Astronomy test study questions (1)

Imagine another solar system, with a star of the same mass as the Sun. Suppose a planet with a mass twice that of Earth (2MEarth) orbits at a distance of 1 AU from the star. What is the orbital period of this planet?

1 year

Approximately how many times larger is our Solar System, compared to the Earth?

1,000,000x

Consider the indicated events in the history of the universe that have helped make human life possible. Rank the events based on when they occurred, from longest ago to most recent.

1. Big Bang & the universe begins to expand 2. elements such as carbon and oxygen first exist 3. nuclear fission begins in the sun 4. earliest life on earth 5. dinosaurs go extinct 6. early humans exist

One arcsecond is what fraction of the full 360 degree horizon?

1/1296000

How many arcseconds are in one degree?

3600

According to modern science, approximately how old is the Sun?

4.5 billion years

Using a telescope, you capture an image of Galaxy X, which is a distance of 65 million light years away. How much younger does the galaxy look in the image, compared to its current age?

65 million years younger

Tidal Forces

A "stretching" force caused by a difference in the gravitational force across a body

What do astronomers mean by a constellation?

A constellation is a region in the sky as seen from Earth

Kepler's Second Law of Planetary Motion

A planet moves faster in the part of its orbit nearer the Sun and slower when farther away, sweeping out equal areas in equal times.

Which of the following scenarios involves energy that we would typically calculate with Einstein's formula E = mc2?

A small amount of the hydrogen in of a nuclear bomb becomes energy as fusion converts the hydrogen to helium.

Which lists astronomy-specific units of distance measurement in the order of smallest to largest?

AU, ly, pc

Compared to the Earth, Saturn's radius is ~9x larger its mass is ~95x greater. If you stood on Saturn's surface, the force of gravity you would feel would be

About the same as on Earth

By studying distant galaxies in the 1920s, Hubble made which of the following important discoveries that led us to conclude that the universe is expanding?

All galaxies outside the Local Group are moving away from us the farther away they are the faster they're going

Celestial Equator

An imaginary circle created by extending Earth's equator into space

Newton's First Law of Motion

An object moves with a constant velocity unless a force acts to change its speed or direction.

When should you feel slightly lighter on Earth's surface?

At midday

At which lunar phase(s) are tides most pronounced (for example, the highest high tides)?

Both new and full moons

What does a "light-minute" measure?

Distance

our "cosmic address"

Earth Our Solar System Our galaxy, the Milky Way The Local Group (a cluster of ~30 galaxies) The Virgo Supercluster (~10,000 galaxies) The greater Laniakea Supercluster (~100,000 galaxies) The Observable Universe

Each of the following lists two facts. Which pair of facts can be used with Newton's version of Kepler's third law to determine the mass of the Sun?

Earth is 150 million km from the Sun and orbits the Sun in one year.

According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?

Earths orbit would not change

Where does the Sun remain above the horizon all day (never setting) on the December solstice?

Everywhere between the Antarctic Circle (latitude 66.5°S) and the South Pole

Newton's Third Law of Motion

For every force there is an equal and opposite reaction force.

Newton's Second Law of Motion

Force (N) = mass (kg) x acceleration (m/s2)

An asteroid that is moving farther from the Sun is gaining _______________ energy.

Gravitational potential

the correct definition and two examples of kinetic energy.

Kinetic energy is the energy an object has due to its motion. Two examples are a car driving down the highway or the movements of the molecules of liquid in a cup of hot coffee.

Kinetic Energy

Massive objects in motion contain Kinetic Energy: K.E. = ½ (mass) x (velocity)2

Kepler's Third Law of Planetary Motion

More distant planets orbit the Sun at slower average speeds, obeying the mathematical relationship: p2 = a3 where "p" is the planet's orbital period in years, and "a" is its average distance from the sun in AU.

Sun reaches zenith (altitude 90 degrees) every day at noon

Not true anywhere on Earth

The celestial equator passes through the zenith

Only if the observer is on the equator

An observer's horizon is parallel with the celestial equator

Only if the observer is on the north or south pole

the correct definition and two examples of potential energy.

Potential energy is energy that is stored. Two examples of potential energy are breakfast cereal, which has chemical potential energy, and a heavy book on the top shelf at the library, which has gravitational potential energy.

Choose the correct definition and two examples of radiative energy

Radiative energy is energy in light. Sunlight carries this form of energy, as do other forms of light including X-rays and radio waves

When space probe Voyager 2 passed by Saturn, its speed increased (but not due to firing its engines). What must have happened?

Saturn must have lost a tiny bit of its orbital energy

Which of the following best explains why the Moon's orbital period and rotation period are the same?

The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.

If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?

The altitude of the north celestial pole equals your latitude.

Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit (well above Jupiter's atmosphere and far from all of Jupiter's moons.) Which of the following statements would be true?

The asteroid's orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on.

Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight?

The ball's gravitational potential energy is greatest at the instant when the ball is at its highest point.

A rock held above the ground has potential energy. As the rock falls, this potential energy is converted to kinetic energy. Finally, the rock hits the ground and stays there. What has happened to the energy?

The energy goes to producing sound and to heating the ground, rock, and surrounding air.

Newton's Universal Law of Gravitation

The gravitational force Fg (in N) between two objects with masses M1 and M2 (in kg), separated by a distance, d (in m), is calculated as: Fg =G M1M2/d2

Kepler's First Law of Planetary Motion

The orbit of each planet about the Sun is an ellipse with the Sun at one focus.

North celestial pole

The point in the northern sky around which the stars all appear to rotate

North celestial pole

The point in the northern sky around which the stars all appear to rotate.

South celestial pole

The point in the southern sky around which the stars all appear to rotate.

Beijing and Philadelphia have about the same latitude but different longitudes. What can be said about the tonight's night sky in these two places?

The sky will look about the same.

Which of the following best describes why we have seasons on Earth?

The tilt of Earth's axis causes different portions of Earth to receive more or less direct sunlight at different times of year.

I live in the United States, and during my first trip to Argentina I saw many constellations that I'd never seen before.

This statement makes sense, because the constellations visible in the sky depend on latitude. Since Argentina is in the Southern Hemisphere, the constellations visible there include many that are not visible from the United States.

Which of the following best describes the origin of ocean tides on Earth?

Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.

Sun rises due east and sets due west on March equinox

True everywhere on Earth

Sun reaches highest point in local sky on June solstice and at high latitudes, Sun never rises on December solstice

True for Northern Hemisphere

Sun traces shortest path across local sky on June solstice and Sun is above horizon for the longest time on December solstice and at high latitudes, Sun never sets on December solstice

True for Southern Hemisphere

Suppose the Moon's orbit were unchanged, but it rotated faster (meaning it did not have synchronous rotation). Which of the following would be true?

We would no longer always see nearly the same face of the Moon.

The South Celestial Pole is 25 ∘ above your southern horizon. What does it tell you?

You are at latitude 25 ∘ S.

What does the universe look like if you zoom out to the largest scale?

a 3-D web like structure with dense clusters of galaxies and empty voids

The planets never travel in a straight line as they orbit the Sun. According to Newton's second law of motion, this must mean that _________.

a force is acting on the planets

Celestial Equator

a great circle projected onto the sky from the Earth's equator

Ecliptic

a great circle traced by the Sun through the celestial sphere over the course of one year

Meridian

a great circle, passing through through the zenith of an observer, from North to South

According to current scientific estimates, when did the Big Bang occur?

about 14 billion years ago

An apple contains ___________ energy that your body can convert into other forms energy.

chemical potential

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them _________.

decreases by a factor of 9

The Sun reaches the zenith (directly overhead) at midday ___________.

everywhere within the tropics (between latitudes 23.5°N and 23.5°S) on two dates each year and on the equator only on the March and September equinoxes

As an interstellar gas cloud shrinks in size, its gravitational potential energy:

gradually transforms into other forms of energy.

Rapidly moving comets have more _______ energy than slowly moving ones.

kinetic

The Milky Way and Andromeda galaxies are among a few dozen galaxies that make up our ____________.

local group

Nuclear fusion in stars converts some of the _____ energy of hydrogen nuclei into light and heat.

mass

A net force acting on an object will always cause a change in the object's _________.

momentum

Newton showed that Kepler's laws are _________.

natural consequences of the law of universal gravitation

The source of energy that keeps the Sun shining today is _________.

nuclear fusion

How often does our entire universe orbit around the milky way galaxy?

once every 230 million years

Nadir

point directly opposite the zenith

Equinox points

points of intersection of the Celestial Equator and Ecliptic

Solstice points

points of maximum angular separation between the Celestial Equator and the Ecliptic(longest/shortest days of the year)

The light from Polaris travels through space in the form of _________ energy.

radiative

What does temperature measure?

the average kinetic energy of particles in a substance

What do astronomers mean by the Big Bang?

the event that marked the beginning of the expansion of the universe

One remarkable night you observe supernovae in four galaxies, which have distances of 10, 20, 30, and 40 million light-years from Earth. Which supernova happened first?

the galaxy 40 mly away

What is the ecliptic?

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

The term observable universe refers to _________.

the portion of the universe that we can see in principle, given the current age of the universe

Compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest to the Sun is:

the same

Suppose that two objects collide. Which will NOT be the same both before and after the collision?

the total temperature of the objects

Due to its much higher density, water heated to 80 degrees (Celsius) contains more ______ energy than air at the same temperature.

thermal

To estimate the central temperature of the Sun, scientists _________.

use computer models to predict interior conditions

Which of the following sorts the features of the cosmic web in order of increasing density?

void, filament, cluster