Astronomy Exam 2 Review

Which of the following changes would cause the fusion rate in the Sun's core to increase? Check all that apply.

An increase in the core temperature A decrease in the core radius

Which of the following is the best answer to the question, "Why does the Sun shine?"

As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.

How can we measure the strength of magnetic fields on the Sun?

By looking for the splitting of spectral lines in the Sun's spectrum.

Nuclear fusion of hydrogen into helium occurs in the __________.

Core

Rank the following layers of the Sun based on the pressure within them, from highest to lowest.

Core, radiation zone, convection zone, photosphere

Rank the following layers of the Sun based on their temperature, from highest to lowest.

Core, radiation zone, convection zone, photosphere

We can see the Sun's _________ most easily during total solar eclipses

Corona

Following are the different layers of the Sun's atmosphere. Rank them based on the order in which a probe would encounter them when traveling from Earth to the Sun's surface, from first encountered to last.

Corona, chromosphere, photosphere

Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.

Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits

Listed following are the different layers of the Sun. Rank these layers based on their distance from the Sun's center, from greatest to least.

From greatest to least- Corona, Chromosphere, photosphere, convection zone, radiation zone, core

Rank the layers of the Sun based on their density, from highest to lowest.

From highest to lowest- Core, radiation zone, convection zone, photosphere, chromosphere, corona

Which of the following best explains why the Sun's luminosity gradually rises over billions of years?

Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.

Why does the Sun emit neutrinos?

Fusion in the Sun's core creates neutrinos.

If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?

Fusion reactions in the Sun have ceased within the past few minutes.

Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate? Check all that apply.

If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts.

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?

It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

When is/was gravitational contraction an important energy generation mechanism for the Sun?

It was important when the Sun was forming from a shrinking interstellar cloud of gas.

Which of the following best describes why the Sun emits most of its energy in the form of visible light?

Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.

A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale" !) Why do you turn down this excellent offer?

Neutrinos rarely, if ever, interact with your computer.

Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?

The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?

The Sun's core would start to heat up and the rate of fusion would increase even more.

How does the Sun's mass compare to Earth's mass?

The Sun's mass is about 300,000 times the mass of the Earth.

What do we mean when we say that the Sun is in energy balance?

The amount of energy released by fusion in the Sun's core equals the amount of energy radiated from the Sun's surface into space.

How can we best observe the Sun's chromosphere and corona?

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

If the Sun's core suddenly shrank a little bit, what would happen in the Sun?

The core would heat up, fusion rates would increase, the core would re-expand.

What do we mean when we say that the Sun is in gravitational equilibrium?

There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.

Why do sunspots appear dark in pictures of the Sun?

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

The Sun's surface seethes and churns with a bubbling pattern. Why?

We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.

Which of the following choices is not a way by which we can study the inside of the Sun?

We can send a space probe into the Sun's photosphere.

Listed following are events or phenomena that occur during either the part of the sunspot cycle known as solar minimum or the part known as solar maximum. Match these items to the correct part of the sunspot cycle.

all are solar maximum except : occurs about 5 to 6 years after a solar maximum (on average)

Most of the Sun's ultraviolet light is emitted from the narrow layer called the ____________ where temperature increases with altitude.

chromosphere

Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles.

chromosphere, photosphere, corona

Energy moves through the sun's ______________ by means of the rising of hot gas and falling of cooler gas.

convection zone

Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is _________.

converted to an amount of energy equal to 4 million tons times the speed of light squared

In which of the following layer(s) of the Sun does nuclear fusion occur?

core

Rank the layers of the Sun's atmosphere based on their temperature, from highest to lowest.

corona, chromosphere, photosphere

Rank the layers of the atmosphere based on the energy of the photons that are typically emitted there, from highest to lowest.

corona, chromosphere, photosphere

The intricate patterns visible in an X-ray image of the Sun generally show _________.

extremely hot plasma flowing along magnetic field lines

Nearly all the visible light we see from the Sun is emitted from the ___________.

photosphere

Rank the layers of the Sun's atmosphere based on their density, from highest to lowest.

photosphere, chromosphere, corona

The ______________ is the layer of the Sun between its core and convection zone

radiation zone