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Earth Science > Chapter 30: Stars > Flashcards

Chapter 30: Stars Flashcards

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1
Q

What is a star?

A

A ball of gases that gives off a tremendous amount of electromagnetic energy (from thermonuclear fusion), starts vary in color

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2
Q

What are spectrographs?

A

Devices that separate light into different colors, or wavelengths

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3
Q

What is a spectrum?

A

Starlight passing through a spectrograph produces a display of colors and lines called a spectrum

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4
Q

What are the 3 types of spectra?

A
  • Emission (bright-line)
  • Absorption (dark-line)
  • Continuous
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5
Q

What is a dark-line spectra? (what does it reveal?)

A
  • All stars have this
  • Bands of color crossed by dark lines where the color is diminished
  • Reveals the star’s composition and tempurature
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6
Q

What happens to the elements in the outer layers of a star?

A

They absorb some of the light radiating within the star

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7
Q

How can scientists determine the elements that make up a star?

A
  • By studying its spectrum

- Different elements absorb different wavelengths of light

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8
Q

What do the colors and lines in the spectrum of a star indicate?

A

The elements that make up the star

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9
Q

What have scientists learn though spectrum analysis?

A

That stars are made up of the same elements that compose Earth

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10
Q

What are the most common elements in stars?

A

1) Hydrogen (mostly)
2) Helium
3) Carbon, oxygen, nitrogen

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11
Q

How is the surface temperature of a star indicated?

A

By its color

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12
Q

What is the range for the temperatures of most stars?

A

2,800 C to 24,000 C

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13
Q

What are the surface temperatures of stars that are:

1) blue
2) red
3) yellow

A

1) 35,000 C (some as high as 50,000 C)
2) 3,000 C
3) 5,500 C

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14
Q

What is the range in sizes of stars?

A

Dwarf stars: as small as Earth
Medium-sized stars: 1,390,000 km
Giant stars: 1,000 times sun’s diameter

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15
Q

How big are most stars visible from Earth? (how far can we see them)

A
  • Medium-sized (similar to our sun)

- Within 100 light years

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16
Q

How dense are stars?

A
  • Many have about the same mass as the sun
  • Can be very dense (and more mass than sun) but still much smaller than the sun
  • Can be less dense (and less mass than sun) but have larger diameter than the sun
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17
Q

What is the apparent motion of a star? (caused by what, in which 2 ways, circular trails)

A

-Motion visible to the unaided eye
-Caused by the movement of Earth
-Curves of light record apparent motion in the northern sky
-Circular trails- stars moving counter-clockwise around a central star called Polaris (North Star)
-Circular pattern caused by the rotation of Earth on its axis
Earth’s revolution around sun- different stars visible during different seasons
-Shifts west slightly every night

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18
Q

What are circumpolar stars? (where are all stars circumpolar, what is one example)

A
  • Stars always visible in night sky
  • In Northern Hemisphere makes them appear to circle Polaris
  • The Little Dipper (in Northern Hemisphere)
  • North Pole- all stars circumpolar
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19
Q

What is the actual motion of a star?

A
  • Rotate on an axis
  • May revolve around another star
  • Either move away from or toward our solar system
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20
Q

What is the Doppler effect?

A
  • The apparent shift in the wavelength of light emitted by a light source moving toward or away from and observer
  • An observed change in the frequency of a wave when the source or observer in moving
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21
Q

What is blue shift? Why does it occur?

A
  • The colors in the spectrum of a star moving toward Earth are shifted slightly toward blue
  • Occurs because the light waves from a star appear to have shorter wavelengths as the star moves toward Earth
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22
Q

What is red shift? Why does it occur?

A
  • A star moving away from Earth has a spectrum that is shifted slightly red
  • Occurs because the wavelengths of light appear to be longer
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23
Q

What color spectra do distant galaxies have? What does it indicate?

A
  • Red-shifted spectra

- Indicates that they are moving away from Earth

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24
Q

What is the nearest star to the Earth? (how far)

A
  • Proxima Centauri

- 4.2 light years (300,000 times the distance from Earth to sun)

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25
Q

What is parallax?

A
  • The apparent shift in a star’s position when viewed from different locations
  • Used by scientists to determine a star’s distance from Earth (for stars within 1,000 light years from Earth)
  • As Earth orbits the sun, a nearby star will appear to shift slightly relative to stars that are farther from Earth
  • Closer = larger shift
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26
Q

How many stars can be seen through telescopes on Earth?

A

3 billion

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27
Q

How many stars are visible from Earth without a telescope?

A

6,000

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28
Q

What does the visibility of a star depend on?

A

Its brightness and distance from Earth

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29
Q

What is a star’s apparent magnitude? (depends on what)

A
  • The brightness of a star as it appears to us on Earth
  • Depends on both how much light the star emits and how far the star is from Earth
  • Lower number = appears brighter from Earth
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30
Q

What is a star’s absolute magnitude?

A
  • Its true brightness
  • How bright the star would appear if all the stars were at a standard, uniform distance from Earth (32.6 light years)
  • Brighter the star actually is = lower number of absolute magnitude
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31
Q

What is a star’s luminosity?

A

The total amount of energy that it gives off each second

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32
Q

What is the Hertzsprung-Russel (H-R) diagram?

A
  • A graph that illustrates the pattern of plotting the surface temperatures of stars against their luminosity
  • Temp- horizontal (highest on the left)
  • Luminosity- vertical (highest at the top)
  • Describes the life cycles of stars
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33
Q

What is the main sequence?

A
  • The temperature and and luminosity for most stars fall within a band that runs diagonally through the middle of the H-R diagram
  • Extends from cool, dim, red stars at the lower right to hot, bright, blue stars at the upper left
  • The sun is in this band
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34
Q

What does Newton’s law of universal gravitation state?*

A
  • All objects in the universe attract each other through gravitational force
  • This force increases as the mass of an object increases or as two objects become closer together
  • Nearby particles pulled toward the area of increasing mass (gravitational pull increases)
  • Nebula becomes denser
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35
Q

What is a protostar?

A
  • The shrinking, spinning region of dense matter begins to flatten into a disk
  • Contracts for several million years
36
Q

What is plasma?

A
  • Separate state of matter
  • Gas becomes so hot- electrons stripped from their parent atoms
  • Nuclei and free electrons move independently
  • A hot, ionized gas that consists of an equal number of free-moving positive ions and electrons
37
Q

What is stellar equilibrium and how is it achieved?

A
  • Achieved when the inward force of gravity is balanced by the outward pressure from fusion and radiation inside the star
  • Makes the star stable in size (as long as the star has an ample supply of hydrogen to fuse into helium)
38
Q

What is the main-sequence stage? (how long are different size stars on this stage)

A
  • Second and longest stage
  • Energy continues to be generated in the core of the star as hydrogen fuses into helium (releases energy, stopping it from contracting)
  • Star with similar mass to sun is in this stage for 10 billion years
  • Larger stars (fuses hydrogen faster)- 10 million years
  • Less massive- hundreds of billions of years
39
Q

When will the sun’s fusion stop? What will happen then?

A
  • 5 billion years, 10% of sun’s original hydrogen converted into helium, fusion will stop in the core
  • Sun’s temp and luminosity will change, sun will move off main sequence
40
Q

What is a star’s third stage?

A
  • Almost all of its hydrogen atoms in core have fused to helium atoms
  • Without hydrogen for fuel, core will contract under its gravity- increases temp of core
  • Transfers energy into thin shell of hydrogen surrounding core
  • Causes hydrogen fusion to continue in the shell of gas
  • Radiates energy outward
  • Outer shell expands greatly
41
Q

What are giant stars?

A
  • A very large and bright star whose hot core has used most of it hydrogen
  • Star’s shell of gases grows cooler as it expands
  • As the gases in the outer shell become cooler, they begin to glow with a reddish color
  • Large surface area- very bright
  • Stars that have about as much mass as the sun
  • Above main sequence on H-R diagram
42
Q

What are supergiants?

A
  • Main-sequence stars that are more massive than the sun will become larger than giants in their third stage
  • Top of H-R diagram
  • 100+ times larger than sun
  • Betelgeuse
  • High luminosity, surfaces relatively cool
43
Q

What is a planetary nebula? (and when does it become one)

A
  • Fusion in the core will stop after the helium atoms have fused into carbon and oxygen
  • Energy no longer available from fusion- enters final stag
  • As the star’s outer gases drift away, the remaining core heats these expanding gases
  • A cloud of gas that forms around a sun-like star that is dying
  • May for a sphere or ring or more complex shapes (ex. a double lobe)
44
Q

What is a white dwarf? How are they formed? (how long, where on H-R, size)

A
  • Planetary nebula disperses, gravity causes the remaining matter in the star to collapse inward
  • The matter collapses until it cannot be pressed any further
  • A white dwarf- hot/extremely dense core of matter is leftover form old star
  • Shine for billions of years before they cool completely, and become fainter
  • Lower left of H-R
  • Hot but dim, very small (size of Earth)
  • Final stage for many stars
45
Q

What is a black dwarf?

A

When a white dwarf no longer gives off light (process is long)

46
Q

What is a nova?

A
  • A star that suddenly becomes brighter (1,000 times brighter)
  • White dwarf revolving around red giant, the gravity of dense white dwarf may capture gases form red giant
  • Gases accumulate on surface, pressure builds up
  • May cause large explosions- releases energy and stellar material into space
  • Fades back to normal brightness within days
  • May become nova several times
47
Q

What is a supernova in a white dwarf star?

A
  • Tremendous explosion- blows itself apart
  • White dwarf accumulates so much mass on its surface that gravity overwhelms the outward pressure
  • Star collapses, becomes so dense that the outer layers rebound and explode outward
  • 1,000’s of times more violent than nova
  • Completely destroys red dwarf and much of red giant
48
Q

What are supernovas in massive stars?

A
  • Part of their life cycle (don’t need secondary star to fuel them)
  • After supergiant stage, these stars contract with a gravitational force that is much greater than that of small-mass stars
  • Collapse- high temp and pressure, thermonuclear fusion begins again (carbon atoms- heavier elements: oxygen, magnesium, silicon)
  • Continues until core is almost entirely iron
  • Iron has stable structure, fusion of iron to heavier elements takes energy form star rather than giving it off
  • Used its supply of fuel- core begins to collapse under own gravity
  • Energy transferred from core to outer layers, explode outward with great force
49
Q

What is a neutron star?

A
  • After supernova, core may contract into very small and dense ball of neutrons
  • A star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons
  • Rotate rapidly
50
Q

What are pulsars? (how do we detect them)

A
  • A rapidly spinning neutron star that emits pulses of radio and optical energy that sweeps across space
  • We detect pulses of radio waves every time the beam sweeps by Earth
51
Q

What is a black hole? (how are they created)

A
  • Some massive stars produce leftovers too massive to become stable neutron stars
  • If the remaining core of a star contains more than 3 times the mass of the sun, the star may contract further under its gravity- force crushes dense star core and leaves black hole
  • An object so massive and dense that even light cannot escape its gravity
52
Q

How can black holes be detected?

A
  • Observed by its effect on a companion star
  • Matter from companion star pulled into black hole
  • Just before matter is absorbed, it swirls around the black hole
  • Gas becomes so hot that X rays are released
  • Scientists try to find the mass of the object that is affecting the companion star
  • Black hole only exists if the companion star’s motion shows that a massive, invisible object is nearby
53
Q

What is a constellation?

A
  • One of 88 regions into which the sky has been divided in order to describe the locations of celestial objects
  • A group of stars organized in a recognizable pattern
54
Q

Where do the names of stars come from?

A
  • Latin
  • Real or imaginary animals
  • Ancient gods
  • Legendary heroes
55
Q

What are binary stars?

A

-Pairs of stars that revolve around each other and are held together by gravity

56
Q

What is the barycenter?

A
  • The center of mass between two stars revolving around each other in systems where two stars have similar masses
  • If one star is more massive than the other, the barycenter will be closer to the more massive star
57
Q

What are multiple-star systems?

A
  • More than half of stars part of them
  • Two or more stars are closely associated, they form multiple star-systems
  • With more than two stars: two stars revolving around barycenter while third star revolves more slowly at a greater distance from the pair
58
Q

What are clusters?

A

Nebulas collapse to form groups of hundreds of thousands of stars

59
Q

What are globular clusters?

A

Have a spherical shape and can contain up to 100,000 stars

60
Q

What is an open cluster?

A

Loosely shaped cluster and rarely contains more than a few hundred stars

61
Q

What is a galaxy?

A
  • A collection of stars, gas, and dust that is bound together by gravity
  • 100,000 light years in diameter
  • 200 billion stars
  • Hundred of billions of galaxies in the universe
62
Q

What are Cepheid variables?

A
  • Giant stars that brighten and fade in a regular pattern
  • Cycles range from 1-100 days
  • Longer cycle = the brighter the star’s visual absolute magnitude is
63
Q

How can scientists calculate the distance to a Cepheid variable

A

By comparing the Cepheid’s absolute magnitude and the Cepheid’s apparent magnitude (this distance tells them the distance to the galaxy in which the Cepheid is located)

64
Q

What is a spiral galaxy? (+barred)

A
  • Has a nucleus of bright stars and flattened arms that spiral around the nucleus
  • Spiral arms consist of billions of young stars, gas, and dust
  • Barred spiral galaxy: some galaxies have a straight bar of stars that runs through the center
65
Q

What is an elliptical galaxy?

A
  • Vary in shape (nearly spherical to very elongated)
  • Extremely bright in the center and do not have spiral arms
  • Have few young stars and contain little dust and gas
66
Q

What is an irregular galaxy?

A
  • Has no particular shape
  • Usually have low total masses and are fairly rich in dust and gas
  • Not very many of them
67
Q

What is the Milky Way galaxy?

A
  • Cloud-like band that stretches across the sky
  • A spiral galaxy in which the sun is one of hundreds of billions of stars
  • Each star orbits around the center of the Milky Way
68
Q

How long does it take the sun to orbit the Milky Way?

A

225 billion years

69
Q

What is the Local Group? Which 2 are closest?

A

30 galaxies within 5 million light years of the Milky Way

The Large and Small Magellanic Cloud are closest- 170 light years

70
Q

What is a quasar?*

A
  • Viewed through an optical telescope
  • Appears as a point of light (like a faint star)
  • Shortened term form quasi-stellar radio source
  • Some project a jet of gas
  • Located in the center of galaxies distant from Earth (very bright when in center)
  • Emits large amount of energy in small volume at high rate (because of giant black hole)
71
Q

What is cosmology?

A
  • The study of the origin, structure, and future of the universe
  • Processes that affect the universe as whole
  • How the universe formed and how it will change
72
Q

How did Hubble determine the speed at which the galaxies were moving away from Earth?

A

By examining the amount of red shift

73
Q

Which galaxies did Hubble find showed the greatest red shift? (what did that mean)

A

Most distant galaxies- meant they were moving away from Earth the fastest

74
Q

What does the big bang theory state?

A
  • Billions of years ago, all the matter and energy in the universe was compressed into an extremely small volume
  • 13.8 billion years ago it exploded and began expanding in all directions (sent all energy and matter outward)
75
Q

What happened as the universe expanded (big bang theory)?

A

Some of the matter gathered into clumps that evolved into galaxies

76
Q

What is currently happening in the universe?

A

-The universe is still expanding and the galaxies continue to move apart from one another

77
Q

What does the expansion of space explain?

A

The red shift that we detect in the spectra of galaxies

78
Q

What is the timeline of events in the big bang theory?*

A

1) .000001 second– cooled to 10 trillion degrees, inflation occurs, protons + neutrons form
2) 1 second– first hydrogen ( and helium + lithium) nuclei form
3) 3 minutes later– universe 75% hydrogen nuclei, 25% helium nuclei, less than 1% lithium
4) 300,000 years– stable atoms begin forming (limit of observable universe)
5) Few hundred million years later– first stars forms, followed soon by galaxies

79
Q

What is cosmic background radiation? How was it detected?

A
  • Low levels of energy evenly distributed throughout the universe
  • Remnant of big bang
  • Detected in every direction using radio telescopes
80
Q

How cold is background radiation?

A
  • 3 degrees C above absolute zero (-273)

- 270 degrees C below zero

81
Q

What are cosmic background radiation “ripples”? (what might they indicate)

A
  • On a map that shows where temperatures differ from average background temperature, ripples become apparant
  • Irregularities in the cosmic background radiation, which were causes by small fluctuations in the distribution of matter in the early universe
  • Ripples may indicate the first stages in the formation of the universe’s first galaxies
82
Q

What does analyzing the ripples in the cosmic background radiation tell us?

A
  • The kinds of matter that humans, the planets, the stars, and the matter between the stars are made of make up only 4% of the universe
  • 23% of universe made up of dark matter
83
Q

What is dark matter?

A

A type of matter that does not give off light but that has gravity that we can detect

84
Q

What is dark energy?

A
  • Makes up most of universe
  • Composed of an unknown material
  • Acts as a force that opposes gravity
  • Some form of undetectable dark energy is pushing galaxies apart (and rate of expansion accelerating)
85
Q

What is evidence that exists for the big bang theory?

A
  • Background radiation

- Ripples- irregularitues in C

86
Q

What is the life of a star like the sun?

A

1) Nebula
2) Protostar
3) Star like the sun (main sequence)
4) Red giant
5) Planetary nebula
6) White dwarf
7) Black dwarf

87
Q

What is the life of a massive star?

A

1) Nebula
2) Protostar
3) Massive star (main sequence)
4) Red supergiant
5) Supernova
6) Neutron star
7) (Black Hole)

Earth Science (16 decks)

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