Unit E Lesson 1: Finding Objects in Space
Completion requirements
Unit E Lesson 1: Finding Objects in Space
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Learning Targets |
Big Question: Historically, how have people on Earth learned about space?
The science of astronomy is special because it is the study of something very far away; most astronomical study is done by indirect observation.
The science of astronomy is special because it is the study of something very far away; most astronomical study is done by indirect observation.
At the end of this inquiry, you should be able to answer the following questions:
- What is the difference between a constellation and a galaxy?
- How do azimuth and altitude give a star’s location?
- What is meant by the term "zenith"?
- What is an asterism?
- What are the three types of galaxies?
- What shape is the pathway of celestial bodies?
Pages 371, 390 to 391, 401 to 402, and 404 in your textbook will help you find objects in space.
Introduction
Have you ever searched for the man in the moon? Or maybe the rabbit in the moon? Do you know if you were born in the year of the horse, or the rat? Do you know your astrological sign?
These traditions are remnants of ancient times when people were beginning to develop an understanding of space and Earth.
These traditions are remnants of ancient times when people were beginning to develop an understanding of space and Earth.
Pre-modern civilizations had a limited ability to share their beliefs and findings.
Consequently, various myths, legends, and traditions describe the natural phenomena that were seen throughout the world, such as the seasons, the movement of the sun across the sky, the stars at night, and the phases of the moon.
Guiding By the Stars
Many cultures developed legends and mythologies around the stars. Page 371 in Science in Action 9 discusses some of these beliefs. Throughout time, humans have tried to make sense of the celestial bodies that they observe but cannot explain fully. The word celestial relates to the sky or heavens. It is related to the French word “ciel” meaning sky or heaven.
Ancient people used the stars to help them in their everyday lives for purposes of navigation, agriculture, and cultural ceremonies. People have always sought to find efficient ways to better their lives. They were trying to understand better the relationship between Earth and space.
Many cultures developed legends and mythologies around the stars. Page 371 in Science in Action 9 discusses some of these beliefs. Throughout time, humans have tried to make sense of the celestial bodies that they observe but cannot explain fully. The word celestial relates to the sky or heavens. It is related to the French word “ciel” meaning sky or heaven.
Ancient people used the stars to help them in their everyday lives for purposes of navigation, agriculture, and cultural ceremonies. People have always sought to find efficient ways to better their lives. They were trying to understand better the relationship between Earth and space.
Watch
Watch the following "Find North with the Stars" video to learn more about the Big Dipper and to learn the basics of navigation by stars.
Constellations and Asterisms
Another interesting aspect of the Big Dipper is that many people incorrectly think it is a constellation. It is not, it is actually an asterism. Asterisms are discussed more in on page 390 of your textbook, the key point being that they are unofficially recognized star groupings. They may or may not be part of constellations, in the case of the Big Dipper, it is part of the constellation Ursa Major. Constellations are the 88 officially recognized regions of the sky.
Another interesting aspect of the Big Dipper is that many people incorrectly think it is a constellation. It is not, it is actually an asterism. Asterisms are discussed more in on page 390 of your textbook, the key point being that they are unofficially recognized star groupings. They may or may not be part of constellations, in the case of the Big Dipper, it is part of the constellation Ursa Major. Constellations are the 88 officially recognized regions of the sky.
The Position of Objects in Space
Have you ever been lost in a strange city or place? How did you determine where you were and how to get to your desired location? Maybe you used a GPS device in the car or on your cell phone. Maybe you used a map to find a route. Maps use latitude and longitude to help people find locations on earth.
But before satellite Global Positioning Systems (GPS), and even before people understood longitude and latitude, what would you use? Prior to the concepts of latitude and longitude becoming commonly understood, people used stars to find their way.
By understanding the placement of the stars and their movement throughout the year, sailors could navigate their way through wide expanses of open water using the stars for guidance. To construct a map of the sky, a system was developed for communicating the position of the stars. On earth, latitude measures distance north and south of the equator and longitude measures distance east and west from the Prime Meridian. All places on Earth can be identified by their unique location using this system. In the sky, the terms azimuth, altitude, and zenith are used to describe the location of a celestial body.
Have you ever been lost in a strange city or place? How did you determine where you were and how to get to your desired location? Maybe you used a GPS device in the car or on your cell phone. Maybe you used a map to find a route. Maps use latitude and longitude to help people find locations on earth.
But before satellite Global Positioning Systems (GPS), and even before people understood longitude and latitude, what would you use? Prior to the concepts of latitude and longitude becoming commonly understood, people used stars to find their way.
By understanding the placement of the stars and their movement throughout the year, sailors could navigate their way through wide expanses of open water using the stars for guidance. To construct a map of the sky, a system was developed for communicating the position of the stars. On earth, latitude measures distance north and south of the equator and longitude measures distance east and west from the Prime Meridian. All places on Earth can be identified by their unique location using this system. In the sky, the terms azimuth, altitude, and zenith are used to describe the location of a celestial body.
Figure 1 – Understanding the difference between azimuth and altitude is an important aspect of positioning objects in space.
Important Navigation Terms
Azimuth is the direction of a compass bearing and measures between 0 and 360 degrees. The azimuth is always the first number determined when a scientist locates a celestial body. This determines the direction to point a telescope to find the celestial body.
Altitude is the height of a celestial body above the horizon, ranging from 0 at sea level to 90 degree straight up. Altitude is the second number in a celestial body’s location, and determines how high in the sky point a telescope.
Zenith is the highest point in the sky directly overhead. It is always 90° straight up overhead.
Azimuth is the direction of a compass bearing and measures between 0 and 360 degrees. The azimuth is always the first number determined when a scientist locates a celestial body. This determines the direction to point a telescope to find the celestial body.
Altitude is the height of a celestial body above the horizon, ranging from 0 at sea level to 90 degree straight up. Altitude is the second number in a celestial body’s location, and determines how high in the sky point a telescope.
Zenith is the highest point in the sky directly overhead. It is always 90° straight up overhead.
Try It!
Practice Worksheet: Azimuth and Altitude
- DOWNLOAD this practice worksheet (S9_UE_S1_L1_azimuth_altitude). If you prefer to use a Google Drive or PDF version of the worksheet, click here.
- To complete the questions on the worksheet, you either need to click here to use this simulation, or watch the video below. The simulation uses
Flash, which may not work on some computers, in that case, use the video. Answer the questions on the worksheet as you use the simulation or watch the video. Pages 401 and 402 in your text are also excellent references for this practice worksheet.
- When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button located below the video.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
Figure 2 – There are several demonstrations of azimuth and altitude available on the Internet, try searching for such demonstrations yourself. The more practice you get, the better.
1. zero degrees
2. 360 degrees
3. -90 degrees
4. 90 degrees
5a.
i. southeast, low
ii. southwest, high
5b. when altitude is smaller, the star is closer to the horizon
5c. azimuth is direction, altitude is height
2. 360 degrees
3. -90 degrees
4. 90 degrees
5a.
i. southeast, low
ii. southwest, high
5b. when altitude is smaller, the star is closer to the horizon
5c. azimuth is direction, altitude is height
Determining the Motion of Objects in Space
You may lose your place on a printed map, but the map will stay in one place while you relocate your position. What if you were using a map to determine your position and navigate your way to a location, but the map was constantly changing? Sometimes, as you zoom in and out on an online map, you can become disoriented, but hitting a reset button will make the original map reappear so that you can begin your search again. Can you imagine trying to use a map with a reset button that took an entire year?
Using the stars for navigation required not only the ability to determine their position but also an understanding of how the night sky would change throughout the year. The Earth rotates counter-clockwise with one complete rotation being completed every 24 hours. Tilted at a degree of 23 degrees, the Earth orbits the Sun over approximately 365 days, one year. To understand the celestial sphere and the motion of objects in the night sky, picture yourself running around an indoor track. You are the Earth as it completes its orbit around the sun.
You may lose your place on a printed map, but the map will stay in one place while you relocate your position. What if you were using a map to determine your position and navigate your way to a location, but the map was constantly changing? Sometimes, as you zoom in and out on an online map, you can become disoriented, but hitting a reset button will make the original map reappear so that you can begin your search again. Can you imagine trying to use a map with a reset button that took an entire year?
Using the stars for navigation required not only the ability to determine their position but also an understanding of how the night sky would change throughout the year. The Earth rotates counter-clockwise with one complete rotation being completed every 24 hours. Tilted at a degree of 23 degrees, the Earth orbits the Sun over approximately 365 days, one year. To understand the celestial sphere and the motion of objects in the night sky, picture yourself running around an indoor track. You are the Earth as it completes its orbit around the sun.
You are running counter-clockwise; the sun is to your left (at the centre of the field). The bleachers on your right represent the stars and galaxies visible to us at night from Earth. As you make your way around the track, you will be
able to see your friends and family members (the stars and galaxies) sitting in the seats only as you approach and pass them. From the other side of the track (orbit), the the huge, bright Sun would prevent you from seeing them. This
is the reason we can see certain constellations only once per year.
But, we can see some stars and galaxies all year round although their positions change slightly. These are the constellations that we can view from the north celestial pole (in the northern hemisphere) or from the south celestial pole (in the
southern hemisphere).
Picture yourself running around the track again — this time, looking up. As you run, you can always see the beams in the roof although their direction appears to change. If there were a picture on the roof, it would appear slightly different to you depending on your position on the track. Similarly, the Big Dipper is an asterism that can be viewed throughout the year at northern latitudes, but its position changes.
Picture yourself running around the track again — this time, looking up. As you run, you can always see the beams in the roof although their direction appears to change. If there were a picture on the roof, it would appear slightly different to you depending on your position on the track. Similarly, the Big Dipper is an asterism that can be viewed throughout the year at northern latitudes, but its position changes.
Watch
Watch the videos below for more information on how to spot stars in the night sky, and then test yourself with the questions below the videos.
Motion of Objects in Space
- Why does the night sky appear to change throughout the year?
- What is the ecliptic?
- What is the celestial sphere?
The night sky appears to change because the Earth orbits around the sun.
The apparent path of the Sun through the sky during the year is an ecliptic.
The celestial sphere is the name given to the very large imaginary “sphere of sky” surrounding Earth.