11

The UniverseThe Universe

Chapter 20Chapter 20

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The Life and Death of StarsThe Life and Death of Stars Stars are huge spheres of hot Stars are huge spheres of hot

gases that emit light and other gases that emit light and other forms of electromagnetic forms of electromagnetic radiation.radiation.

The distance between stars is The distance between stars is measured in light years (the measured in light years (the distance that light travels in distance that light travels in one year).one year).

Star produce energy by Star produce energy by nuclear fusion, fusing nuclear fusion, fusing hydrogen in to helium.hydrogen in to helium.

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Layers of a StarLayers of a Star Core(15,000,000 K-site of Core(15,000,000 K-site of

nuclear fusion)nuclear fusion) Radiative Zone (2,500,000 K)Radiative Zone (2,500,000 K) Convective Zone (1,000,000 Convective Zone (1,000,000

K)K) Photosphere(6000 K-layer that Photosphere(6000 K-layer that

produces light)produces light) Chromosphere(4000-50,000K-Chromosphere(4000-50,000K-

layer that produces color)layer that produces color) Corona(2,000,000 K-layer that Corona(2,000,000 K-layer that

produces ultraviolet rays)produces ultraviolet rays)

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Studying StarsStudying Stars Stars are classified by Stars are classified by

brightness.brightness. Absolute magnitude is the Absolute magnitude is the

brightness of a star at a brightness of a star at a distance of 10 parsecs.distance of 10 parsecs.

Apparent magnitude is the Apparent magnitude is the brightness of a star as seen brightness of a star as seen from the earth.from the earth.

Color of a star indicates the Color of a star indicates the temperature of a star.temperature of a star. Hotter stars are blue in color.Hotter stars are blue in color. Cooler stars are red in color.Cooler stars are red in color.

The spectral lines can indicate The spectral lines can indicate the composition of a star. the composition of a star.

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Fate of StarsFate of Stars The Hertzsprung-Russell The Hertzsprung-Russell

diagram is a graph of all the diagram is a graph of all the stars in the Milky Way Galaxy.stars in the Milky Way Galaxy. The temperature is on the The temperature is on the

x-axis.x-axis. The luminosity or The luminosity or

brightness is on the y-axis.brightness is on the y-axis. Our sun is a main Our sun is a main

sequence star (typical).sequence star (typical).

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Birth of a StarBirth of a Star

Stars are born from a Stars are born from a cloud of gas or dust cloud of gas or dust called a nebula.called a nebula.

The cloud condenses to The cloud condenses to form a protostar.form a protostar.

The protostar becomes a The protostar becomes a star when the core of the star when the core of the star reaches 15,000,000 star reaches 15,000,000 K and nuclear fusion K and nuclear fusion begins.begins.

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Star LifeStar Life

The more massive stars The more massive stars live for millions of years.live for millions of years.

The less massive stars The less massive stars live for billions of years.live for billions of years.

Through out the life of Through out the life of stars, elements are fused stars, elements are fused into larger elements into larger elements (hydrogen to helium to (hydrogen to helium to carbon to oxygen to iron).carbon to oxygen to iron).

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Life Cycle of StarsLife Cycle of Stars

Stars that are less Stars that are less massive go from a massive go from a main sequence star to main sequence star to a red giant and a red giant and finishes as a dwarf finishes as a dwarf star.star.

Stars that are more Stars that are more massive go from a massive go from a giant star to a giant star to a supernova.supernova.

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End of a Star’s LifeEnd of a Star’s Life Star that are less than 1.4 Star that are less than 1.4

solar masses will use up all solar masses will use up all of its hydrogen and helium of its hydrogen and helium and become a white dwarf.and become a white dwarf.

Stars that are between Stars that are between 1.4-3.0 solar masses will 1.4-3.0 solar masses will produce a Type I produce a Type I supernova, leaving a supernova, leaving a neutron star.neutron star.

Stars that are greater than Stars that are greater than 3.0 solar masses produce 3.0 solar masses produce a Type II supernova, a Type II supernova, collapsing and producing a collapsing and producing a black hole. black hole.

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GalaxiesGalaxies A galaxy is a collection of A galaxy is a collection of

millions or billions of stars.millions or billions of stars. Galaxies are grouped in Galaxies are grouped in

clusters. clusters. The Milky Way is a spiral The Milky Way is a spiral

galaxy (galaxy (our galaxyour galaxy).). Types of Galaxies (Types of Galaxies (by shapeby shape):):

Spiral galaxies (Spiral galaxies (blue starsblue stars).). Elliptical galaxies (Elliptical galaxies (red red

starsstars).). Irregular galaxies.Irregular galaxies.

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QuasarsQuasars

Quasars are the most Quasars are the most distant and most distant and most radiant objects in the radiant objects in the universe (universe (center of center of distant galaxiesdistant galaxies).).

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Origin of the UniverseOrigin of the Universe

The universe is The universe is everything in space.everything in space.

The Big Bang Theory The Big Bang Theory states that the universe states that the universe began with a gigantic began with a gigantic explosion 10 to 20 billion explosion 10 to 20 billion years ago.years ago.

Proof of the theory is the Proof of the theory is the red shift of stars showing red shift of stars showing the universe is the universe is expanding.expanding.

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Future of the UniverseFuture of the Universe

The universe will keep The universe will keep expanding forever expanding forever ((HubbleHubble).).

The expansion of the The expansion of the universe will gradually universe will gradually slow down, and the slow down, and the universe will approach a universe will approach a limit in size.limit in size.

The universe will stop The universe will stop expanding and start to fall expanding and start to fall back in on itself.back in on itself.

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Tools to Study the UniverseTools to Study the Universe Reflecting telescopes Reflecting telescopes

use mirrors to magnify use mirrors to magnify the image.the image.

Refracting telescopes use Refracting telescopes use lenses to magnify the lenses to magnify the image.image.

Radio telescopes collect Radio telescopes collect radio waves to study the radio waves to study the stars.stars.

Spectroscopes analyze Spectroscopes analyze the light given off by stars the light given off by stars to indicate composition, to indicate composition, movement and movement and temperature of stars.temperature of stars.

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Reflecting TelescopeReflecting Telescope

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Refracting TelescopeRefracting Telescope

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Radio TelescopeRadio Telescope

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One of the greatest advancements in astronomy One of the greatest advancements in astronomy was the telescope. Which is the correct order of was the telescope. Which is the correct order of

advancements?advancements?

0 0

21

7

A.A. Radio- refracting-Radio- refracting-reflectingreflecting

B.B. Reflecting – Reflecting – refracting –radiorefracting –radio

C.C. Refracting-Refracting-reflecting-radioreflecting-radio

D.D. Radio- reflecting-Radio- reflecting-refractingrefracting

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Why do astronomers measure interstellar Why do astronomers measure interstellar distances in light years instead of kilometers or distances in light years instead of kilometers or

miles?miles?

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27A.A. Light years are a Light years are a

measure of time.measure of time.B.B. Miles and kilometers are Miles and kilometers are

too small of a unit. too small of a unit. C.C. Miles and kilometers are Miles and kilometers are

too large of a unit.too large of a unit.D.D. I don’t have a clue . . . I don’t have a clue . . .

help me!help me!

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2020

Which of the following correctly shows the age Which of the following correctly shows the age progression of an average star?progression of an average star?

1 1

23

2

A.A. Main sequenceMain sequence→White →White Dwarf→Red Giant Dwarf→Red Giant →Nebula→Nebula

B.B. Red Giant Red Giant →White →White Dwarf →Main Sequence Dwarf →Main Sequence →Nebula→Nebula

C.C. Nebula Nebula →Main →Main Sequence →Red Giant Sequence →Red Giant →White Dwarf→White Dwarf

D.D. White Dwarf White Dwarf →Red →Red Giant →Main Sequence Giant →Main Sequence →Nebula→Nebula

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What is the next likely stage of a What is the next likely stage of a protostar?protostar?

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45

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A.A. Super GiantsSuper Giants

B.B. NovaNova

C.C. Main SequenceMain Sequence

D.D. Neutron StarNeutron Star

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What type of galaxy is shown in the What type of galaxy is shown in the picture?picture?

0

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A.A. Irregular Irregular

B.B. SpiralSpiral

C.C. EllipticalElliptical

D. I have no idea … I need help!!! D. I have no idea … I need help!!!

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Review QuestionsReview Questions

Which unit is used to measure the Which unit is used to measure the distance between stars?distance between stars?

light yearlight yearWhich type of telescope uses mirrors to Which type of telescope uses mirrors to

see stars?see stars? reflecting telescopereflecting telescopeWhat happens to a star at the end of its What happens to a star at the end of its

life, that is more than 3 solar masses?life, that is more than 3 solar masses?supernova to a black holesupernova to a black hole

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Review QuestionsReview Questions

What is the color of stars that are cooler?What is the color of stars that are cooler? redredWhat is the type of brightness of a star What is the type of brightness of a star

when it is observed from the earth?when it is observed from the earth?apparent brightnessapparent brightnessWhat is graphed on the x-axis of the H-R What is graphed on the x-axis of the H-R

diagram?diagram? temperature temperature

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Review QuestionsReview Questions

What is graphed on the y-axis of the H-R What is graphed on the y-axis of the H-R diagram?diagram?

brightness or magnitudebrightness or magnitudeHow does a star produce energy?How does a star produce energy? fusionfusionHow do we know that the universe is still How do we know that the universe is still

expanding?expanding? red shiftred shift

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Review QuestionsReview Questions

Name the three types of galaxies.Name the three types of galaxies. irregular, spiral, ellipticalirregular, spiral, ellipticalWhat is used to classify galaxies?What is used to classify galaxies?shapeshapeWhat is the color of very hot stars?What is the color of very hot stars?blueblueName the three types of telescopes.Name the three types of telescopes. reflecting, refracting, radioreflecting, refracting, radio

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Review QuestionsReview Questions

How do you calculate the distance that How do you calculate the distance that light travels in one year?light travels in one year?

Multiply the number of seconds in a year Multiply the number of seconds in a year by the speed of light.by the speed of light.

What is the speed of light?What is the speed of light?300,000 km/s 300,000 km/s What is the name of the theory of the What is the name of the theory of the

creation of the universe?creation of the universe?Big BangBig Bang

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Review QuestionsReview Questions

What do we call the most distance objects What do we call the most distance objects in the universe?in the universe?

quasars.quasars.How long ago did the Big Bang take How long ago did the Big Bang take

place?place?10 to 20 billion years ago10 to 20 billion years agoWhat will the sun turn into when it dies?What will the sun turn into when it dies?white dwarfwhite dwarf

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Review QuestionsReview Questions

Which galaxy do we live in?Which galaxy do we live in? Milky WayMilky Way What type of galaxy is the Milky Way?What type of galaxy is the Milky Way? spiralspiral Which type of galaxy has old red stars?Which type of galaxy has old red stars? ellipticalelliptical Which type of galaxy has young blue stars?Which type of galaxy has young blue stars? spiralspiral

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Review QuestionsReview Questions

What can the spectrograph tell us about a What can the spectrograph tell us about a star?star?

compostion, temperature, and whether the compostion, temperature, and whether the star is approaching us or going awaystar is approaching us or going away

Who proposed that the universe is Who proposed that the universe is expanding by the red shift?expanding by the red shift?

Edwin HubbleEdwin HubbleWhat does hydrogen fuse into in a star?What does hydrogen fuse into in a star?heliumhelium

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Review QuestionsReview Questions

When does a star change from a nebula and When does a star change from a nebula and protostar to a star?protostar to a star?

The core of the star heats up to 15 million K to The core of the star heats up to 15 million K to begin nuclear fusion.begin nuclear fusion.

What happens to a medium size star (1.4 to 3.0 What happens to a medium size star (1.4 to 3.0 solar masses) when it dies?solar masses) when it dies?

supernova to a neutron starsupernova to a neutron star What do you call the brightness of a star at the What do you call the brightness of a star at the

distance of 10 parsecs?distance of 10 parsecs? absolute magnitudeabsolute magnitude

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Review QuestionsReview Questions

What happens to a star from birth to What happens to a star from birth to death?death?

nebula to proto star to either a white dwarf, nebula to proto star to either a white dwarf, supernova to neutron star or supernova to supernova to neutron star or supernova to black holeblack hole

How is the mass of the star related to the How is the mass of the star related to the length of life of a star?length of life of a star?

low mass, long life; high mass, short lifelow mass, long life; high mass, short life