Name. Exploring Comets II

Transcription

1 Name Exploring Comets II

2 When you have completed this work, you should know and understand the following: Standard Description Passed Understand and correctly use unit vocabulary. III.1.d III.1.e/ III.2.a-d Compare and contrast comets, asteroids, and meteoroids/ meteors/meteorites. Report on how technology has helped us learn more about the Earth and the objects in the Solar System.

3 What Comets Are Made Of Emily Sohn Science News for Kids July 25, 2007 Astronomers are watching a comet break into pieces, practically before their eyes. Their observations, reported by scientists at Johns Hopkins University's Applied Physics Laboratory in Laurel, Md., are giving surprising insight into the structure of these space objects. Comets are fairly small (about 12 miles across or less) balls of ice, rock, and dust that make long, noncircular orbits around the Sun. When a comet gets near the Sun, the star's heat melts some of it, creating what looks like a tail. At this stage, it looks somewhat like a tadpole. When the comet 73P/Schwassmann-Wachmann 3 broke apart in June 2006, it produced at least 68 chunks, including this large piece, called Fragment B. H. Weaver/JHUAPL, M. Mutchler and Z. Levay/STScI, NASA, ESA Comets sometimes burst into pieces when the Sun's heat turns their ice into water vapor. By studying these chunks, astronomers can compare the material at the center of a comet with material at its surface. The scientists expected that a comet's center would look different from its surface. That's because comets probably formed at the same time as the solar system, so the material at the center has probably remained unchanged for just as long. The surface material, on the other hand, is changed by the Sun's radiation. For the new study, the Johns Hopkins team observed the breakup of a comet called 73P/Schwassmann-Wachmann 3 (SW3). The comet orbits the Sun every 5.34 years. pg. 1

4 In 1995, SW3 split into at least five chunks. In June 2006, it passed within a relatively close 11.7 million kilometers (7.3 million miles) of Earth. Around that time, it disintegrated even more. Scientists counted 68 fragments. The two largest chunks are called B and C. Each is several hundred meters wide. The scientists studied both chunks using NASA's Infrared Telescope Facility and the Keck II telescope, both on Hawaii's Mauna Kea. The researchers found that B and C have nearly identical compositions, with the same proportions of substances such as water and carbon dioxide. Those results suggest that comets have maintained more of their original form than scientists had expected. "We were really lucky" that the comet came close enough for astronomers to make observations soon after a breakup, says lead researcher Neil Dello Russo. Because this was the first study of its kind, the scientists don't yet know whether all comets are the same, inside and out. Describe comets (of what are they made, size, etc.) pg. 2

5 Comet Comparisons Observe this image of Comet Machholz. Comet Machholz. This image is a 6-minute exposure at 05:00 U.T. taken on January 2, 2005 taken with a 7.5 cm telescope. Write a description of this comet based on your observations. pg. 3

6 Read the following descriptions of this comet from three different astronomers. Astronomer 1 Comet Machholz. This image is a 6-minute exposure at 05:00 U.T. taken on January 2, As you re looking at this image, north is up and west is to the right. The width is about 3 degrees and the height about 2 degrees. The camera is a 3 aperture, f/4.0. This image of Machholz shows the two constituents of a comet s coma, the ion tail extending up to the left in the anti-solar direction and the dust cloud and tail extending down and slightly to the right that was blown off the comet many days previously. Astronomer 2 This image of Comet Machholz was taken by Gary Emerson. It is a 6-minute exposure taken at 05:00 U.T. on January 2, As you re looking at this image, North is up and West is to the right. The width is about 3 degrees and the height about 2 degrees. The image was taken with a 7.5 cm telescope with a 30 cm focal length (f/4=focal length/ aperture). The comet dominates the image presented here and the background stars can be seen through the coma. The extent of this coma is about 1.8 degrees East-West and about 1.6 degrees North-South. The coma has a condensation and there are two jet-like structures seen. One is at ~70 degrees East of North and linear in its bright streaks and has dark lanes in it. The second is at ~60 degrees South of West and has less structure than the first one. The space between the two jets could be described as a broad and diffuse fan. Astronomer 3 This is a very interesting picture of comet Machholz. The comet is quite obvious against the backdrop of stars. The coma is nearly 30 arcminutes across (that is about the width of the full Moon) but stars can still be seen through the diffuse cloud of dust and gas! There are also two extensions from the coma - the two tails of the comet. The ion/gas/ plasma tail points off to the left while the dust tail points down in the image. The dust tail is less defined than the gas tail. It is interesting to note that the tails appear to be pointing in different directions. The gas tail always points away from the sun, so we can deduce that the sun is somewhere in the direction off the right side of the image. But figuring out the exact geometry is difficult because it is hard to tell if the tails are just short or appear to be short because they may also be pointing roughly away from us. pg. 4

7 Read the descriptions a second time. This time look for details that are in two or more of the descriptions. Complete the Venn diagram in order to compare and contrast the descriptions from these three astronomers. Comet Machholz pg. 5

8 Comparing Comets (an activity from NASA s STARDUST Mission: Think SMALL in a Big Way Guide) Background Information Comets are so small that, even when viewing through a large telescope, they are just points of light in the sky. For this activity, you will play the role of cometary scientist, observing and comparing the surfaces of two comet nuclei from close range. The image on the left is the surface of comet Wild 2 (pronounced Vilt ), taken from the Stardust spacecraft in January 2004 at a distance of about 237 km. The image on the right is the surface of comet Tempel 1, taken from the Deep Impact Impactor spacecraft in July 2005 at a distance of about 1500 km. Comet Wild 2 taken by the Stardust spacecraft January 2004 during its encounter. Comet Temple 1 taken by the Deep Impact probe on July 4, 2005, just before it smashed into the comet. Based on your observations of these images, how are the nuclei of the two comets similar? How are they different? Use the Venn Diagram below to help organize your descriptions. Write your descriptions that are unique to comet Wild 2 on the left. Write your descriptions that are unique to comet Tempel 1 on the right. For those features that are common to both comets, write the descriptions in the middle, where the two circles intersect. Observations can be qualitative (using word descriptions) or quantitative (using numbers and measurements). pg. 6

9 Comet Wild 2 Comet Tempel 1 Note In comparing the comets, you may note the following. Some descriptions include only observations, while some include interpretation too. We suggest including observations only, then adding interpretation as a separate step. When you are comfortable with the observations and have experience, the interpretation flows as in the case with some experienced astronomers. pg. 7

10 Questions and Analysis 1. How can you tell the Sun s position in relation to this image? Provide two reasons for your answer. For locating the Sun s position, look at the shadows and the location of the bright spots on each nucleus. 2. Based on your comparisons and contrasts, why do you think are the two surfaces different? What factors may have caused these differences? 3. What questions do you have about these two bodies? How would you go about answering these questions? Refer to the handouts containing background for cratering/collisions for comparing comet surfaces: pg. 8

11 Comet Cinquain A cinquain is a five-line poem. It follows this pattern: Line 1: One word subject of the poem Line 2: Two words describe subject Line 3: Three action ing words - describe something your does Line 4: Phrase that describes something about your subject Line 5: One or two words renames what your poem is about (a synonym) Your assignment is to write three cinquain poems about comets Here is your opportunity to use your creativity. Have fun doing this assignment. Examples of cinquains. Mercury Inner, little Freezing, melting, rotating Is the smallest planet Planet Neptune Far, blue Blowing, chilling, intriguing Farthest planet from Sun Gas Giant Dawn Vesta, Ceres Exploring, traveling, seeking Exploring the asteroids Space Probe pg. 9

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15 Comets Trading Cards Materials 3x5 cards Colored pencils or crayons You have probably seen various kinds of trading cards. Some of these feature sports figures and include information about the player, statistics relating to his or her skill as an athlete, and a picture. Similar cards exist for action figures. Procedure 1. Select three comets and make a trading card for each comet. 3. Gather information for your cards. A table is a good way to organize the information. Each card needs at least five facts about that object. Each card needs to include enough information that someone who knows nothing about the object will learn something from reading it. 4. Design your cards (picture on front, facts on back). Front of Card Back of Card pg. 13

16 5. Make your trading cards. (Note: Place your cards in this workbook when you turn it in.) Comets Fact Sheet (from Kidsastronomy.com) Comets are among the most brilliant and most rare objects in the night sky. These soaring beacons with their beautiful tails come from the outer realms of the Solar System. What are comets? A comet is a small world which scientists sometimes call a planetesimal. They are made out of dust, and ice. Kind of like a dirty snowball. Where do they come from? Comets come from two places: The Kuiper Belt, and the Oort Cloud. Imagine a place far far away, at the very edge of the Solar System. A place where millions of comets can be seen swishing around in every direction. These Icy comets are orbiting the Sun in two different places, both of which are very distant. One place is called the Oort cloud, and the other is called the Kuiper Belt. Why do Comets leave their home in the Oort Cloud or Kuiper Belt? A comet will spend billions of years in the Kuiper Belt or Oort Cloud. Sometimes two comets will come very close to each other, or even crash into one another. When this happens, the comets change directions. Sometimes their new path will bring them into the Inner Solar System. This is when a comet begins to shine. Up until now, the comet has been among millions of others exactly the same, but as they approach the warmer Inner Solar System they begin to melt leaving behind magnificent tails. Unfortunately Comets don't live very long once they enter the warmer part of the Solar System. Just like a snowman melts in the summer, comets melt in the Inner Solar System. Although it is the most glorious part of their lives, traveling through the Inner Solar System eventually kills them. After several thousand years, they melt down pg. 14

17 to a little bit of ice, and dust, not nearly enough to leave a tail. Some even melt away completely. Would it be safe to fly through the tail of a comet? Unlike a recent blockbuster movie showing a space ship flying past giant rocks the size of houses, a comets tail is actually quite safe. The only thing that would hit your ship would be microscopic pieces of dust. Many people think that a comets tail is always following behind it, but actually, the coma, or tail can be either behind the comet or in front of it. Which way the tail is pointing depends on where the Sun is. That's right, the Sun's heat and radiation produce a wind called the Solar Wind, as a comet gets close to the Sun it begins to melt. The gas and dust that melt off are blown away from the Sun by the solar winds. So if a comet is traveling towards the Sun then the tail will follow behind, but if the comet is traveling away from the Sun the tail will be in front of the comet. Comets The Great Comet of 1811 was a comet that was visible to the naked eye for around 260 days. In October 1811, at its brightest. In December one length of the tail extended for over 60 degrees (120 times the apparent size of the Moon). It was categorized as a great comet, the 54th in recorded history, and one of eight in the 19th century. It was discovered by Honore Flaugergues in April. The sightings continued until June when it was lost to solar glare, it was recovered in August. The comet brightened as it neared the Sun in September. The comet nucleus was estimated at km in pg. 15

18 diameter and the orbital period was calculated at 3,757 years (later adjusted to 3,065 years). At the mid-point of War and Peace, Tolstoy describes the character of Pierre observing this comet. 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 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 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 pg. 16

19 Comet Hyakutake - On January 30, 1996, Yuji Hyakutake (pronounced "hyah-koo-tahkay"), 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 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 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. pg. 17

20 Comet Swift-Tuttle - 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 West - It was discovered photographically by Richard M. West on August 10, 1975, and reached peak brightness in March During peak brightness, observers reported that it was bright enough to study during full daylight. The comet has an estimated orbital period of 558,000 years. During the passage of Comet West into the inner solar system, possibly for the first time in 500,000 years, its nucleus was observed to split into four fragments as it passed within 30 million km of the Sun. The fragmentation of the nucleus was, at the time, one of very few comet breakups observed, one of the most notable previous examples being the Great Comet of pg. 18

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24 Hubble Witnesses Fireworks From Comet Collision 1. What was the purpose of the Deep Impact mission? 2. Describe the makeup of a comet. 3. Why were the Hubble Space Telescope and other space telescopes involved in the Deep Impact mission? pg. 22

25 4. If you could ask a Deep Impact scientist several questions about the mission, what would they be? a. b. c. d. 5. If you were an astronomer, what question(s) about the solar system would you want to investigate? a. b. c. d. pg. 23