astronomy exam 2

A refractory material is a material that

can withstand high temperatures without melting or vaporizing.

What is the most important factor in determining whether or not a planet will be rocky like terrestrial planets or gaseous like giant planets?

the planet’s distance from the Sun

Which is the best description of a moon?

any natural satellite of a planet or asteroid

When astronomers began searching for extrasolar planets, they were surprised to discover Jupiter-sized planets much closer than 1 AU from their parent stars. Why is this surprising?

These planets must have formed at larger radii where temperatures were cooler and then migrated inward, which is thought to be a rare phenomenon.

According to the conservation of angular momentum, if an ice-skater who is spinning with her arms out wide slowly pulls them close to her body, she will

spin faster

What is the habitable zone?

the distance from a star where liquid water can exist

Because energy must be conserved, a collapsing cloud of gas must

heat up

How many exoplanets are known (that is, have been confirmed) to exist?

more than 3000

What is a protostar?

a large ball of gas not yet hot enough at its core to be a star

Detecting a planet around another star using the transit method is difficult because the

planet must pass directly in front of the star.

When you push your palms together and rub them back and forth, you are demonstrating one way of converting ________ energy into ________ energy.

kinetic; thermal

Which method can be used to determine the radius of an extrasolar planet?

transit

Approximately how much mass was there in the protoplanetary disk out of which the planets formed, compared to the mass of the Sun?

< 1 percent

The smallest grains of dust stick together in an accretion disk by which force?

electrostatic force

The Kepler Mission is designed to search for extrasolar planets using the ________ method.

transit

If you want to find naturally occurring volatile materials that formed with the Solar System, you should look

on the outer parts of the Solar System.

The difference in composition between the giant planets and the terrestrial planets is most likely caused by the fact that

the terrestrial planets are closer to the Sun.

Using the Doppler effect data shown in the figure below, what is the approximate orbital period of the extrasolar planet?

6 years

Conservation of angular momentum slows a cloud’s collapse

mostly along directions perpendicular to the cloud’s axis of rotation.

The darkest part of the Moon’s shadow is the

umbra

For a person who lives at a latitude of +40°, when is the Sun directly overhead at noon?

never

If you are observing a partial solar eclipse, you must be standing in the

Moon’s penumbra.

Solar and lunar eclipses are rare because

the Moon’s orbital plane is tipped by 5.2° relative to Earth’s orbital plane about the Sun.

At approximately what time does a full Moon rise?

6 pm

Tidal forces are caused by

the difference between the strength of the gravitational pull of the Moon and Sun on either side of Earth.

The Moon undergoes synchronous rotation, and as a consequence the

rotational period of the Moon equals the orbital period of the Moon around Earth.

On which day of the year does the Sun reach its northernmost point on the celestial sphere?

summer solstice

During a lunar eclipse the Moon can appear red. This is caused by

light traveling through the Earth’s atmosphere.

When the Sun and Moon are separated by 90 degrees in the sky, _________ tides occur on Earth when the strength of the tides are _________ than normal.

neap; lower

Earth’s rotation rate is slowing because of

tidal forces from the Moon.

If Earth’s axis were tilted by 5° instead of its actual tilt, how would the seasons be different than they are currently?

Winters would be warmer.

The Moon always keeps the same face toward Earth because of

tidal locking.

During summer above the Arctic Circle

the Sun can always be seen

At which of the possible times below could the waxing gibbous moon be seen rising?

3 pm

According to the figure, the approximate amount of time between a high tide and a low tide at a given location is about

6 hrs

If tonight the Moon is in the waxing gibbous phase, in three days the phase of the Moon will be

full

The distance between Earth and the Moon

is slowly increasing

When the Northern Hemisphere experiences fall, the Southern Hemisphere experiences

spring

During which lunar phase do solar eclipses occur?

new

In the figure shown below, the direction of the disk’s rotation is indicated. What is the direction of the protostellar Sun’s rotation?

in the same direction as the disk’s rotation

Of the following methods, the age of the Solar System can be determined most accurately by

radioactive dating of rocks retrieved from the Moon.

What is the age of our Solar System?

4.6 billion years

Comets and asteroids are

material left over from the formation of the planets.

Which of the following is a terrestrial planet?

venus

Which of the following is a giant planet?

jupiter

Once a planetesimal is large enough, it grows by

attracting more material through gravitation.

That fact that all major Solar System objects orbit the Sun in the same direction, and mostly with the same direction of spin, is the original evidence for

the nebular hypothesis.

Which of these three lunar surfaces shown in the figure below is the oldest?

A

If a radioactive element has a half-life of 10,000 years, what fraction of it is left in a rock after 40,000 years?

1/16

The icy planetesimals that remain in the Solar System today are called

comet nuclei.

What have astronomers and geologists studied to arrive at the same conclusions about Earth’s origins?

meteorites

The layers of the Sun’s atmosphere, from innermost to outermost, are

photosphere, chromosphere, corona.

In the figure labeled below, which solar layer is the chromosphere?

e

The surface of the Sun appears sharp when we look at it in visible light because

the photosphere is thin compared with the other layers in the Sun.

The solar spectrum is an example of a(n) ________ spectrum

absorption

The hottest layer of the solar atmosphere is the

corona

The Sun’s chromosphere appears red because

its spectrum is dominated by Hα emission.

The figure below shows the Sun during a solar eclipse at visible wavelengths. Which part of the Sun is visible around the shadow of the Moon?

chromosphere

In a sunspot, the umbra is

cooler than the penumbra.

Sunspots appear dark because they have ________ than those of the surrounding gases.

temperatures that are lower

Which of the following are created by solar magnetic activity?

all of these

The magnetic field of the Sun is continuously produced and deformed by

its differential rotation.

If you observe a maximum number of sunspots right now, how long would you have to wait to see the next solar maximum?

11 years

The Sun’s magnetic field reverses direction every

11 years

Solar wind particles hit the surface of the Moon, but they don’t make it to the surface of the Earth because the Earth

has a magnetic field while the Moon does not

Some restaurants place food under infrared heat lamps so that it stays warm after it has been cooked. This is an example of energy being transported by

radiation

What is the approximate temperature at the center of the Sun?

1.5 × 10⁷ K

Density, temperature, and pressure increase as you move inward in the interior of the Sun. This means that the weight of the star pushing inward at a given radius ________ as you move toward the core.

increases

The balance of energy in the solar interior means that

the energy production rate in the core equals the rate of radiation escaping the Sun’s surface.

What do astronomers mean when they say that the Sun makes energy by hydrogen burning?

The Sun is fusing hydrogen into helium and releasing energy.

The energy that fuels the Sun is generated

only in its core

The solar neutrino problem was solved by postulating that

neutrinos oscillate between three different types.

The detection of solar neutrinos confirms that

the Sun’s core is powered by proton-proton fusion

If the core of the Sun were hotter than it is now, how would the Sun’s energy production change?

It would produce more energy per second than it does now.

Hydrostatic equilibrium is a balance between

pressure and gravity.

The majority of the Sun’s energy comes from

hydrogen fusion

Which of these can travel directly from the center of the Sun to Earth in about 8 minutes?

neutrinos

The net result of the proton-proton chain of nuclear reactions is that four protons are converted into

one helium nucleus, as well as energy, positrons, and neutrinos.

We can determine how density changes with radius in the Sun using

helioseismology.

The interior zones of the Sun are distinguished by

their modes of energy production transport.

How does the fact that the surface of the Sun rings like a bell help us better understand the Sun?

It helps us understand the solar interior better.

Which force is responsible for holding the protons and neutrons in the nucleus of an atom together?

strong nuclear force

Approximately how long does it take the photons released in nuclear reactions in the core of the Sun to exit the Sun?

100,000 years