Homework Questions Chapters 1-3

If we had detected a signal from an advanced civilization in 2013 which was located at a distance of 7 light-years from the Sun, in what year was the signal actually transmitted? 2013 2020 2006 2007

2006 Any message we send (radio or laser beam) will travel at the speed of light Will cover each LY in one year's time length For it to travel 7 light years it would take 7 years

Which of the following locations for the telescope would allow you to measure distances to the most distant stars? a telescope on a clear mountaintop on Earth a telescope on Mars a telescope orbiting Earth a telescope placed on the same orbit of the Sun as Earth, but on the opposite side of the Sun a telescope on the Moon the location would not affect the maximum distance to which the telescope could detect parallax

As you can see in the parallax diagram in the video or your textbook, the base of the parallax triangle is the Earth-Sun distance, and making this baseline distance larger would increase the parallax angle to any star, making the angle easier to measure. Of the choices given, only locating the telescope on Mars would make this baseline distance larger. Therefore, the telescope on Mars would be able to measure parallax for more distant stars than it would in any of the other locations. mars --> not farther away but move westward away from earth so angle is wider

Stellar parallax exists only because Earth orbits the Sun. Therefore, if the ancient Greeks had measured stellar parallax, they would have known that their belief in an Earth-centered universe was wrong. Why didn't the ancient Greeks measure stellar parallax? The Greeks thought all the stars were the same distance away, residing on a celestial sphere. Some Greeks actually did measure it, but they did not understand the importance of their measurements. Their belief in an Earth-centered universe meant that they did not expect parallax, and therefore did not look for it. Even for the nearest stars, parallax angles are too small to measure with the naked eye

Even for the nearest stars, parallax angles are too small to measure with the naked eye The nearest stars (the three stars of the alpha Centauri system) are located a little over 4 light-years away. As discussed in the video, this gives them a parallax angle smaller than 1 arcsecond, which is far too small to detect with the naked eye. Because the ancient Greeks did not have telescopes, they could not measure stellar parallax.

The picture below shows the Milky Way Galaxy *add pic T/F

False Andromeda galaxy Can't see milky way

The solar system formed 1.5 billion years after the Big Bang T/F

False Big bang occured 13 billion years ago Solar system around 4 billion years ago

Shortest to Longest Wavelength

Gamma Rays, X Rays, Ultraviolet, Visible Light, Infrared, Radio Waves Shorter wavelength = Higher frequency = Higher energy ALL HAVE THE SAME SPEED! The speed of light is a constant (in empty space) for all forms of light, meaning that all forms of light travel at the same speed, regardless of wavelength, frequency, or energy.

According to the nebular theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? Its mass, temperature, and density all increased. It got hotter, its rate of rotation increased, and it flattened into a disk. It gained energy, it gained angular momentum, and it flattened into a disk. Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the jovian planets, and central temperatures rose to more than a trillion Kelvin.

It got hotter, its rate of rotation increased, and it flattened into a disk. Heating is a consequence of conservation of energy, faster rotation is a consequence of conservation of angular momentum, and flattening is a consequence of collisions between objects in a spinning system.

Suppose that two asteroids are orbiting the Sun on nearly identical orbits, and they happen to pass close enough to each other to have their orbits altered by this gravitational encounter. If one of the asteroids ends up moving to an orbit that is closer to the Sun, what happens to the other asteroid? It will end up on an orbit that is farther from the Sun. It will also end up on an orbit that is closer to the Sun. It will become much cooler. It will stay on its original orbit.

It will end up on an orbit that is farther from the Sun. Total energy must be conserved, so if one asteroid loses energy and moves to a closer orbit, the other must gain energy and move to a more distant orbit.

Inward migration is a hypothesis used to explain why some stars do not have planets at all some stars do not have Jupiter-sized planets Jupiter-sized planets are seen orbiting close to some stars Terrestrial-sized planets are seen orbiting far from some stars

Jupiter-sized planets are seen orbiting close to some stars

Suppose you want to observe the apparent retrograde motion of Mars. How long will you need in order to see it? About an hour A few days Many months One night

Many months - planet moving against background stars - retrograde: Earth catches up and passes Mars in its orbit while Mars takes 1.88 years to fully rotate - much slower than Earth - retrograde: when planets move westward and then eastward - every planet farther from the sun than Earth can have retrograde (b/c Earth moves faster than all of these planets) - mercury and venus don't have retrograde (closer to sun)

In what way do planets move through our sky differently than the stars? The planets move across our sky each night, but the stars do not. The planets move across our sky from west to east each night, whereas the stars go from east to west. Each night, all planets and stars move across the sky but planets move across our sky faster than the stars. Over a few weeks, we see planets move relative to the stars, but we do not see the stars move relative to one another.

Over a few weeks, we see planets move relative to the stars, but we do not see the stars move relative to one another.

Notice that in the view through the camera, the parallax is larger (the apparent movement is larger) for the man than for the trees, and that the mountains do not appear to shift at all. Why?

The amount of parallax depends on an object's distance, with larger parallax for nearer objects.

Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you? The Doppler shift of the star's spectrum The wavelengths of spectral lines in the star's spectrum Whether the star's spectrum has more emission lines or more absorption lines The peak energy of the star's thermal radiation

The wavelengths of spectral lines in the star's spectrum Different chemical elements and ions produce different sets of spectral lines.

The region of our solar system between Mercury and Mars has very few asteroids, whereas the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars? There were very few planetary leftovers in this region because most of the solid material was accreted by the terrestrial planets as the planets formed. It was too hot for asteroids to form in this part of the solar system. All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter. Gravity was too weak to allow asteroids to form in this part of the solar system.

There were very few planetary leftovers in this region because most of the solid material was accreted by the terrestrial planets as the planets formed.

Cepheid Variables are stars that can be used as "standard candles" to determine the distance to nearby galaxies

True

The Nice Model explains how a planet the size of Neptune could be located so far from the Sun T/F

True

Why does Stellar Parallax occur? We view nearby stars from different positions in Earth's orbit at different times of year. We view nearby stars from different positions on Earth as Earth rotates on its axis. Nearby stars move at higher speeds relative to the Sun than more distant stars. Nearby stars move in tiny circles as Earth orbits the Sun.

We view nearby stars from different positions in Earth's orbit at different times of year.

Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________. a longer wavelength a shorter wavelength a higher intensity

a shorter wavelength

This diagram represents the solar nebula early in history and shows the location of the frost line. If you discover an object that is made of metal, rock, and ice in which region of the solar system did it form? a. 1 b. 2 c. 3 d. 4

a. 1 - just the sun b. 2 - rock and metal c. 3 - rock, metal, and ice d. 4 - rock, metal, and Hydrogen compounds The terrestrial planets grew from "seeds" of metal and rock, whereas the jovian planets grew from seeds that also contained large amounts of hydrogen compounds that condensed only in the cold outer solar system.

Place the following items in order of actual physical size, from smallest to largest a. planet, star, solar system, galaxy b. planets and stars are about the same size, solar system, galaxy c. star, planet, galaxy, solar system d. planet, star, galaxy, solar system e. star, planet, solar system, galaxy

a. planet, star, solar system, galaxy

What type of visible light spectrum does the Sun produce? a continuous spectrum an emission line spectrum an absorption line spectrum

an absorption line spectrum The Sun can simplistically be pictured as a hot interior light source surrounded by a thin, cooler layer of gas (the Sun's photosphere). The interior produces a continuous spectrum, while the overlying gas acts like a cloud to produce absorption lines. The interior of the Sun effectively produces a continuous spectrum. These photons escape to space....only after passing through a thin, cooler layer of gas atthe Sun's surface

Based on the way scientists view the study of astrobiology, failing to find life on other worlds would represent ________. proof that the search was a waste of time evidence that we have been searching in the wrong way, because life must exist somewhere besides Earth proof that Earth is the only inhabited planet in the universe an important lesson that would help us understand the conditions that made life on Earth possible

an important lesson that would help us understand the conditions that made life on Earth possible

Far from the Sun in a spherical cloud surrounding the solar system we find a. Orion's belt b. Oort cloud c. Asteroid belt d. Kuiper belt

b. Oort cloud

Where are the most of asteroids found? a. between the Sun and Mercury b. between the orbits of Mars and Jupiter c. between the orbits of jovian planets d. in the Kuiper belt e. in the Oort cloud

b. between the orbits of Mars and Jupiter the asteroid belt!

How do scientists estimate how old the solar system is? a. look up answer in a book b. measure the abundances of radioactive elements in meteorites, and use their half-lives to calculate the age c. measure speeds and distances of galaxies, and calculate the time it took for them to travel that distance d. measure how fast the Sun is losing energy and how much energy it has to lose

b. measure the abundances of radioactive elements in meteorites, and use their half-lives to calculate the age

The great contribution of Tycho Brahe was to a. discover that planets orbit the Sun in elliptical orbits with varying speed b. observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion

b. observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion

What is wrong with the planetary orbit shown? (slight elliptical circle with sun at center) a. shape of orbit is not an ellipse as Kepler's first law requires b. the Sun is not at one focus, as Kepler's first law requires c. orbital path violates Kepler's third law d. there's nothing wrong with this orbit

b. the Sun is not at one focus, as Kepler's first law requires

A radioactive isotope is a. an unstable nucleus that gives off radio waves b. unstable nucleus that spontaneously breaks apart c. stable nucleus that is formed from the fission of a large unstable nucleus d. nucleus that is formed from the fusion of two other nuclei

b. unstable nucleus that spontaneously breaks apart fission (breaks a part) Carbon-14 → unstable (radioactive)

The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________. still be an absorption spectrum appear as a continuous rainbow of colors appear completely dark be an emission line spectrum

be an emission line spectrum Because the cloud absorbs light from the hot source, conservation of energy demands that it must re-emit light with the same total amount of energy. However, this re-emitted light is sent in all directions, not just along the direction from which it originally came. Therefore, if we view the cloud from a location from which we can see only the light that the cloud itself emits, we will see an emission line spectrum.

How many arcseconds are in one degree? a. 60 b. 360 c. 3600 d. 100 e. 1000

c. 3600 1" = 60 arc minutes 60*60 = 3600 arcseconds

A smooth distribution of radiation across a broad range of wavelengths is referred to as a. emission line spectrum b. absorption line spectrum c. continuous spectrum d. broad spectrum

c. continuous spectrum

According to our theory of the solar system formation, what are asteroids and comets? a. shattered remains of collisions between planets b. chunks of rock or ice that were expelled from planets by Volcanoes c. leftover planetesimals that never accreted into planets d. chunks of rock or ice that condensed after the planets and moons finished forming

c. leftover planetesimals that never accreted into planets b. chunks of rock or ice that were expelled from planets by Volcanoes --> where Oxygen may have come from If we see oxygen in an atmosphere it must be due to recent volcanic eruption or there's life there Methane and oxygen are indicates of life

Our solar system consists of a. sun, planets, and nothing else b. sun and several nearby stars, as well as the planets and other objects that orbit these stars c. sun and all the objects that orbit it d. few hundred billion stars bound together by gravity

c. sun and all the objects that orbit it

The possibility of extraterrestrial life was first considered a. after the invention of the telescope b. only during the past few decades c. thousands of years ago during ancient times d. at the turn of the 20th century

c. thousands of years ago during ancient times

In the context of life in the universe, which of the following discoveries of astronomy suggests that enormous numbers of habitable worlds may exist in the universe? a. laws of physics are the same everywhere b. universe is very old c. universe is very large d. building blocks of life are common

c. universe is very large

Compared to Jupiter and Saturn, Uranus and Neptune contain a much higher proportion of hydrogen compounds have no ring systems are substantially larger are much more massive

contain a much higher proportion of hydrogen compounds

Rank the following... condensation of solid particles contraction of solar nebula accretion of planetesimals large cloud of gas and dust clearing the solar nebula

contraction - decreasing size (compression) Once the solar wind helped clear away the remaining gas in the solar nebula, the era of planet formation was essentially over. Remember that all these stages occurred over a period of millions of years, ending about 4 1/2 billion years ago.

The farthest bright galaxies that modern telescopes are capable of seeing up to a. 1 million LY away b. 10 million LY away c. 1 billion LY away d. 10 billion LY away e. 1 trillion LY away

d. 10 billion LY away

What do we mean by the frost line when we discuss the formation of planets in the solar nebula? a. It is another way of stating the temperature at which water freezes into ice. b. It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds. c. It is the altitude in a planet's atmosphere at which snow can form. d. It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

d. It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

Suppose you view the solar system from high above Earth's North Pole, which of the following statements about planetary orbits will be true? a. all planets except Uranus orbit the sun counterclockwise; Uranus orbits in opposite direction b. inner planets orbit Sun clockwise while outer planets orbit Sun counterclockwise c. inner planets orbit Sun counterclockwise while outer planets orbit Sun clockwise d. all planets orbit counterclockwise around the Sun

d. all planets orbit counterclockwise around the Sun all planets orbit/revolved counterclockwise!

According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn? a. ices were able to condense at the distance of Jupiter and Saturn, but only rock and metal could condense at the distances of Uranus and Neptune b. colder gas in the outer regions of the solar nebula had less gravity and therefore could not gather up into such large balls as it could closer in c. size differences are thought to be a random coincidence d. particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula

d. particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula

What do we mean by the half-life of a radioactive isotope? a. amount of time a person can be exposed to radiation without getting sick b. time for half the number of radioactive nuclei to become stable nuclei c. amount of time for half of the nuclei to become radioactive d. time for half the number of radioactive nuclei to decay

d. time for half the number of radioactive nuclei to decay

The mysterious component of the universe which appears to be pushing galaxies apart is referred to as dark matter anti-gravity inflation dark energy

dark energy

Which of the following best describes the Milky Way Galaxy? a. spiral galaxy with disk about a billion kilometers in diameter and containing between 100 million and 1 billion stars b. spiral galaxy with disk about 100,000 LY in diameter and containing about 100,000 stars c. spherically shaped collection of stars including our solar system and about a dozen other solar systems, stretching about 4 LY in diameter d. spherically shaped collection of about 1 million stars that is about 100 LY in diameter e. spiral galaxy with a disk about 100,000 LY in diameter and containing between 100 billion and 100 trillion stars

e. spiral galaxy with a disk about 100,000 LY in diameter and containing between 100 billion and 100 trillion stars

An alternative to the nebular theory for the formation of the solar system suggests that the planets formed from blobs of gas that had been gravitationally pulled out of the Sun during the near-collision with another star. This idea is referred to as the collision-ejection hypothesis tidal distortion hypothesis encounter hypothesis fragmentation hypothesis

encounter hypothesis

For planets orbiting the Sun, period (p) and orbital distance (a) obey the relation p2 = a3

explains why Earth orbits the Sun at a faster average speed than Mars. Kepler's third law

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

explains why Earth's distance from the Sun varies over the course of each year. Kepler's first law

A line between a planet and its Sun sweeps out equal areas in equal times

explains why Earth's orbital speed varies over the course of each year. Kepler's second law

An object moves at constant velocity if there's no net force acting on it

explains why a spaceship with no forces acting on it will continue moving even if it has no fuel. Newton's first law: An object at rest tends to stay at rest and an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force

Force = Mass * Acceleration

explains why applying a force to a baseball with your arm can cause the baseball to accelerate from rest to the speed at which it leaves your hand. Newton's second law

The video shows a collapsing cloud of interstellar gas, which is held together by the mutual gravitational attraction of all the atoms and molecules that make up the cloud. As the cloud collapses, the overall force of gravity that draws the cloud inward (x) because (x)

gradually becomes stronger the strength of gravity follows an inverse square law with distance.

The most abundant materials in solar nebular metals hydrogen and helium gases hydrogen compounds like water, methane, and ammonia rocks

hydrogen and helium gases

In the outer regions of the solar nebula where temperatures were low, only hydrogen compounds could condense as ices only rock and iron could condense hydrogen and helium gases (inert gas - doesn't combine with everything else) were able to condense in addition to rock and iron, hydrogen compounds also condensed as ices

in addition to rock and iron, hydrogen compounds also condensed as ices

As the cloud shrinks in size, its central temperature (x) as a result of its (x)

increases gravitational potential energy being converted to thermal energy

Gravitational Force

multiply the two masses, divide by their distance squared

The neon "OPEN" sign appears reddish-orange because __________. neon atoms emit only yellow and red photon seach yellow and red photon emitted by neon carries more energy than each blue and violet photon emitted neon atoms emit many more yellow and red photons than blue and violet photons the yellow and red photons emitted by neon travel much faster than the blue and violet photons and so reach our eyes first

neon atoms emit many more yellow and red photons than blue and violet photons The many more lines in the yellow and red parts of the spectrum are what make "pure" neon lights look red or orange. (When you see "neon lights" glowing with other colors (besides reddish-orange), it is generally because they contain additional elements (besides neon) making them glow.)

Thermal radiation is defined as ________. radiation in the form of emission lines from an object radiation that is felt as heat radiation with a spectrum whose shape depends only on the temperature of the emitting object radiation produced by an extremely hot object

radiation with a spectrum whose shape depends only on the temperature of the emitting object It's called thermal radiation because it depends on temperature. Stefan-Boltzmann Law • Each square meter of a hotter object's surface emits more light at all wavelengths. Wien's Law • Hotter objects emit photons with a higher average energy.

On a scale in which the distance from the Sun to the Earth is about 15 meters, the distance from the Earth to the Moon is ________. small enough to fit within your hand about 1 meter about 5 meters about 30 meters

small enough to fit within your hand

Observations of stellar parallax therfore provide direct evidence that: stars move through space some stars are more distant than others Earth is smaller than the Sun Earth orbits the Sun

some stars are more distant than others Earth orbits the Sun In other words, stellar parallax provides direct proof that Earth is not stationary at the center of the universe, but rather is a planet orbiting the Sun; if Earth did not move around the Sun, there would be no apparent shift in stellar positions. In addition, the fact that different stars have different amounts of parallax proves that stars lie at different distances from us.

As the cloud shrinks in size, its rate of rotation (x) because (x)

speeds up its total angular momentum is conserved

For every force there's an equal and opposite reaction force

tells us that, when you are pushing on a table, the table is pushing up on you with a force that precisely balances the force of your push. Newton's third law