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Life Cycle of Stars
Transcript of Life Cycle of Stars
Sirius A is a massive main sequence star
Our sun is a main sequence star.
How a black hole might appear...
without black hole
with black hole
Just like you, stars go through
life cycles also. Stars are born,
go through different phases of their
life, and eventually die.
Besides the names of the stages and fact that stars are made of different
materials, the other main difference
between us and them is time - stars "live" from anywhere between millions to trillions of years.
Stars begin their lives (and end
them eventually as well) in nebulas.
A nebula is a huge cloud of dust and gas.
*Gravity pulls material together
*New star becomes more dense
*New star gets hotter as hydrogen begins combining into helium (you know what this is, right? nuclear fusion!)
---->and a star begins its life cycle
Mrs. Vander Wolde and her
older sister - Mrs. Vander Wolde
is in the nebula stage...
Main sequence stars
Massive main sequence stars
Neutron stars & pulsars
After a star forms, it enters the second and
longest stage of its life cycle known as
the main sequence.
A main sequence star can stay in this stage for millions to a trillion years.
A star is a main sequence star for most of its
lifetime. Each of you, 8th graders, would be
in your main sequence of life, if you were a star. Your teachers would also be in the main sequence of life as stars. (Careful with those comments - your teachers aren't THAT old!)
After the main sequence stage, an average-sized star becomes a red giant. This happens when the star has used up all of its hydrogen.
*The atmosphere of the star grows very large and cools, forming a red giant.
*The center of the star shrinks.
Does anything happen differently with larger stars?
Large stars also go through a main sequence stage, the longest stage of their lives as well.
Massive stars also become red and giant, but they become even larger, so they have earned the name red supergiants.
The last stages of a star's life cycle are like the golden years that your grandparents or great grandparents are living.
In the final stage of an average-sized star’s life cycle is when it becomes a white dwarf.
A white dwarf is a small hot star; the leftover center of an older star.
Massive blue stars use their hydrogen much faster than stars like the sun do. At the end of its life, a blue star may explode in a large, bright flash called a supernova.
A supernova is a gigantic explosion in which a massive star collapses.
The explosion is so powerful that it can be brighter than an entire galaxy for several days.
After a supernova occurs, the materials in the center of a supernova are squeezed together to form a new star.
A star that has collapsed under gravity to the point at which all of its particles are neutrons is called a neutron star.
If a neutron star is spinning, it is called a pulsar.
Sometimes the leftovers of a supernova are so massive that they collapse to form a black hole.
A black hole is an object that is so massive that even light cannot escape its gravity.
A Tool for Studying & Comparing Stars
*In 1911, a Danish astronomer named Ejnar Hertzsprung (IE nawr HUHRTS sproong) compared the brightness and temperature of stars on a graph. Two years later, American astronomer Henry Norris Russell made some similar graphs. Although these astronomers used different data, they had similar results.
*The combination of their ideas is now called the Hertzsprung-Russell diagram or H-R diagram.
*This diagram shows the relationship between a star’s surface temperature and it absolute magnitude.
Here's one version of the H-R Diagram.
a. Temperature is on the bottom
b. Absolute magnitude (brightness) is along the side(s)
c. The diagonal pattern on the H-R diagram where most stars lie, is called the main sequence.
Wow, after all that, are you starstruck yet?
Mr. Hoegh's daughter
in the "nebula" stage
Mrs. Kindrat, are the
squirrels hiding today?? :(
Looking sharp today, Mr. Wilson!