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astronomy > final > Flashcards

final Flashcards

0
Q

which scientist discovered that the equations he had derived predicted an expanding universe, then modified his equations to eliminate this expansion?

A

Albert Einstein

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1
Q

what do cosmologists study

A

origin, structure and evolution of the universe

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2
Q

why is the universe expanding

A

spacetime itself is expanding, carrying the galaxies (superclusters of galaxies) with it.

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3
Q

which on of the following statements is a correct description of the expansion of the universe

A

spacetime is something real, with galaxies inside it; as spacetime expands, the galaxies( or superclusters of galaxies) are carried along by the expansion

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4
Q

what is the cosmological redshift

A

stretching of the wavelengths of photons as they travel through expanding space

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5
Q

the cosmological redshift of the light from very distant galaxies is caused by the

A

expansion of space, stretching the photon’s wavelength while the photon is traveling toward earth

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6
Q

what is it that keeps localized regions of space, such as things on earth, planetary systems, star clusters, and whole galaxies, from participating in the general expansion of the universe?

A

mutual gravitational attraction between objects in these systems

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7
Q

what is the cosmic microwave background radiation?

A

radiation left over from the Big Bang after the universe expanded and cooled

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8
Q

the cosmic background radiation is

A

low intensity radio noise, with a 3K blackbody temperature, almost uniform in intensity in all directions.

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9
Q

the cosmic background radiation is the

A

electromagnetic remnants of the explosion in which the universe was born.

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10
Q

good evidence for an original Big Bang that “created” our universe comes from

A

a background “glow” of microwaves, with blackbody temperature of about 3k

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11
Q

in relation to the universe, what does isotropy mean

A

the universe looks the same in all directions

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12
Q

what do we mean when we say that the universe is homogeneous

A

at any given time, the universe looks the same at all locations

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13
Q

how many fundamental forces are there in nature at the present time under normal conditons

A

four: strong, weak, electromagnetic and gravitational

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14
Q

what is the range of the electromagnetic force (the maximum distance over which it acts?

A

infinity

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15
Q

which is the four fundamental forces holds the electrons in the atom/

A

electromagnetic force

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16
Q

what is the gravitational force ( the maximum distance over which it acts)

A

infinity

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17
Q

what makes gravity the main force determining the large scale structure of the universe

A

while the electromagnetic force of a charged particle has an infinite range, it is usually screened and limited by the existence of charges of the opposite sign. Ordinary matter has only one sign and therefore does not screen other gravitational forces.

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18
Q

what are quarks

A

component particles making up protons and neutrons

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19
Q

what are the particles that make up protons and neutrons

A

quarks

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20
Q

most quasar produce their strongest emissions in which region of the electromagnetic spectrum

A

infrared

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21
Q

what is the most outstanding feature of a quasar compared with other objects in deep space

A

prodigious output of energy

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22
Q

quasars in our universe are

A

relatively common. Over 10000 have been identified so far

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23
Q

quasars all appear to be

A

moving away from us at very high speeds, up to about 90 of the speed of light

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24
Q

the specific characteristics that identify most quasars are

A

bright, starlike appearance with very high redshifts and hence very large distances indicating very energetic sources.

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25
Q

an intense radio source is found to coincide with a starlike object whose spectrum contains a pattern of intense emission lines in in the visible range that matches that of the Lyman uv hydrogen spectral lines but is very redshifted. what is this object

A

quasars

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26
Q

the extreme redshifts of quasar spectra are caused by

A

very high recession speeds of the sources away from the Milky Way galaxy

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27
Q

compared with the total output of energy from the Milky Way galaxy, what is the equivalent output of a typical quasar?

A

100 times brighter

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28
Q

seyfert galaxies are

A

active galaxies with bright starlike nuclei

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29
Q

seyfert galaxies are a distinct class of galaxies because they

A

have very bright, very hot starlike central cores with variable energy output

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30
Q

which of one of the following properties do seyfert galaxies and the Milky Way galaxy share

A

spiral galaxy classification

31
Q

sayfert galaxies are

A

spiral galaxies with extremely active cores

32
Q

which of the following objects is not classified as an active galaxy?

A

barred spiral

33
Q

the central engine of an active galaxy appears to be

A

a supermassive black hole at the center of an accretion disk and material being projected out perpendicular to the disk in both directions.

34
Q

for gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must

A

be almost perfectly placed on a line between Earth and the quasar.

35
Q

the mechanism that appears to generate two extensive regions of rado emission near active galaxies is

A

the double image of a single source behind the galaxy produced by gravitational lensing by the galaxy

36
Q

in observation of a double quasar image produced by gravitational lensing, fluctuations on the intensity of one image appear to be delayed compared with equivalent variations on the other image.

A

the optical path through the gravitational lens producing one images is longer than that for the other image.

37
Q

what is an Einstein ring

A

example of the image formed by a gravitational lens.

38
Q

who developed the classification system that divides galaxies into spiral, elliptical, and irregular and classifies spirals by the size of their nuclear region and the tightness of winding of their arms

A

edwin hubble

39
Q

what is the basic shape of a spiral galaxy

A

round, flat disk with long lanes of stars that curve outward from a round nuclear region of uniform brightness

40
Q

which of the following terms does not name one of the four main categories of galaxies in the Hubble classification scheme

A

starbursts

41
Q

what is the hubble classification for a spiral galaxy with a large nuclear region and tightly wound arms

A

sa

42
Q

what is the hubble classification for a spiral galaxy with a oderately sized nuclear region and moderately wound arms

A

sb

43
Q

what is the hubble classification for a spiral galaxy with a small nuclear region and loosely wound arms

A

sc

44
Q

according to the hubble classification scheme, an sc galaxy has a

A

small central bulge and loosely wound spiral arms

45
Q

a typical spiral galaxy has —– stars in a disk of diameter—ly

A

10 -11, 10-5

46
Q

spiral galaxies are classified in terms of increasing tightness of their spiral arms as types Sa, Sb, Sc. However many spiral galaxies are aligned edge on to earth and their spiral arms cannot be seen. which other parameter that is directly related to spiral arm tightness can be easily seen edge-on and can therefore be used to provide this classification.

A

size of the nuclear bulge

47
Q

a particular galaxy appears round , with a nuclear region of uniform brightness and an outer region that is broken up into curved but fuzzy and poorly defined lanes of stars and light gas clouds. How would this galaxy be classified

A

flocculent spiral

48
Q

a particular galaxy appears round with a nuclear region of uniform brightness and an outer region that is broken up into long curved well defined lanes of stars and light gas clouds. How would this galaxy be classified

A

grand design spirals

49
Q

one difficulty with the density wave theory is that

A

we are unsure of the mechanism that produces the energy output necessary to sustain the density wave.

50
Q

according to the theory of self propagating star formation, the spiral arms of flocculent spiral galaxies are broad and poorly designed because

A

the spiral arm segments are defined only by the relatively short-O and B type stars.

51
Q

why do the spiral arms show up so clearly in spiral galaxies

A

stars are spread almost uniformly over the galaxy( outside the nuclear bulge) but the brightest stars occur only in the spiral arms, where their brightness and the fact that they illuminate gas clouds make the arms stand out.

52
Q

why is the Milky Way Galaxy different from most spiral galaxies

A

The Milky Way has at least four spiral arms, whereas most galaxies have only two.

53
Q

how does the amount of dust and gas in a spiral galaxy vary with the classification of the galaxy

A

the most loosely wound galaxy, Sc, has the most dust and gas in its arms.

54
Q

what is an SBc galaxy

A

galaxy with a small nuclear bulge and loosely wound arms starting from the ends of a straight bar through the nuclear bulge.

55
Q

what is an elliptical galaxy

A

galaxy with an elliptical outline and a smooth distribution of brightness but no apparent structure.

56
Q

elliptical galaxies look far less impressive than spiral galaxies because

A

they contain no gas and dust clouds or young hot stars

57
Q

what name is give to a galaxy with a smooth distribution of brightness and a round shape

A

E0

58
Q

which of the following statement is not a characteristic of elliptical galaxies

A

elliptical galaxies have a disk and a central bulge but no spiral arms

59
Q

an elliptical galaxy typically contains which of the following primarily old kind of stars.

A

primarily old metal poor stars

60
Q

an astronomer studying a galaxy finds that its spectrum shows only old, low mass, population II stars and photographs of the galaxy show little or no interstellar gas or dust. what kind of galaxy i this astronoer studying

A

elliptical galaxy

61
Q

how are the magellanic clouds the two nearby satellite galaxies of thee milky way galaxy classified

A

irregular galaxies

62
Q

the megellanic clouds as seen from the southern hemisphere are examples of what type of objects.

A

irregular galaxies

63
Q

in which of the following types of galaxies is star formation no longer occuring.

A

elliptical galaxies

64
Q

recent evidence suggests that galaxies formed

A

from the mergers of hundreds of smaller objects

65
Q

when swirling eddies of gas rich matter in the universe collide and form a disk centered on an especially massive black hole and lot of dark matter we believe the following type of galaxy will form

A

normal spiral

66
Q

overall through space galaxies are

A

concentrated on the surface of huge open spaces or voids like soap bubbles

67
Q

how are galaxies spread throughout the universe

A

clusters of galaxies exist that are themselves often clustered into superclusters. Clusters and superclusters appear t be distributed on surfaces surrounding empty regions of space.

68
Q

The Milky Way galaxy is a

A

member of a small cluster of galaxies

69
Q

what is the local group

A

clusters of about 40 galaxies of which the Milky Way is one

70
Q

what is a rich cluster of galaxies

A

cluster containing thousands of galaxies

71
Q

what i a poor cluster of galaxies

A

a cluster containing a few dozen galaxies

72
Q

collision between galaxies

A

can las hundreds o millions of years

73
Q

what is a starburst galaxy

A

galaxy with an unusually large number of new born stars

74
Q

globular clusters

A

can be formed in collision of galaxies and thus can be young if the collision occurred recently

75
Q

as much as 90% of the matter in the universe may be unseen dark matter “ Where is this dark matter

A

Dark matter appears to be concentrated in spherical haloes around galaxies but extends several times the radius of visible matter

76
Q

dark matteer in clusters of galaxies

A

is distributed mostly in and around the galaxies in a cluster, not in the voids between galaxies

astronomy (3 decks)

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