Astr 2

Front 1

Radio waves travel through space at what speed?

Back 1

at the speed of light, 3 × 10^8 m/s

Front 2

In 1675, Rømer measured the speed of light by

Back 2

timing eclipses of Jupiter's satellites, which appeared to occur later when Earth was
farther from Jupiter.

Front 3

Around 1670, Isaac Newton performed a crucial experiment on the nature of light when he

Back 3

demonstrated that the colors that make up white light are intrinsic, not produced by
the glass through which the light passes.

Front 4

Around 1801, Thomas Young in England showed that light behaves as a wave by

Back 4

shining light through two closely spaced slits and observing the resulting pattern of
light on a white screen.

Front 5

Visible light occupies which position in the whole electromagnetic spectrum?

Back 5

between infrared and ultraviolet

Front 6

As a newly formed star continues to contract, its temperature increases while the
chemical nature of the gas does not change. What happens to the peak wavelength of its
emitted radiation?

Back 6

It moves toward shorter wavelengths (e.g., IR to visible).

Front 7

The range of temperatures in the Kelvin (absolute) scale between the freezing point
and boiling point of water is

Back 7

100 degrees

Front 8

A blackbody is an idealized object that

Back 8

reflects no light and emits light in a manner determined by its temperature.

Front 9

Suppose we compare the energy flux emitted from two heated spheres. Both are at the
same temperature, but one sphere has twice the radius of the other. The flux emitted
from the larger sphere is

Back 9

the same as the flux emitted from the smaller sphere.

Front 10

In the revolution that overtook physics around 1900, the assumption that Max Planck
made to solve the problem concerning the spectrum of radiation emitted by a hot
blackbody was that

Back 10

all radiation is emitted in small, discrete packets, or quanta, of energy, each quantum
having an energy that is inversely proportional to the wavelength of the light.

Front 11

The physical force that holds the components of an atom together is the

Back 11

electromagnetic attraction between the nucleus and the electrons.

Front 12

The spectrum of sunlight, when spread out by a spectrograph, has what characteristic
appearance?

Back 12

continuous band of color, crossed by innumerable dark absorption lines

Front 13

Why is the sky blue?

Back 13

he air molecules scatter blue light better than red light, so more blue light reaches
our eyes.

Front 14

The atomic number that designates the position of an element in the periodic table is
equal to the

Back 14

number of protons in the nucleus of the atom.

Front 15

One neutral atom of 13C has how many particles?

Back 15

19: 6 protons, 7 neutrons, 6 electrons

Front 16

Consider an atom in which electron transitions can involve three energy levels:
highest energy, middle, and lowest energy. In the resulting emission line spectruline with the shortest wavelength is produced by the transition from

Back 16

highest to lowest.

Front 17

If light from a hot, dense star is viewed through a cool cloud of gas

Back 17

only specific wavelengths of light will be removed from the spectrum.

Front 18

If two photons in a vacuum have different energies, what can we say about the
wavelengths of these photons?

Back 18

The higher-energy photon has the shorter wavelength.

Front 19

An electron is in the n = 3 energy level in a hydrogen atom. What can you say about
the spectral series in which it can participate?

Back 19

If it gains energy it can participate in the Paschen Series; if it loses energy it can
participate in the Lyman Series or the Balmer Series.

Front 20

The spectrum of a star shows an equivalent set of dark absorption lines to those of the
Sun, but with one exception: Every line appears at a slightly longer wavelength, shifted
toward the red end of the spectrum. What conclusion can be drawn from this
observation?

Back 20

The star is moving away from Earth.

Front 21

Light enters the smooth, flat surface of a glass from the vacuum of space (e.g., a
spacecraft window). What is the speed of light inside the glass compared to that in a
vacuum?

Back 21

Since the glass is denser than the vacuum, it is slower.

Front 22

What is the refraction of light?

Back 22

The change in direction of a light ray as it crosses from a less dense, transparent
material to a more dense one

Front 23

When a light ray in air or a vacuum enters the surface of a piece of perfectly smooth,
flat glass at an angle, it

Back 23

bends toward the perpendicular to the surface.

Front 24

A typical refracting telescope is made up of

Back 24

a long-focal-length lens at the front and a short-focal-length lens at the rear (next to
your eye as you look through the telescope).

Front 25

For many years, the Palomar telescope (5 m diameter) in California was the largest
fully steerable telescope in the world; in the 1990’s that honor fell to the first of the two
Keck telescopes (each of diameter 10 m) in Hawaii. How many times larger is the light-
gathering power of the Keck telescope than the Palomar telescope?

Back 25

4 times larger

Front 26

A refracting telescope has an objective lens of focal length 80 cm, a diameter of 10
and an eyepiece of focal length 5 cm and diameter 1 cm. What is the magnifying
power of this telescope?

Back 26

16x

Front 27

When light from the concave primary mirror of a telescope is reflected by a small
secondary mirror through a hole in the primary, it is called a

Back 27

Cassegrain focus telescope.

Front 28

The prime focus cage of a telescope whose primary mirror is 3 m in diameter has a
diameter of 0.5 meters. What fraction of the incoming light is obstructed by this cage?

Back 28

about 3%

Front 29

What is chromatic aberration in a telescope?

Back 29

The light of different colors comes to a focus at different points inside the telescope.

Front 30

The largest refracting telescope in the world is the 102-cm (40 in.) diameter telescope
at Yerkes Observatory, built in 1897. Refracting telescopes with larger diameter have
never been built because they would

Back 30

sag too much under their own weight.

Front 31

In the reflection of a beam of light from a flat surface, the relationship between the
angle of incidence i between the perpendicular to the surface and the incident beam and
the angle of reflection between the perpendicular and the reflected beam is

Back 31

r is equal to i.

Front 32

A reflecting telescope in which light is reflected by one curved mirror and a second
plane mirror at 45° to the original beam, to reach a focus at the side of the telescope, is
being used at its

Back 32

Newtonian focus.

Front 33

To produce the sharpest images of very distant objects, the best shape for the cross-
section of a large astronomical mirror should be

Back 33

parabolic.

Front 34

A spherical mirror suffers from spherical aberration because

Back 34

different parts of the mirror focus the light at different distances from the mirror.

Front 35

In telescopes, the angular resolution is worse for

Back 35

smaller diameter lenses or mirrors and longer wavelength electromagnetic radiation.

Front 36

If all effects caused by Earth's atmospheric variations (seeing) could be removed from
the visible image of a star obtained with one of the 10-m diameter Keck telescopes on
Hawaii, what would be the angular resolution achievable by this telescope in arcseconds
for light of wavelength 500 nm? (1 nm = 10
9
m)

Back 36

0.0125 arcsec

Front 37

What does the word “seeing” mean to an astronomer using a telescope?

Back 37

The twinkling and blurring of the image due to air currents in Earth's atmosphere.

Front 38

During the past few decades a number of techniques have been developed to enhance
the performance of optical and radio telescopes. These include all of the following
except one. Which one is the exception?

Back 38

building refracting telescopes comparable in size to the largest reflecting telescopes

Front 39

What is the main reason for combining many radio telescopes together into an
interferometer with large distances between telescopes?

Back 39

to obtain much sharper images of sources

Front 40

Orbital eccentricity is a number that describes the

Back 40

shape of the orbital ellipse.

Front 41

The CCD (charge-coupled device) is

Back 41

an array of small light-sensitive cells that can be used in place of photographic film to
obtain a picture.

Front 42

Astronomy from space vehicles is particularly useful because the telescope

Back 42

is above Earth's absorbing and distorting atmosphere and can measure radiation over a very wide wavelength range.

Front 43

Our planetary system consists of

Back 43

large and small planets, some accompanied by moons as large as the smaller planets.

Front 44

Compared to the orbital distance of the Earth from the Sun, the equivalent orbital
distances for the Jovian planets are

Back 44

more than 5 times greater.

Front 45

Most of the planets orbit the Sun on or close to the

Back 45

ecliptic plane.

Front 46

The best way to measure the mass of a planet is to measure the

Back 46

gravitational pull of the planet on an orbiting satellite or a nearby spacecraft.

Front 47

The Jovian planets have high masses and generate powerful gravitational fields, yet they have low average densities. What does this indicate about their interiors?

Back 47

They are composed mainly of very light elements, such as H and He.

Front 48

Which of the following general statements about all of the planets in the planetary
system is true?

Back 48

They orbit the Sun in the same direction.

Front 49

The next planet beyond Saturn is Uranus. The distance from the orbit of Saturn to the
orbit of Uranus is about the same as

Back 49

the distance from Saturn to the Sun.

Front 50

Consider the seven largest satellites in the solar system. The presence of an
atmosphere correlates with

Back 50

none of the above.

Front 51

A nitrogen molecule (N2) has a mass of 4.7 × 10
−26
kg, and a carbon dioxide molecule
(CO2) has a mass of 7.3 × 10
−26
kg. On a day when the temperature is 18°C (64°F), the N2
molecules will have a

Back 51

greater average speed than the CO2 molecules but the same average kinetic energy.

Front 52

On Mars, the temperature can reach 290 K and the escape speed is 5.0 km/sec. What
is the average speed of a carbon dioxide molecule (mass = 7.31 × 10
−26
kg) at this
temperature, and what can you say about the retention of carbon dioxide on Mars?

Back 52

The average speed is 0.4 km/sec, so Mars should retain its carbon dioxide.

Front 53

The asteroid Vesta, located in the main asteroid belt between the orbits of Mars and
Jupiter, is spherical in shape with a radius of 265 km and a mass of 3.0 × 1020 kg. What is
the minimum speed at which you could propel yourself upward and not fall back down?

Back 53

388 m/s

Front 54

The asteroid belt exists between the orbits of which planets?

Back 54

Mars and Jupiter

Front 55

The trans-Neptunian objects (such as Eris, Pluto, Sedna, Quaoar, etc.) are

Back 55

small worlds of rock and ice, most of which orbit within the Kuiper belt.

Front 56

What is the basic difference between comets and asteroids?

Back 56

Comets are mostly composed of ices, while asteroids are mainly composed of rocks.

Front 57

Planets and satellites with a large amount of surface cratering generally have
insignificant atmospheres. Why are these two conditions correlated?

Back 57

A large amount of cratering implies a small size, and this, in turn, implies a low
escape speed.

Front 58

The age of the solar system has been dated rather precisely to 4.56 billion years.
What method was used to determine this number?

Back 58

determining the age of meteorites by radioactive dating

Front 59

In general, small bodies in the solar system are less likely than large bodies to possess
a planet-wide magnetic field. Why should we expect size and magnetism to be
correlated?

Back 59

A small body cools more rapidly and is less likely to possess a molten, liquid interior
— one requirement for planet-wide magnetism.

Front 60

A theory of the origin of the solar system must take into account all important general
properties of the planets. These include three of the four properties listed below. Which
one is not an important general property of the planets?

Back 60

The magnetic fields of the planets are produced by a variety of mechanisms.

Front 61

Together, hydrogen and helium account for what percentage of the total mass of all
matter in the universe?

Back 61

98%

Front 62

Where in the universe are heavy elements with masses greater than that of helium
being produced at this time?

Back 62

central cores of stars

Front 63

The most likely mechanism for the solar system's formation appears to be

Back 63

that a cloud of gas and dust condensed to form the Sun, while planets formed later by
condensation and accretion within the nebular disk.

Front 64

Our solar system seems to have formed about how long ago?

Back 64

5 billion years ago

Front 65

The half-life of radiogenic 14C is 5730 years. How long must you wait until 90% of
the original sample remains?

Back 65

less than 5730 years

Front 66

It is found by the radioactive age-dating technique that only one-quarter of the
original sample of a radiogenic element taken from a rock remains, so the time is
calculated to be two half-lives. What does this time represent?

Back 66

the time since the rock was formed

Front 67

The three common substances believed to have been important in planet formation
are

Back 67

rocks, ices, and gas.

Front 68

The process of accretion in planetary formation is the

Back 68

slow accumulation of solid particles by gravity and collision into larger, solid objects.

Front 69

The steps in the process of formation of the large, outer planets were

Back 69

accretion of planetesimals to form a core, followed by gravitational capture of
hydrogen and helium gas.

Front 70

How are many of the satellites of the Jovian planets thought to have formed?

Back 70

From a disk of material around the planet, similarly to the way the planets formed
around the Sun

Front 71

A T Tauri wind is

Back 71

a rapid expulsion of the tenuous outer layers of a young star.

Front 72

What type of search technique has discovered the largest number of planets around
the stars other than the Sun?

Back 72

Looking for tiny variations in the star's radial velocity, caused by the gravitational
pull of one or more planets orbiting the star.

Front 73

We measure the mass of an extrasolar planet by

Back 73

using Newton's law of gravity, using the measured distance from the star and its
gravitational pull on the star.

Front 74

What properties of an extrasolar planet can be learned from the transit method?

Back 74

) mass, radius, chemical composition, and temperature

Front 75

What is surprising about the extrasolar planets that have been discovered?

Back 75

Many of them are giant planets like Jupiter, orbiting at distances characteristic of terrestrial planets.