Astro Sfa 105 Ch 16 Dark Matter, Dark Energy

Front 1

What is the term for the unidentifiable type of mass, that is completely invisible to our eyes, and telescopes, that is the dominant source of gravity in the universe?

Back 1

Dark matter

Front 2

What is the "glue" that holds galaxies like our own together?

Back 2

Gravity of dark matter

Front 3

Do we know what the Universe is made of?

Back 3

"We do not know"

Front 4

What are stars and gas clouds made mostly of?

Back 4

Hydrogen
Helium
Small amounts of heavier elements mixed in.

Front 5

T or F
We now believe that the vast majority of the Universe is made of atoms.

Back 5

False,
We now beleive that the vast majority of the Universe IS NOT made of atoms

Front 6

T or F
The actual nature of dark matter and dark energy remain completely unknown.

Back 6

True

Front 7

What is the term we give to whatever unseen influence is causing the observed gravitational effects we observe?

Back 7

Dark Matter

Front 8

T or F
Mounting evidence is suggesting that the expansion of the universe is actually accelerating.

Back 8

True

Front 9

What is the term most commonly given to whatever it is that may be causing the expansion of the universe to accelerate?

Back 9

Dark Energy

Front 10

List 2 other terms that are interechangeable with the term, "dark energy?"

Back 10

1. Quintessence
2. Cosmological constant

Front 11

T or F
More scientists are more comfortable with the idea of dark matter than with dark energy.,

Back 11

True

Front 12

What obscures our view of disk stars more than a few thousand light-years away from us?

Back 12

Interstellar dust

Front 13

T or F
Radio waves penetrate interstellar dust.

Back 13

True

Front 14

T or F
Clouds of atomic hydrogen gas emit a spectral line at the radio wavelength of 21 centimeters.

Back 14

True

Front 15

What tells us a cosmic cloud's velocity toward or away from us?

Back 15

Doppler shift of the 21-cdentimeter line.

Front 16

What is the term for the model used to summarize the results of orbital velocity measurements which plots the orbital speed of objects against their orbital distance?

Back 16

Rotation curve

Front 17

T or F
The inner planets of our solar system orbit at faster speeds than outer planets.

Back 17

True

Front 18

T or F
The gravitational force holding a planet in its orbit decreases with distance from the Sun?

Back 18

True

Front 19

What happens to the rotation curve in regards to speed with increased distance in our solar system?

Back 19

It drops-off.

Front 20

T or F
The rotation curve of any astronomica system whose mass is concentrated toward the center must drop off.

Back 20

True

Front 21

T or F
Most of the mass of the Milky Way is not concentrated at its center.

Back 21

Trure

Front 22

What happens to the orbits of progressively more distant gas clouds in the Milky Way?

Back 22

Gas clouds must encircel more and more mass.

Front 23

What shape of the Milky Way's rotation curve indicates that most of our galaxy's mass lies well beyond our Sun?

Back 23

The flatness of the Milky Way's rotation curve.

Front 24

Where is the most of the mass of the Milky WAy located?

Back 24

In the Sperical halo that surround the disk.

Front 25

What amount of mass is estimated to be in the spherical halo?

Back 25

10 X the mass of the disk.

Front 26

What characteristic of the Spherical halo leads us to believe that the luminous part of the Milky Way's disk is like the tip of the iceberg, marking only the center of a much larger clump of mass?

Back 26

We have detected very little radiation coming from the spherical halo.

Front 27

How do we determine the amount of dark matter in a galaxy?

Back 27

By comparing the galaxy's mass to its luminosity/ or more formally:
mass-to-light ratio?

Front 28

What do we use a galaxy's mass-to-light ratio to determine?

Back 28

The amount of dark matter in a galaxy.

Front 29

What percent of the composition of typical spiral galaxies is dark matter?

Back 29

90%

Front 30

What percent of the composition of typical spiral galaxies is matter in the form of stars?

Back 30

10%

Front 31

T or F
We can use rotation curves to estimate the amount of dark matter in elliptical galaxies.

Back 31

False

Front 32

Why can't we use rotation curves to estimate the amount of dark matter in elliptical galaxies?

Back 32

The motions of stars in elliptical galaxies are disorganized.
We cannot assemble their velocities into a sensible rotation curve

Front 33

T or F
Every star in an elliptical galaxy has a slightly different Doppler Shift.

Back 33

True

Front 34

What happens to the spectral line for an elliptical galaxy?

Back 34

Broadens the line spanning a range of wavelengths.

Front 35

The greater the broadening of a galaxy's spectral line, the ____________ the stars must be moving.

Back 35

The greater the broadening of a galaxy's spectral line, the FASTER the stars must be moving.

Front 36

What is the formula for an object's mass-to-light ratio?

Back 36

TOTAL MASS divided by TOTAL VISIBLE LUMINOSITY:

1Msun/1Lsun

Front 37

What is the resulting unit of measure for a mass-to-light ratio?

Back 37

solar mass per solar luminosity

Front 38

Who discovered dark matter in clusters of galaxies?

Back 38

Fritz Zwicky

Front 39

When did Zwicky argue that clusters of galaxies held enormous amount of "mysterious stuff?"

Back 39

During the 1930s.

Front 40

T or F
The mass of dark matter in clusters appears to be as much as 50 times the mass in stars.

Back 40

True

Front 41

List the 3 ways of measuring cluster masses:

Back 41

1. measure speeds of galaxies orbiting the center of a cluster;
2. studying the X-ray emision from hot gas between the cluster galaxies;
3. observing how the clusters bend light as gravitational lenses.

Front 42

What is the term for the hot gas that fills the space between the galaxies in a galaxy cluster?

Back 42

Intracluster Medium

Front 43

What is primarily emitted from intracluster medium?

Back 43

X-raysThe total mass of the cluster.

Front 44

What does the temperature of intracluster medium depend upon?

Back 44

The gravitational equilibrium of the gas.

Front 45

What is the term for massive objects that bend light beams passing nearby?

Back 45

Gravitational lenses.

Front 46

What force does all of our understanding of dark matter rest on?

Back 46

Gravity

Front 47

What is the name for the category of particles that make up most of the mass of ordinary matter?

Back 47

Baryons

Front 48

What is the term for ordinary matter?

Back 48

Baryonic matter

Front 49

What is the term for extraordinary matter?

Back 49

Nonbaryonic matter

Front 50

What is the term used to describe dark matter?

Back 50

It is EXTRAORDINARY.

Front 51

T or F
Matter need not be extraoridnary to be dark.

Back 51

True

Front 52

What is the name given to the trillions of faint red stars, brown dwarfs, and Jupiter-size objects left over from theMilky Way's formation that still roam our galaxy's halo, providing much of its mass?

Back 52

MACHOs

Front 53

What does MACHOs stand for?

Back 53

Massive Compact Halo Objects

Front 54

What is the term given to dim, starlike or planetlke objects?

Back 54

MACHOs

Front 55

T or F
MACHOs are too faint for us to see directly.

Back 55

True

Front 56

What do we observe that reveals to us that MACHOs exist?

Back 56

The duration of a lensing event.

Front 57

What is thought to make up most of the dark matter in the Milky Way, baryonic or nonbaryonic matter?

Back 57

Nonbaryonic matter

Front 58

What term is used to describe particles like neutrinos that only interact with other forms of matter through the force of gravity and a force called the weak force?

Back 58

Weakly interacting particles

Front 59

Why cannot dark matter in galaxies be made of neutrinos?

Back 59

1.Because neutrinos travel through the universe at enormous speeds; and
2. Neutrinos can easily escape a galaxy's gravitational pull

Front 60

What is the term given to the hypothetical particles thought to move more slowly than neutrinos, so that their mutual gravity could hold together a large collection of them?

Back 60

WIMPs

Front 61

What does the term WIMPs stand for?

Back 61

Weakly Interacting Massive Particles

Front 62

What is the size of the "Massive Particles" in WIMPs?

Back 62

subatomic particles

Front 63

Which is thought to be the larger particle, WIMPs or neutrinos?

Back 63

Neutrinos

Front 64

What is the other term given to WIMPs?

Back 64

Cold Dark Matter

Front 65

What is thought be many astronomers to make up the vast majority of dark matter of all matter in the universe?

Back 65

WIMPs

Front 66

T or F
WIMPs can produce photons.

Back 66

False
WIMPs cannot produce photons.

Front 67

T or F
Galaxies and clusters of galaxies seem to contain more luminous matter than dark matter.

Back 67

FALSE
Galaxies and clusters of galaxies seem to contain more DARK MATTER than luminous matter.

Front 68

What is suspected to have caused the galaxies and clusters to pull together?

Back 68

Gravitational attraction of dark matter.

Front 69

Why are stars, galaxies, and clusters of galaxies considered "gravitationally bound systems"?

Back 69

Because their gravity is strong enough to hold them together.

Front 70

What has conpletely overwhelmed the expansion?

Back 70

Gravity

Front 71

What is preventing our solar system, our galaxy, and our Local Group of galaxies from expanding?

Back 71

Gravity

Front 72

What is "peculiar velocity"?

Back 72

The component of a galaxy's velocity relative to the Milky Way that deviates from the velocity expected by Hubbles' law

Front 73

What is the term given to large scale clusters that are parts of even bigger gravitationally bound systems that are still in the early stages of formation?

Back 73

Superclusters

Front 74

What are seen as groups of clusters that are more immense that clusters of galaxies?

Back 74

Large-scale structures

Front 75

In our corner of the universe, how are galaxies arranged?

Back 75

In huge chains and sheets of galaxies that span millions of light-years

Front 76

What is the term for the giant empty regions that lie between the chains and sheets of galaxies on astronomical maps?

Back 76

Voids

Front 77

What is the name for the recent mapping of our corner of the universe that has measured redshifts for nearly a million galaxies spread across about one fourth of the sky?

Back 77

Sloan Digital Sky Survey

Front 78

What is the term for the structure on an astronomical map of our corner of the universe that extends more than 1 billion light-years from end, to end?

Back 78

Sloan Great Wall, a part of the Sloan Digital Sky Survey

Front 79

T or F
Hubble established that the galaxies in the universe are rapidly flying towards one another.

Back 79

False,
Hubble established that the galaxies in the universe are rapidly flying AWAY from one another.

Front 80

List the 2 general categories that answer what are possible outcomes of the fate of the universe:

Back 80

1.if gravity is strong enough, expansion will someday halt and the universe will begin collapsing, eventually ending in a cataclysmic crunch; or
2. if the expansion can overcome the pull of gravity, the universe will continue to expand forever, growing ever colder as its galaxies grow ever farther apart.

Front 81

What is the question re: the universe and its gravity?

Back 81

Is the universe expanding fast enough to escape its own gravitational pull and keep on expanding forever?

Front 82

What is the term for the precise density marking the dividing line between eternal expansion and eventual collapse?

Back 82

critical density

Front 83

T or F
The universe does NOT appear to contain enough dark matter to prevent it from expanding forever.

Back 83

True

Front 84

T or F
Expansion of the universe appears to be speeding up.

Back 84

True

Front 85

What is the term for the mysterious repulsive force that is seems to be pushing all the universe's galaxies apart?

Back 85

Dark energy

Front 86

List the 4 categories that astronomers consider as the possibilities for the fate of the universe?

Back 86

1. recollapsing
2. critical
3. coasting
4. accerlerating

Front 87

What 3 categories of possible fates of the universe assume that gravity is the only force that affectgs the expansion rate of the universe?

Back 87

1. recollapsing
2. critical
3. coastal

Front 88

What category of possible fates of the universe ends with a "Big Crunch" when the galaxies will come crashing back, together, and the entire universe ends in a "Big Crunch"?

Back 88

Recollapsing

Front 89

What is the category of possible fates of the universe relies on the theory that the universe will never collapse but will expand more and more slowly as time progresses?

Back 89

Critical

Front 90

What possible fate of the universe relies on the density of all of the universe equals the critical density?

Back 90

Critical

Front 91

What is a "flat universe"?

Back 91

Mathematically speaking, the overall geometry of the universe is flat, because it stops expanding after infinite time.

Front 92

What 3 categories of possible fates of the universe assume that there is no dark energy?

Back 92

1. recollapsing
2. critical
3. coastal

Front 93

What category of possible fates of the universe relies on the theory that the matter density of the universe is smaller than the critical density, and the collective gravity of all its matter cannot halt the expansion?

Back 93

Coastal

Front 94

What category of possible fates of the universe sees the universe as expanding forever, with little change in its rate of expansion?

Back 94

Coastal

Front 95

Why is the coastal category so named?

Back 95

Because the expansion will continue to COAST forever.

Front 96

What is another name for a coasting universe?

Back 96

Open universe - because its overall geometry is more like the open surface of a saddle that like the closed surface of a sphere?

Front 97

What type of universe has the geometrical shape of a saddle?

Back 97

Open or coastal universe

Front 98

What category of possible fates of the universe relies on a theory of dark energy exerting a repulsive force that causes the expansion of the universe to accelerate with time, it causes the expansion rate to grow with time?

Back 98

Accelerating universe

Front 99

What is another name for a "recollapsing universe"?

Back 99

Closed universe

Front 100

Why is a closed universe, or recollapsing universe, so named?

Back 100

Mathematical calculations show that it must have an overall geometry that closes upon itself like the surface of a sphere, but in more dimiensions.

Front 101

What is the term given to Einstein's fudge factor?

Back 101

Cosmological constant

Front 102

What did Einstein consider to be his "greatest blunder" of his career?

Back 102

Invention of the cosmological constant

Front 103

T or F
The idea of a cosmological constant as a valid explanation is gaining ground.,

Back 103

True

Front 104

Which type of universe requires the least amount of time to arrive at the current separation between galaxies?

Back 104

Recollapsing universe

Front 105

What is the name that is given to the repulsive force that is causing the acceleration in the expansion of the universe?

Back 105

Dark energy

Front 106

T or F
Dark energy exists.

Back 106

WELL< we don't really know.