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Interactive H-R Diagram ray.org/labs/star_life/hr_interactive.html ray.org/labs/star_life/hr_interactive.html

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The Universe Universe is space and everything in it. Universe is space and everything in it.

How do measure distance in space? Light Year- the distance that light travels in one year through space. − 1 light year = 9.5 trillion km or 5.9 trillion miles (Speed of light is 300 million m / s, or 186,000 miles / s )

How are stars classified? -Stars are classified by size, temperature, and brightness. Size: Stars can range from small, medium, giant (huge), and supergiant. Temperature: It is opposite! Blue White Yellow Red-orange Red HOT COLD Brightness: Absolute Magnitude: The brightness the star would have if it were at a standard distance from earth. The actual brightness of a star. Apparent Magnitude : The brightness of the star as seen from earth. How bright a star looks.

H-R Diagram A graph that shows the relationship between a star’s surface temperature and it’s absolute magnitude (luminosity).

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H-R Diagram

A star is born A star is made up of a large amount of gas in a relatively small volume. A star is made up of a large amount of gas in a relatively small volume. A nebula, on the other hand, is a large amount of gas and dust spread out in an immense volume. A nebula, on the other hand, is a large amount of gas and dust spread out in an immense volume. All stars begin their lives as parts of nebulas. Gravity can pull some of the gas and dust in a nebula together. All stars begin their lives as parts of nebulas. Gravity can pull some of the gas and dust in a nebula together. The contracting cloud is then called a protostar. The contracting cloud is then called a protostar. A star is born when the contracting gas and dust become so hot that nuclear fusion starts. A star is born when the contracting gas and dust become so hot that nuclear fusion starts.

Lifetimes of Stars How long a star lives depends on how much mass it has. How long a star lives depends on how much mass it has. Stars with more mass have shorter lives than those with less mass. Stars with more mass have shorter lives than those with less mass. Small stars use up their fuel more slowly than large stars, so they have much longer lives. Small stars use up their fuel more slowly than large stars, so they have much longer lives. Generally, stars that have less mass than the sun use their fuel slowly, and can live for about 200 billion years. Generally, stars that have less mass than the sun use their fuel slowly, and can live for about 200 billion years. Medium- mass stars like the sun live for about 10 billion years. Medium- mass stars like the sun live for about 10 billion years.

Death of Stars When a star begins to run out of fuel, the center of the star shrinks and the outer part of the star expands. The star becomes a red giant or supergiant. When a star begins to run out of fuel, the center of the star shrinks and the outer part of the star expands. The star becomes a red giant or supergiant. All main sequence stars eventually become red giants or supergiants. However, what happens next depends on the mass of the stars. All main sequence stars eventually become red giants or supergiants. However, what happens next depends on the mass of the stars. When a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole. When a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole.

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White Dwarf Small and medium stars become red giants and then white dwarfs. Small and medium stars become red giants and then white dwarfs. Their outer layers expand to become red giants. Their outer layers expand to become red giants. Eventually, the outer parts grow bigger still and drift out into space. Eventually, the outer parts grow bigger still and drift out into space. The blue white hot core is left behind causing a white dwarf. The blue white hot core is left behind causing a white dwarf. When there is no more energy it becomes a black dwarf. When there is no more energy it becomes a black dwarf.

Black Holes The most massive stars- those having more than 40 times the mass of sun- become black holes when they die. The most massive stars- those having more than 40 times the mass of sun- become black holes when they die. After this kind of star becomes a supernova, more than five times the mass of the sun may be left. After this kind of star becomes a supernova, more than five times the mass of the sun may be left. The gravity of this mass is so strong that the gas is pulled inward, packing it into a smaller and smaller space. The gravity of this mass is so strong that the gas is pulled inward, packing it into a smaller and smaller space.

Neutron Stars A dying giant or supergiant star can suddenly explode. Within hours, the star blazes millions of times brighter. A dying giant or supergiant star can suddenly explode. Within hours, the star blazes millions of times brighter. The explosion is called a supernova. The explosion is called a supernova. After a star explodes, some material from the star is left behind. This material may become part of a nebula. After a star explodes, some material from the star is left behind. This material may become part of a nebula. This material may form a neutron star. This material may form a neutron star. Neutron stars are even smaller and denser than white dwarfs. Neutron stars are even smaller and denser than white dwarfs.

Galaxies A large grouping of stars in space Currently over 50 million galaxies in the universe 3 Types Spiral Irregular Elliptical

Spiral Galaxy Spiral arms w/ a bulge in the center. Milky Way is a spiral galaxy

Elliptical Galaxy Elongated shape Very bright centers w/ very little dust or gas Contain mostly old stars

Irregular Galaxy Irregular shape Located close to spiral galaxies

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“Main Sequence” Sun-like and Smaller Stars Due to the mass of the star, fusion occurs (hydrogen is fused together releasing light and heat) Stars the size of our sun can undergo fusion for 10 billion years. After all of the helium undergoes fusion, it becomes a white dwarf. As the fuel continues to dwindle the star eventually becomes a black dwarf. As the hydrogen runs out and helium undergoes fusion, the star turns into a red giant.

“Giants” Huge Stars (1.5-3X the mass of the sun) The remnants of the explosion could become a neutron star The remnants of the explosion could become a neutron star Stars this size usually undergo fusion for less time than the sun-like stars. Stars this size usually undergo fusion for less time than the sun-like stars. As a supergiant can suddenly explode into a supernova. As a supergiant can suddenly explode into a supernova. As the hydrogen runs out and helium undergoes fusion, the star turns into a super giant. As the hydrogen runs out and helium undergoes fusion, the star turns into a super giant.

“Super Giants” Giant Stars (over 3X the mass of the sun) A dying supergiant can explode into a supernova. As the hydrogen runs out helium and undergoes fusion, the star turns into a supergiant. Due to the immense mass, the material may be pulled by gravity inward, packing the gas so tightly a black hole is formed.

Quasars Quasar is a distant galaxy with a black hole at its center. Quasar is a distant galaxy with a black hole at its center. As enormous amounts of gas revolve around such objects as a black hole, the gas heats up and shines brightly. As enormous amounts of gas revolve around such objects as a black hole, the gas heats up and shines brightly.