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Astronomy
Second Semester Review Concepts
Study Ideas
The distance between the Earth and the
Moon varies as the Moon orbits about the
Earth.
Which of the following is not a kind of
geological feature found on the Moon?
A. Scarp
B. Crater
C. Maria
D. Rille
Basalt, a dense congealed lava rock rich in
iron, is the primary material in the Moon's
Maria.
One result of bombardment of the Moon's
surface is a layer of broken, pulverized, and
powdered rock called
Regolith.
Based on a comparison between the
amount of cratering seen in the highlands
versus the maria, it is possible to conclude
that the main bombardment of the Moon
occurred
Shortly after the Moon formed a few billion
years ago.
The primary reason the Moon lacks an
atmosphere is because.
The Moon lacks sufficient gravity to retain
an atmosphere.
Which statement about the Moon's orbit is
true?
A. The Moon is in synchronous rotation as
it orbits the Earth.
B. The Moon is in a geosynchronous orbit
around the Earth.
C. The Moon's orbit is aligned with the
Earth's orbit.
D. The Moon rotates in the opposite
direction than it orbits the Earth.
Which of the following theories for the origins
of the Moon is general accepted by
astronomers?
A. The Moon formed alongside the Earth (the
twin theory).
B. The Moon is the result of a collision between
the Earth and a Mars sized object in the early
days of the Solar System (the collision theory).
C. The Moon was originally a bulge on the
Earth that was flung off by the rapidly spinning
Earth (fission theory).
D. The Moon formed somewhere else and was
later captured by the Earth (capture theory).
If the Moon were farther from the Earth,
compared to now, the tides would be
Less tall all the time.
Why do we always see only one side of the
Moon?
The Moon is tidally locked with the Earth.
From the observation that the same side of
the Moon always faces the Earth, one can
conclude that
The Moon completes one rotation each time
it completes an orbit about the Earth.
When our Earth becomes tidally locked with
the Moon,
The Moon will always be visible only from
one side of the Earth.
An astronaut on the Moon would see only
one side of the Earth.
Based on our understanding of our own
solar system, which of the following would
be most surprising to observe in an extrasolar system of planets?
A. The planets nearest to the star have a
lower density than the planets farther out.
B. Several planets show large tilts of their
rotation axis compared to the plane of their
orbits.
C. All the gas giants have moons.
D. Several planets have dense atmospheres
containing carbon compounds.
Which of the following is not a method
used by astronomers to detect and study
exoplanets?
A. Rotational mapping.
B. Gravitational lensing.
C. Doppler shift.
D. Transit detection.
E. Direct imaging
The Sun, the Earth, Jupiter, and Saturn's
icy moons are all very different
environments.
But all formed from the same basic group
of chemicals.

Given that Mercury, Mars, and some of the
moons of the gas giants are covered with
craters, why do we not see lots of impacts
happening today?
The Sun's heat drove the remaining dust and
gas out of the part of the solar system with
planets, and gravitational interactions ejected
most of the larger debris.

Thinking about the formation of the solar
system, what trend in composition would
you expect to see from the inside to the
outside of the asteroid belt?
Rockier asteroids progressing towards ones
with more hydrogen and carbon
compounds.
How many stars are there in our Solar
System?
One
How many planets are there in our Solar
System?
8
Which planets have densities similar to that
of the Earth's?
Mars and Mercury.
In our Solar System, an object is called a
planet if
It orbits the Sun.
It has the round shape.
It has cleared its neighborhood.
Pluto is classified as a dwarf planet
because
It has not cleared its neighborhood.
A spherical region that surrounds the Solar
System and extends up to about 100,000
AU from the Sun is called the
Oort cloud.
What is the name of the nebula from which
our Solar System was formed?
Solar nebula
Which property of the solar nebula was the
most influential in giving the planets their
characteristics?
Temperature
The process in which a gas cools and its
molecules stick together to form liquid
particles is called
Condensation.
Which was the last part of the planetforming process?
Formation of the atmosphere of the
planets.
Exoplanets are
Planets around stars other than the Sun.
Why is it difficult to observe an exoplanet
directly through a telescope?
Exoplanets are small compared to their
parent star, so they reflect only a small
portion of the star's light.
What is gravitational lensing?
The focusing and brightening of starlight by
the gravitational field of the foreground
star, when there is a perfect alignment with
the observer.
According to the nebular hypothesis, which
of the following sequences of events are
chronologically correct?
Interstellar cloud, solar nebula, accretion,
collisions between planetesimals, planets.
Comets are _____ while asteroids are
_____.
Icy; rocky
Small planets do not have significant
atmospheres because their _____ is weak.
Gravity
Compared to the _____ planets the ______
planets have _____.
Terrestrial; Jovian; many satellites
Astronomers believe that the satellites of
the Jovian planets were _____.
Planetesimals orbiting the growing planet.
What features are unique to Earth?
Canyons.
Volcanoes.
An atmosphere.
Precipitation.
None of these features are unique to Earth.
The red coloration seen on the Martian
surface originates from
The iron minerals in the surface rocks
combining with oxygen in the atmosphere
causing the surface to rust.
Which planet has the hottest surface
temperature?
Venus
The Coloris Basin found on Mercury was
probably formed by what process?
An impact from a planetesimal.
Which planet has a greenhouse effect?
Venus
Earth
List the terrestrial planets in decreasing
order of their mass.
Earth, Venus, Mars, Mercury
Mercury lacks an atmosphere because
Its smaller size means it has gravitational
attraction that is too weak to hold onto an
atmosphere.
Which terrestrial planet has the most
moons?
Mars
Which planet shows the largest variation of
day and night temperatures?
Mercury
Which terrestrial planet is tilted upside
down?
Venus
Which of the terrestrial planets have the
most similar atmospheric compositions?
Venus and Mars
Which of the other terrestrial planets is
closest in size to the Earth?
Venus
The surface of Mercury resembles the
Moon's surface in that they are both
______.
Heavily cratered
______ is the smallest of the terrestrial
planets.
Mercury
______ is the largest of the terrestrial
planets.
Earth
The atmosphere of Venus consists mainly of
______.
Carbon dioxide
The clouds of Venus consist mainly of
______.
Sulfuric acid
The Valles Marineris is ______ on the
surface of Mars.
A 4000 km canyon
The atmosphere of Mars consists mainly of
______.
Carbon dioxide
Mars' axial tilt and spin are most similar to
_____.
The Earth's
Mercury's ________ and, therefore, the
planet does not have seasons.
Axial tilt is zero
Venus‘ extremely high surface
temperatures are due to
The composition of its atmosphere.
Of all the terrestrial planets, ______ has
the largest daily temperature variation.
Mercury
Evidence that there is a considerable
amount of water frozen under the surface
of Mars is provided by all of the following
except
Periodic eruptions of geysers when
subsurface ice is melted by volcanic
activity.
Mercury features long, steep cliffs in its
crust called "scarps" which probably
formed
Like giant wrinkles as the crust cooled and
shrank.
Maps of Venus have been made by
Bouncing radio waves off the planet from
satellites and the Earth.
List the outer planets in order of increasing
mass?
Uranus, Neptune, Saturn, Jupiter
What type of dunes exists on Titan?
Ice crystal dunes.
Of the outer planets, _________ has the
smallest diameter.
Neptune
Which of the out planets has rings?
Jupiter.
Saturn.
Uranus.
Neptune.
All of the outer planets have a ring system.
Which is the smallest of the outer planets?
Neptune
What observational evidence suggests that
Uranus was struck by a large planetesimal
early in its formation?
Uranus' rotational axis is tipped over.
Which is the largest planet?
Jupiter
Which planet's rotation axis is closest to its
orbital plane?
Uranus
Which planet has the most extreme
seasons?
Uranus
Which planet has the lowest density?
Saturn
Which satellite has lakes of liquid methane
near its poles?
Titan
Although Saturn and Jupiter have similar
compositions their outer appearances are
different because
Saturn's cooler temperatures allow for the
formation of a hazy layer of ammonia
clouds that surrounds the planet.
How does the mass of Jupiter compare to
the rest of the planets in the Solar
System?
Jupiter's mass is greater than all the other
planet masses combined.
What is the largest satellite (moon) in the
Solar System?
Jupiter's moon, Ganymede
Scientists believe a liquid water ocean
might exist on the moon Europa.
What causes the blue appearance of the
planet Uranus?
Uranus' atmosphere contains methane that
strongly absorbs red colors from the
sunlight.
What prompted astronomers to search for
Neptune?
Uranus was not following the precise orbit
predicted by Newtonian physics.
The appearance of an aurora indicates that
The planet has a magnetic field.
The following are a common characteristics of
the Jovian planets
Mostly composed of hydrogen and helium.
Thick atmosphere.
Lack of solid surface.
Ring systems and satellites.
What chemical compound is responsible for
Uranus and Neptune's color?
Methane.
Why do astronomers believe that the Jovian
planets are composed mainly of hydrogen
and helium?
Because the Jovian planets have low
densities.
Why do astronomers believe that the Jovian
planets must contain rocky material in their
cores?
Because silicates and irons were part of the
overall composition of the solar nebula.
The colors of Jupiter's clouds suggest the
presence of ______.
Organic molecules
The powerful _____ Jupiter is a result of
the ______ and ______ in the interior of
the planet.
Wind on; Coriolis effect; heat generated
________ is the largest of the Galilean
moons.
Ganymede
The Great Red Spot on Jupiter is _____.
A giant vortex that has persisted for over
300 years
______ has the lowest density of all the
planets in the solar system.
Saturn
The rings of Saturn consist primarily of
_____.
Water ice
Astronomers believe chondrite meteorites
are about 4.6 billion years old—formed
when the solar system formed—because
Radioactive dating can be used to
determine their age.
All of the asteroids in the asteroid belt
together have a tiny fraction of the Earth's
mass.
Asteroids need to have enough material to
have an average diameter of about
_________ for gravity to pull them into a
spherical shape.
1000 km
Infrared observations are used to
determine the mass of asteroids because
The infrared radiation is the glow of heat
from the asteroid, and larger asteroids emit
more infrared light.
Asteroids
Can range is size from a few meters to
many hundreds of kilometers.
Fragments that do not completely burn in
the atmosphere and eventually fall on the
Earth are called
Meteorites
A meteor shower occurs when the left over
debris of a _______ intersects with our
atmosphere to produce the beautiful
streaks of light.
Comet
Comets belong to the
Kuiper belt and Oort cloud.
Planet __________ creates the gaps in the
asteroid belt called Kirkwood gaps.
Jupiter
The gaps created by the planet Jupiter in
the asteroid belt are called _______.
Kirkwood gaps
The short-period comets originate in
_______ and the long-period comets
originate in _______.
Kuiper belt; Oort cloud
Meteor showers are generally named
After the constellation from which they
appear to diverge.
Objects of the Kuiper belt were detected by
the Hubble Space Telescope.
What is the evidence for the existence of
the Oort cloud?
The fact that new comets continue to
appear indicates that a distant reservoir of
icy bodies must exist.
The Leonid meteor shower occurs in mid
November. The radiant of the meteor
shower is in the constellation of Leo.
The shower occurs when the Earth crosses
the path of an old comet.
The tail of a comet always points _____.
Away from the Sun
The typical size of a comet's nucleus is
_____.
10 km
Approximately how massive is the Sun as
compared to the Earth?
300,000 times
If you could manage to stand on the Sun,
you would weigh approximately ____ times
more than your weight on the Earth.
30
The sunlight we receive on the Earth
originates from the Sun's
Photosphere.
The hottest part of the Sun is
The core.
The Sun's core is generating energy in the
form of ________.
Gamma rays
Sunspots are dark because they are
Slightly cooler regions meaning they emit
less light than the surrounding areas.
Which part of the Sun is not in hydrostatic
equilibrium?
Corona
The solar wind is created in the Sun's
_______.
Corona
Flare is the name of a sudden, highly
energetic, eruptive explosion on the surface
of the Sun.
The diameter of the Sun is determined by
measuring its ____ and _____.
Distance; angular size
The surface temperature of the Sun can be
measured using ____.
Wien's law
The Sun's composition by the % of mass is
71% ____, 27% _____ and 2% _____.
Hydrogen; helium; other elements
The energy in the Sun's core is produced
by
Fusion of hydrogen to helium.
The Sun's atmosphere consists of the
_____ and the _____.
Chromosphere; corona
____ provides a way to measure the speed
of seismic waves in the Sun.
The Doppler effect
The Sun rotates _____ at its equator than
at its poles.
Faster
A solar prominence is essentially
A plasma confined to a magnetic tube
sticking out of the surface of the Sun.
Since nuclear fusion in the Sun creates
energy from matter, why doesn't it violate
the law of conservation of energy?
Matter and energy are equivalent, as
expressed by Einstein's equation E = mc2.
Generally speaking, activity on the surface
of the Sun is primarily driven by
Electromagnetism.
The photosphere
Is the layer of the Sun where it transitions
from being opaque to transparent.
The Zeeman effect, in which energy levels
of electrons are shifted and produce a
corresponding split in spectral lines
observed, is used to measure _________
at the Sun's surface.
Magnetic field strength
The solar cycle is a result of the
Differential rotation of the Sun.
Although the Sun's core has a density much
greater than rock it is considered a gaseous
object because
The Sun's high internal temperatures
prevent the atoms from bonding together
to form a liquid or a solid.
What is parallax?
The apparent shift in position of an object
caused by a change in the observer's
position.
Parallax measurements of the distances to
the nearest stars use _____ as a baseline.
Earth's orbit
The relative brightness of the stars as we
see them in our sky is represented by their
Apparent magnitude
Luminosity (absolute brightness) of a star
depends on its ___________.
Temperature and Radius
If it were possible to move a star closer to
the Earth then its apparent magnitude
number would ______ while its absolute
magnitude number would _______.
Decrease; stay the same
80% of ________ type stars have orbiting
companions.
O and B
In which binary system can we observe
both the stars separately and follow their
orbits around each other?
Visual binary system.
The H-R diagram is a diagram plotting the
stars according to their
Luminosity and temperature.
The star Aldebaran is a red giant, and is
much more luminous than the Sun. What
conclusions can be drawn from this fact?
Aldebaran is cooler than the Sun, but has
larger diameter than the Sun.
The star Aldebaran is cooler and much
more luminous than the Sun. Where do you
expect to find Aldebaran in the H-R
diagram?
Top right
Binary star systems are very important
because they allow
Measurement of star masses.
What is the difference between
spectroscopic and visual binaries?
In a visual binary we can see two distinct
stars; in spectroscopic binaries, the images
of the two stars can not be resolved.
The study of eclipsing binary stars is very
important because it allows astronomers to
determine
The diameters of stars
Stars on the main sequence have different
luminosities because
They have different masses.
If a main sequence, giant, and a supergiant
all have the same spectral class, what
characteristic is known to make these stars
different?
Luminosity.
_____ can be used to measure the _____
of nearby stars.
Interferometry; radius
The parallax of a star is ____ usually
measured in ____.
An angle; arcseconds
The amount of energy emitted by a star
each second is the ____ and is measured in
____.
Luminosity; Watts
The luminosity of a star is determined by
the star's ___ and ____.
Diameter; surface temperature
The Balmer lines correspond to
wavelengths in the ____ part of the
spectrum of a ____ atom.
Visible; hydrogen
____ binary star systems are important
because they allow astronomers to
determine the mass and the ____ of the
stars in the system.
Eclipsing; diameter
White dwarfs have ____ spectral lines than
red giants.
Wider
How does Rigel, a bluish star, surface
temperature compare to Betelgeuse, a
reddish star.
Rigel's surface temperature is greater than
Betelgeuse's.
Brown dwarfs are
Object massive enough to fuse deuterium
but not massive enough to sustain
hydrogen fusion.
The most important property that
determines the evolution of a star is its
Mass.
When do we say that a star is born?
When fusion of hydrogen atoms into helium
atoms start.
Protostars shine brightest in
Infrared.
If a star is in hydrostatic equilibrium
Its radiation pressure outwards and
gravitational forces inwards are in balance.
In which stage of a star's evolutionary cycle
does it spend the most time?
The main sequence.
The process in which two or more lighter
elements combine to form a single heavier
element is called
Nucleosynthesis.
When the outer envelope of a red giant is
ejected, the remaining exposed core of a
low mass star is called a
White dwarf.
After a star leaves the main sequence
It now fuses hydrogen into helium in a shell
outside the core.
What characteristic do all stars on the main
sequence share?
They are all fusing hydrogen into helium in
their cores.
What makes variable stars useful in
determining star distances?
Their luminosity can be determined from
their pulsation period.
How do most of the heavier elements up to
iron form in the Universe?
By nucleosynthesis in the cores of massive
stars.
How do astronomers test models of stellar
evolution?
By comparing the paths in the H-R diagram
predicted by models with the H-R diagrams
of star clusters.
The Sun formed from the gravitational
collapse of a cold ___.
Interstellar cloud
____ is the most significant force that
determines the evolution of stars.
Gravity
When a star moves off the main sequence
and becomes a red giant it is brighter
because
The size of the star increases.
Hydrostatic equilibrium is the balance
between _____ of a star and _____.
The internal pressure; gravity
The CNO cycle produces energy by fusing
Hydrogen into helium.
After the hydrogen in the star's core is
depleted the core
shrinks and heats up.
During a star's main sequence portion of its
life it does not change size appreciably. This
observation indicates that
The Sun produces about the same amount
of energy as it radiates into space.
The last fusion product possible in stars is
_________ because _________.
Iron; fusing iron nuclei absorbs energy; it
does not liberate it
___________ are hot, compact stars
whose mass is comparable to the Sun's and
size to the Earth's.
White dwarfs
A __________ happens when a single high
mass star explodes.
Type II supernova
This event recurs and happens when one of
the companions in the binary system is a
white dwarf.
Nova
___________ are hot, compact remnant
stars whose mass is typically between one
and several times that of the Sun, but their
size is only 10 km or less.
Neutron stars
Two important properties of young pulsars
are
Extremely rapid rotation and a strong
magnetic field.
The escape velocity inside a black hole is
Greater than the speed of light.
A method for identifying a black hole is to
Look for its effect on nearby companions.
The Chandrasekhar limit is the largest
______ a white dwarf can have.
Mass
The temperature of black holes is estimated
to be ____.
Less than 1 millionth of a degree
Black holes emit radiation in the form of
______ waves known as Hawking
radiation.
Electromagnetic
The first pulsars were observed using
_______ telescopes.
Radio
The fast rotation of neutron stars is a
consequence of _____.
The law of conservation of angular
momentum
Astronomers use _____ to determine the
magnetic field of white dwarfs.
The Zeeman splitting of spectral lines
Why do white dwarfs have high
temperatures?
Heat left over from their formation
Gravitational waves
Are traveling distortions of space and time.