Chapter 30 Section 1 Chapter 30 Section 1 HandoutHandout

Characteristics of StarsCharacteristics of Stars

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What is a star?What is a star? A ball of gases that gives off a tremendous A ball of gases that gives off a tremendous

amount of electromagnetic energy.amount of electromagnetic energy.

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How does the color of stars seen from How does the color of stars seen from Earth differ from their actual color?Earth differ from their actual color? From Earth, stars appear as tiny specs of From Earth, stars appear as tiny specs of

white light, but they actually vary in color.white light, but they actually vary in color.

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How do astronomers learn about stars?How do astronomers learn about stars? By analyzing the light that stars emit.By analyzing the light that stars emit.

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What are spectrographs?What are spectrographs? Devices that separate light into different Devices that separate light into different

colors.colors.

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What are the three types of spectra?What are the three types of spectra? EmissionEmission AbsorptionAbsorption ContinuousContinuous

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What does a star’s dark-line spectrum What does a star’s dark-line spectrum reveal?reveal? The star’s composition and temperature.The star’s composition and temperature.

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What is true of the layers of a star?What is true of the layers of a star? The inner layers are very hotThe inner layers are very hot The outer layers are somewhat coolerThe outer layers are somewhat cooler

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Elements in the outer layers of a star Elements in the outer layers of a star absorb:absorb: Some of the light radiating from within the Some of the light radiating from within the

star.star.

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What do the colors and lines in the What do the colors and lines in the spectrum of a star indicate?spectrum of a star indicate? The elements that make up the star.The elements that make up the star.

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What is the most common element in What is the most common element in stars?stars? Hydrogen (H)Hydrogen (H) Helium (He)Helium (He)

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Matching star color with star temperature.Matching star color with star temperature. Less than 3,500Less than 3,500ooCC

RedRed

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Matching star color with star temperature.Matching star color with star temperature. 10,000-30,00010,000-30,000ooCC

Blue-whiteBlue-white

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Matching star color with star temperature.Matching star color with star temperature. 3,500-50003,500-5000ooCC

OrangeOrange

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Matching star color with star temperature.Matching star color with star temperature. 5,000-6,0005,000-6,000ooCC

YellowYellow

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Matching star color with star temperature.Matching star color with star temperature. 7,500-10,0007,500-10,000

WhiteWhite

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What is indicated by a star’s color?What is indicated by a star’s color? The surface temperature of the star.The surface temperature of the star.

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What color are the coolest stars?What color are the coolest stars? RedRed

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What is the diameter of the sun?What is the diameter of the sun? 1,390,000 km1,390,000 km

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Stars that are very dense may have:Stars that are very dense may have: More mass than the sun and still be much More mass than the sun and still be much

smaller than the sun.smaller than the sun.

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What two kinds of motion are associated What two kinds of motion are associated with stars?with stars? Actual motion and apparent motion.Actual motion and apparent motion.

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What causes the apparent motion of the What causes the apparent motion of the stars, which we can see with the unaided stars, which we can see with the unaided eye?eye? The movement of the Earth.The movement of the Earth.

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What causes the circular trails of light What causes the circular trails of light seen in long-exposure photographs of the seen in long-exposure photographs of the stars?stars? The rotation of Earth on its axis.The rotation of Earth on its axis.

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In the Northern Hemisphere, the In the Northern Hemisphere, the movement of stars called circumpolar movement of stars called circumpolar stars makes them appear:stars makes them appear: To circle Polaris, the North Star.To circle Polaris, the North Star.

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What is true of all visible stars at the North What is true of all visible stars at the North pole?pole? They are circumpolar.They are circumpolar.

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What are three types of actual motion that What are three types of actual motion that stars may have?stars may have? They rotate on an axisThey rotate on an axis They may revolve around another starThey may revolve around another star They either move away from or toward out They either move away from or toward out

solar system.solar system.

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What is the Doppler effect?What is the Doppler effect? The apparent shift in wavelength of light The apparent shift in wavelength of light

emitted by a light source moving toward or emitted by a light source moving toward or away from an observer.away from an observer.

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What does the fact that most distant What does the fact that most distant galaxies have red-shifted spectra indicate?galaxies have red-shifted spectra indicate? That those galaxies are moving away from That those galaxies are moving away from

Earth.Earth.

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What is a light-year?What is a light-year? The distance that light travels in one year.The distance that light travels in one year.

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How many kilometers does light travel in How many kilometers does light travel in one year?one year? 700 trillion km700 trillion km 700,000,000,000,000 km700,000,000,000,000 km

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When we witness an event on the sun, When we witness an event on the sun, when did it actually take place?when did it actually take place? About 8 minutes before we see it.About 8 minutes before we see it.

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Except for the sun, what star is nearest to Except for the sun, what star is nearest to Earth?Earth? Proxima CentauriProxima Centauri

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What is parallax and how do scientists use What is parallax and how do scientists use it?it? The apparent shift in a star’s position when The apparent shift in a star’s position when

viewed from different locations.viewed from different locations. Scientists measure it to determine a relatively Scientists measure it to determine a relatively

close star’s distance from Earth.close star’s distance from Earth.