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Unit 7: Comparing Planets

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Unit 7: Comparing Planets Unit 7: Comparing Planets This material was developed by the Friends of the Dominion Astrophysical Observatory with the assistance of a Natural Science and Engineering Research Council PromoScience grant and the NRC. It is a part of a larger project to present grade-appropriate material that matches 2020 curriculum requirements to help students understand planets, with a focus on exoplanets. This material is aimed at BC Grade 6 students. French versions are available. Instructions for teachers ● For questions and to give feedback contact: Calvin Schmidt [email protected], ​ ● All units build towards the Big Idea in the curriculum showing our solar system in the context of the Milky Way and the Universe, and provide background for understanding exoplanets. ● Look for Ideas for extending this section, Resources, and Review and discussion ​ ​ ​ ​ ​ questions at the end of each topic in this Unit. These should give more background on ​ each subject and spark further classroom ideas. We would be happy to help you ​ expand on each topic and develop your own ideas for your students. Contact us at ​ the [email protected]. ​ ​ Instructions for students ● If there are parts of this unit that you find confusing, please contact us at [email protected] for help. ​ ● We recommend you do a few sections at a time. We have provided links to learn more about each topic. ● You don’t have to do the sections in order, but we recommend that. Do sections you find interesting first and come back and do more at another time. ● It is helpful to try the activities rather than just read them. ● Explore the “Ideas for extending this section” and “Resources” sections at the end of each topic in this Unit - they aren’t just for teachers! Learning Objectives ● The BC curriculum requires students to learn about: ○ the “Components of our solar system” ○ “Extreme environments” This unit covers part of that requirement by discussing and comparing properties of Earth and other planets. ○ “First Peoples perspectives regarding aurora borealis and other celestial phenomena” Friends of the DAO - ExoExplorations - https://centreoftheuniverse.org/exoexplorations 1 ​ ○ “How has the exploration of extreme environments on Earth and in space changed in the last decade?” and also “Canada’s contribution to exploring extreme environments” (in the context of planets) ○ How to use ratios and percentages to compare quantities. Make measurements using conventional units. Use tables to interpret data. Learning Outcomes ● Students will learn about different properties of planets and see the great variety that exist and how they differ. ● Students will not be limited to talking about planets in our solar system and will learn about planets around other stars in order to expand the range of environments and see our solar system as one of many. Materials and tools needed for the activities ● Activity One ● Activity Two ● Activity Three ● Activity Four Time Required ● Lesson time - 90 minutes ● Activity time ○ Activities One and Two : 10 to 15 minutes each ○ Activities Three and Four : 10 minutes each Contents The activities are marked in yellow. ​ ● Many environments, many worlds ● Telescopes help us understand what planets are ○ Activity One: Resolving Power of your eye ● What a Planet is and isn’t ● Basic Differences Between Planets ○ Activity Two: Comparing Sizes and Masses ○ Activity Three: How much do you weigh on different planets? ● Exoplanet Types ● Moons ● Rings ● Volcanoes ● Planets, Magnets, and Aurora ○ Activity Four: Discover Earth’s magnetic field ● Atmospheres Friends of the DAO - ExoExplorations - https://centreoftheuniverse.org/exoexplorations 2 ​ ● Oceans and lakes ● Changes in environment ● Spacecraft and their importance in planetary exploration M any environments, many worlds If you travel on planet Earth, in person or virtually, you soon learn that it is not the same everywhere. There are regions like Antarctica where there is ice and snow year round. There are places like the Sahara where there are huge waves of sand and where it barely ever rains. There are undersea environments where the pressures are huge and it is always pitch black. There are mountain tops that poke high into our atmosphere where the air pressure is low and it is hard to breath. Humans like to live in environments where it is not at the extremes of temperature or pressure on the Earth. Our study of planets was limited to those in our solar system until the last thirty years, but we now know of 4,201 planets in 3,176 solar systems (as of August 15, 2020, according to ​ ​ Wikipedia). More are being discovered all the time, mostly using special telescopes in space designed just for that purpose. For comparison, all of the planets mentioned in all of the Star Trek series total less than 400. Planets have been found not just in our Milky Way but in distant galaxies. The word “exoplanet” refers to any planet outside of our solar system. In our galaxy alone may contain hundreds of billions of planets, according to current evidence and estimates. Most of the planets found so far have been found using the Transit method - see our Exoplanet ​ Transit Activity on our ExoExplorations page to learn more about it. ​ T elescopes helped us understand what the planets are The ancients knew very little about what planets were. To them, they were points of light in the night sky that looked similar to stars but moved over weeks or months. We call them “planets”, Greek for “wanderer”, for that reason. Some ancient people, who had little else to go on, thought they were special for that ability and reasoned that they might be gods with special powers to move around the sky. Some, like Venus and Jupiter, were at times brighter than the brightest stars. Some had distinct colours: Mars was always red, Jupiter yellowish, and Venus a pure white. But other than the basic properties people saw with their eyes, people knew very little about them until the invention of the telescope. Friends of the DAO - ExoExplorations - https://centreoftheuniverse.org/exoexplorations 3 ​ Galileo heard about the telescope in 1609 and made one for himself, and turned it towards the planets. Even in his small telescope he could see that planets weren’t just points of light like stars. Jupiter was a circular disk and Venus showed phases like our Moon, which proved it was ball-shaped (try holding a ball near a flashlight in the dark see similar phases). In Jupiter’s case he could see it had points of light slowly moving around it, and argued that they were moons, just as Earth has a moon. He and other astronomers proved that planets were worlds. When Galileo looked at Saturn in 1610 he thought that Saturn had two large moons, one on either side that touched the planet. His telescope was then only about as good as a cheap pair of today’s binoculars. A few years later he looked again and described them variously as handles, ears, or arms. It wasn’t until about 50 years later that telescopes were good enough to reveal that they were rings not touching the planet. Progress was slow. Figure 1: Galileo’s drawings of Saturn in 1610 and 1614 The planets known since ancient times - Mercury, Venus, Mars, Jupiter, Saturn - were all bright, so to learn more about them astronomers usually just required telescopes that could see more detail. We learned in Unit 3 - Seeing Stars, that bigger telescopes gather more light, but they also allow us to see more detail. The wider the telescope, the sharper the image. If you have a telescope twice as wide, you should see twice as much detail, at least as far as the optics of the telescope are concerned. Activity One shows you how to measure how well your eye can see detail. A ctivity One - Resolving Power of your Eye The following activity shows that the detail you can see is dependent on your eye and distance. Your eye has a lens in it that is similar to Galileo’s telescopes, which also used a simple lens up front to collect and focus light. R equired tools and materials: ● This link: Resolving Power of the Eye ​ ● A tape measure Friends of the DAO - ExoExplorations - https://centreoftheuniverse.org/exoexplorations 4 ​ ● A pen or pencil and some paper ● Optional: a printer and some tape, binoculars, glasses (if you wear glasses), some friends to compare results Step 1 - The “Resolving Power of the Eye” link above contains an image. You can show the ​ image on your screen (use something bigger than a phone) or print it out and tape it to a wall. One figure shows a series of grey lines while the other is a solid grey. If you are looking at it close up, it is obvious that one is lines and the other is a continuous grey. Step 2 - Write down how far your face is from the screen or paper when you look at it close up. ​ If you wear glasses, take them off. Can you still see the lines as being separate? If you are doing this with someone else you should each record what you see separately. Step 3 - Move away in increments of half a metre, starting at half a metre, and record whether ​ or not you can still see the lines as being separate. If you have glasses, record how it looks with and without your glasses. Step 4 - Keep going until the square with lines looks the same as the square without lines. ​ There will be different distances for this with and without your glasses, and if you are doing it with a partner they will likely have a different distance at which this happens.
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