Astronomy Final

Front 1

The periods of Cepheid variable stars are straightforwardly related to their corresponding

Back 1

luminosities

Front 2

The escape velocity is greater than the speed of light
within

Back 2

a black hole.
a Schwarzschild radius.
an event horizon.

Front 3

The value of a Schwarzschild radius is dependent upon
the initial _______ of a collapsing stellar core ("stellar corpse").

Back 3

mass

Front 4

Suspected candidates for stellar black holes are detected _________ in a binary star system.

Back 4

indirectly as x-ray sources

Front 5

The Sun is a member of the Milky Way galactic

Back 5

disk

Front 6

Observation of distant parts of the Milky Way Galaxy
would be severely limited if used only the visible part
of the electromagnetic spectrum. Why?

Back 6

interstellar dust blocks visible light

Front 7

Radio observations can provide information about the
Milky Way Galaxy that we cannot learn from observations in visible light because

Back 7

radio waves are able to pass through clouds of dust

Front 8

At a distance of 10 kpc from the center of the Milky Way Galaxy, the Sun takes 225 _______ to complete one orbit.

Back 8

million years

Front 9

Due to a departure from _________, astronomers have concluded that there is a lot of dark matter in the galactic halo.

Back 9

kepler's third law

Front 10

halo stars follow

Back 10

RANDOMLY INCLINED,
APPROXIMATELY CIRCULAR ORBITS.

Front 11

As a galaxy ages, the percentage of heavier elements
in the newer stars should

Back 11

increase

Front 12

The density of stars is highest in the galactic

Back 12

nucleus

Front 13

The Milky Way and the Andromeda Galaxy will collide in about five _______.

Back 13

billion years

Front 14

The core or nucleus of the Milky Way Galaxy shows evidence of the current existence of a ______ Thus, billions of years ago, the Milky Way would have looked like a ________

Back 14

supermassive black hole; quasar

Front 15

Cepheid variables are important in calculating

Back 15

the distances to galaxies

Front 16

Hubble found that the objects that were first called
spiral nebulae are instead spiral galaxies. He achieved this by observing

Back 16

cepheid variables in them

Front 17

Measurements of the total mass in clusters of galaxies indicate that they contain far more mass than is visible to us. The "missing mass" is now known to be

Back 17

cold dark matter

Front 18

The Sun is one of about how many stars in the Milky Way Galaxy?

Back 18

400 billion

Front 19

The Milky Way is a member of a cluster of about _______ called the Local Group.

Back 19

30 galaxies

Front 20

The Large and Small Magellanic Clouds are

Back 20

small nearby galaxies

Front 21

The Andromeda Galaxy (M31) is a member of a cluster of _______ called the Local Group

Back 21

30 galaxies

Front 22

Observations of the ______ of Cepheids in distant galaxies are used to determine the distances
of those galaxies.

Back 22

distances and apparent magnitudes

Front 23

A megaparsec is equal to

Back 23

10^6 parsecs

Front 24

The look-back time for a galaxy 1 Mpc away is equal
to 3.26 _______ years.

Back 24

million

Front 25

Hubble's constant has units of

Back 25

VELOCITY DIVIDED BY DISTANCE,
NAMELY, (KM PER SECOND)/MPC.

Front 26

Hubble's law applies to

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individual clusters of galaxies

Front 27

The galaxy type with the largest number of stars consists of

Back 27

elliptical galaxies

Front 28

The Milky Way is

Back 28

a barred spiral galaxy

Front 29

When galaxies "collide," the individual stars

Back 29

mostly do not collide

Front 30

The famous neighboring Andromeda galaxy is

Back 30

a normal spiral galaxy

Front 31

The lobes of a radio galaxy are ______ the visual component of the galaxy

Back 31

much larger than

Front 32

Quasars, radio galaxies, and Seyfert galaxies are examples of

Back 32

active galaxies

Front 33

The large redshifts observed in the spectra of quasars
indicate that they appear to be _____ at great velocities.

Back 33

receding

Front 34

Hubble's-law interpretation of the quasars is that they are

Back 34

far away and moving away quickly

Front 35

A quasar with a z value of 10 is moving _______ the speed of light.

Back 35

AT AN APPRECIABLE FRACTION
OF

Front 36

According to Olbers's paradox, if the Cosmos had ex-
isted forever, then the night sky would be

Back 36

bright and hot

Front 37

The Big Bang or primordial explosion occurred approximately _______ years ago.

Back 37

14 billion

Front 38

The age of the universe is approximately _____ years old

Back 38

14 billion

Front 39

A closed Universe, with spherical geometry, starting
with a Big Bang and ending with a Big Crunch, is one in which the average density is ______ the critical density.

Back 39

greater than

Front 40

an open universe is one that

Back 40

will never stop expanding

Front 41

present knowledge indicates that the universe

Back 41

is open

Front 42

If the average density of the universe were smaller
than the critical density, the universe would be

Back 42

negatively curved and open

Front 43

The measured primordial or cosmic background radiation can be explained by

Back 43

the big bang model

Front 44

If galaxy X is four times more distant than galaxy Y,
then according to Hubble's law, galaxy X appears to
be receding

Back 44

four times faster

Front 45

The main observational problem in determining the
Hubble constant for galaxies at great distances lies
in the measurement of their _____. This problem has
been overcome (but only in the past 15 years!) with
the systematic use of Type Ia supernovae as standard
candles.

Back 45

distance

Front 46

The primordial nucleosynthesis predicted by the laws
of nuclear/particle physics provides the overall proportions of ______ and other light elements
in the Cosmos (such as lithium-7). These values are in excellent agreement with their observed counterparts.

Back 46

hydrogen, helium

Front 47

Only one of the following is not manifestly support-
ing evidence in favor of the Big Bang (it does not contradict it either).

Back 47

galactic rotation curves

Front 48

What is the primary form of evidence that has led
astronomers to conclude that the expansion of the universe is accelerating?

Back 48

observation of type Ia supernovae

Front 49

The determination of distances to far-away galaxies
has led to the conclusion that the universe is expanding at

Back 49

an accelerated rate

Front 50

The fact that the universe is "accelerated" is explained by the assumption that it contains large amounts of "exotic stuff" known a

Back 50

dark energy, vaccuum energy, quintessence, cosmological-constant energy

Front 51

The list of all distinct fundamental interactions of the present Cosmos consists of

Back 51

weak, strong, electromagnetic, and gravitational

Front 52

The weak (nuclear) force is responsible for

Back 52

radioactivity and cosmic alchemy

Front 53

the strong (nuclear) force is responsible for

Back 53

THE BINDING OF QUARKS IN-
SIDE PROTONS AND NEUTRONS, AS
WELL AS THE BINDING OF PROTONS AND NEUTRONS INSIDE THE NUCLEUS.

Front 54

A proton is made up of more elementary particles known as

Back 54

up and down quarks

Front 55

The list of all distinct fundamental interactions during the era of "grand unication" (before 10
35 seconds after the Big Bang) is thought to consist of (a) gravitational interaction (1 force).

Back 55

GRAND-UNIFIED ELECTRONU-
CLEAR FORCE AND GRAVITATION
(2 FORCES).

Front 56

The inflationary model of the Big Bang provides an early period of exponential inflation at about 10^-35 seconds after the Big Bang. This inflation is qualitatively reminiscent of (but more dramatic than) the
current ______ of the Cosmos and is also due to
______.

Back 56

ACCELERATION;
A COSMOLOGICAL CONSTANT

Front 57

Our current knowledge of the early Cosmos can be extrapolated, with more or less precision, to almost the
end of the Planck era. This is the era when all the fundamental interactions, even gravity, were unified. However, our best theories fail there: we have candidates known as quantum gravity, superstrings, etc,
but space and time cease to have their usual meaning. The end of this era is where science ends and speculation begins; this time happened approximately
_____ after the Big Bang!

Back 57

10^-43 seconds

Front 58

The Tully-Fisher method of measuring distances to spiral galaxies depends on the relationship between a galaxy's absolute magnitude (luminosity) and its

Back 58

rotation rate

Front 59

the horizon and flatness problems

Back 59

ARE SOLVED BY THE INFLATION-
ARY MODEL OF THE BIG BANG.

Front 60

As the universe cooled, it eventually reached a temperature of 3,000 K and protons were able to capture and hold electrons to form neutral hydrogen. This process is known as

Back 60

recombination

Front 61

the cosmological background radiation is

Back 61

the redshifted radiation from the
time atoms were first formed in
the early universe.

Front 62

In the early universe

Back 62

Only light elements were synthesized.

Front 63

Which of the following statements denes what we mean by dark energy?

Back 63

It is a name given to whatever
is causing the expansion of the
universe to accelerate with time.

Front 64

Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?

Back 64

Dark matter is the dominant form of mass in both clusters and in individual galaxies.

Front 65

What is the distinguishing characteristic of what we call ordinary or baryonic matter?

Back 65

It consists of atoms or ions with
nuclei made from protons and
neutrons.

Front 66

Some matter may consist of what astronomers call
MACHOs (massive compact halo objects). Which of the following would not be considered a type of MACHO if it were found in the halo of the galaxy?

Back 66

neutrino

Front 67

When we speak of the large-scale structure of the universe, we mean

Back 67

the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe.

Front 68

Which of the following best sums up current scientic
thinking about the nature of dark energy?

Back 68

Dark energy probably consists of
the quantum fluctuations of the
vacuum.

Front 69

The event horizon of a black hole that results from the collapse of a 5MSun body will be

Back 69

15 km in radius

Front 70

The beautiful red supergiant Betelgeuse is a single star with a mass of approximately 17MSun this qualifies it as a "heavyweight." What is its eventual fate?

Back 70

It will produce a supernova and
leave behind a black hole.

Front 71

Which of the following is not a piece of observational evidence that one of the bodies in the binary system Cygnus X-1 is a black hole?

Back 71

The companion star is an "old"
supergiant.

Front 72

X-rays emitted from the vicinity of a black hole actually originate

Back 72

from just above the event horizon, on the accretion disk.

Front 73

Imagine that our Sun were suddenly replaced by a
black hole of the same mass (1 solar mass). What would happen to the Earth in its orbit?

Back 73

Nothing- the Earth's orbit would remain the same

Front 74

X-rays emitted from the vicinity of a black hole actually originate

Back 74

from just above the event horizon, on the accretion disk.

Front 75

What do we mean by the singularity of a black hole?

Back 75

It is the center of the black hole,
a place of infinite density where
the known laws of physics break
down.

Front 76

Which statement concerning black hole masses and Schwarzschild radii is not true?

Back 76

In a binary system with a black
hole, the Schwarzschild radius
depends on the distance from
the black hole to the companion
star.

Front 77

Consider a black hole, surrounded by an accretion disk, in a close binary star system. One foolhardy
day, a daring space traveller decides to become a hero by crossing the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least to start the process of killing him first)?

Back 77

X-rays from the accretion disk.

Front 78

Consider a binary star system consisting of a 30MSun black hole and a 70MSun red supergiant. They orbit about their common center of mass in 1/10 of a year
(i.e., say, 36.5 days) in approximately circular orbits. What is their separation distance a in AUs?

Back 78

1 AU

Front 79

The relative wavelength change
=0 of a receding galaxy (i.e., moving away from us) is 10%. What is the recession speed of this galaxy?

Back 79

c/10

Front 80

Suppose that we know that a galaxy 5 million lightyears away is receding at 20 miles per second. What would be the Hubble constant based on this single
galaxy

Back 80

(4 mi/s)/mly