astronomy answers

Stellar evolution has been best understood by:

analyzing the properties of a large number of stars at a single instant.

What quantities must be measured in order to calculate the luminosity of a star?

Brightness and Distance

What determines the location of a star on the main sequence?

mass

Massive stars:

burn their fuel rapidly, so they have shorter lifetimes than low-mass stars.

An astronomer observes a cluster of stars and constructs an HR diagram like Figure 11.6. What can he or she learn from the region marked "X"?

the age of the cluster

Which of the following correctly orders the spectral types of stars from hottest to coolest ?

OBAFGKM

A star's position on the main sequence does not tell us

its chemical composition

Astronomers must take many factors into account when modeling individual stars. Which of the following is not a factor?

Distance between stars

Astronomers must take many factors into account when modeling individual stars. what are they

limitations of computers

star mass

star composition

Choose the statement about variable stars that is not true.

Their luminosity may be continually increasing.

How would parallax measurements of stars made from Jupiter differ from those made from Earth?

Parallax for a given star would be greater.

The more massive the star,

the hotter it is as a main-sequence star.

Two neighboring stars are seen with significant differences in composition. What is not likely to be true of these stars?

They were born together

What does the HR diagram of a cluster not tell astronomers?

The rotation of the cluster

What does the main sequence show?

the distribution of core hydrogen-fusing stars by mass

What is the definition of a standard candle?

an object whose luminosity is known without needing to know its distance.

Wien's law tells us that

in blackbodies, temperature and peak radiation wavelength (color) are related.

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Why does Jupiter gives off more energy than it receives from the Sun?

gravitational contraction

The giant planets all have:

strong magnetic fields, ring systems, rapid rotation.

The Roche limit is the:

distance at which tides destroy an orbiting object.

The key physical process determining the structures of the giant planets is:

pressure

The colors of the cloud bands on Jupiter and Saturn are due primarily to differences in their

chemical compositions.

Which of the giant planets was predicted to exist mathematically before it was ever seen through a telescope?

Neptune

Which of the following occurred earliest in Earth's evolutionary process?

Differentiation

Which of the following has most strongly shaped Venus's surface?

Volcanism

Which terrestrial world experiences the strongest greenhouse effect?

Venus

The major difference in the composition of Earth's atmosphere compared to the atmospheres of Venus and Mars is a direct consequence of

Life on earth

Mars, Venus, and Earth are much less heavily cratered than Mercury and the Moon. This is explained by the fact that

Mars, Venus, and Earth were geologically active for a longer period of time than Mercury and the Moon.

Which terrestrial planet has the strongest magnetic field?

Earth

Which is not a reason that we suspect Mars once had liquid water on its surface?

Mapping satellites have detected dry riverbeds.

Rovers have detected minerals that must have formed in the presence of liquid water.

Mapping satellites have detected outflow channels coming from impact craters.

Our understanding of Earth's interior comes primarily from:

Earthquakes

When a cup of coffee cools through rising and falling motions of the fluid, we say it undergoes:

Convection

The oxygen in Earth's atmosphere was first created 2.3 billion years ago by:

Photosynthesis

Earth's original atmosphere escaped into space because:

It was composed of the lightest elements, hydrogen and helium

Tides are caused by:

The differential gravity of the Moon and Sun

The most widely accepted theory for the formation of the Moon in the ____________ hypothesis.

Impact

In the absence of a greenhouse effect, what would happen to Earth's oceans?

They would freeze over.

A meteor shower occurs when:

Earth passes through a comet's orbit

Hot Jupiters provide evidence for:

Planetary migration

The radial velocity method is best at detecting exoplanets with ___________ orbital radii and ___________ masses.

Small; large

The physical principle most directly responsible for the shape of planetary systems is:

Conservation of angular momentum

What property of the protoplanetary disk was most responsible for differentiation between the planets?

Temperature

What are the three requirements for an object to be classified as a planet, and why is Pluto no longer considered a planet?

The speed of a light wave:

Is independent of its other properties.

Place the following varieties of light in order, from lowest to highest frequency.

Microwave, infrared, visible, ultraviolet, gamma rays

Consider the two energy level diagrams below for two identical atoms.

Suppose that the electron in each atom drops to the lowest energy state (E1), or the ground state, from the energy level shown in each diagram. (The electron in Atom 1 begins at the fourth energy state, E4, and the electron in Atom 2 begins in the second energy state, E2.)

What is true about the wavelength of the photon emitted by each atom as a result of the transition?

The wavelength of the photon emitted by Atom 2 will be greater than the wavelength of the photon emitted by Atom 1.

The figure above shows blackbody spectra for three different stars. Which star appears reddest to the naked eye?

Star C (lowest)

The graph below show the opacity of the Earth's atmosphere as a function of wavelength. According to this graph, what wavelength region(s) can we not observe here on the ground? Choose all that apply.

1: Gamma Rays, X-Rays, and UV Light ; 3: Infrared Light ; 5: Long-wavelength Radio Waves

Which of the following is NOT an advantage of a reflecting telescope over a refracting telescope?

Mirrors provide stronger magnification than lenses.

You observe two stars, Star A and Star B, with your naked eye which appear to have the same brightness. What is true about the luminosity of these two stars?

Not enough information to decide

An astronomer takes a spectrum of a nearby star. She finds that its absorption lines all appear at shorter wavelengths than expected from laboratory measurements. She should conclude that the star is:

Moving toward her

Which type of spectrum would be observed in each of the three examples below?

Continuous Emission Absorption

In the heliocentric model, retrograde motion occurs when:

Earth catches and passes another planet in its orbit.

Which of the following observations provided the most direct challenge to the geocentric model of solar system orbits?

Phases of Venus

An object travels at 10 m/s through interstellar space. If no forces act upon it, it will:

Continue with the same velocity

Why do astronauts feel "weightless" inside the International Space Station?

They follow the same orbit as the space station.

Which of the following was NOT a reason the geocentric worldview was so popular in Europe in 1400 CE?

The geocentric model had been continuously improved by European astronomers over the previous millennium.

How would the strength of the force between the Moon and Earth change if the mass of the Earth were made two times greater than its current mass?

The force would double

Kepler's laws

(1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci. (2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time. (3) The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun.

At what time of day does a first quarter moon rise?

noon

The constellation Libra is high in the sky at noon during the month of October (though it cannot be seen next to the bright Sun). At what time of year is it high in the sky at midnight?

April

Two people, one in the Brazilian city of Manaus (near the equator) and one in New York City (near 40 degrees north latitude), observe the Sun at noon on June 21. How will their views of the Sun compare?

The Sun will appear higher in the sky to the observer in Manaus.

You observe a lunar eclipse. In what phase must the Moon be in?

Full

Solar eclipses are rare because:

The Moon's orbit around the Earth is tilted with respect to the Earth's orbit around the Sun.

The summer season in Norman is caused by:

The tilt of the Earth's axis with respect to its plane of orbit

Ptolemy's formulation of the geocentric model provided the first successful set of predictions for the:

Retrograde motion of the planets

Which of the following in a necessary part of a good scientific theory?

Well-tested

The characteristic that most clearly distinguishes modern astronomy from its use in the ancient world is:

The Scientific Approach

Sally lives two orders of magnitude farther from your house than April does. If April lives one mile away from you, Sally might live __________ miles away.

100

Which of the following was a way in which prehistoric cultures used astronomy?

For navigation

In the simplest form of the scientific method, which of the following correctly describes the sequence in which it proceeds?

Observation, hypothesis, experiment