Midterm 1
Short Answer (+1-3pts)
Record the answers to these questions directly on the exam and NOT on the scantron.
Describe two of Kepler’s three laws of planetary motion. (+2pts)
1) Planets orbit around the Sun in an ellipse with the Sun at one focus of the ellipse.
2) The line joining a planet and the Sun sweeps out equal areas in equal times.
Because of this when a planet is closer to the Sun in its orbit, it moves faster than when the planet is
farther away from the Sun.
3) The squares of the period of revolution is proportional to the average distance cubed. (p2  a3)
What does the abbreviation P.M. stand for? (+1pt) (Hint: The answer is not my name)__Post Meridian________
Describe specifically what causes the temperature variations that we experience as the seasons on the Earth. To
earn full points, please be as specific as possible. (+3pts)
1) The revolution of the Earth around the Sun
2) The tilt of the Earth:
The tilt of the Earth affects the temperature on the Earth in two ways:
a) Number of daylight hours- When the Earth is tilted towards the Sun during the summer, the number of
hours that the Sun is above the horizon is the longest (warmer temperatures result). When the Earth is
tilted away from the Sun during the winter, the number of hours that the Sun is above the horizon is the
shortest (cooler temperatures result).
b) Angle of the Sun’s rays hitting the Earth- When the Earth is tilted towards the Sun during the summer,
the Sun appears higher in the sky and the Sun’s rays hit the Earth more directly, the rays are more
concentrated, warmer temperatures result. When the Earth is tilted away from the Sun during the winter,
the Sun appears lower in the sky and the Sun’s rays hit the Earth at an angle, the rays are more spread out,
cooler temperatures result.
Express 4.2 x10-5 in regular format (+2pts): ______.000042__________________
Express 4.2 x10-3 in regular format (+2pts): ______.0042_________________
In scientific notation, the negative in the exponent means that is it a fraction or a small number less than
1 so in normal format, you would put the decimal in front. The exponent tells you how many places you
have to move the decimal to the left.
a) What is precession? b) How long does the cycle of precession last? c) What causes it to occur? (+3pts)
a) Precession is the wobble or slow circular motion of the Earth’s axis of rotation. The star that lines up
with the Earth’s North pole is defined as the North star, but since the axis wobbles, the North Pole points
in different directions over 26,000 years, thus for many years we may not have a North Star or the North
Pole will point to a different bright star other than Polaris.
b) It takes 26,000 years to complete one full wobble.
c) The Sun has a huge gravitational pull on the Earth because it is massive and the Moon has a huge
gravitational pull on the Earth because it’s close. The combined gravitational pull of the Sun and the
Moon on the Earth causes precession to occur.
Approximately how old is our Universe? _______14 billion years old____________ (+1pt)
Note: Don’t confuse this with the age of the Solar System.
What are the four components of the scientific method? (To earn full credit, you must use the same terms that
we used in the classroom) (+2pts)
Observe/Ask Questions, Hypothesize, Test, and Modify, Reject, or Theorize
Describe why during totality of a lunar eclipse, the Moon isn’t completely dark but instead turns a deep red
color. (+2pts)
During totality of a lunar eclipse, the Moon isn’t completely dark because some of the light from the Sun
still reaches the Moon because the Earth’s diffracts (bends) the red component of the sunlight onto the
Moon.
What is an annular eclipse? To earn full points, please include as much detail as possible. Include in your
answer whether it is a type of solar or a type of lunar eclipse. (+3pts)
An annular eclipse is a solar eclipse, when the Moon is in the new phase and gets between the Earth and
the Sun. But during this type of solar eclipse, the Moon’s distance is slightly farther away than its
average distance from the Earth so that it does not completely cover all the Sun. Instead there seems to be
a ring of light around the Moon. This is because since the Moon is slightly farther away than its average
distance from the Earth, the angular size of the Moon is slightly less than the angular size of the Sun so
that it cannot complete cover the Sun when the alignment occurs.
Short Answer (+4pts)
Record the answers to these questions directly on the exam and NOT on the scantron.
Ptolemy’s theory and Copernicus’ theory both explained the retrograde motion of planets. Explain a) what is
retrograde motion b) the differences between the two theories and how they explained why retrograde motion
occurred in each of these theories.
a) Retrograde motion is when a planet appears to change direction in the sky from the Earth’s point
of view. It is the apparent backwards and forward motion of a planet. In actuality, the planet is
not changing directions, it just appears to do so.
b) Ptolemy said that we live in a geo-centric Universe. Here planets exhibit retrograde motion
because they orbit on epicycles, which is a small circle on top of the larger circular orbit. Its
motion on the epicycle around the Earth makes it appear to move forward and backwards and
exhibit retrograde motion.
Copernicus explained retrograde motion by stating that we live in a heliocentric Universe where
the planets orbit around the Sun. He explains retrograde motion by stating that the inner planets
such as the Earth orbit the sun faster than the outer planets, such as Mars. Thus when the Earth
passes Mars in its orbit, it appears that the slower moving Mars is moving backwards with respect
to the stars. This view is the correct explanation for retrograde motion. Mars is not really
changing direction, it just appears to do so from our point of view. It’s kind of like when you are
passing a slower moving car. When you’ve passed it, it looks like it is moving backwards from
you.
Galileo made two important telescope observations that proved a theory. a) Which theory did it help prove
(heliocentric or geocentric theory)? b) Describe in detail what the two observations were and why they proved
that theory.
1) He saw objects orbiting around Jupiter. These later were known as the four largest moons of Jupiter.
But this observation showed that the geo-centric theory was incorrect because according to this theory,
the Earth is at the center of the Universe and every other object in space should orbit it. Obviously the
moons of Jupiter were not orbiting the Earth so this observation contradicted the geo-centric theory.
2) He saw that Venus goes through a full cycle of phases just like our moon does. In Ptolemy’s model of
the geo-centric theory (which was widely accepted at the time), Venus would orbit the Earth in an
epicycle, and the Sun would also orbit the Earth. Because of that, the only phases you would expect to
see are the new and crescent phases. It would be impossible to see the other phases that Venus. exhibited
Midterm 2
Completion (+1pt)
Complete each sentence or statement.
What year did human beings first walk on the Moon? _______1969______________
What are telescopes that use two lenses to collect light and bring it to a focus called?
_____refracting____________
What is the name of another object in our Solar System besides the Earth and Mars that could potentially have
liquid water on it? __Europa or Enceladus__________________
What type of object is Pluto now according to the IAU? _____dwarf planet__________________
What is the lunar soil that consists of very fine sandy material on the Moon called? _____regolith____________
How long does it take for Mars to rotate? _____24 hours___________
What is the side of the Moon that always faces the Earth called? ____the Near Side_____________
Short Answer (+2pts each)
How did the ozone layer affect the evolution of life on Earth?
The ozone layer was important because it partially blocked the high energy ultra-violet radiation from the
Sun and because of this, life was able to move from the water (which protected it from the ultra-violet
radiation) to live on land.
Note: Many of you got this question partially correct by mentioning that it helped to block dangerous
radiation from the Sun, but I was looking for specifically what type of radiation from the Sun is
dangerous, ie ultravolet and also the fact that this was the key to having the first land species evolving.
Some of you mentioned that the ozone allowed photosynthesis to occur so that oxygen can be created. It
is the other way around, photosynthesis, which produced oxygen allowed the ozone layer to exist since
ozone is made of three oxygen atoms.
Some of you mentioned that it allowed life to evolve. This is not necessarily true because life was able to
evolve without the ozone layer, it just evolved in the oceans instead of on land.
Scientists have discovered compelling evidence for past and current liquid water on Mars. Describe two
discoveries that were made of Mars that demonstrates liquid water has existed or still exists on Mars.
There are erosional features all over the surface of Mars such as dried up riverbeds and gullies that
indicate the presence of liquid water. In addition, the surface of Mars is covered in iron oxide (rust) that
may indicate iron exposed to liquid water. Spirit and Opportunity found sedimentary rock and hematite
which can only be formed in liquid water. Recently the Mars Reconnaissance Orbiter found Recurring
Slope Linea, which are seasonal streaks of hydrated salts that indicate the presence of liquid water.
List two specific geographical locations in the world that were mentioned in the lecture where professional
research observatories are located in. (note, do not include the location for Fremont Peak Observatory as part
of your answer since this is not a professional observatory).
Some locations of observatories that I mentioned were: Arizona, Chile, Hawaii, Canary Islands, New
Mexico, and Puerto Rico.
a) Which planet has two moons? b) What is the name of one of its two moons?
a) Mars b) Phobos and Deimos
a) What is the layered structure of the interior of the Earth called? b) What causes this layered structure to
form?
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a) differentiation b) differentiation occurred on the Earth when the Earth was just forming, it was entirely
molten. Gravity caused the most dense material (iron and nickel) to sink to the bottom and the lower
density material (granite and basalt) to float to the top. (This is like the demonstration I showed you in
class of the layered structure of the oil, vinegar, soap, and water that I poured into a glass).
Short Answer (+3pts)
a) What is happening to the distance of the Moon, is it moving farther away or getting closer to the Earth? b)
What is causing the Moon’s distance to change over time? (+3pts)
a) The Moon is slowly moving farther away from the Earth. b) This is because of conservation of angular
momentum. The Moon exerts tides on the Earth, which causes tidal friction that slows down the Earth’s
rotation. But according to the conservation of angular momentum, the momentum that is lost by the Earth
as it slows down in its rotation is equal to a gain in momentum of the Moon, which makes it move away
from the Earth so the net momentum of the Earth Moon system remains the same.
a) Which terrestrial planet experiences the most extreme temperature variation (that is it can be both
extremely hot and extremely cold). b) Discuss two reasons why this planet has the most extreme variations in
temperature in our Solar System.
a) Mercury
b)
1. It is a very slow rotator: 59 days. So the sun hits one side of it for about 30 days straight (the
surface gets up to 660 deg there) and the opposite side receives no sunlight for 30 days straight
(on this side, it cools down to -280 deg).
2. It has a very thin atmosphere: Since it doesn’t have much of an atmosphere, the temperature does
not circulate around the planet. (i.e. the heat from the hot side of the planet does not reach the
cool side of the planet.
Note: Many of you put Venus. Venus is just a very hot planet; its temperature is never cold.
Short Answer (+4pts to 5pts each)
a) What are planets that orbit around another star called? (+1pt) b) Describe two methods that astronomers
have developed to detect these planets. (+3pts) c) Describe one property (as discussed in the lecture) in some of
these other solar systems that is very different than ours.(+1pt)
a) Exoplanets are planets that are located outside of our Solar System. They orbit around another star (not
our Sun)
Note: Some of you put Dwarf planets…Dwarf planets are objects like Pluto that exist in our Solar System
and orbit around our Sun. They are objects that have not cleared the neighborhood around their orbits.
1)
Stellar Wobble: Since the planet is orbiting around the star, it has a gravitational pull on the central star
and causes the star to wobble. Astronomers can detect the wobble of the star by observing the star’s
absorption line spectrum and seeing if it exhibits the Doppler effect. If it does, it means that the star is
wobbling back and forth. The absorption line spectrum has a blueshift (shift to shorter wavelengths)
when the star moves towards us and a redshift (shift to longer wavelengths) when the star moves away
from us.
2)
Planetary Transits: If a star has a planet orbiting around it, the planet would on occasion cross the disc of
the star (this is called a transit) and dims its light. Astronomers monitor the brightness of the star with
time, and if the brightness dims, then they can tell that a planet is transiting the star. This method is
currently being used by the Kepler spacecraft.
a) When did our Solar System form? (+1pt) b) Describe in detail how our Sun and our planets were formed
(+3pts)
4.6 billion years ago the solar system started out as a huge cloud of gas and dust (solar nebula). If the gas
in the material is dense enough, most of it collapses to the center to form the star. The rest of the gas and
all the dust get flung out into a disk. The dust debris in the disk orbit around the central star and collide
with each other. If the collisions are slow enough, the particles accrete (stick together) by gravity and
grow larger and larger with time until they become planetesimals. The planetesimals grow larger as they
sweep up more of the dust debris and become protoplanets when they are spherical in shape. The
protoplanets continue to grow in size by sweeping up all the material in its path and become planets.
Note: Some of you said the Big Bang Theory. The Big Bang theory explains how the Universe was
formed, not the birth of the solar system. The Solar System was formed about 10 billion years after the
Big Bang and there was no explosion.
a) List the names of the inner/terrestrial planets in their correct order from the Sun. (+2pts all or nothing) b)
List the names of the outer/Jovian planets in the correct order from the Sun. (+2pts all or nothing)
a) Mercury, Venus, Earth, Mars (MVEM) b) Jupiter, Saturn, Uranus, Neptune (JSUN)
Midterm 3
Completion (+1pt)
Complete each sentence or statement.
Asteroids that cross the Earth’s orbit are called ___Near_____ ___Earth_____ (two words) Asteroids.
The “fingerprint” of a gas that allows astronomers to determine the chemical composition of the gas is called a
____spectrum___________.
Name one type of eruption of gas associated with the presence of sunspots that can occur on the Sun.
___any of these: solar flare/prominence/filament/coronal mass ejection________________
The baby/young stage of a star where it has 2 jets called bipolar outflows and an accretion disk around it is
called a:
_____proto-star___________
What kind of light is also called visible light? _____white light__________
A cloud of gas and dust that represents the birth stage of stars is called a: ____nebula___________
What is a system of at least two stars in orbit around the center of mass called? ____binary__________
Short Answer (+2 pts)
What is the definition of the wavelength of light. You can describe it and/or include a CLEAR drawing.
The distance between two consecutive peaks or minima of a wave.
What are the two places that comets are located in called?
Kuiper Belt and Oort Cloud
Note: Some of you said the Asteroid Belt. Only Asteroids live there. There are no comets in the asteroid belt.
Describe in detail what causes meteor showers to occur on the Earth.
When a comet gets close to the Sun, it leaves some debris behind from the dust tail. This debris gets trapped in orbit
around the Sun. If the debris crosses the Earth’s orbit, meteor showers can occur every year when the Earth runs into
the debris and the material gets burned up in the Earth’s atmosphere causing more than average numbers of meteors to
be seen. Each meteor shower is associated with the dust debris left behind by a different comet.
What are the two tails that comets possess when they come close to the Sun made of?
Gas and dust
Note: Some of you said ice and dust. Although comets are made of ice and dust. Their tails are produced by
vaporization of the ices due to the Sun’s heat. When the ices vaporize, they turn into gas.
Short Answer (+3-5 points each)
a) What are the two types of star clusters called? b) Describe three specific differences between the two types of
star clusters (as discussed in class). (+4pts)
a) Globular Cluster and Open Clusters
b)
Globular Cluster
Tightly bound stars
Thousands to millions of stars
Red, Orange, Yellow stars
Shaped like a Sphere
Open Clusters
Loosely bound stars
Dozens to hundreds of stars
Blue stars
Gas cloud surrounding the stars
Describe a) What causes sunspots to appear to be dark? b) How long is the sunspot cycle? c) What causes the
sunspots to occur on this regular cycle? (+4pts)
a) Sunspots are dark because they are regions of the Sun that are cooler.
b) In these regions, intense magnetic field lines loop out of the photosphere and suppress the hot gas from
rising causing the spots to be cooler (dark) compared to the rest of the Sun.
c) 11 years
Note: Some of you put 1 month. This is the time it takes for the Sun to rotate, not the sunspot cycle (which is
the cycle it takes for the Sun to have maximum number of sunspots).
a) What is the adult stage of a star called (when it is in hydrostatic equilibrium and starts to shine)? b)
Describe the process that allows an adult star to produce the energy that allows it to shine. Please be specific in
your description. (+3pts)
a) Main Sequence b) They shine by the nuclear reactions that occur in the core of the star. The type of nuclear
reaction in a main sequence star is hydrogen fusion. The net result of this fusion is the 4 hydrogen fuse together to
form one helium atom and in the process releases energy that allows the star to shine. It releases energy during this
process because the mass of 4 hydrogen is a little more than 1 helium atom. That extra mass gets converted to energy
according to Einstein’s equation: E=mc2 .
a) What caused dinosaurs (and 2/3 of all species) all over the world to become extinct. To earn full credit,
please be specific. b) When did this extinction occur? (+3pts)
a) Dinosaurs became extinct when a large asteroid impacted the Earth. The debris from the impact was circulated all
around the Earth by the Earth’s atmosphere, which blocked out sunlight for several months causing the Earth to cool
down. B) 65 million years ago.
Note: Many of you confused the word asteroid with meteors and meteor showers.
Describe the difference between a meteor, meteorite, and meteoroid.(+3pts)
The difference is their location:
Meteoroids: Chunks of rock floating in space.
Meteor: When these pieces of rock or debris falls through the Earth’s atmosphere and gets burned up.
Meteorite: If the piece is large enough it can survive the atmosphere and fall and hit the surface.
Essay (+8 pts)
a) What will happen to a low mass star like our Sun after it uses up all its hydrogen in the core? (to earn full
credit, you need to describe the properties of and name the old age and elderly stage of the star) b) Contrast
this with what will happen to a high mass star after it uses up all its hydrogen in the core?(to earn full credit,
you need to describe the properties of and name the old age and elderly stage of the star)
a)
During the old age stage of a low mass star like our Sun, hydrogen fusion stops when the hydrogen runs
out in the core. When nuclear fusion stops in the core, there is no outward force to oppose the inward
force due to gravity. This causes the core to contract. As the core contracts, the temperature in the core
rises. This temperature rise in the core causes the gas in the outer envelope of the star to expand up to
200 times its previous size. As the outer envelope expands, the star cools down and its color changes to
red. When it cools down, it turns into a red giant. Inside the core the temperature now rises to 100
million K. At this high temperature, helium starts to fuse into carbon and oxygen which allows the star a
new lifeline and allows it to be stable again for a short time. But eventually the helium runs out in the
core and there is only carbon and oxygen. The core collapses again and shrinks to be about the size of the
Earth. This object which represents the elderly stage of a low mass star is called a white dwarf. At this
point the star is white hot, but it never reaches high enough temperature for the fusion of carbon and
oxygen so the star starts to cool down and fade without any energy source. Eventually the star will dim
and become a black dwarf. In the meanwhile, the outer envelope continues to expand and cool as it
expands away from the star. The outer envelope becomes a planetary nebula, which is about the size of
a Solar System.
Note: This is what will happen to our Sun more than 5 billion years from now when it runs out of fuel.
When it becomes a planetary nebula, it will be as large as the entire Solar System.
b)
The old age stage of a high mass star starts out similar to a high mass star except that when it runs out of
hydrogen in its core, it has many lifelines and the core contracts many times. Each time the core
contracts, it produces heavier and heavier elements until iron is produced in the core. Iron is the heaviest
element that can be produced in a high mass star. With each envelope contraction, there is an envelope
expansion. Since the envelope has expanded multiple times, it has enlarged to be up to 1000 times its
previous size and is now a red super giant. When there is iron in the core of the star, nuclear fusion
stops, and the core tries to contract further, but since there is so much mass being compressed in so little
space (like trying to compress too much clothing in a small luggage), there is a resistance to the
contraction due to all the atoms crowded together. The star then explodes. This explosion is called a
supernova. However when the star explodes, it leaves behind an ultra-dense core. If the core is less than
2 times the mass of our Sun, it is called a neutron star because in the core, the atoms are so compressed
together that the electrons do not have room to orbit around the nucleus; instead they combine with the
protons in the nucleus to form neutrons. If the core is more than 2 times the mass of our Sun, the gravity
of this core is so strong that it will collapse past the neutron star stage, become infinitely dense, and
swallow up its own light. This object is called a black hole.