Letot 1
STELLAR EVOLUTION
By Kyle Letot
Grade Level: 6-8
Objectives
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1. A student will be able to distinguish between the different types of stars on a HR diagram.
2. A student will be able to formally define laws related to the celestial objects orbiting stars.
3. A student will be able to distinguish the differences in apparent magnitude and absolute
magnitude.
4. A student will be able to place where and how a star is born.
5. A student will be able to explain how the Hertzsprung-Russell (H-R) diagram can be used to
deduce luminosity and temperature of stars.
Engage 1
What is a Star?
-Students divulge into knowledge about stars.
Engage 2
How long do stars live?
-Students will identify misconceptions about the age of stars.
Explore 1
What are the different stars?
-using cut outs to explain the different types of stars.
Explore 2
HR Diagram part One
-explaining the importance of luminosity and temperature. Include a
Bunsen burner to explain color in temperature.
Explore 3
HR Diagram part Two
-using colored suns, students will create their own HR diagram.
Explore 4
How do Stars work?
-a lab using balloons in visual.
*Warning! Please do not perform the lab if a latex allergy is prevalent
in the classroom.
Explore 5
A Timeline of a Star
-classic timeline activity about the life of a star.
Explore 6
Distances from here to there
-a short lab activity will introduce spatial distance from Sun to the
planets.
Letot 2
Explain 1
Star and Evolution
-review of the engage questions.
Explain 2
Distance in the Universe
-watch a short video about distance in space.
Elaborate 1
Interpreting the classifications
-a short quiz on the differences of stars
Elaborate 2
A day in the life of a star
-a quiz on the life and death of stars
Letot 3
ENGAGE ONE
What is a Star?
https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcQpZx3hs_6DgQCJ7PW_Iac9HeDCo6oLk1r4rSguPPyEJR0_h1H0
It is seen every day. It rises in the east and sets in the west up above in the sky. When you look
up, you know what it is…do you?...
Answer the following questions below with complete answers to the best of your knowledge.
1. What is a Star?
2. What is one example of a star? What is another?
3. What is a Star made of?
(If you have seen the Lion King you should know!)
http://www.youtube.com/watch?v=QZDk1cbKp7s
Letot 4
ENGAGE TWO
How old are Stars?
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTgX5OsrBGWIFWRwEDqKE1aBgTjNlCf0NBFmtwNh4NMCwX7rtVp
Ever heard of how old a Star is? Well to tell you the truth they are really
old. In fact they are older than the grandparents of your great
grandparents’ parents. Whew! Now that you know that stars are very
old, how old do you think is old?
Below right down several guesses to how old you think stars normally
are. When you have done so, write a short statement as to why you
chose that number approximation.
Letot 5
EXPLORE ONE
What Types of Stars Exist?
Wait! There is more than one kind of star out there? Actually there are
several different types of stars in existence. We only see only type
everyday which is the Sun. The Sun is what we call a Main Sequence
star. There are also white dwarfs, super giants, red giants, neutron stars,
and Protostars.
Protostar: A protostar is what you have before a star forms. It is a cloud of gas
that over time pressure and gravity push down to make it collapse into a star.
Main Sequence Star: The majority of all stars in our galaxy, Main Sequence
stars are of medium heat and live for about 10 billion years.
Red Giant: Stars that are nearing the end of their lives. The fuel that keeps
them going is running out, so the inner core contracts while the outer layer
expands.
Supergiant Star: These stars are just like the red giant stars, except much
bigger. The Blue Supergiants begin to burn Helium and become hotter. (This
explains why some are blue.)
Letot 6
White Dwarfs: These stars are one of the ends of a star. They are small,
very dense, hot star that is made mostly of carbon. They are what remain of
a red giant after the core is depleted.
Neutron Star: Another end of a star, Neutron stars are very small and super
dense. They are tightly compacted of nuetrons.
References of image URLs
http://subarutelescope.org/Pressrelease/2005/03/01/fig1.jpg
http://www.williamsclass.com/EighthScienceWork/ImagesEighth/Sun-MainSequence.jpg
http://www.passmyexams.co.uk/GCSE/physics/images/stars-life-red-giant.jpg
http://features.cgsociety.org/newgallerycrits/g29/492029/492029_1333390157_large.jpg
http://www.celestiamotherlode.net/catalog/images/screenshots/various/extrasolar_stars_White_Dwarf_Sirius_B_1__Frank_Gregorio.jpg
http://www.mpia-hd.mpg.de/~yildirim/MyPage/Neutron_Stars_files/A%20Neutron%20Star.jpg
Letot 7
EXPLORE TWO
The Hertzsprung - Russell diagram
(The HR Diagram)
The HR diagram is a diagram that shows the different types of stars in groupings
based upon temperature and luminosity (brightness). This interactive lab shows the
importance of luminosity and temperature on placing stars on the HR diagram. The
positive numbers on the luminosity axis (y axis) indicate a higher brightness.
Before we begin we’ll take a quick look at a Bunsen burner to discuss how
temperature and color of stars relate.
*Example: If a star is very bright but has a cool temperature, it would be a Supergiant.
Below is the website you will need to click on to begin the interactive lab. Once
you have the website pulled up, please click on the picture above and begin.
Complete the lab by determining the brightness and temperature of each different
star using the diagram as a guide. Click the check box to determine if you are right,
if not continue to work on the lab.
http://aspire.cosmic-ray.org/labs/star_life/hr_diagram.html
Letot 8
EXPLORE THREE
The Hertzsprung - Russell Diagram
(The HR Diagram)
Now that you have determined brightness and temperature, do you
think you can make your own HR diagram? Students will need to get
into groups of four-five. I will pass out a large sheet of paper with an x
and y axis already done for you based upon temperature and brightness.
Each group will receive tape and a small pack of colored paper circles.
Each circle will represent a star. Place these stars on the diagram in the
proper spot based upon the temperature and luminosity written on each
star. Once your group has placed the stars, use a marker and circle the
groupings of stars, naming the different types.
http://cse.ssl.berkeley.edu/segwayed/lessons/startemp/hr.gif
Letot 9
EXPLORE FOUR
How Do Stars Work?
*If there are students with a latex allergy, please revise or do not perform lab!
As we have mentioned before, stars are celestial objects made out of gas and are held
together by the force of gravity. Balloons are also made out of gas and held together by a force of
gravity, in this case it is an elastic covering. In this practical lab we will use balloons to explain
the concept of stars and how they work in the Universe. Before we begin, I will put a little rice
kernel into each balloon to represent a neutron star.
Each student will get a single balloon to blow up. This particular balloon will represent a single
star. Using this balloon, I will explain how gravity is holding the stars in place, just as the elastic
covering of rubber on the balloon is holding the air in. (I will include that stars do NOT have a
membrane such as the balloon, rather the balloon has visual similarities that students can see and
touch without the harming effects of an actual star.) Next I will point out how the air we used to
blow up the balloon is like the elements of hydrogen and helium that make up the inside of star.
The star has an inner and outer core. Once the star uses up all the hydrogen, it expands from a
Main Sequence Star into a Red giant. The inner core collapses while the outer core expands.
Students will blow up their balloons a little larger to create a giant star. Here we will pause as I
explain that as the star dies, it’ll continue to expand even larger. We will blow up our balloon
more at this point. I’ll say that the Blue Supergiants burn helium giving their bluish tint and
expanding even larger. Then I will just mention the death of a star can go either one of two ways:
1. It can implode on itself causing a planetary nebula then a white dwarf which will eventually
turn into a black dwarf once all the heat is lost. 2. It may explode into a Supernova creating
either a super dense Neutron star or a black hole. Inside of the balloons, students will now notice
the rice kernel. This represents the size of the star after it explodes. Now a Neutron star (as one
option) the kernel is what is left of a once giant star.
*When students pop the balloons, it will be done in a controlled environment and not by
anything other than a sharp pencil or pin.
Letot 10
EXPLORE FIVE
The Timeline of a Star
In the previous lab, we have explored how a star works. Now that we know how a
star functions, we’ll need to find out the stages of its life. The life cycle of a star
occurs in one of two ways. One way being that the origin is a Stellar Nebula, the
birthplace of stars. Stars then become a Main Sequence leading into a red giant
before becoming a Planetary Nebula (growing bigger then imploding), ending with
a white dwarf star. The second way is the origin is a Stellar Nebula, becoming a
larger Main Sequence star, becoming a supergiant which will lead to a supernova
(explosion).The cycle concludes with a neutron star or a black hole as the final
outcome.
*The following link leads to more information on the life cycle of a Star.
http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html
http://sc663ahenjz.weebly.com/uploads/1/3/0/6/13067854/6213087_orig.jpg
Letot 11
Students will receive little cards of these stars to put into chronological order. The
cards will engage the students and answer if they understand the lifecycle of a star.
Letot 12
EXPLORE SIX
Distances from Here to There
The distances between Earth and other stars are farther than to get to anywhere else
on Earth. You may think that to get from your home to another continent is a long
way away, but really, it is a mere fraction of the distance. To explain this concept,
the students and I will act out a practical lab using our Solar System as a basis for
the larger distances in space. To describe these long distances, the term “light year”
is used. A light year is the distance it takes for light to travel in space to a certain
object. Light travels at around 186,282 miles per second. The nearest star to our
solar system is Proxima Centauri and it is around 4.2 light years away. To better
understand such large differences we are going to experiment using a football field
and our solar system. Ten students will participate as each planet and the Sun. The
Sun will start off at the beginning of the end zone. Next the four inner planets (or
terrestrial) cram close together simulating the closer knit orbits. These planets are
Mercury, Venus, Earth, and Mars. Then we have the four gas planets; Jupiter,
Saturn, Uranus, and Neptune. These planets are much farther away from the Sun
and are more spaced out in their orbit. Our final planet Pluto is so far away that we
would have to place a child one-two more football fields away. Therefore on this
paper, Pluto cannot be located.
Letot 13
EXPLAIN ONE
Star and Evolution
Now that you have answered the questions let’s go over what you know.
1.
A star is a large celestial object in the sky. Stars can be seen in the
night sky depending on the time of the year. One star may be visible in
the sky in the winter, but come spring it may not be there anymore.
Polaris known as the North Star is the only star seen year round. If you
look to the edge of the handle of the Big Dipper, you can see it right
above.
2.
One example of a star is the Sun. The Sun is a star, but merely one
type. It is not the biggest one out there either. Another is Polaris the
North Star, or Proxima Centauri, the closest star to our Sun. There are
many more, but we’ll get to that later.
3.
A star is made of the elements hydrogen and helium and is selfsustaining. By being self-sustaining, it uses its own energy to burn and
thrive. It is held together by its own gravity and the internal nuclear
reactions are balanced by the flow of energy to the surface. Gravity is
what keeps us here on the ground as well as our very own gas planets
intact.
Letot 14
This mini quiz does not count towards your grade. I wanted to know
what you knew so we can learn from there.
Drumroll please!
The answer is…
Five million to nearly 15 billion years old! The age of an individual star
varies as they were all made at different times and have different life
spans. Stars can range from a few million to a several billion years old.
The oldest star that has been yet discovered is HE 1523-0901. It is
estimated to be around 13.2 billion years old.
Stars can be very old. We don't know exactly what the average age stars
get to be because they all die at different ages. The light that travels to
Earth from a star gives us estimation on how old they are. However by
the time the light travels through space, the star may already be dead and
we didn’t know yet.
It is estimated that our star- the sun- is over 4.6 billion years old. It is
estimated that it will live for around another 5 billion years before it
dies. So that would make it around 10 billion years!
Just a reminder,
One billion years is one thousand million years. So just think that for
every 1,000,000 * 1,000 = 1,000,000,000. That is a LOT of years!
Letot 15
EXPLAIN TWO
Distance in the Universe
Continuing what we have learned about distance in space, we will watch a short
video introducing and identifying this concept. Remember that a light year is
186,282 miles per second. That's equal to more than 670 million mph (1.08 billion
km/hr). So the distance light travels in a year is known as the light-year, and it's
equivalent to 5.88 trillion miles (9.46 trillion km). As we watch the video, there
may be mathematical terms that are not fully understood. I will pause and explain.
We will review the video and I will answer any questions after watching.
http://www.astronomy.com/Equipment/HowTo/2013/01/Observing%20Basics%20Distances%20in%20Space.aspx
As you watch Michael, the speaker on the video, think about just how fast the
speed of light is.
If time, I have a second video that introduces a quick tour of the Universe starting
inside our Solar System and working our way out to the edge of the Universe.
http://www.youtube.com/watch?v=iZJb6yFDKIw
Letot 16
ELABORATE ONE
Interpreting the Classifications
1. What is a light year? How fast does light travel?
2. Why are certain supergiant stars blue?
3. What is a Main Sequence Star? Name at least three defining factors.
4. What two elements make up a star?
5. Where are stars born? What is it?
6. Describe a black hole and how it is formed.
7. Name the different types of stars. Include whether they are hot, semi hot, or cool as well
as if they are bright, semi bright, or dim. You may write the answer on the back.
Letot 17
ELABORATE TWO
A Day in the Life of a Star
1.
Name both of the two patterns of a star’s life cycle. Include all the
steps. You may draw out the steps, but include labels as to what they are
as well.