astronomy chapter 1
What is the meaning of the word cosmos?
the sum total of all matter and energy that is everything within and between all galaxies
Which of the following has your “address” in the correct order?
you, Earth, solar system, Milky Way, Local Group, Local Supercluster
About where is our solar system located within the Milky Way Galaxy?
about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk
Roughly how many stars are in the Milky Way Galaxy?
Modern telescopes are capable of seeing bright galaxies up to about
10 billion light-years away
Suppose we imagine the Sun to be about the size of a grapefruit. How big an area would the orbits of the eight planets of the solar system cover?
the size of a typical campus
What do we mean when we say that the universe is expanding
average distances are increasing between galaxies
The age of the universe is
between 10 billion and 16 billion years
How are galaxies important to our existence?
Galaxies recycle heavy elements produced in stars into future generations of stars
Earth is made mostly of metals and rocks. Where did this material come from?
it was produced by nuclear fusion in stars
What is nuclear fusion?
the process of combining lightweight nuclei to make heavier nuclei
Why did Carl Sagan say that we are star stuff?
Nearly every atom from which we are made once (before the solar system formed) was inside of a star
Which of the following statements does not use the term light-year in an appropriate way?
it will take me light-years to complete this homework assignment
One light-hour is the distance that light travels in an hour. How far is this, in kilometers?
1.08 billion km
Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?
the one that is farthest away
What do we mean by the observable universe?
the part of the universe that could be observed in principle, including things that may require future technologies
Suppose we imagine the Sun to be about the size of a grapefruit. Which of the following describes the size and distance of Earth on the same scale?
Earth is the size of a point about 15 meters away from the Sun
What is the sun mainly made of?
hydrogen and helium
Which of the following is smallest?
size of a typical planet
Which of the following is largest?
size of a typical galaxy
On the 1-to10-billion scale, about how far is it to the nearest stars besides the sun?
Suppose we imagine the Sun to be about the size of a grapefruit. How far away are the nearest stars (the three stars of Alpha Centauri)
If we use 1 millimeter to represent 1 light-year, how large in diameter is the milky way galaxy?
Which of the following best describes the Milky Way Galaxy?
a spiral galaxy with a disk about 100,000 light-years in diameter and containing between 100 billion and 1 trillion stars
How long would it take to count all the stars in the Milky Way Galaxy at a rate of one star per second?
several thousand years
How many galaxies are there in the observable universe?
roughly (within a factor of 10) he same as the number of stars in our galaxy
If you represented each star by a grain of sand, how much sand would it take to represent all the stars in the universe?
more than all the sand on all the beaches on Earth
On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, how long has human civilization (i.e., since ancient Egypt) existed?
a few seconds
On a cosmic calendar, in which the history of the universe is compressed into 1 year, when did the dinosaurs become extinct?
in late December
On a cosmic calendar, in which the history of the universe is compressed into 1 year, when did Kepler and Galileo first discover that we live on a planet in a solar system?
1 second ago
On a cosmic calendar,in which the history of the universe is compressed into one year, how long is the average human life span?
Approximately how fast are you moving with the rotation of Earth?
What is an astronomical unit?
the average distance from Earth to the Sun
Which of the following statements about the ecliptic plane is not true?
it is the plane of the Moon’s orbit around Earth
Patterns of stars in constellations hardly change in appearance over times of even a few thousand years. why?
the stars in our sky actually move rapidly relative to us-thousands of kilometers per hour-but are so far away that it takes a long time for this motion to make a noticeable change in the patterns in the sky
How long does it take our solar system to complete one orbit around the Milky Way Galaxy
230 million years
Which of the following statements about the Milky Way Galaxy is not true?
Our solar system is located very close to the center of the Milky Way Galaxy
Which of the following correctly lists speeds from slowest to fastest?
Earth’s speed of rotation on its axis, Earth’s speed of revolution about the Sun typical speeds of stars in the local solar neighborhood relative to us, the speed of our solar system orbiting the center of the Milky Way Galaxy, the speeds of very distant galaxies relative to us
Most of the mass in the Milky Way Galaxy is located
in the halo (above/ below the disk)
The distribution of the mass of the Milky Way Galaxy is determined by
studying the rotation of the galaxy
From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that
the universe is expanding
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, and the farther away they are, the faster they’re going
Imagine that we put a raisin cake into the oven, with each raisin separated from the others by 1 cm. An hour later, we take it out and the distances between raisins are 3 cm. If you lived in one of the raisins and watched the other raisins as the cake expanded, which of the following would you conclude?
more distant raisins would be moving away from you faster
Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
Copernicus, Kepler, and Galileo; about 400 years ago
Which of the following is not a general difference between a planet and a star?
all planets are made of rock and all stars are made of gas
Our solar system consists of
the sun and all the objects that orbit it
A typical galaxy is a
collection of a few hundred million to a trillion or more stars, bound together by gravity
Which of the following best describes what we mean by the universe?
the sum total of all matter and energy
What do astronomers mean by the Big Bang?
the event that marked the beginning of the expansion of the universe
What do we mean when we say that the universe is expanding?
Average distances between galaxies are increasing with time
Based on observations of the universal expansion, the age of the universe is about
14 billion years
A television advertisement claiming that a product is light-years ahead of its time does not make sense because
it uses “light-years” to talk about time, but a light-year is a unit of distance
The term observable universe refers to
that portion of the universe that we can see in principle, given the current age of the universe
On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is
small enough to fit within your hand
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars beside the Sun?
about the distance across the United States
The number of stars in the Milky Way Galaxy is approximately
a few hundred billion
An astronomical unit is
the average distance between EArth and the Sun
What is the ecliptic plane?
the plane of EArth’s orbit around the sun
How long does it take the Earth to compete one orbit around the Sun?
Using the idea discussed in your textbook, in what sense are we “star stuff”?
Nearly every atom from which we are made was once inside of a star
When we look at an object that is 1,000 light-years away we see it
as it was 1,000 years ago
Suppose we look at two distant galaxies: galaxy 1 is twice as far away as galaxy 2. in this case,
we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than galaxy 2
Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
the planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart
If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?
several thousand years
the total number of stars in the observable universe is about
the same as the number of grains of sand on all the beaches on Earth
Where is our solar system located within the Milky Way Galaxy?
roughly halfway between the center and the edge of the visible disk of the galaxy
If we imagine the history of the universe compressed into one year, dinosaurs became extinct
Relative to the age of the universe, how old is our solar system?
it is about one-third the age of the universe
How do the spreads at which we are moving with Earth’s rotation and orbit compare to the speeds of more familiar objects?
Earth’s rotation carries most people around the axis faster than a commercial jet travels, and Earth’s orbit carries us around the Sun faster than the Space Shuttle orbits Earth
Why do the patterns of the stars in our sky look the same from year to year?
because the stars in the constellations are so far away
Astronomers infer that the universe is expanding because distant galaxies all appear to
be moving away from us, with more distant ones moving faster
Which statement about motion in the universe is not true?
the mysterious dark matter is the fastest-moving material in the universe
When did humans learn that the Earth is not the center of the universe?
within the past 500 years