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Science > chapter 19 stars, galaxies, and the universe > Flashcards

chapter 19 stars, galaxies, and the universe Flashcards

1
Q

spectrum

A

the band of color produced when white light passes through a prism

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2
Q

apparent magnitude

A

the brightness of a star as seen from the Earth

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3
Q

absolute magnitude

A

the brightness that a star would have at a distance of 32.6 light-years fro Earth

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4
Q

light-year

A

the distance that light travels in one year; about 9.5 trillion kilometers

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5
Q

parallax

A

an apparent shift in the position of an object when viewed from different locations

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6
Q

red giant

A

a large, reddish star late in its life cycle

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7
Q

white dwarf

A

a small, hot, dim star that is the leftover center of an old star

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8
Q

H-R diagram

A

Hertzsprung-Russell diagram, a graph that shows the relationship between a star’s surface temperature and absolute magnitude

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9
Q

main sequence

A

the location on the H-R diagram where most stars lie

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10
Q

supernova

A

a gigantic explosion in which a massive star collapses and throws its layers into space

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11
Q

neutron star

A

a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons

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12
Q

pulsar

A

a rapidly spinning neutron star that emits rapid pulses of radio and optical energy

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13
Q

black hole

A

an object so massive and dense that even light cannot escape its gravity

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14
Q

galaxy

A

a collection of stars, dust, and gas bound together by gravity

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15
Q

nebula

A

a large cloud of dust and gas in interstellar space; a region in space where stars are born or where stars explode at the end of their lives

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16
Q

globular cluster

A

a tight group of stars that looks like a ball and contains up to 1 million stars

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17
Q

open cluster

A

a group of stars that are close together relative to surrounding stars

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18
Q

quasar

A

a very luminous, starlike object that generates energy at a high rate; quasars are thought to be the most distant objects in the universe

19
Q

cosmology

A

the study of the origin, properties, processes, and evolution of the universe

20
Q

big bang theory

A

the theory that states the universe began with a tremendous explosion 13.7 billion years ago

21
Q

How does color indicate the temperature of a star?

A

red and yellow stars burn cooler than blue stars

22
Q

How can a scientist identify a star’s composition?

A

Because different elements absorb different wavelengths of light, astronomers can tell what elements a star is made of from the light they observe from the star

23
Q

How do scientists classify stars?

A

Stars are classified by temperature, brightness, and size.

24
Q

How do astronomers measure distances from Earth to stars?

A

Astronomers use the unit light-year to tell distance between Earth and stars. They use the star’s parallax and math to calculate the actual distance to stars that are close to Earth. A star with a large parallax is closer to Earth than a star with a small parallax.

25
Q

What is the difference between apparent motion and actual motion of stars?

A

The apparent motion of objects in the sky is related to Earth’s motion rotating on its axis. Each star is moving in space, but because they are so far away it is hard to see.

26
Q

How is brightness of stars measured?

A

The brightest stars in the sky are called first-magnitude. The dimmer the star, the larger the magnitude is. Using just our eyes, the dimmest stars we can see are sixth magnitude. Using large telescopes, scientists can see stars as dim as 29th magnitude.

27
Q

Name different types of stars.

A

main-sequence, giant, supergiant, white dwarf

28
Q

nuclear fusion

A

the process in which hydrogen changes to helium when a star becomes denser and hotter

29
Q

blue stars

A

very massive blue stars are not in the main sequence very long. They quickly use up the hydrogen in their cores, expand, and turn into giants or supergiants.

30
Q

White dwarf stars

A

small, hot stars

leftover centers of old stars

31
Q

the Sun

A

an average star
main sequence
is 1 solar diameter and has 1 solar mass

32
Q

giants and supergiants

A

an old star that has run out of hydrogen, the center shrinks inward and the outer parts expand outward

33
Q

red dwarf stars

A

low-mass stars

remain on main sequence a long time

34
Q

identify 3 types of galaxies

A

spiral, elliptical, irregular

35
Q

describe the contents and characteristics of galaxies

A

galaxies are composed of billions of stars and some planetary systems too.

36
Q

spiral galaxy

A

example: Andromeda

have a bulge at the center and spiral arms made up of gas, dust, and new stars

37
Q

elliptical galaxy

A

example: M87
massive blob
1/3 of all galaxies
very bright centers with very little dust and gas

38
Q

irregular galaxy

A

example: Large Magellanic Cloud

galaxies that don’t fit into any other class

39
Q

describe the big bang theory

A

13.7 billion years ago all the contents of the universe was compressed under extreme pressure, temperature, and density in a very tiny spot. Then the universe rapidly expanded and matter began to come together and form galaxies.

40
Q

What evidence supports the big bang theory?

A

in 1964 two scientists found radiation coming from all directions in space. One explanation for this radiation is that it is cosmic background radiation left over from the big bang.

41
Q

describe the structure of the universe.

A

the universe has a structure that is loosely repeated over and over again.

42
Q

what are 2 ways scientists calculate the age of the universe?

A

by measuring the distance from Earth to various galaxies

by calculating the ages of old, nearby stars

43
Q

what will happen if the universe expands forever?

A

if the universe expands forever, stars will age and die and the universe will become cold and dark after many billions of years.

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