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Astronomy > Exam #3 > Flashcards

Exam #3 Flashcards

1
Q

how is a star’s distance measured?

A

Light year (9.5 trillion kilometers, 5.8 trillion miles)

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2
Q

What is a Parsec (pc)?

A

a star’s parallax is equal to one arc second- about 3.3 light years

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3
Q

Luminosity
brightness (magnitude)
absolute magnitude

A

Measuring stars

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4
Q

-the amount of radiation leaving a star per unit of time
-measured in solar units
-Sun =1

A

the luminosity of a star

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5
Q

-the brightness of a star appears to have, related to the distance
-measures on the absolute magnitude scale
-Sun = -26.7

A

The apparent brightness (magnitude) of a star

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6
Q

-a stars apparent magnitude when viewed an 10pc
-Sun = 4.8

A

Absolute Magnitude

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7
Q

-Spectral classes- classified by spectral signatures, from decreasing temperature
-O,B,A,F,G,K,M
-O is very hot, M is cooler
-Sun is a G class star

A

Measuring Temperature

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8
Q

-measure in radius compared to the sun
-Sun = 1

A

Stellar Size

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9
Q

-Shows the relation between stellar Brightness (absolute magnitude) and temperature
-Made by plotting (graphing) each star’s luminosity (brightness) and temperature

A

Hertzsprung-Russell Diagram

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10
Q

-Main-sequence stars
-Giants (or red and blue giants)
-Super Giants
-White Dwarfs

A

Parts of an H-R Diagram

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11
Q

-90% of all stars
-band through the center of the H-R diagram
-sun is in the main sequence
-Red and dwarfs- lower-right of the H-R diagram

A

Main-sequence stars

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12
Q

-very luminous
-large
-red -upper-right of the H-R diagram
-Blue- Upper-left of the H-R Diagram

A

Giants (or red and blue giants)

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13
Q

-very large giants
-only a few percent of all-stars
-very top of the H-R diagram

A

Super Giants

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14
Q

Fainter than main-sequence stars
* Small (approximate the size of Earth)
* Lower-central area on the H-R diagram
* Not all are white in color
* Perhaps 10 percent of all stars

A

White dwarfs

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15
Q

mass/volume

A

Density

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16
Q

Stars that fluctuate in brightness

A

Variable Stars

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17
Q

-pulsating variables
-eruptive variables

A

types of variable stars

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18
Q

-fluctuate regularly in brightness
-expand and contract in size

A

pulsating variable stars

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19
Q

-explosive event
-sudden brightening
-called a nova

A

eruptive variable stars

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20
Q

2 stars orbiting around a common center of mass

A

Binary Stars

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21
Q

-visual binaries
-spectroscopic binaries (most common)
-eclipsing binaries (much rarer)

A

types of binaries

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22
Q

separated enough to be observed

A

visual binaries

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23
Q

-too distance to be resolved as 2 distinct stars
-detected by back-and-forth Doppler shifts of their spectral lines

A

Spectroscopic binaries

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24
Q

observed by the decrease in starlight intensity as a member passed in front of the other

A

eclipsing binaries

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25
Q

-cloud of dust and gases- nebula

A

Interstellar Medium

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26
Q

between the stars

A

the vacuum of space

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27
Q

-bright nebulae
-dark nebulae
-planetary nebulae

A

Types of nebulae

28
Q

-glows if it is close to a very hit star
-emission nebula
-reflection nebula

A

bright nebulae

29
Q

-not close to any bright star
-appear dark
-contains the material that forms stars and planets

A

dark nebula

30
Q

– Less diffuse than other nebulae
– Originate from remnants of dying Sun-like stars

A

planetary nebulae

31
Q

two opposing forces in a star are

A

gravity-contracts
thermal nuclear energy-expands

32
Q

stars exist because of

A

gravity

33
Q

-birth
-protostar
-main-sequence
-Red Giant
-burnout and death

A

stellar evolution stages

34
Q

in dark, cool, interstellar clouds
-gravity contracts clouds and temperature rises
-radiates long-wavelength (red) light
-becomes a protostar

A

birth

35
Q

-gravitational contraction of gaseous cloud continues
-core reaches 10 million K
-hydrogen nuclei fuse
-become helium nuclei
- the process is called hydrogen burning
-energy is released
-outward pressure increases
-outward pressure balanced by gravity pulling in
-star becomes a stable main-sequence star

A

protostar

36
Q

-Stars age at different rates
-massive stars use fuel faster and exist for only a few million years
-small stars use fuel slowly and exist for perhaps hundreds of billions of years
-90 percent of a star’s life is in this stage

A

Main-sequence stage

37
Q

-hydrogen burning migrates outward
-star’s outer envelope expands
-surface becomes red
-core is collapsing as helium is converted to carbon
-eventually all nuclear fuel is used
-gravity squeezes the star

A

Red Giant Stage

38
Q

-final stage depends on mass
-possibilities
-low-mass star- .5 solar mass, red giant collapses, becomes a white dwarf
-medium-mass star- between .5 and 3 solar masses, red giant collapses, planetary nebula forms, becomes a white dwarf
-massive star- over three solar masses, red giant supergiant, H-He-C-O-Ne-Mg-Si-Fe, terminates in a brilliant explosion called a supernova, interior condenses, may produce a hot, dense object that is either a neutron star or a black hole

A

burnout and death stage

39
Q

-small (some no larger than Earth)
-dense
-can be more massive than the sun
-spoonful weighs several tons
-atoms take up less space
-electrons displaced inward
-called degenerate matter
-hot surface
-cools to become a black dwarf

A

White Dwarf

40
Q

-Type I
-Type II

A

Supernovae

41
Q
  • involves two objects
    -a sharp rise in brightness followed by a steady, gradual decline
A

Type I Supernova

42
Q
  • involves one object
    -a sharp rise in brightness followed by a “plateau” of emission months after the peak outburst
A

Type II Supernova

43
Q

-forms from a more massive star
-star has more gravity
-squeezes itself smaller
-remnant of a supernova
-gravitational force collapses atoms
-electrons combine with protons to produce neutrons
-small size
-pea size samples weigh 100 million tons, same density as an atomic nucleus
-strong magnetic field

A

Neutron Star

44
Q

-more dense than a neutron star
-Schwarzschild Radius: critical radius at which the escape speed equals the speed of light
-intense surface gravity lets no light or event escape, known as the event horizon
-as matter is pulled into it, it becomes very hot and emits X-rays
-likely candidate is Cygnus X-1, a strong X-ray source

A

Black Hole

45
Q

-Spiral Galaxy (barred)
-Glactic Disk consists of a thin plane of matter that flattens to the galactic bulge at the center
-galactic halo: roughly spherical ball of faint old stars

A

structure of the galaxy

46
Q

-about 400 billion stars
-100,000 light year wide
-13,000 light year thick
-sun is about 25,000 light year from the galactic center
-sun is located 100 billion times that of the sun, potentially accounted for by dark matter
-Sagittarius A star” a potential black hole at the galactic center

A

survey of the galaxy

47
Q

-spiral galaxy
-barred spiral galaxy
-elliptical galaxy
-irregular galaxy

A

4 basic types of galaxies

48
Q

-arms extending from nucleus
-about 30 percent of all galaxies
-large diameter up to 125,000 light years
-contains both young and old stars

A

Spiral galaxy

49
Q

-stars arranged in the shape of a bar
-generally quite large
-about 10 percent of all spiral galaxies

A

barred spiral galaxy

50
Q

-ellipsoidal shape
-about 60 percent of all galaxies
-most are smaller than spiral galaxies; however, they are also the largest galaxies known

A

elliptical galaxy

51
Q

-lacks symmetry
-about 10 percent of all galaxies
-contains mostly young stars
-includes magellanic clouds

A

irregular galaxy

52
Q

-group of galaxies
-some contain thousands of galaxies
-local group- our own group of galaxies, contains at least 28 galaxies
-supercluster- huge swarm of galaxies, may be the largest entity in the universe

A

galactic clusters

53
Q

-galaxies that exhibit high luminosity, are very energetic

A

active galaxies

54
Q

-active galaxies emitting high amounts of energy in the radio spectrum at large distances called lobes

A

radio galaxies

55
Q

-the most powerful and luminous active galaxies
-exhibit a very high redshift (very distant)

A

Quasars or quasi-stellar objects

56
Q

galaxies frow in size by the merging of smaller galaxies

A

Hierarchical formation

57
Q

galaxies can morph by colliding with or interacting with other galaxies

A

galaxy evolution

58
Q

study of the universe, including its properties, structure, and evolution

A

cosmology

59
Q

strings of galaxy clusters

A

filaments

60
Q

large areas where few galaxies reside

A

voids

61
Q

The universe is
-Homogeneous- the same everywhere
-isotropic- the same in all directions

A

cosmological principle

62
Q

the recessional speed of galaxies is proportional to their distance
-recessional velocity= Ho x distance

A

Hubble’s law/ expanding universe

63
Q

-most galaxies exhibit a red doppler shift
-moving away
-far galaxies have greatest shift

A

expanding universe

64
Q

-model that most accurately describes birth and current state of the universe
-cataclysmic explosion 13.7 billion years ago
-accounts for other galaxies moving away from us
-universe was once confined to a “ball” that was supermassive, dense, and hot

A

big bang theory

65
Q

cosmic force proposed to be responsible for the acceleration of the Universe (Hubble expansion)

A

dark energy

66
Q

final fate depends on the average density of the universe
-if the density is more than the critical density, then the universe would contract
-current estimates point to less than the critical density and predict an ever-expanding, or open, universe

A

fate of the universe

Astronomy (4 decks)

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