Astronomy & Cosmology Midterm 1

What is a Star?

A large, glowing ball of gas that generates heat and light through nuclear fusion

What is an asteroid?

a small rocky body orbiting a star

What is a comet?

An object made of gas, ice, and dust that orbits around a star

What is a star system?

A star and all material that orbits it, including its planets, moons, asteroids, and comets. (e.g.: Solar System)

What is a nebula?

a cloud of gas and dust
Interstellar = "between the stars"

What is a galaxy?

A group of billions of stars, all held together by gravity and orbiting a common center.

What is the Universe?

The sum of all matter and energy; that is, everything within and between all galaxies

What is our cosmic address?

Earth, Solar System, Milky Way, Local Group, Local Supercluster, Universe

What were the 3 planetary motions proposed throughout history?

- Geocentric Model: planets and sun move around Earth

- Heliocentric Model: Planets move around the Sun

- Gravitational Model: Sun and planets move in response to each other

What is Occam's razor principle?

the simplest explanation is usually correct

What is the difference between hypotheses, theory, and paradigm

Hypothesis: Education Guess

Theory: Powerful model that uses simple principles to explain many observations, which has survived repeated and varied testing. (Ex: Newton's Law of Gravity)

Paradigm: General pattern of though (Ex: Newtonian Physics & Quantum Physics)

Your professor proposes the hypothesis that all the geese at Rutgers live on Livingston Campus. What is the most compelling scientific evidence against this hypothesis?

A. You take a cell phone picture of a goose on Busch Campus.

B. A Nobel-prize-winning biologist from Harvard writes in the New York Times that the hypothesis is rubbish.

C. Your roommate recalls seeing a goose on Livingston Campus last weekend.

D. The statistical analysis of a Rutgers business school professor suggests that the hypothesis is probably incorrect.

E. Your professor also claims to have been abducted by aliens.

A

What do you get when you multiply 2×10^22 by 3×10^-10?
A. a headache
B. 6×10^32
C. 6×10^12
D. 5×10^32
E. 5×10^12

C

What are the SI Units for the following:
Length:
Mass:
Time:
Angle:

SI units (metric system)
length: meter or kilometer
mass: gram or kilogram
time: second or year
angle: degree, arcmin, or arcsec

Millenium Falcon pilot Han Solo has boasted that his ship "made the Kessel Run in less than 12 parsecs." Which of the following quantities corresponds to 12 parsecs?

A. 39 light-years.
B. 39 years.
C. 39 kilograms.
D. 10^39 years.
E. 10^39 kilograms.

A

parsec (pc) = 3.26 light-year

The angular size of your finger at arm's length is about 1 degree; how many arc seconds is this?

A. 60 arc-seconds
B. 600 arc-seconds
C. 60 x 60 = 3600 arc-seconds

C

The Andromeda galaxy (M31) has an angular size of 178 arcminutes when seen from the Earth. Which statement is true?
A. M31's angular size is 178/3600 degrees.
B. M31's angular size is 178/3600 arcseconds.
C. M31's angular size is 178/60 degrees.
D. M31's angular size is 178/60 arcseconds.
E. It is rude to comment on a galaxy's angular size.

C

In this image of sunset on the planet Tatooine, what can we say for sure about the two suns?
A. They have about the same physical size.
B. They have about the same angular size.
C. They have about the same angular and physical sizes.
D. They have about the same distance.E. Nothing really.

B

Just look at this image

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What are Celestial Coordinates?

Earth-centered coordinates aligned with the Earth's rotation axis

Horizontal vs Celestial: Observer in New Jersey

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What is the North Star?

The North Star does not move at all.
The North Star lies on the Meridian
The North Star leads to due North
The angle the star makes with the Horizon is equal to the latitude
Was used as a navigation tool

In which direction is the observer facing?
A. Toward the South
B. Toward the North
C. Toward the East
D. Toward the West

B

Imagine that from your current location, you observe a star rising directly in the east. When this star reaches its highest position above the horizon, where will it be?

A. High in the Northern Sky
B. High in the Southern Sky
C. High in the Western Sky
D. Directly Overhead

B

Where would the observer look to see the star indicated by the arrow?
A. High in the Northeast
B. High in the Southeast
C. High in the Northwest
D. High in the Southwest

B

What is the ecliptic?

The path the Sun appears to trace around the celestial sphere each year

If you take the bus from Livingston Campus to Cook Campus, what will have changed w/r to the celestial sphere?
A. The ecliptic.
B. The horizon.
C. The celestial equator.
D. The north celestial pole.
E. Cook Campus is on a different planet, right?

B

What type of star can be seen from New Brunswick at night all year long?
A. Any star that is close to one of the zodiac constellations.
B. Any star that is close to the celestial equator.
C. Any star that is close to the north celestial pole.
D. There is no star that is visible from New Brunswick all year long.
E. Jennifer Lawrence and her co-stars, at the local movie theater.

C

Why do seasons occur?

The tilt of Earth's axis causes sunlight to fall differently on Earth at different times of the year

Why does the tilt of the Earth have a more significant effect on the seasons than the change in distance between the Earth and the Sun?

The change in distance is only about 3%, so the tilt of the Earth overwhelms the effects of the change in distance.

If the tilt of Earth's axis to its orbital plane was 40 degrees, instead of 23.5, but its distance from the sun remained the same, what would happen to the seasons?
A. They wouldn't change much.
B. They would become less extreme winter and summer would be more alike.
C. They would become more extreme winter colder and summer warmer.
D. All of earth would get colder
E. All of earth would get warmer

C

Suppose it is December 21st, and the Sun passes through your zenith at noon. Where are you?
A. The equator.
B. The Tropic of Cancer (23.5°N latitude).
C. The Tropic of Capricorn (23.5°S latitude).
D. The Arctic Circle (66.5°N latitude).
E. The north pole.

C

Why are different stars seen in different seasons?
A. because of Earth's axis tilt
B. because stars move during the year
C. because as Earth orbits the Sun, we see the sun in front of different constellations
D. because of precession

C

What is the difference between rotation vs revolution

Rotation = an object (star, planet, moon) spinning around its own axis

Revolution = one object (earth) orbiting around other object (sun)

What is a sidereal day?

The time it takes the Earth to rotate one full turn on its axis (23 hours 56 minutes).

What is a solar day?

The time is taken for the Sun to appear at the same position in the sky
-24 hours

Earth's Tilt at Summer Solstice

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Earth's Tilt at Winter Solstice

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Why is Winter Colder than Summer?

-Because the sun is lower midday during winter so the same shaft of sunlight is spread out over a larger area

-The days are longer

-The incident angle at which light from the sun hits earth

If the tilt of the Earth's axis to its orbital plane was 40 degrees instead of 23.5, but its distance from the Sun remained the same, what would happen to the seasons?

A) They would not change much
B) They would become less extreme winter and summer would be more alone
C) They would become more extreme winter colder and summer warmer
D) All of Earth would get colder
E All of Earth would get warmer

C

What is the best definition of a sidereal day?
A. The time it takes a planet to spin on its axis relative to the stars.
B. The time it takes a planet to spin on its axis relative to the Sun.
C. The time it takes a planet to orbit the Sun.
D. The time it takes the Sun to spin on its axis relative to the stars.
E. A day that only seems real when you are on the other side of it.

A

What would happen if the Earth spun on its axis more slowly than it does now, but the time it takes to orbit the Sun stayed the same?
A. The Earth's solar day would get longer, and the Earth's sidereal day would stay the same.
B. The Earth's sidereal day would get longer, and the Earth's solar day would stay the same.
C. The Earth's solar and sidereal days would both get longer, but the difference between them would stay the same.
D. The Earth's solar and sidereal days would both get longer, and the difference between them would get larger.
E. We would attract unwanted attention from the Klingons.

D

phases of the moon

-The moon orbits the sun
-Half the moon faces the Sun and the other half faces away from the Sun
-We see the moon from different perspectives; as a result, we see the different combinations of bright and dark faces.

What is the difference of waxing and waning of the moon phases?

Waxing: Moon visible in the afternoon/evening. Gets 'fuller' and rises later each day

Waning: Moon visible late night / early morning. Gets 'less full' and sets later each day.

When the phase of the moon is full,

A) The moon and sun are on opposite sides of Earth
B) The moon and sun are on the same side of Earth
C) The moon and Earth are on opposite sides of the Sun
D) The moon is closer to earth than normal.
E) the moon is further from earth than normal

A

At approximately what time would you see a full Moon on your meridian?
A. After a party that got a little out of control.
B. noon
C. 6 pm
D. midnight
E. 6 am

D

If you see the moon rising at midnight, what phase is it?
A. full
B. first quarter
C. new
D. third quarter
E. triple witching hour

D

Suppose you lived on the Moon near the center of the side that always faces Earth. Which of the following would you NOT see?
A. the Sun rising and setting
B. stars rising and setting
C. the Earth rising and setting
D. the Earth passing through a full cycle of phases
E. the Sun crossing your meridian every four weeks

C

What is a lunar eclipse?

-Earth's shadow on the Moon
-Full moon

What is a solar eclipse?

-Shadow of moon falls on a narrow region of earth
-New moon

What are the different kinds of shadows?

Umbra = completely shadowed
Penumbra = partly shadowed

Suppose you observe a lunar eclipse tomorrow. The earliest possible time for the next solar eclipse would be about
A. 12 hours later.
B. 15 days later.
C. 1 month later.
D. 1 year later.
E. 18 years later.

B

Different types of lunar eclipes

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If there is going to be a total lunar eclipse tonight, then you know that the moon's phase is
A)full
B)new
C)First or third quarter

A

What is the best description of Eratosthenes's experiment?
A. He used the depth of the well in Syene and the distance between Syene and Alexandria to estimate the distance to the center of the Earth.
B. He used the distance to the Earth's center and the change in latitude (angle) between the two cities to estimate the distance between Syene and Alexandria.
C. He used the distance between the two cities and the distance to the Earth's center to estimate the change in latitude (angle) between Syene and Alexandria.
D. He used the change in latitude (angle) between Syene and Alexandria and the distance between the two cities to estimate the distance to the center of the Earth.
E. He took a wild guess and got lucky.

D

A picture of retrograde motion of Mars

What was the geocentric model?

In a geocentric model, Earth is at the center of the revolving planets and stars.

picture that explains retrograde motion

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What is parralax

The apparent change in position of an object when you look at it from different places

In the modern heliocentric model of the Solar System, the apparent retrograde motion of Saturn

A. is an optical illusion caused by Saturn's rings.
B. occurs because Saturn is observed from a moving Earth.
C. occurs because Saturn moves on an epicycle.
D. occurs because Saturn orbits the Sun in a retrograde sense.
E. occurs because Saturn is moving backward in time.

B

Heliocentrism vs. Geocentrism

helio- sun is the center
Geo- earth is the center

What is the greatest elongation?

The point when the planet appears as far away from the Sun as it possibly can. - Elongation is the angle between the Sun and a planet.

Why cant we see mercury and venus?

Because Mercury and Venus are between the Sun and us, we only see them in the west after sunset and in the east before sunrise.

If you're on the surface of the Earth, which of the the following celestial objects can never be seen on the meridian at midnight?
A. the Moon
B. Venus
C. Mars
D. Jupiter
E. Saturn

B

Which phase of Venus provides the strongest evidence that Venus orbits the Sun rather than Earth?
A. new
B. crescent
C. first quarter
D. full
E. third quarter

D (gibbous)

what is an elliptical orbit?

An oval shaped path, used to describe the shape of the Earth's orbit around the Sun

the orbit of a planet about the sun is an ellipse with the sun at one focus

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Suppose a comet orbits the Sun such that its semimajor axis is 10 AU and the closest it gets to the Sun is 2 AU. At the point in its orbit when it is moving slowest, how far is the comet from the Sun?
A. 2 AU
B. 10 AU
C. 12 AU
D. 18 AU
E. Not far enough.

D

Suppose we plot the shape of planetary orbits and the corresponding speed versus time. Which of the following combinations is correct?

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Halley's comet is about 0.6 AU from the Sun at perihelion, and its orbital period is 75.3 yr. How far is it from the Sun at aphelion?

*use P^2=a^3* where "P" is period, and "A" is length of semimajor axis

a^3=P^2=5670
a=17.8
perihelion + aphelion = 2a = 35.6 AU
-----> aphelion = 35 AU

If Earth were 4 times its current distance from the Sun, the time it would take Earth to complete one orbit of the Sun would be

P^2=a^3

B

What is the formula for Kepler's Third Law?

P^2= a^3/m.
P= period in years
a= semimajor axis in AU
M= Mass of the central body in earth masses

If Earth were in orbit around a star with 4 times the mass of the Sun, but still at a distance of 1 AU from that star, the time it would take to complete one orbit would be (use: P^2=a^3/M)
A. 0.25 years.
B. 0.5 years.
C. 1 year.
D. 2 years.
E. 4 years.

B

If Earth were 4 times its current mass but still orbiting the Sun at its current (1 AU) distance, the time it would take to complete one orbit would be (use : P^2=a^3/M)
A. 0.25 year.
B. 0.5 year.
C. 1 year.
D. 2 years.
E. 4 years.

C

Which two pieces of information could be used to determine the mass of Neptune?

A. Neptune's distance from the Sun and how long it takes to orbit the Sun.
B. The semimajor axes of the two moons of Neptune.
C. The orbital periods of any two moons of Neptune.
D. The orbital period and mass of any single moon of Neptune.
E. The orbital period and semimajor axis of any single moon of Neptune.

E

There is a black hole at the center of the Milky Way. A star orbits it with a semimajor axis a = 920 AU and period P = 14.5 yr. What is the mass of the black hole (in units of Msun)?

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Which of the following is an example of motion that is not accelerated?
A. An airplane taxiing along a straight taxiway at a steady speed.
B. An airplane speeding up along a runway towards takeoff.
C. An airplane bouncing up and down in flight due to atmospheric turbulence.
D. An airplane banking (making a turn) as it approaches Newark Airport.
E. An airplane slowing down after it lands.

A

Which of the following has no net force acting on it?.
A.An airplane taxiing along a straight taxiway at a steady speed.
B. An airplane speeding up along a runway towards takeoff.
C. An airplane bounces up and down in flight due to atmospheric turbulence.
D. An airplane banking (making a turn) as it approaches Newark Airport.
E. An airplane slowing down after it lands.

A

Amy places a lead block on an iron block on the table and hits both of them with the same force. The lead block is twice massive as the iron block. The acceleration of the lead block is

A) Four times that of the iron block
B) Two times that of the iron block
C) The same as that of the iron block
D) Half that of the iron block
E) One fourth that of the iron block

D

An elevator moves upward at a constant speed of 7 m/s. The net force on a 50 kg woman inside the elevator is (use F=ma)
A. zero
B. 500 N
C. -500 N
D. None of the other answers.
E. 350 N

A

In a head-on collision, which is greater, the force of the car on the truck or the force of the truck on the car?

A. The force the truck exerts on the car is greater.
B. The force the car exerts on the truck is greater.
C. The forces are the same.
D. It depends on which vehicle is moving faster.

C

from here lecture 8

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As I stand on the stage, Earth's gravitational force on my body

A. Is blocked because the stage is in the way.
B. is zero because I am not moving.
C. is balanced by the force of the stage on my body.
D. is causing me to accelerate.
E. is weighing on my mind.

C

You stand holding onto a pole near the edge of a merry-go-round that turns at a constant speed. Which of the following best describes your motion?

A. You are not accelerating because you are moving at constant speed.
B. You are not accelerating because gravity is not making you fall.
C. You are accelerating because your speed is increasing.
D. You are accelerating because your speed is decreasing.
E. You are accelerating because the direction of your motion is changing.

E

Suppose you swing a ball on a string on a circle around your head. What would happen if you let go of the string, and why?

A. According to Newton's first law of motion, the ball would fly off in a straight line.
B. According to Newton's first law of motion, the ball would continue to move in a circle.
C. According to Newton's second law of motion, the ball would accelerate away from you.
D. According to Newton's third law of motion, you would feel a force away from the ball.
E. According to Murphy's law, the ball would break a window and you would have to pay for it.

A

Suppose you swing a ball on a string on a circle around your head. What would happen if you let go of the string, and why?
A. Trajectory 1
B. Trajectory 2
C. Trajectory 3
D. Trajectory 4

C

Which statement about the force on the ball (before it is released) is true?
A. There is no net force on it.
B. There is a net force in the "forward" direction in which the ball is moving.
C. There is a net force in the "backward" direction, opposite from the direction in which the ball is moving.
D. There is a net force toward Prof. Zimmermann.
E. There is a net force away from Prof. Zimmermann.

D

What happens to the effect of gravity on you as you move away from the source? (Newton's universal Law Of Gravitation)

The force of gravity gets weaker, but you have to move really far away to notice the effect.

Suppose Earth collapsed down to one tenth of its present size (diameter), while retaining all of its present mass. Compared to your present weight, your weight would be: (use f=g((m1*m2)/r^2))
A. Increased by a factor of 10
B. Increased by a factor of 100
C. Remain the same
D. Decreased by a factor of 1/100
E. Decreased by a factor of 1/10

B

According to Newton's laws, the Earth and Moon pull on each other with the same strength of force. What can we say about their accelerations?
A. The Moon accelerates but the Earth does not.
B. The Earth and Moon have the same acceleration.
C. The Earth has a smaller acceleration because it is more massive.
D. The Earth has a higher acceleration because it is more massive.
E. The Earth and Moon accelerate in the same direction.

C

Considering only the force of gravitational attraction,which of the following statements is false?
A. You are attracted to every other student in this room.
B. Every other student in this room is attracted to you.
C. If another student is more massive than you, you are more strongly attracted to that student than the student is to you.
D. For each of your fellow students, you are as strongly attracted to the other student as the other student is to you.
E. Gravity is actually a little creepy!

C

What was the Cavendish Experiment and why is it important?

The Cavendish experiment was significant not only for measuring Earth's density (and thus its mass) but also for proving that Newton's law of gravitation worked on scales much smaller than those of the solar system

Which is false about the Cavendish experiment?

A. In the Cavendish experiment, it helps to use masses of large density as this allows the distance between masses to be reduced.
B. The Cavendish experiment helps us determine the mass of the Earth, if we know the Earth's radius and the acceleration of gravity.
C. The Cavendish experiment, performed on the surface of Mars, can tell us what Newton's gravitational constant is.
D. The Cavendish experiment, performed on a spacecraft falling into a black hole, would yield the same value for the gravitational constant as when performed on Earth.
E. If the Cavendish experiment were conducted on the moon, the gravitational acceleration of the moving masses would be about 1/6 of that measured on Earth.

E

Gravity at work: Tidal Forces

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If the length of a day was 6 hours instead of 24, how many high tides would there be every day?
A. 1
B. 2
C. 4
D. 8
E. None of the other answers.

B

The four Galilean moons (Io, Europa, Ganymede, and Callisto, in order of increasing distance from the planet) are all tidally locked to Jupiter. Which statement about these moons is false?
A. An observer on Jupiter would always see the same face of Callisto.
B. An observer on Callisto would always see the same face of Ganymede.
C. An observer at the center of the side of Callisto that faces Jupiter would never see the planet set.
D. An observer at the center of the side of Callisto that faces away from Jupiter would never see Ganymede at all.
E. Anagrams of the moons' names include "oi," "our ape," "edgy name," and "last coil."

B

Because Pluto and Charon have tidally locked each other, they are different from the Earth/Moon system. Which of the analogies stated below is false?
A. Pluto and Charon orbit the Sun, just like the Earth and the Moon orbit the Sun.
B. Pluto is more massive than Charon, just like the Earth is more massive than the Moon.
C. Pluto and Charon revolve around their common center of mass, just like the Earth and the Moon revolve around their common center of mass.
D. Charon always sees the same side of Pluto, just like the Moon always sees the same side of the Earth.
E. Pluto always sees the same side of Charon, just like the Earth always sees the same side of the Moon.

D

What are orbital resonances?

Galilean moons, again: in the time it takes Ganymede to make one orbit of Jupiter, Europa makes exactly two orbits, and Io makes exactly four orbits of Jupiter.•

Coincidence? No!

Io, Europa, and Ganymede have a stable orbital resonance, which is maintained by the regular gravitational tugs they give each other as they orbit the planet.

Describe the orbital resonances of Neptune and pluto?

In the time it takes Neptune to make three complete orbits around the fun, Pluto can only make two complete orbits of the sun.

Saturn's moons Mimas and Tethys, have orbital periods of 0.94 and 1.88 days, respectively, defining a stable 2:1 orbital resonance. Which statement about these moons is correct?

A) An observer of Mimas would always see the same face of Tethys would always see the same face of Mimas at all times.
B) An observer on Tethys would always see the same face of Mimas at all times.
C) Mimas and Tethys will never be on the same side of Saturn at the same time
D)Mimas will pass between Tethys and Saturn once in every two of its orbits around Saturn.
E) Once Mimas is fully operational, the Galactic Empire will use it to destroy Tethys

D