Chapter 16

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 part of the Sun has the greatest density?

core

The antimatter version of an electron is called a

d. positron

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 very close to each other, which the nuclei in the oceans cannot do

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

nuclear fission

The material inside the Sun is in the form of a

plasma

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

the process was not well understood until the 1930's

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 proteins 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

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 particles has the lowest mass? a. a neutrino b. a proton c. a neutron d. an electron e. the nucleus of a hydrogen atom

a. a neutrino

Which of the following is NOT an experiment that is searching for neutrinos coming from the Sun? a. looking for radioactive argon atoms in a tank of cleaning fluid deep in an underground mine b. looking for changes in the Doppler shift of lines in the atmosphere of the Sun c. looking for radioactive gallium in a vast quantity of ordinary gallium d. looking with sensitive light meters in a giant vat of pure water deep underground in Japan e. all of the above are ways to search for neutrinos

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

Which of the following is a way for astronomers to learn more about the interior of the Sun? a. study the corona during eclipses of the Sun b. study the oscillations (pulsations) of the Sun's surface c. follow the orbit of Mercury, the closest planet to the Sun d. take photographs of the Sun in the light absorbed by hydrogen atoms e. study the accounts in ancient legends of the realm where the devil is supposed to live

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

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. a photon (wave) of gamma-rays b. a positron c. a neutrino d. a deuteron e. an x-ray produced after radiation has interacted with matter in the core

c. a neutrino

Which of the following statements about helioseismology experiments is FALSE: a. the pulsations these experiments measure take about an hour to emerge from the Sun's interior b. small changes in the velocity of the waves of pulsation coming from inside the Sun help astronomers figure out the structure of the Sun's interior c. helioseismology measures waves that are set up by the motion of neutrinos from the core of the Sun d. a typical pulsation takes about 5 minutes to complete a full cycle from maximum to minimum speed and back again e. Helioseismology allows astronomers to look under a sunspot and see how it works

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

Which of the following is NOT one of the fundamental particles that we find inside atoms? a. protons b. neutrons c. positrons d. electrons e. all four of the above are found in most atoms

c. positrons

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? a. we have found many more neutrinos than we expected in our underground experiments b. new protostars shine by gravitational collapse (the heat of clumping) c. the dating of radioactive rocks show that the Earth and thus the Sun are billions of years old d. most of the Sun is made of antimatter (which explodes when it touches matter) e. the C-N-O cycle can also produce helium

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

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

Which of the following statements about antimatter is true ? a. antimatter is only a theory, we have no evidence that it exists b. antimatter only exists in Earth laboratories; it cannot be made in stars c. antimatter cannot be made in laboratories; we have tried but it just can't be done d. when a particle of matter and the corresponding particle of antimatter meet, they become pure energy e. our telescopes clearly see many nearby antimatter stars in the Milky Way galaxy

d. 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? a. All the experiments had technical problems detecting neutrinos, which are very "antisocial" and thus very hard to catch b. The experiments worked OK, but they found no neutrinos at all; not a single one c. All the neutrinos found in these experiments were one of the other two types of neutrinos, not the electron neutrino that we expect coming from nuclear fusion in the Sun d. Now that they are working right, the chlorine experiments have found all the neutrinos that our models of the Sun have predicted should be coming e. The chlorine experiments found only between 1/3 the number of electron neutrinos arriving from the Sun that our models predicted should be coming

e. The chlorine experiments found only between 1/3 the number of electron neutrinos arriving from the Sun that our models predicted should be coming

Which of the following is NOT a product of the first step in the p-p chain of nuclear fusion? a. a form of hydrogen b. a positron c. a neutrino d. a deuteron e. a form of helium

e. a form of helium

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? a. the antimatter in the Sun would make the meteorites explode before they could do this b. a mass of meteorites equal to the mass of the Earth would have to fall in every century c. the meteorites would eventually increase the mass of the Sun and change the orbits of the planets d. since the Sun is made of gas, it does not have enough gravity to pull in meteorites e. more than one of the above

e. more than one of the above

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 gammy-ray energy

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

measuring the pulsations of the Sun from stations around the world

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

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

radiation

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

slow contraction

When two light elements collide to undergo nuclear fusion,

some of the energy in their mass is released

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

speed of light

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

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