Chapter 16 Astro

Who pays the bill for the energy generated by nuclear fusion in the Sun? In other words, where does the energy pouring out of the Sun come from ultimately?

a little bit of mass is lost in each fusion reaction and is turned into energy (the Sun is losing mass)

Which of the following particles has the lowestmass?

a neutrino

What happens to the positron created during the p-p chain of nuclear reactions inside the Sun?

it quickly collides with an electron and turns into gamma-ray energy

Which of the following is NOT an experiment that is searching for neutrinos coming from the Su

looking for changes in the Doppler shift of lines in the atmosphere of the Sun

The Global Oscillations Network Group (GONG) Project is engaged in:

measuring the pulsations of the Sun from stations around the world

The material inside the Sun is in the form of a

plasma

The antimatter version of an electron is called a

positron

Which of the following is a way for astronomers to learn more about the interior of the Sun?

study the oscillations (pulsations) of the Sun's surface

Which part of the Sun has the greatest density?

the core

A friend (who does not have the new awareness which you have gained from this course) suggests that the mechanism that keeps the Sun shining as brightly as it does is the burning of coal. You brilliantly challenge his theory! Your challenge comes in several related steps; which of the following is one of those steps?

the dating of radioactive rocks show that the Earth and thus the Sun are billions of years old

In the formula E=mc2, the letter c stands for

the speed of light

Astronomers and physicists now believe they know what is happening to the missing neutrinos from the Sun (the neutrinos that our theories say should be emerging from the Sun, but our experiments in that underground mine could not find). These neutrinos are:

turning into a different type of neutrino in a neutrino oscillation

Which of the following statements about antimatter is true ?

when a particle of matter and the corresponding particle of antimatter meet, they become pure energy

Which of the following best describes the first set of experiments, using chlorine traps, that were searching for electron neutrinos from the Sun?

The chlorine experiments found only 1/3 the number of electron neutrinos arriving from the Sun that our models predicted

When did scientists begin to understand how the Sun produces all the energy that it does?

The process was not well understood until the 1930's

Which of the following is NOT a product of the firststep in the p-p chain of nuclear fusion?

a form of helium

At the end of the p-p chain of nuclear fusion in the Sun, hydrogen nuclei have been converted into:

a helium nucleus

According to the formula E=mc2,

a little bit of mass can be converted into a substantial amount of energy

Which of the following, produced at the core of the Sun, will take the shortest time to emerge from the Sun's photosphere (surface)?

a neutrino

Physicists Kelvin and Helmholtz in the last century proposed that the source of the Sun's energy could be:

a slow contraction

When great currents of hot material rise inside the Sun (and cooler material sinks downward), energy is being transferred by a process known as:

convection

In the Sun, when a positron and an electron collide, they will produce:

energy in the form of a gamma ray

If the "fuel" for nuclear fusion is nuclei of hydrogen, and the Earth's oceans are filled with hydrogen atoms in water all being jostled together, why isn't there a lot of fusion happening in our oceans?

for hydrogen nuclei to fuse, they must get veryclose to each other, which the nuclei in the oceans cannot do

Which of the following statements about helioseismology experiments is FALSE:

helioseismology measures waves that are set up by the motion of neutrinos from the core of the Sun

In an earlier era, some scientists suggested that the energy of the Sun comes from meteorites (or, more properly, meteoroids) falling into it and converting their falling motion into heat. Which of the following is part of the argument that shows this mechanism will not work?

more than one of these choices is correct

When a large nucleus breaks apart (or is broken apart) into two smaller pieces, this is called

nuclear fission

Today we realize that the source of energy for the Sun is a process called

nuclear fusion

The Sun is an enormous ball of gas. Left to itself, a ball of so many atoms should collapse under its own tremendous gravity. Why is our Sun not collapsing?

nuclear fusion in the core keeps the temperature and the pressure inside the Sun at a high enough level so that gravity is balanced

Where in the Sun does fusion of hydrogen occur?

only in the core

Which of the following is NOT one of the fundamental particles that we find inside atoms?

positrons

When energy is first produced by fusion deep in the core of the star, that energy moves outward mostly by what process?

radiation

When two light elements collide to undergo nuclear fusion,

some of the energy in their mass is released

The strongest force we know is

the nuclear force which holds nuclei together

A college friend of yours who has been postponing taking any science courses hears you talking about the generation of nuclear energy in the Sun and makes the following observation: "The whole idea of the atomic nucleus is pretty ridiculous. If an oxygen nucleus consists of eight protons and eight neutrons, the charge on that nucleus is positive. Since even I learned in high school that like charges repel, such a nucleus would find all its positive protons repelling and quickly fall apart." How would you answer his argument?

the nuclear force, which is attractive over short distances like the nucleus, and stronger than electricity, holds the nucleus together

If it takes an average of 14 billion years before any proton inside the Sun will undergo fusion, and the Sun is only about 5 billion years old, why do astronomers believe that fusion is going on there now?

there are an enormous number of protons inside the Sun, and some of them will fuse much sooner than the average

The process of fusion that keeps our Sun shining begins with which building blocks?

two protons