final exam Flashcards
(49 cards)
If we imagine the history of the universe compressed into one year, the first dinosaurs walked on Earth
about 6 days ago.
How do the speeds at which we are moving with the Earth’s rotation and orbit compare to the speeds of more familiar objects?
The Earth’s rotation is carrying most people around the axis faster than a commercial jet travels, and the Earth’s orbit is carrying us around the Sun faster than the Space Shuttle orbits the Earth.
When we look at an object that is 1,000 light-years away we see it
as it was 1,000 years ago.
Why do the patterns of the stars in our sky look the same from year to year?
Although these stars move quite fast by human standards, they are so far away that it would take thousands of years for their motion to be noticeable to the eye.
Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case
We are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2.
Which of the following has your “cosmic address” in the correct order?
You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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
Astronomers infer that the universe is expanding because distant galaxies all appear to
be moving away from us, with more distant ones moving faster.
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
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.
Using the ideas discussed in the text, in what sense are we “star stuff”?
Nearly every atom from which we are made was once inside of a star.
When did humans learn that the Earth is not the center of the universe?
Within the past 500 years
Relative to the age of the universe, how old is our solar system?
It is between about one-quarter to one-half the age of the universe
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?
They are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the remaining planets are spread much farther apart, with Pluto more than a half a kilometer from the Sun.
How are galaxies important to our existence?
Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.
What kinds of objects lie in the halo of our galaxy?
globular clusters
What kinds of objects lie in the disk of our galaxy?
O and B stars, gas and dust, open clusters, old K and M stars
What makes up the interstellar medium?
gas and dust
How does the interstellar medium obscure our view of most of the galaxy?
It absorbs visible, ultraviolet, and some infrared light.
How can we see through the interstellar medium?
by observing in high-energy wavelengths such as X rays and long wavelengths of light such as radio
waves
All the iron on Earth originated from
nuclear fusion within the cores of high-mass stars.
Why are we unlikely to find Earth-like planets around halo stars in the Galaxy?
Halo stars formed in an environment where there were few heavy elements to create rocky planets.
What produces the 21-cm line that we use to map out the Milky Way Galaxy?
atomic hydrogen
Compared with our Sun, most stars in the halo are
old, red, and dim and have fewer heavy elements
