Astronomy Exam 1

• Correct order of planets
you, Earth, solar system, Milky Way, Local Group, Local Supercluster
• About where is our solar system located within the Milky Way Galaxy?
is 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?
100 billion
• 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 old
• Why does 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 is largest? -
size of a typical galaxy, bigger than - 1 light-year, distance to the nearest star (other than our Sun), size of Pluto's orbit
• On the 1-to-10-billion scale, about how far is it to the nearest stars besides the Sun?
4,400 kilometers
• What is an astronomical unit?
the average distance from Earth to the Sun
• These following statements are true about the ecliptic plane
It is the plane of Earth's orbit around the Sun, During a lunar eclipse, the Moon lies in the ecliptic plane, The nodes of the Moon's orbit lie in the ecliptic plane, During a solar eclipse, the Moon lies in the ecliptic plane
• Which of the following best describes the modern definition of a constellation?
a region of the celestial sphere
• When we look into the band of light in our sky that we call the Milky Way, can we see distant galaxies? Why or why not?
No, because the stars, gas, and dust of the Milky Way block us from seeing them
• What is a circumpolar star
a star that always remains above your horizon
• What makes the North Star, Polaris, special
It appears very near the north celestial pole
• You are standing on Earth's equator. Which way is Polaris, the North star
on the northern horizon
• Why do we have seasons on Earth
As Earth goes around the Sun and Earth's axis remains pointed toward Polaris, the Northern and Southern hemispheres alternately receive more and less direct sunlight
• Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere?
The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight
• Which of the following statements about lunar phases is true?
It is possible to have two full Moons during January, but not during February
How long is the lunar cycle?
• the lunar cycle is 29 1/2 days.
• If the Moon is setting at noon, the phase of the Moon must be -
third quarter
• In which direction does a quarter Moon rise?
• Suppose you live on the Moon. How long is a day (i.e., from sunrise to sunrise)?
a lunar month
What conditions are required for a lunar eclipse?
The phase of the Moon must be full, and the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun
• What causes the apparent retrograde motion of the planets?
As Earth passes another planet, the other planet appears to move backward with respect to the background stars, but the planet's motion does not really change
• Why were ancient peoples unable to detect stellar parallax
They did not have the ability to measure very small angles.
• How many arcseconds are in 4
• The astrology practiced by those who cast predictive horoscopes can be tested by
comparing how often the predictions come true to what would be expected by pure chance
• following statements about scientific theories are true?
, A theory can never be proved beyond all doubt; we can only hope to collect more and more evidence that might support it
• This comes directly from Kepler's third law?
Venus orbits the Sun at a slower average speed than Mercury
• These are true
Venus is more massive than Mercury., Venus has a thicker atmosphere than Mercury, Venus is larger than Mercury
• From Kepler's third law, a hypothetical planet that is twice as far from the Sun as Earth should have a period of -
more than 2 Earth years
• How did the Ptolemaic model explain the apparent retrograde motion of the planets
It held that the planets moved along small circles that moved on larger circles around Earth.
• How did Eratosthenes estimate the size of Earth in 240 B.C.?
by comparing the maximum altitude of the Sun in two cities at different latitudes
• What is the acceleration of gravity of Earth
9.8 m/s^2 downward
• If an object's velocity is doubled, its momentum is
• In which of the following cases would you feel weightless?
falling from a roof
• A skater can spin faster by pulling her arms closer to her body or spin slower by spreading her arms out from her body. This is due to
conservation of angular momentum
• Which of the following scenarios correctly demonstrates the transformation of mass into energy as given by Einstein's equation, ?
When hydrogen is fused into helium, whether in the Sun or in a nuclear bomb, the mass difference is turned into energy
• According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will
decrease by a factor of 9.
• According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
increase by a factor of 4.
• 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
• If your mass is 65kg on Earth, what would your mass be on the Moon?
65 kg
• Grass (that is healthy) looks green because
it reflects green light and absorbs other colors
• The wavelength of a wave is
the distance between two adjacent peaks of the wave
• How are wavelength, frequency, and energy related for photons of light?
Longer wavelength means lower frequency and lower energy
• When white light passes through a cool cloud of gas, we see
an absorption line spectrum
• Thermal radiation is defined as
radiation that depends only on the emitting object's temperature
• A gas heated to millions of degrees would emit
mostly X rays
• If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet
The planet is rotating