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A lesson on the role of comets in our Solar System

Instructors’ Guide

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s appropriate for ages 12 and up keywords: comets, Kuiper Belt, minor planets, Oort Cloud, orbit, Solar System, water A product of Inspi ring Science Educat ion created by Pamela L. Gay CosmoQuest.org/EducatorsZone cosmoquest.org

DiggingIntoComets A lesson on the role of comets in the Solar System

This lesson was written by Pamela L. Gay and was created for Inspiring Science Education January 2015 produced in collaboration with CosmoQuest (SIUE) and Galileo Teacher Training Program (NUCLIO) Creative Commons Attribution-NonCommercial (CC BY-NC) 2014 you may distribute, remix, and build upon this work non-commercially, but must retain & provide credit to the original authors, and license derivative works on the same terms. Funding for this project was provided by the European Commission’s Framework 7.

Table of Contents OVERVIEW FOR EDUCATORS ........................................................................................................................... 1 ENGAGEMENT: BUILDING A COMET .............................................................................................................. 3 EXPLORE: HOW ARE COMETS DISCOVERED (PART 1) ............................................................................ 6 EXPLAIN: COMET SURVIVAL ............................................................................................................................ 7 EXPLORE: HOW ARE COMETS DISCOVERED (PART 2) ............ ERROR! BOOKMARK NOT DEFINED. ELABORATE: WHERE DO COMETS ORIGINATE .......................................................................................... 1 EVALUATE: ARE ALL COMETS COMING FROM THE SAME PLACE? ...................................................... 1 ENGAGEMENT: BUILDING A COMET .............................................. ERROR! BOOKMARK NOT DEFINED.

DiggingIntoComets: The role of comets in the Solar System

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Instructors’ Guide Overview for Educators Objective The solar system is littered with Ice. The bulk of this material orbits quietly in the outer Solar System, but sometimes, something disturbs the ice and it comes plunging in toward the Sun. In this Hangout, we will discuss comets, how we explore them, and how they brought water to worlds like Earth.

Grade Level appropriate for ages 12 and up (US 6th grade & higher)

Time Required Minimum: 120 minutes.

Keywords comets, Kuiper Belt, minor planets, Oort Cloud, orbit, solar system, water

Next Generation Science Standards (Adaptable for 1, 5, MS, HS): • ESS1.B: Earth and the Solar System • ESS1-2: Developing and Using Models • ESS1-3: Analyze & interpret data to determine scale properties of objects in

the Solar System • SEP 2: Developing & Using Models • CCC 7: Stability & Change

Big Science Questions • All material in the Universe is made of very small particles. • The composition of the Earth and its atmosphere and the processes occurring within them

shape the Earth’s surface and its climate.

Aspects of Inquiry Cycle


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Sequence of activities (minimum 2 class periods or 1 lab block) Engage: Build a comet Explore: How are comets discovered with photometry Explain: How do comets last so long by looking at their orbits over time. Elaborate: Where do comets come from Evaluate: Are all comets coming from the same place?

Materials needed Supplies to make a soft ball-sized comet

• Rubber Mallet (preferable) or hammer • Window cleaner containing ammonia • 2 heavy-duty garbage bags • Large bowl or tub • Cooler or ice chest for storage • Large plastic serving spoon • Each group or student needs • Oven mitts • Gallon-sized bag with secure zip top • Water (~1/3-1/2 cup per student) • Dry ice (3/4 cup) • Dirt and/or sand (~3/4–1 cup) • Pebbles or small rocks • Dark corn syrup or cola (~1 Tbl) • Charcoal briquettes (1/2 brick)

Hardware and software • Salsa-J (http://bit.ly/SalsaJ) • Celestia (http://bit.ly/Celestia-en)

Pre-Requisite Knowledge • Planets and other objects move on elliptical orbits around the Sun • Phases of matter include solid, liquid, gas • The heat/brightness of the Sun and other heat sources decreases with distance

Useful Knowledge • Familiarity with Celestia


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Instructors’ Guide Engagement: Building a Comet Time required: 25 minutes as demo (optional: 40 minutes as a hands-on-activity)

Resources and references: This activity is based on the Dark Skies, Bright Kids activity “Comets – A Physical Model,” which can be found at http://bit.ly/DSBKcomets

Context: Begin with a discussion that allows you to judge the knowledge and misinformation the students have about comets. Learning Goal: Understand what happens to comets on approaching the Sun. Prior to Class: Arrange all of the ingredients to build a comet on a large surface where students will not be working and where the comet will be clearly visible. Cover the surface with one garbage bag and then line the bowl with the other garbage bag. Discussion Activity and Questions: Begin by building a comet. As your first step, break apart the dry ice with the mallet as needed to create many small pieces. Explain to the students that comets are largely made of frozen carbon dioxide (dry ice) and water. Mix these substances, and point out both of these substances are on Earth; we exhale carbon dioxide which makes up 0.04% of our atmosphere, and water is one of the primary constituents of our body and covers the majority of the surface of the planet. Next, talk about how comets contain; silicates like the dirt and rocks found on earth, ammonia like can be found at the grocery store, and complex organic materials such as those found in corn syrup or cola. Mix all of these ingredients together thoroughly.

• Ask students to describe what they see with words and to make a sketch. They should note that it is a dirty snowball. Have them estimate how much of the surface is shiny versus dirty. They should also note that it is giving off a gas they can see. Use this to point out that ice can melt to liquid or sublimate to gas.

• Ask students what they observe happening when the dry ice is in the warm room versus in the cold cooler the ice came in. They should note that the ice melts/sublimates when it is warm. Use this to explain that in the early solar system, any ice formed inside of the asteroid belt was melted and anything further away was able to survive.

Vocabulary Discussion Go over the vocabulary and the diagram on the next page. Discuss:

• What part of the comet did you make above? The nuclei

• What part of the comet is the gas most like? The coma

• When will a comet reflect the most light? When it is close to the sun because it will be bigger / have more surface to reflect the light, and the sunlight is brighter on the comet.


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Vocabulary: • Coma – Nebulous envelope forming the surrounding the nucleus of the comet. • Comet – A celestial object in orbit around the Sun with a nucleus of ice and dust, which

forms a tail of gas, and dust pointing away from the Sun on its approach. • Meteor Shower – A number of meteors that radiate from a specific point in the sky on a

given date yearly. Showers occur when Earth passes through comet debris. • Nuclei – The solid core of the comet. Typically this is only a few kilometers or less in

size. A dormant / inactive comet has no other parts. • Orbit – The motion of celestial objects around each other when they are bound by

gravity. • Phases of Matter – The states in which matter can exist - a solid, liquid, gas or plasma. • Sublimation – Change in the state of matter directly from solid to gas without passing

through the liquid phase. • Tail – Debris from the head of a comet that points away from the Sun. The tail has two

components; an ion tail of charged particles that points straight away from the sun, and a dust tail that gets left behind by the comet’s motion.


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Formative assessment question The correct answer is underlined and in italics.

1. What would happen to a comet if it was put in an orbit like Mercury's, that is nearly circular and keeps the comet near the Sun?

a. It would go through periodic outbursts of activity as new gas was exposed to the sunlight.

b. The Sun's gravity would tear it apart very quickly, and the chunks would spiral into the sun.

c. It would turn into a planet covered in water. d. It would form a tail and coma that would initially grow quite large, and would

then shrink as the comet's mass decreases until the comet falls apart.

Evaluation questions Note: These are PISA-style questions designed to judge the level of comprehension. All answers are correct, but the answer selected reflects the understanding. The answers are consistently sorted from low-performer to high-performer.

1. What happens to a comet as it approaches the Sun? a. The nucleus will give off gas that the Sun reflects off of, making the comet more

easily visible. b. The gas around the nucleus expands to ~10,000 times the size of the nucleus and a

tail forms. c. The nucleus' mass is reduced as it sublimates into light-reflecting gas that

surrounds the comet and is pushed by sunlight into a tail.

2. It has so far proven impossible to see objects in the very distant Oort cloud with a

telescope on Earth. Comets are said to come from the Oort cloud. Active comets have tails that are easily seen and very large. Why can't Oort cloud objects be seen?

a. Objects in the Oort cloud have no coma or tail. b. Objects in the Oort cloud are inactive, and the nuclei alone are only about 10km

diameter across, which is too small to see from Earth. c. The Oort Cloud doesn't get enough light to cause sublimation, and to the comet

nuclei alone has too small a reflective surface.


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Instructors’ Guide Explore: How are comets discovered (part 1) Time required: 25 minutes

Resources and references: You can find a Salsa-J instruction manual at http://bit.ly/SalsaJ-instruct

Context: Comets are discovered via images of the same area of the sky that are taken several days apart. In this activity, students will look for a comet in an image set. Activity: Break students into pairs and at computers. One student will be the pilot (the person who uses the keyboard and mouse) and the other will be the navigator (instructing the navigator what to do). Use a timer such as that found on a phone to have them swap roles every 4 minutes.

1. Have students open a provided set of images in Salsa-J 2. Students should convert the opened images into a stack using

Image > Stack > Images to Stack 3. Once the stack is created, it can be animated using

Image > Stack > Start Animation 4. Students should then look for a moving object in the image. Once it is found, students

should make a table of date/time of the image and the comet’s position (X,Y), and then plot their points.

5. Once the moving object has been found, students should also discuss anything else they notice in the images.

Discuss: 1. What causes the comet to move through the images?

Its orbit 2. What factors might affect the way (including rate) the comet moves through the images?

- changing alignment between the Earth and the comet - the comet changing speed as it approaches the Sun

Related Activities:

• Finding Asteroids in Astrometrica by Faulkes Telescope Project A lesson using Astrometrica http://bit.ly/1DxBwEv

• Comets and Coronal Mass Ejections by Texas Instruments A math intensive lesson at http://bit.ly/1BEqMj9


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Instructors’ Guide Explain: Comet Survival Time required: 30 minutes

Learning Goal: Students should understand that comets spend most of their time beyond the asteroids.

Resources and references: You can find Celestia instructions at http://bit.ly/Celestia-instruct. You can get the “Catalog of Comets” data file from http://bit.ly/Celestia-Comets. Note to Instructors: Before class, you should download the Catalogue of Comets. It will come as a zip file. Unzip this file and copy the resulting DIRL_comets_v#.##.ssc file to into the extras folder in your application folder (you may have to create this folder). NOTE: There are two parts to the student handout packet for this section: hypothesis building and the activity.

Activity Context: Explain to students that comets like Halley's comet have been observed for centuries, even though they sublimate off material everytime they get near the Sun. Ask student's to consider what must be true about how long comets are near the Sun in order for this to be true. Allow the students to talk amongst them selves while they develop their own written hypothesis. They should also discuss how to test their hypothesis.

Additional Historic Context: • "Halley's Comet was spotted by ancient greeks," by Mike Wall, space.com

• "How Halley's Comet sightings changed history over the past 2500 years," by Alasdair Wilkins, io9.com

Activity: Break students into pairs at computers. One student will be the pilot (the person who uses the keyboard and mouse) and the other will be the navigator (instructing the navigator what to do). Use a timer such as that found on a phone to have them swap roles every 4 minutes.

1. Have students pick a periodic and non-periodic comet (preferred) or two periodic comets. Groups should try not to select the same comets. Once the comets are selected use the Internet to look up the periodic comet’s next perihelion date, and the non-periodic comet’s last perihelion.

2. Create a spreadsheet that has the following columns: date, day, distance 3. For each comet do the following:

a. Look down on the inner solar system by going to: Location è Go To Object and setting it up as shown in Figure 1

b. Set the time to the time of the last perihelion by going to: Time è Set Time (You should now see the comet in your field of view).

Figure 1


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c. Compare the orbit of the comet with that of the planets. Look both at its shape and at its orientation (angle/tilt). To change your viewpoint, use the Pitch, Yaw, and Roll options under the Direction menu.

d. Watch the comet move through the solar system from the perspective of the surface of the Sun. To do this, change the Distance in the “Go to Object” window to 0.0046 au.

e. To see the distance to the comet in the upper left hand corner, click Location è Select, and search on your comet. Press return to select it. Your view may not change. That’s ok.

f. Advance time until the comet’s distance has increased by roughly 1AU. Write down this date and distance in the chart. Repeat this until the comet is at least 10 AU away

4. The date the comet is closest to the Sun is "Day 1." Subtract this date from each subsequent date to get the number of days since the comet was closest to the Sun, and put this in the day column.

5. Make one plot showing distance (Y) from the Sun versus days (x) for both comets.

An example table and plot is shown below.

Discussion Context: Students should compare their comets and draw conclusions about general cometary motion by creating a combined graph.

Combining Data: On a central computer, have each student copy in their comet's data. The first column of the table is for the Days, and each subsequent column should be labled with the name of a different comet and should contain the distance of the comet. This table will have a lot of blank cells. That is ok. Once all the data is entered, highligh all the columns and make a plot of day versus distance showing all of the comets.

Needed Concept: Recall from math: The slope of the line is the change in X over the change in Y.

EXAMPLE


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Discuss: • When did the students see the comet moving fastest?

in the beginning, when still near the Sun • Where is the slope of the line always the steepest? This is where the comet is moving the

fastest. near the Sun

• What happens to the slope of the line as the comet gets farther from the Sun? it flattens out

• A typical comet orbit is tens of years. Where must the comet spent most of this time? beyond 10AU, far from the Sun

Comets: • A list of short-period / periodic comets can be found here http://bit.ly/shortPcomets • A list of period-period / non-periodic comets can be found here http://bit.ly/longPcomets • Comets included as of DIRL_comets_v3_02.ssc

o Non-periodic comets: § C/1965 S1 (Ikeya-Seki) § C/1995 O1 (Hale-Bopp) § C/1996 B2 (Hyakutake) § C/2004 Q2 (Machholz)

o Periodic Comets: listed below

Name Next Perihelion Pyears

2P/Encke 3/10/17 3.3 4P/Faye 5/29/14 7.55 6P/d'Arrest 3/2/15 6.54 7P/Pons-Winnecke 1/30/15 6.37 8P/Tuttle 8/27/21 13.6 9P/Tempel 1 8/2/16 5.52 10P/Tempel 2 11/14/15 5.38 11P/Tempel-Swift-LINEAR 8/26/14 6.37 12P/Pons-Brooks 4/21/24 70.85 13P/Olbers 6/30/24 69.5 14P/Wolf 12/1/17 8.74 15P/Finlay 12/27/14 6.75 16P/Brooks 2 6/7/14 6.14 17P/Holmes 3/27/14 6.88 21P/Giacobini-Zinner 9/10/18 6.62 22P/Kopff 10/25/15 6.45 23P/Brorsen-Metcalf 6/8/59 70.52 24P/Schaumasse 11/16/17 8.24 26P/Grigg-Skjellerup 10/1/18 5.31 27P/Crommelin 5/27/39 27.4 28P/Neujmin 1 3/11/21 18.17 29P/Schwassmann-Wachmann 1 3/7/19 14.65


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30P/Reinmuth 1 8/19/17 7.33 31P/Schwassmann-Wachmann 2 7/6/19 8.7 32P/Comas Sola 10/17/14 8.8 33P/Daniel 8/22/16 8.06 35P/Herschel-Rigollet 2/17/92 155 36P/Whipple 5/31/20 8.5 37P/Forbes 5/3/18 6 38P/Stephan-Oterma 11/10/18 37.72 39P/Oterma 7/11/23 19.43 40P/Vaisala 1 11/15/14

41P/Tuttle-Giacobini-Kresak 4/23/17 5.41 42P/Neujmin 3 4/8/15 10.71 43P/Wolf-Harrington 8/19/16 6.14 44P/Reinmuth 2

45P/Honda-Mrkos-Pajdusakova 12/31/16 5.25 46P/Wirtanen 12/12/18 5.44 47P/Ashbrook-Jackson 6/10/17 8.3 48P/Johnson 8/12/18 6.96 49P/Arend-Rigaux 7/15/18 6.72 50P/Arend 2/8/16 8.27 51P/Harrington 3/28/16

52P/Harrington-Abell 3/7/14 7.53 53P/Van Biesbroeck 4/29/16 12.53 54P/de Vico-Swift-NEAT 4/15/17 7.31 55P/Tempel-Tuttle 5/20/31 33.22 56P/Slaughter-Burnham 7/18/16 11.54 57P/duToit-Neujmin-Delporte 5/22/15 6.42 58P/Jackson-Neujmin

59P/Kearns-Kwee 60P/Tsuchinshan 2 12/11/18 6.78

61P/Shajn-Schaldach 62P/Tsuchinshan 1 11/16/17 6.63

63P/Wild 1 64P/Swift-Gehrels 65P/Gunn 10/16/17 6.8

66P/du Toit 67P/Churyumov-Gerasimenko

6.45 68P/Klemola 11/9/19 10.82 69P/Taylor 3/18/19 6.95 70P/Kojima 10/20/14

71P/Clark 6/30/17 5.52 72D/Denning-Fujikawa 7/11/14

73P/Schwassmann-Wachmann 3 3/16/17 5.36


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74P/Smirnova-Chernykh 1/26/18 8.53 75D/Kohoutek 7/9/14

76P/West-Kohoutek-Ikemura 77P/Longmore 5/13/16 6.83

78P/Gehrels 2 4/2/19 7.22 79P/du Toit-Hartley

80P/Peters-Hartley 11/10/14 81P/Wild 2 7/20/16 6.41

82P/Gehrels 3 6/28/18 8.43 83D/Russell 1

84P/Giclas

6.96 85P/Boethin Lost 11.22 86P/Wild 3

87P/Bus 12/19/13 6.51 88P/Howell 4/6/15 5.5 89P/Russell 2 12/14/16

90P/Gehrels 1 6/19/17 91P/Russell 3

7.66

92P/Sanguin 93P/Lovas 1 3/11/17

94P/Russell 4 10/27/16 6.6 96P/Machholz 1 10/27/17 5.24 97P/Metcalf-Brewington

98P/Takamizawa

7.4 99P/Kowal 1 4/12/22 15.06 100P/Hartley 1 4/2/16 6.31 101P/Chernykh 1/13/20

102P/Shoemaker 1 4/2/16 103P/Hartley 2 4/20/17 6.47

104P/Kowal 2

6.18 105P/Singer Brewster

6.46

106P/Schuster 7/20/14 7.31 107P/Wilson-Harrington 2/5/14 4.29 108P/Ciffreo 10/18/14 7.26 109P/Swift-Tuttle 7/12/26 133.28 110P/Hartley 3

6.86

112P/Urata-Niijima

6.64 113P/Spitaler

7.09

114P/Wiseman-Skiff

6.87 115P/Maury

8.79

116P/Wild 4 1/11/16 6.48 117P/Helin-Roman-Alu 1 3/27/14 8.29 118P/Shoemaker-Levy 4 6/16/16 6.45


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119P/Parker-Hartley 4/2/14 8.84 120P/Mueller 1

8.39

121P/Shoemaker-Holt 2

9.96 122P/de Vico

74.35

123P/West-Hartley

7.59 124P/Mrkos 4/9/14 6.04 125P/Spacewatch

5.53

126P/IRAS

13.42 127P/Holt-Olmstead 3/17/16 6.4 128P/Shoemaker-Holt 1-A 1/10/17 9.51 128P/Shoemaker-Holt 1-B

9.59

129P/Shoemaker-Levy 3 2/11/14 8.96 130P/McNaught-Hughes

6.67

131P/Mueller 2

7.06 132P/Helin-Roman-Alu 2 5/21/14 8.28 133P/7968 Elst-Pizarro

5.62

134P/Kowal-Vavrova 5/21/14 15.55 135P/Shoemaker-Levy 8 11/1/14 7.5 136P/Mueller 3 5/31/16 8.59 137P/Shoemaker-Levy 2

9.55

138P/Shoemaker-Levy 7

6.89 139P/Vaisala-Oterma 12/10/17 9.61 140P/Bowell-Skiff

16.18

141P/Machholz 2-A

5.23 141P/Machholz 2-D

5.22

142P/Ge-Wang

11.05 143P/Kowal-Mrkos

8.93

144P/Kushida 8/30/16 7.6 145P/Shoemaker-Levy 5 8/31/17 8.43 146P/Shoemaker-LINEAR 6/30/16 8.08 147P/Kushida-Muramatsu 2/27/16 7.43 148P/Anderson-LINEAR

7.07

149P/Mueller 4

9.02 150P/LONEOS 7/24/16 7.67 151P/Helin

14.1

152P/Helin-Lawrence

9.54 153P/Ikeya-Zhang

366.51

154P/Brewington

10.78 155P/Shoemaker 3

17.09

156P/Russell-LINEAR 4/16/14 6.82 157P/Tritton 6/10/16 6.31 158P/Kowal-LINEAR

10.26

159P/LONEOS

14.32


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160P/LINEAR

7.92 161P/Hartley-IRAS

21.43

162P/Siding Spring

5.32 163P/NEAT

7.3

164P/Christensen

6.97 Evaluation questions (can be used for pre/post testing) Note: These are PISA-style questions designed to judge the level of comprehension. All answers are correct, but the answer selected reflects the understanding. The answers are consistently sorted from low-performer to high-performer.

1. You had the opportunity to build a model of a comet. Comets are remains of the nebula that formed our solar system. Research about their constitution, trajectories, etc is crucial for our understanding of our own origins. Which statement best describes comets?

a. Comets can originate from different parts of the Solar System and studying their orbits can provide clues on where they were formed.

b. While approaching the Sun comets suffer different physical transformations due to the proximity to our star. The study of the tails that form during such approach are important for analysing the constitution of these objects.

c. Some scientists claim that comets might be responsible for the origin of water on planet Earth. The study of their orbits, their composition, etc might be important to better understand the origin of life on Earth. Models built in laboratory might greatly help us understand such possibilities.

2. Comets change in appearance as they approach the Sun. At great distances, from the distance of Jupiter and beyond, it is extremely cold and comets are completely frozen. As they come through the inner solar system, passing Mars and coming toward the Sun, they sublimate gas and some of their material streams off as an ion tail. How can a comets' evolution best be described?

a. Comets are fossils of the formation of the Solar System and carriers of important information abou the birth of our Star and planets.

b. Comets can evolve with time and according with their interaction with the surrounding environment. They develop a tail when they approach the Sun constituted by a gas tail and a dust tail. They can extend to many kilometers in space. Parts of comets can fall on Earth and be seen in the so called "shooting stars", in other words, little rocks that eventually hit the surface of our planet.

c. Comets gas tails are formed due to ionization happening due to the interaction with sunlight. They are carried away from the Sun by solar wind. The dust tail is formed by small solid particles and is gently carried away from the comets due to the pressure of sunlight.


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3. By studying different comets you probably have noticed that they might come from different distances to the Sun, with different periods, different inclination angles when compared to the Sun-Earth system. Describe the beautiful dance of objects in the Solar System form its birth till today.

a. Many comets coming from the Oort cloud where not originally born there but ended up there after collisions with other objects in crowded places of the Solar System

b. Some comets might have originated in the Kuiper Belt, the region where we can find Pluto and many other dwarf planets. Many have the same characteristics as the objects we call trans-Neptunians.

c. We know today that the region where we find Pluto has hundreds of other objects, some perhaps even bigger than Pluto itself. The Oort cloud is another such region, populated by hundreds, if not thousands of objects, remains of the nebula that originated the Solar System. Despite strong belief of the scientific community there is no proof of its existence. It is believed that it is located 100 times further away than the Kuiper Belt.

4. Comets are not always bright objects and it is fundamental to know their existence and to carefully track their orbits. Summarize their actual behavior.

a. Scientists are regularly observing the night sky in search of yet unknown objects. Some are so small that can pass undetected.

b. Asteroids and comets can pose threats to our planet. Thus it is of the uttermost importance to know where they are. The largest objects, in particular those with high albedo, are already known. The challenge is to find those that are small and/or don't reflect the sun's light efficiently. This is of course related to their size and composition.

c. A technique that is very often used to track such objects is to observe the same area of the sky and try to spot objects that move from one image to the other and that are yet unknown. This works requires a lot of effort and careful analysis of thousands of images. Students can do this as part of their schoolwork acquiring important research skills while doing this


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Instructors’ Guide Elaborate: Where do comets originate Time required: 10 minutes

Context: Students should understand that comets originate in icy regions in the outer solar system.

Discuss: 1. Where do comets spend most of their time?

beyond the orbit of the asteroids (where they will stay frozen) 2. Does this prove or disprove the students’ hypothesis?

Vocabulary: • Perihelion – The closest point to the Sun on an orbit. • Aphelion – The furthest point from the Sun on an orbit. • Meteor Shower – A number of meteors that radiate from a specific point in the sky on a

given date yearly. Showers occur when Earth passes through comet debris.

Figure: Halley’s Comet’s orbit (by Steven Dutch, University of Wisconsin - Green Bay).

Instructors’ Guide Evaluate: Are all comets coming from the same place? Time required: 10 minutes

Context: Students should understand that comets with different kinds of orbits come from different places.

Discuss: 1. Comparing data across the classroom, do the orbits of short- and long- period comets

have different orientations? short-period comets are more often in the plane of the solar system/ long-period comets are more randomly aligned

2. If comets are creating by something changing the orbit of an icy body, where do comets originate short-period comets come from in the plane of the solar system somewhere at or beyond Neptune (this is the Kuiper Belt) long-period comets come from a distant cloud of ice (this is the Oort Cloud)

Image from http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/scale.html

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