Unit E Lesson 3: The Universe
Completion requirements
Unit E Lesson 3: The Universe
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Learning Targets |
Big Question: What is understood currently about how
matter
is distributed in the Universe?
The science of astronomy is special because it is the study of something very far away; so far, in fact, that most astronomers never get a chance to see what they study in person.
The science of astronomy is special because it is the study of something very far away; so far, in fact, that most astronomers never get a chance to see what they study in person.
At the end of this inquiry, you should be able to answer the following questions:
- What is an astronomical unit?
- When is an astronomical units used?
- What is a light-year? When is a light-year used?
- What is the lifecycle of a Sun-like star?
- What is the lifecycle of a Massive star?
- How is a star born?
- When does a black hole form?
- How does the Hertzsprung-Russell (H-R) Diagram graph stars?
Pages 379 to 382 and 384 to 389 in your textbook will help you answer these questions.
Watch
Measuring Distance in Space
Just as you would not describe the distance between Edmonton and Calgary in millimetres, using kilometres is too small to describe the vast distances in space. Astronomers needed a better unit of measure. One Astronomical Unit (AU) is the average distance from the Sun to the Earth.
However, even the Astronomical Unit is too small to describe the distances between stars and galaxies. Watch the video below and see how even the distance between Earth and the Sun is a very small distance in the universe.
To describe the distances between stars and galaxies better, scientists use much larger distance units. The light-year, which is equal to the distance light travels in a year. Light travels at a speed of 300 000 km/s and can travel 9.5 trillion km in a single year.
Another large unit is the parsec, which is about 3.26 light years or 31 trillion km. The parsec name is a combination of parallax and arcsecond, which are very important concepts to understand for professional users powerful telescopes. Challenge yourself – read more about the parsec and see if you can understand how the unit came about.
When you are ready to have your mind blown about the size of the universe, it would be a good idea to watch this video!
Just as you would not describe the distance between Edmonton and Calgary in millimetres, using kilometres is too small to describe the vast distances in space. Astronomers needed a better unit of measure. One Astronomical Unit (AU) is the average distance from the Sun to the Earth.
However, even the Astronomical Unit is too small to describe the distances between stars and galaxies. Watch the video below and see how even the distance between Earth and the Sun is a very small distance in the universe.
To describe the distances between stars and galaxies better, scientists use much larger distance units. The light-year, which is equal to the distance light travels in a year. Light travels at a speed of 300 000 km/s and can travel 9.5 trillion km in a single year.
Another large unit is the parsec, which is about 3.26 light years or 31 trillion km. The parsec name is a combination of parallax and arcsecond, which are very important concepts to understand for professional users powerful telescopes. Challenge yourself – read more about the parsec and see if you can understand how the unit came about.
When you are ready to have your mind blown about the size of the universe, it would be a good idea to watch this video!
Figure 1 – The astronomical unit is the average distance from the Earth to Sun... the average distance is used because the orbit of Earth around the Sun is not a perfect circle.
The following video, "How do Astronomers measure distances in Space", provides additional information about distance in space. Think about the following important question as you watch the video, and refer to pages 379 to 382 in your textbook if you
need more help pondering the question:
How is looking into space like looking into the past?
The Structure of the Universe
Study the following graphic carefully – it provides a very good start to studying the structure of the universe.
Study the following graphic carefully – it provides a very good start to studying the structure of the universe.
Interactive
The Milky Way
This BrainPOP video reviews the The Milky Way. Click here to watch it.
You will need a username and password to access the video.
This BrainPOP video reviews the The Milky Way. Click here to watch it.
You will need a username and password to access the video.
- Username: 0099
-
Password: students
Try It!
Practice Worksheet: The Life Cycle of a Star
- DOWNLOAD this practice worksheet (S9_UE_S1_L3_star_lifecycle). If you prefer to use a Google Drive
or PDF version of the worksheet, click here.
- Answer the questions on the worksheet as you work through the readings and videos in this lesson. Be sure to read pages 384-389 in your textbook, and also view the Life Cycle of Stars interactive below.
- When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
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 – This image describes the star life cycle, it can be very helpful in answer questions on your practice worksheet.
Figure 3 – A nebula.
Figure 4 – A protostar.
The Birth of a Star
A
nebula
is the first step in a star’s existence. A nebula is an accumulation of
interstellar matter, the gases and dust that exist in areas of space.
Gravity is an integral component of the birth and life cycle of a star. As the clouds of gas and dust that form a nebula spin, gravitational forces act on the particles, causing a small area to collapse. As this area becomes denser, the temperature increases in the core, creating a protostar .
Depending on the amount of matter accumulated into the protostar, the star becomes either Sun-like (less mass) or massive (more mass). Massive stars not only have more mass than Sun-like stars have, but they are brighter and hotter. Sun-like stars and massive stars are both referred to as being in the main sequence. Main sequence means that the stars are converting hydrogen to helium in their cores. Stars spend most of their existence in this state, usually millions or even billions of years.
When you have completed reviewing the star life cycle stages below, be sure to read pages 384 to 389 in Science in Action to review.
Gravity is an integral component of the birth and life cycle of a star. As the clouds of gas and dust that form a nebula spin, gravitational forces act on the particles, causing a small area to collapse. As this area becomes denser, the temperature increases in the core, creating a protostar .
Depending on the amount of matter accumulated into the protostar, the star becomes either Sun-like (less mass) or massive (more mass). Massive stars not only have more mass than Sun-like stars have, but they are brighter and hotter. Sun-like stars and massive stars are both referred to as being in the main sequence. Main sequence means that the stars are converting hydrogen to helium in their cores. Stars spend most of their existence in this state, usually millions or even billions of years.
When you have completed reviewing the star life cycle stages below, be sure to read pages 384 to 389 in Science in Action to review.
Figure 5 – A massive star
Figure 6 – A Sun-like star.
Figure 7 –Lower temperature star
When all the hydrogen is converted to helium, stars have completed their main sequence. When all their “fuel” is used up, both massive stars and Sun-like stars begin to cool. This cooling causes two effects that you may find strange:
- Stars become much larger at this stage due to the nuclear reactions that occur as the core collapses.
- As stars become cooler, they appear to be red, which signifies a lower temperature in stars.
At this stage, the process for massive stars and Sun-like stars differs substantially:
Sun-like stars → red giant → white dwarf → black dwarf
Figure 8 –White dwarf
The nuclear fusion reactions occurring in red giants eventually end, causing:
As a white dwarf cools, scientists assume that it will eventually form into a small, dark black dwarf. However, this cooling may take so long that it is possible that no white dwarf has ever cooled enough to become a black dwarf.
As the fusion reactions end in red supergiants, the core collapsing causes the star to explode in a supernova. After a supernova has occurred, the core may start spinning into a neutron star, or it may continue to collapse until it becomes an exceptionally dense black hole.
- The core to collapse
-
The temperature to increase
- The star to shrink, becoming a white dwarf
As a white dwarf cools, scientists assume that it will eventually form into a small, dark black dwarf. However, this cooling may take so long that it is possible that no white dwarf has ever cooled enough to become a black dwarf.
As the fusion reactions end in red supergiants, the core collapsing causes the star to explode in a supernova. After a supernova has occurred, the core may start spinning into a neutron star, or it may continue to collapse until it becomes an exceptionally dense black hole.
massive stars →
red supergiant → supernova → neutron star or black hole
Figure 9 –supernova
Figure 10 –neutron star
Figure 11–black hole
Interactive
Life Cycle of Stars
-
This BrainPOP video examines the Life Cycle of Stars.
Click here
to watch "Life Cycle of Starts".
You will need a username and password to access the video.
- Username: 0099
-
Password: students
Check Your Understanding
Size, Brightness, and Temperature of Stars
If you look carefully at the diagram in Figure 12, you will notice that instead of the temperature increasing on the X-axis from left to right, it decreases. Blue is hottest and red is coolest. The Y-axis graphs the brightness of a star. The 1 in the middle of the axis is the approximate luminosity of the Sun. Those plotted below are dimmer and those plotted above are brighter.
Use Figure 1.18 on page 385 in your textbook to match the identified stars (A, B, C, D, E) in Figure 1 with the various kinds of stars.
Consider the size, brightness, and temperature of each of the following stars:
If you look carefully at the diagram in Figure 12, you will notice that instead of the temperature increasing on the X-axis from left to right, it decreases. Blue is hottest and red is coolest. The Y-axis graphs the brightness of a star. The 1 in the middle of the axis is the approximate luminosity of the Sun. Those plotted below are dimmer and those plotted above are brighter.
Use Figure 1.18 on page 385 in your textbook to match the identified stars (A, B, C, D, E) in Figure 1 with the various kinds of stars.
Consider the size, brightness, and temperature of each of the following stars:
Massive stars
are larger, hotter, and brighter than Sun-like stars. They are hotter and smaller than red giants or red supergiants.
Figure 12 – The size, brightness, and temperature of stars.
Red giants
are larger than Sun-like stars but smaller than red supergiants.
Red supergiants
are the largest, reddest stars.
Sun-like stars
have a luminosity of about 1.
White dwarfs
are the smallest stars.