calculations show that it will pass 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 bright comet with a nucleus of 1 to 2 miles flew-by Earth. It had one of the longest tails ever observed. The Hubble Space Telescope studied this comet in great detail. This is not Comet Hyakutake's first visit to the inner Solar System. It is believed that it was here about 8,000 years ago. Its orbit will not return for about 14,000 years. Comet Halley Comet Halley is 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 Each time this comet's orbit pg. 16

19 approaches the Sun, its 9,mile nucleus sheds ice and rock into space. This debris forms an orbiting trail. When falling to Earth, it is called the Orionids meteor shower. Comet Halley will return to the in 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 The Hubble Space Telescope took many spectacular pictures as the comet's pieces crashed into Jupiter. 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. Short-period comets (orbital periods of less than 200 years) tend to come from the Kuiper Belt a region beyond the orbit of Neptune similar in shape to the asteroid belt. Long-period comets (orbital periods of more than 200 years) tend to come from the Oort Cloud. Based on the reading, complete the table below. s Comet Comet Hale-Bopp Comet Swift-Tuttle Comet Hyakutake Comet Halley How Long It Takes to Orbit Sun (Years) Where It Came From pg. 17

20 Myths vs. Reality, Comets Myth Comets come from regions outside the Solar System. Reality Comets are part of the Solar System. Scientists believe they come from either the Kuiper belt or the Oort cloud. The comets that we see every 100 years (or less) come from the Kuiper belt. Comets that we see 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 structure is different. Asteroids are mostly rock with some ice. Comets are mostly ice with some rock. Myth Comets always have tails. Reality Comets do not always have tails. They develop a fuzzy 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. pg. 18

21 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. Reality Beyond Pluto's orbit is a group of icy objects known as the Kuiper Belt. Short-period comets come from there. Farther still is a sphere of icy bodies, called the Oort Cloud, Long-period comets come from there. Short-period comets visit the inner Solar System regularly. Long-period comets visit once in a while. Myth There is empty space between the planets. Reality There is gas and dust between the planets. Comets are responsible for depositing some of the gas and dust found in the inner Solar System. Identifying Comets 1. List two facts about comets. a. pg. 19

22 b. 2. List a myth about comets. pg. 20

23 Asteroid, Comet, or Meteor? Place an X in the appropriate boxes to indicate characteristics of asteroids, comets, and meteors. Asteroid Comet Meteor Made of ice, dust, and gas. Appears as a streak in the sky. Made of rock and/or metal. Orbits the Sun. Often called shooting stars. Sometimes called a dirty snowball. Orbits between Mars and Jupiter. Most are found in the Oort Cloud or Kuiper Belt. pg. 21