question

Which of the following observational techniques is most appropriate for measuring Doppler shifts?

answer

Spectroscopy (taking a spectrum)

question

One of the absorption lines of hydrogen has a rest wavelength of 656 nm (at rest means with respect to the observer, like in a lab). You observe several stars and measure the wavelength of this same hydrogen absorption line in each star. Based on the measured wavelength of this line, which star is moving towards the Earth the fastest?

answer

630 nm

question

Which of the following statements about X-rays and radio waves is not true?

answer

X-rays travel through space faster than radio waves

question

Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?

answer

Several kilometers

question

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

answer

The cloud is cool and lies between you and a hot star

question

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

answer

Its surface is cooler than the surface of the Sun

question

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

answer

The star is moving toward us

question

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?

answer

The total amount of light in the spectrum tells us the star's radius

question

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

answer

It is closer to the stars

question

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

answer

Gamma rays, X-rays, ultraviolet, visible light, infrared, radio

question

Which of the following is always true about images captured with X-ray telescopes?

answer

They are always shown with colors that are not the true colors of the objects that were photographed

question

The spectra of most galaxies show redshifts. This means that their spectral lines ________.

answer

have wavelengths that are longer than normal

question

What is the purpose of adaptive optics?

answer

It reduces blurring caused by atmospheric turbulence for telescopes on the ground

question

What is the purpose of interferometry?

answer

It allows two or more small telescopes to achieve the angular resolution of a much larger telescope

question

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

answer

Photons of different energy behave differently and require different collection strategies

question

Why are astronauts weightless in the Space Station?

answer

Because the Space Station is constantly in free-fall around the Earth

question

Suppose that the Sun shrank in size but that its mass remained the same. What would happen to the orbit of the Earth?

answer

Earth's orbit would be unaffected

question

Imagine another solar system, with a star more massive than the Sun. Suppose a planet with the same mass as Earth orbits at a distance of 1 AU from the star. How would the planet's year (orbital period) compare to Earth's year?

answer

The planet's year would be shorter than Earth's

question

Which of the following best describes the origin of ocean tides on Earth?

answer

Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth

question

At which lunar phase(s) are tides most pronounced (for example, the highest high tides)?

answer

New and Full moons

question

Which of the following best explains why the Moon's orbital period and rotation period are the same?

answer

The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period

question

The astronauts feel weightless in the International Space Station, which orbits the Earth once every 90 minutes. Why?

answer

Because they are falling around the Earth

question

Consider the elliptical orbit of a comet around the Sun. Where in its orbit is the comet moving the fastest?

answer

when it is closest to the Sun

question

The Moon is constantly falling toward Earth.

answer

True

question

Consider the statement "There's no gravity in space." This statement is:

answer

Completely false

question

If the Moon were closer to Earth, high tides would:

answer

be higher than they are now

question

Approximately where is it currently high tide on Earth?

answer

On the portion of Earth facing directly toward the Moon and on the portion of Earth facing directly away from the Moon

question

How did the Ptolemaic model explain the apparent retrograde motion of the planets?

answer

The planets moved along small circles that moved on larger circles around the Earth.

question

When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

answer

Copernicus used perfect circles for the orbits of the planets.

question

Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit?

answer

Winter

question

According to Kepler's third law (p2 = a3), how does a planet's mass affect its orbit around the Sun?

answer

A planet's mass has no effect on its orbit around the Sun

question

All the following statements are true. Which one follows directly from Kepler's third law (p2 = a3)?

answer

Venus orbits the Sun at a slower average speed than Mercury

question

Galileo challenged the idea that objects in the heavens were perfect by ________.

answer

observing sunspots on the Sun and mountains on the Moon

question

Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?

answer

Phases of Venus

question

Which of the following is not consistent with the major hallmarks of science?

answer

Science consists of proven theories that are understood to be true explanations of reality.

question

Which of the following is not part of a good scientific theory?

answer

A scientific theory cannot be accepted until it has been proven true beyond all doubt

question

Imagine for a moment that despite all the evidence, Earth actually is not rotating and orbiting the Sun. Which of these hypothetical observations (none of them are real) would be inconsistent with our Sun-centered view of the solar system?

answer

We discover a small planet beyond Saturn that rises in the west and sets in the east each day

question

What do we mean by a geocentric model of the universe?

answer

A model designed to explain what we see in the sky while having the Earth located in the center of the universe

question

What was the Ptolemaic model?

answer

An Earth-centered model of planetary motion published by Ptolemy

question

The great contribution of Nicholas Copernicus was to ________.

answer

create a detailed model of our solar system with the Sun rather than Earth at the center

question

The great contribution of Tycho Brahe was to ________.

answer

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

question

Which of the following was not observed by Galileo?

answer

Stellar parallax

question

Which of the following is not one of, nor a direct consequence of, Kepler's Laws?

answer

The force of attraction between any two objects decreases with the square of the distance between their centers.

question

Which of the following statements about scientific models is true?

answer

A model can be used to explain and predict real phenomena

question

How did Eratosthenes estimate the size of Earth in 240 B.C.?

answer

by comparing the maximum altitude of the Sun in two cities at different latitudes

question

Why did Ptolemy have the planets orbiting Earth on "circles upon circles" in his model of the universe?

answer

to explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky

question

The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?

answer

We could not see it at all

question

When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting ________.

answer

higher in the sky

question

Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?

answer

To the right of Polaris; that is, 90 degrees counterclockwise from its current position

question

In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because ________.

answer

our evening view of space depends on where Earth is located in its orbit around the Sun

question

The Sun's path, as viewed from the equator, is highest in the sky on ________.

answer

the spring and fall equinoxes

question

Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?

answer

The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.

question

How does Earth's varying distance from the Sun affect our seasons?

answer

It doesn't --- Earth's orbital distance plays no significant role in the seasons.

question

Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?

answer

Your friend will also see a crescent moon

question

Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?

answer

New Earth

question

You observe a full moon rising at sunset. What will you see at midnight?

answer

A full moon high in the sky

question

All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?

answer

The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.

question

For most of history, the lack of observable stellar parallax was interpreted to mean that ________.

answer

Earth is stationary at the center of the universe

question

During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?

answer

Earth is catching up with and passing by Mars in their respective orbits.

question

Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by ________.

answer

the Galileo spacecraft that orbited Jupiter in the 1990s

question

What is the ecliptic?

answer

The path the Sun appears to trace around the celestial sphere each year

question

If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?

answer

The altitude of the north celestial pole equals your latitude.

question

Each choice below describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.)

answer

Earth's rotation defines a day. The cycle of the Moon's phases takes about a month. Earth's orbit defines a year. Earth's cycle of axis precession takes 26,000 years.

question

If we have a new moon today, when we will have the next full moon?

answer

in about 2 weeks

question

We cannot see a new moon in our sky because ________.

answer

a new moon is quite near the Sun in the sky

question

Lunar eclipses can occur only during a ________.

answer

full moon

question

During the time that a planet is in its period of apparent retrograde motion: ________.

answer

Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars

question

When we look at an object that is 1,000 light-years away we see it ________.

answer

as it was 1,000 years ago

question

Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case ________.

answer

we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2

question

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?

answer

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.

question

Why do the patterns of the stars in our sky look the same from year to year?

answer

Because the stars in the constellations are so far away

question

Which of the following is not a general difference between a planet and a star?

answer

All planets are made of rock and all stars are made of gas

question

Place the following items in order of actual physical size, from smallest to largest.

answer

Planet, star, solar system, galaxy

question

Rank the following 4 items by how long it takes for light to reach us from these objects, from shortest to longest.

answer

Sun, Pluto, center of the Milky Way, the Andromeda Galaxy

question

Rank the following 3 items from nearest to farthest. Hint: the Orion Nebula is a cloud of gas in which young stars are being born within the Milky Way, about 1500 light-years away.

answer

Alpha Centauri, Orion Nebula, star in the center of the Milky Way

Astro Midterm 1 – Flashcards

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