astronomy 1-3 hw

The Sun appears to rise and set in our sky because Earth ___ once each day.

rotates

The fact that we always see the same face of the Moon tells us that the Moon

rotates with the same period that it orbits Earth.

The mathematical form of Kepler's third law measures the period in years and the __ in astronomical units (AU

semimajor axis

For people in Australia, the first day of spring is approximately ___

september 21

Our ___ is moving toward the star Vega at about 70,000 km/hr.

solar system

If a person were standing in the Moon's partial shadow (penumbra) during a solar eclipse, he/she would see ___

the Sun with a portion of it blocked by the Moon

Define light-year.

the distance light travels in one year, which is about 9.46 trillion kilometers

If you are watching a lunar eclipse in which the Moon is in Earth's partial shadow, you will see ___

the entire Moon, but slightly dimmer than normal.

Suppose we observe a galaxy that is 13 billion light-years away. Which of the following can we conclude?

the galaxy was formed before the universe was 1 billion years ago

If there is going to be a total lunar eclipse tonight, then you know that:

the moon's phase is full

The total number of stars in the observable universe is roughly equivalent to

the number of grains of sand on all the beaches on Earth

If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then

the planets are marble-size or smaller and the nearest stars are thousands of miles away.

If the expansion of the universe is accelerating, then the rate at which galaxies were moving apart in the past was

less than the rate at which they are moving apart today

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

local group

If Earth's mass were half its actual value but its radius stayed the same, the escape velocity of Earth would be

lower than it's actual value

Galileo's contribution to astronomy included:

making observations and conducting experiments that dispelled scientific objections to the Sun-centered model.

Two stars that are in the same constellation

may actually be very far away from each other.

Our entire solar system orbits around the center of the ___ about once every 230 million years.

milky way galaxy

The Moon takes roughly 28 days to complete one orbit around Earth. If the orbital radius of the Moon were twice its actual value, its orbital period would be

more than 56 days

Stars that have the highest apparent brightness are

nearby and very luminous

In Ptolemy's Earth-centered model, when would Venus appear directly behind the Sun as viewed from Earth?

never

When would you expect to see Venus high in the sky at midnight?

never

Starting with a new moon, list the phases of the moon in order:

new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, waning crescent

A point at which the Moon crosses Earth's orbital plane is called a(n)

node

If the Moon's orbit were not tilted with respect to the ecliptic, solar eclipses would occur ____

once a month

The age of our solar system is about

one-third of the age of the universe

You are one year older each time Earth ___ about the Sun

orbits

During some lunar eclipses, the Moon's appearance changes only slightly, because it passes only through the part of Earth's shadow called the

penumbra

According to Kepler's second law, Pluto will be traveling fastest around the Sun when at

perihelion

Two planets are observed going around a star. Planet Xoron has an orbital period that is twice as long as planet Krypton. Which planet has a shorter average orbital radius?

planet Krypton

If gravity is the only force that plays a role in the evolution of the universe, and the mass density is less than the critical mass density, which plot correctly shows the evolution of the universe?

plot B

Referring to the plot from the previous question, if gravity is the only force that plays a role in the evolution of the universe, and the mass density is greater than the critical mass density, which plot correctly shows the evolution of the universe?

plot c

Consider the hypothetical observation "a planet beyond Saturn rises in west, sets in east." This observation is not consistent with a Sun-centered model, because in this model _____

the rise and set of all objects depends only on Earth's rotation

Based on what you have learned, why is it generally hotter in summer than in winter?

the sun is higher in the sky, and we have more hours of daylight

The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:

the universe is expanding

Do you think Northern Hemisphere summers are warmer or colder than Southern Hemisphere summers on Mars?

they are colder

Do you think Northern Hemisphere winters are warmer or colder than Southern Hemisphere winters on Mars?

they are warmer

Massive-star supernovae are not good standard candles because

they have different luminosities since they have different masses

A week after full moon, the Moon's phase is:

third quarter

Two observers, one in northern Canada and the other in Australia, are looking at the Moon on the same day. The observer in Canada sees a Third Quarter Moon. What does the observer in Australia see?

third quarter moon

Anyone looking from the night side of Earth can, in principle, see a(n)

total lunar eclipse

A(n) ____ can occur only when the Moon is new and has an angular size larger than the Sun in the sky.

total solar eclipse

Suppose the Moon were three times smaller than it really is, but its distance from Earth remained the same. Which type of eclipse would never occur?

total solar eclipses

In January, Earth's rotation axis points in the direction of the star Polaris. Where does it point in July?

toward the star Polaris

On Dec. 21, the Sun is directly above the __

tropic of Capricorn (latitude = 23.5 degrees S)

A partial lunar eclipse begins when the Moon first touches Earth's ____

umbra

On average, galaxies are getting farther apart with time, which is why we say our ___ is expanding.

universe

If the Earth were tilted 90 degrees (rather than 23.5 degrees), summer in the Arctic would be _______ summer in Colorado.

warmer than

An astronomer looks at the Andromeda galaxy (the other large galaxy in the Local Group) through her telescope. How long ago did that light leave Andromeda?

2.5 million years

How many arcminutes are in a full circle?

21,600'

The Moon's angular size is about 1/2. What is this in arcminutes?

30'

About how long would it take for a radar pulse to travel round trip from Earth to Neptune and back again to Earth?

8 hours

An astronomical unit is:

Earth's average distance from the Sun

While an observer on Earth sees a total solar eclipse, an astronaut is on the near side of the Moon. What would the astronaut see?

Earth's day side with a dark spot moving across it.

Which of the following planets has essentially no seasons at all?

Jupiter (axis tilt = 3.1°)

According to Kepler's third law,

Jupiter orbits the Sun at a faster speed than Saturn.

You discover an asteroid that orbits the Sun with the same 1-year orbital period as Earth. Which of the following statements must be true?

The asteroid's average (semimajor axis) distance from the Sun is 1AU1AU.

Define astronomical unit.

The average distance between Earth and the Sun, which is about 149.6 million kilometers.

When we say the universe is expanding, we mean that

The average distance between galaxies is growing with time

As a comet orbits around the Sun, its maximum speed is twice its minimum speed. What can we say about its orbit?

The comet is twice as far from the Sun at aphelion as at perihelion.

During an annular solar eclipse, ____

The moon is too far away from the Earth to block the entire sun

In the Greek geocentric model, the retrograde motion of a planet occurs when:

The planet actually goes backward in its orbit around Earth.

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

The sky will look about the same

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

about 14 billion years ago

A solar eclipse that occurs when the new moon is too far from Earth to completely cover the Sun can be either a partial solar eclipse or a(n)

annular eclipse

According to Kepler's second law, Jupiter will be traveling most slowly around the Sun when at

aphelion

Which two things are needed to determine a standard candle's distance from Earth?

apparent brightness and luminosity

Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky?

at noon

When would a new Venus be highest in the sky?

at noon

Light received from a galaxy at the far end of the Local Supercluster was emitted roughly ____________.

10^8 years ago

Jupiter orbits the Sun at an average distance of 5.203AU and takes 11.86years to complete each orbit. Based on these facts, which statement is true?

11.86^2 = 5.203^3

How many arcseconds are in a full circle?

1296000"

What is the Moon's angular size in arcseconds?

1800"

A supernova is observed in a galaxy 2,000 million light-years away. How long ago did the supernova occur?

2 billion years ago

In Ptolemy's Earth-centered model for the solar system, Venus always stays close to the Sun in the sky and, because it always stays between Earth and the Sun, its phases range only between new and crescent. The following statements are all true and were all observed by Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?

We sometimes see gibbous (nearly but not quite full) Venus.

If stars existed but galaxies did not

We would not exist because we are made of material that required recycling in galaxies

When is the Sun highest in the sky at noon for people living in Sydney, Australia?

Winter solstice (Dec. 21)

The north celestial pole is 35 degrees above your northern horizon. What does it tell you?

You are at latitude 35 degrees N

Based on what you have learned, which statement best describes how variation in the Earth-Sun distance affects the seasons?

he variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons.

If the orbital distance of Earth was greater than its actual value, the maximum distance a star could be away from Earth for its distance to be determined using the parallax method (with current telescopes) would be

high than the actual upper limit

If the orbital distance of Earth was greater than its actual value, the parallax angle to nearby stars would be

higher

Which of the following is the least accurate method for determining cosmic distances?

hubble's law

On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?

in September

On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form?

in early September

When we say that a planet has a highly eccentric orbit, we mean that:

in some parts of its orbit it is much closer to the Sun than in other parts.

When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been

incomplete

We never see a crescent Jupiter from Earth because Jupiter ____

is farther than Earth from the Sun

If the Sun rises precisely due east,

it must be the day of either the March or the September equinox.

Because we live in an expanding universe, distant galaxies are farther away from us today than they were when the light we see from them started on its journey to us. So what do we mean when we say that a galaxy is 7 billion light-years away?

it's light has taken 7 billion years to reach us

On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?

just a few hours before midnight on December 31

The earliest radio broadcasts on Earth were emitted about 100 years ago. Approximately where are these initial radio waves now? (Radio waves are a type of radiation, so they travel at the speed of light)

just passing relatively local stars in our galaxy

A planet is discovered orbiting the star 51 Peg with a period of four days (0.01 years). 51 Peg has the same mass as the Sun. Mercury's orbital period is 0.24 years, and Venus's is 0.62 years. The average orbital radius of this planet is

less than Mercury's

Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law

Earth travels faster in its orbit around the Sun in January than in July.

Kepler's first law states that the orbit of each planet is an ellipse with the Sun at one focus. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's first law? A. Earth is slightly closer to the Sun on one side of its orbit than on the other side. B. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. C. The Sun is located slightly off-center from the middle of each planet's orbit. D. All the planets orbit the Sun in nearly the same plane. E. Venus orbits the Sun faster than Earth orbits the Sun. F. Inner planets orbit the Sun at a higher speed than outer planets.

A. Earth is slightly closer to the Sun on one side of its orbit than on the other side C. The Sun is located slightly off-center from the middle of each planet's orbit.

Which sequence is correctly ordered from smallest to largest? A. Earth, Moon's orbit, the Sun, Neptune's orbit B. Earth, the Sun, the Moon's orbit, Neptune's orbit C. Earth, the Moon's orbit, Neptune's orbit, the Sun

A. Earth, Moon's orbit, the Sun, Neptune's orbit

Which of the following is not true about a scientific theory? A. Even the strongest theories can never be proved true beyond all doubt. B. A theory is essentially an educated guess. C. A theory must explain a wide range of observations or experiments.

B. A theory is essentially an educated guess.

Why do the planets orbit the Sun (i.e. why don't they crash into the Sun)?

Although the planets experience a force of gravity from the Sun, since they are moving, their trajectories bend around the Sun rather than lead directly into the Sun.

For which model would the universe begin recollapsing the soonest? A. A universe with lots of dark energy and two times the critical mass density. B. A universe with no dark energy and two times the critical mass density. C. A universe with no dark energy and exactly the critical mass density. D. A universe with no dark energy and less than the critical mass density.

B. A universe with no dark energy and two times the critical mass density.

All of the following statements are true. Which one can be explained by Kepler's third law? A. The Sun is not in the precise center of Saturn's orbit. B. Venus orbits the Sun at a faster orbital speed than Earth. C. Earth is slightly closer to the Sun in January than in July. D. All the planets orbit the Sun in nearly the same plane. E. Mars moves faster in its orbit when it is closer to the Sun than when it is farther from the Sun.

B. Venus orbits the Sun at a faster orbital speed than Earth.

Why do we essentially see the same face of the Moon at all times?

Because the Moon's rotational and orbital periods are equal.

All of the following statements are true. Which one can be explained by Kepler's second law? A. The Sun is not in the precise center of Saturn's orbit. B. Earth is slightly closer to the Sun in January than in July. C. Mars moves faster in its orbit when it is closer to the Sun than when it is farther from the Sun. D. All the planets orbit the Sun in nearly the same plane. E. Venus orbits the Sun at a faster orbital speed than Earth.

C. Mars moves faster in its orbit when it is closer to the Sun than when it is farther from the Sun.

Which of the following statements best describes what astronomers mean when they say that the universe is expanding? A. The average distance between stars in the Milky Way Galaxy is increasing with time. B. All objects in the universe, including Earth and everything on it, are gradually growing in size. C. The average distance between galaxies is increasing with time. D. The universe itself is not growing, but our knowledge of the universe is increasing with time. E. The observable universe is growing larger in radius at a rate of one light-year per year.

C. The average distance between galaxies is increasing with time.

Kepler's third law states that a planet's orbital period, p, is related to its average (semimajor axis) orbital distance. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's third law? A. All the planets orbit the Sun in nearly the same plane. B. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. C. Venus orbits the Sun faster than Earth orbits the Sun. D. The Sun is located slightly off-center from the middle of each planet's orbit. E. Earth is slightly closer to the Sun on one side of its orbit than on the other side. F. Inner planets orbit the Sun at higher speed than outer planets.

C. Venus orbits the Sun faster than Earth orbits the Sun. F. Inner planets orbit the Sun at a higher speed than outer planets.

Which of the following can you observe about Venus with the naked eye? Select all that apply. A. Venus is visible at midnight when it is in its full phase B. When Venus is brightest, it is visible all night long C. Venus sometimes shines brightly in the eastern sky shortly before dawn D. Venus sometimes shines brightly in the western sky shortly after sunset

C. Venus sometimes shines brightly in the eastern sky shortly before dawn D. Venus sometimes shines brightly in the western sky shortly after sunset

Which of the following lies in the ecliptic plane? A. A line connecting Earth's north and south poles B. A line connecting Earth and Polaris C. Earth's equator D. Earth's orbital path around the Sun

D. Earth's orbital path around the Sun

Suppose the moon's orbital position is located as shown in the figure below. At what time will the moon be highest in the sky?

Dusk

Kepler's second law states that as a planet orbits the Sun, it sweeps out equal areas in equal times. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's second law? A. Inner planets orbit the Sun at a higher speed than outer planets. B. Earth is slightly closer to the Sun on one side of its orbit than on the other side. C. The Sun is located slightly off-center from the middle of each planet's orbit. D. Venus orbits the Sun faster than Earth orbits the Sun. E. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. F. All the planets orbit the Sun in nearly the same plane.

E. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun.

When we see Saturn going through a period of apparent retrograde motion, it means:

Earth is passing Saturn in its orbit, with both planets on the same side of the Sun

When is the Sun in the Northern part of the sky at noon for people who live on the equator?

From March 21 until Sep. 21

Which of the following was not a major advantage of Copernicus's Sun-centered model over the Ptolemaic model?

It made significantly better predictions of planetary positions in our sky.

A couple hours before sunrise, the Moon appears near the western horizon as shown below in the View from Earth window. Which of the orbital positions marked by letters best corresponds to the orbital position of the Moon?

H

If an astronomer claims to have discovered an object with a very eccentric orbit, which of the following best describes the orbital trajectory of the object?

It looks like a very squashed oval.

Based on what you have learned, which of the following planets would you expect to have seasons most like Earth's?

Mars (axis tilt = 25.2°)

Could we see a galaxy that is 20 billion light-years away?

No, because it would be beyond the bounds of our observable universe.

Could this be a real orbit for Earth?

No, because the sun cannot be in the center of an ellipse, but at a focus on the ellipse

In winter, Earth's axis points toward the star Polaris. In spring, the axis points toward

Polaris

Which of the following is not true about scientific progress?

Science advances only through the scientific method

Why doesn't a total lunar eclipse occur every month?

Sometimes the Moon is above or below Earth's shadow during a full moon.

What is the cause of the lunar phases (i.e. why doesn't the Moon look the same every day)?

The Moon's orbit around Earth causes different amounts of the illuminated side of the Moon to be visible from Earth

For any particular location on Earth, why are lunar eclipses observed more frequently than solar eclipses?

The Moon's shadow covers only a small portion of the Earth

You've now seen that Earth's varying distance cannot be the cause of our seasons. So what is the cause of the seasons?

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

In what sense are telescopes like time machines?

They allow us to see distant objects as they were long in the past.

Which of the following planets should have the most extreme seasons?

Uranus (axis tilt = 97.9°)

Earth is slightly closer to the Sun in January than in July. How does the area swept out by Earth's orbit around the Sun during the 31 days of January compare to the area swept out during the 31 days of July?

both areas are the same

Which type of standard candle is the most appropriate for determining the distance to nearby galaxies (like the Andromeda Galaxy)?

cepheid variables

If the Earth did not have a tilt, the weather during June in Colorado would be __

colder

If the Earth were tilted 45 degrees (rather than 23.5 degrees), winters in Colorado would be ___

colder

Tycho Brahe's contribution to astronomy included:

collecting data that enabled Kepler to discover the laws of planetary motion.

Suppose two comets, comet A and comet B, were orbiting the Sun, having the same average orbital radii. If comet A had a higher eccentricity than comet B, which comet would, during some portion of its orbit, have the highest orbital speed?

comet a

Roughly what time of day is a Third Quarter Moon highest in the sky?

dawn

The extent to which Mars' orbit differs from a perfect circle is called its

eccentricity

Earth orbits in the shape of a/an ___ around the Sun

ellipse

If the actual mass density of the universe is greater than the critical density and there is no dark energy, then the universe would

eventually stop expanding and begin contracting

Earth is located at one ___ of the Moon's orbit.

focus

By how many orders of magnitude is the distance to the nearest stars greater than the orbital radius of Neptune?

four

Which moon phase would occur after a waxing gibbous?

full moon

In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is ___

full whenever it is on the opposite side of the Sun from Earth

On your way to work about two hours after sunrise, you notice the moon setting. What phase is it in?

gibbous

Which Venus phase would be impossible to see (from Earth) if Venus orbited Earth as described in Ptolemy's Earth-centered model?

gibbous (nearly full)

When it is summer in Australia, the season in the United States is

winter

If Earth's orbit were very eccentric, but the average distance from the Sun were still 1 AU, its orbital period

would still be a year