ASTR 1110 Chapter 16
Which of the following best describes the first set of experiments, using chlorine traps, that were searching for electron neutrinos from the Sun? All the experiments had technical problems detecting neutrinos, which are very "antisocial" and thus very hard to catch. 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. 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. The experiments worked OK, but they found no neutrinos at all; not a single one. The chlorine experiments found only between 1/3 the number of electron neutrinos arriving from the Sun that our models predicted should be coming.
The chlorine experiments found only between 1/3 the number of electron neutrinos arriving from the Sun that our models predicted should be coming.
At the end of the p-p chain of nuclear fusion in the Sun, hydrogen nuclei have been converted into: a helium nucleus antimatter and nothing else carbon nuclei heavy hydrogen nuclei
a helium nucleus
According to the formula E=mc2, when two masses collide, we always get a lot of light. mass has to travel at the speed of light before it can produce any energy. a little bit of mass can be converted into a substantial amount of energy. energy can travel much faster than light (in fact its speed can be the speed of light squared).
a little bit of mass can be converted into a substantial amount of energy.
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? heavy nuclei are breaking apart into lighter nuclei. the Sun is spinning more slowly as time goes on; rotation energy is lost. a little bit of mass is lost in each fusion reaction and is turned into energy (the Sun is losing mass). material (like meteorites) is falling into the Sun and being vaporized to produce energy.
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, produced at the core of the Sun, will take the shortest time to emerge from the Sun's photosphere (surface)? an x-ray produced after radiation has interacted with matter in the core a positron a photon (wave) of gamma-rays a neutrino
a neutrino
Physicists Kelvin and Helmholtz in the last century proposed that the source of the Sun's energy could be: radioactive rocks nuclear fusion meteorites falling in a slow contraction the annihilation of antimatter
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 radiation equilibrium conduction
convection
When a positron and an electron collide, they will produce: hydrogen energy in the form of a gamma ray a neutron a deuteron
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? on Earth, only hydrogen that is in deep mines under the Earth is far enough underground for fusion. for hydrogen to fuse, the nuclei must first join together in long chains of atoms. the hydrogen in our oceans is the wrong type of hydrogen for fusion. for hydrogen nuclei to fuse, they must get very close to each other, which the nuclei in the oceans cannot do.
for hydrogen nuclei to fuse, they must get very close 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. 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. a typical pulsation takes about 5 minutes to complete a full cycle from maximum to minimum speed and back again. the pulsations these experiments measure take about an hour to emerge from the Sun's interior. Helioseismology allows astronomers to look under a sunspot and see how it works.
helioseismology measures waves that are set up by the motion of neutrinos from the core of the Sun.
What happens to the positron created during the p-p chain of nuclear reactions inside the Sun? it turns quickly into a neutrino, which can escape from the Sun. it ultimately forms an anti-helium nucleus. it quickly collides with an electron and turns into gamma-ray energy. it merges with a proton to become a deuterium (heavy hydrogen) nucleus.
it quickly collides with an electron and turns into gamma-ray energy
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? the antimatter in the Sun would make the meteorites explode before they could do this. a mass of meteorites equal to the mass of the Earth would have to fall in every century. the meteorites would eventually increase the mass of the Sun and change the orbits of the planets. since the Sun is made of gas, it does not have enough gravity to pull in meteorites. more than one of the above.
more than one of the above.
Which of the following particles has the lowest mass? neutrino proton electron neutron
neutrino
When a large nucleus breaks apart (or is broken apart) into two smaller pieces, this is called equilibrium breaking nuclear fission nuclear binding
nuclear fission
Today we realize that the source of energy for the Sun is a process called nuclear fusion mechanical to thermal energy conversion radioactivity Kelvin-Helmholtz contraction
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? the gravity of the planets around the Sun pulls its material outward, preventing collapse. neutrinos from the core exert an enormous pressure on the layers of the Sun as they travel outward; this pressure is more than enough to keep our star from collapsing. the pressure of the corona keeps the Sun's main body of gases confined to a small volume. nuclear fusion in the core keeps the temperature and the pressure inside the Sun at a high enough level so that gravity is balanced.
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 only in the layer where there is a lot of convection going on pretty much throughout the entire body of the Sun only near the photosphere (its visible surface layer)
only in the core
The material inside the Sun is in the form of a liquid ball of iron atoms solid plasma
plasma
The antimatter version of an electron is called a antitron positron proton neutrino
positron
Which of the following is NOT one of the fundamental particles that we find inside atoms? positrons protons electrons neutrons
positrons
When energy is first produced by fusion deep in the core of the star, that energy moves outward mostly by what process? radiation conduction none of the above convection
radiation
When two light elements collide to undergo nuclear fusion, some of the energy in their mass is released. only one survives; the other turns into a release of pure energy. the total mass involved increases. the positive charges in the nuclei attract, pulling the nuclei together faster and faster.
some of the energy in their mass is released.
Which of the following is a way for astronomers to learn more about the interior of the Sun? follow the orbit of Mercury, the closest planet to the Sun. study the corona during eclipses of the Sun. study the oscillations (pulsations) of the Sun's surface. take photographs of the Sun in the light absorbed by hydrogen atoms.
study the oscillations (pulsations) of the Sun's surface.
Which part of the Sun has the greatest density? the photosphere the convection region the core the corona
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 the theory! Your challenge comes in several related steps; which of the following is one of those steps? the C-N-O cycle can also produce helium. most of the Sun is made of antimatter (which explodes when it touches matter). the dating of radioactive rocks show that the Earth and thus the Sun are billions of years old. new protostars shine by gravitational collapse (the heat of clumping). we have found many more neutrinos than we expected in our underground experiments.
the dating of radioactive rocks show that the Earth and thus the Sun are billions of years old.
The strongest force we know is gravity, which holds the Earth and the Sun together electricity, which pulls unlike charges together the nuclear force which holds nuclei together none of the above
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 neutrons in the nucleus are negative, so they cancel the positive charge on the protons. the electrons outside the nucleus repel the protons and keep them inside the nucleus. the nuclear force, which is attractive over short distances like the nucleus, and stronger than electricity, holds the nucleus together.
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? fusion begins with particles even lighter than protons, which fuse more easily. most of the fusion inside the Sun involves carbon, not protons; carbon fuses much more quickly. there are an enormous number of protons inside the Sun, and some of them will fuse much sooner than the average. much more fusion takes place in the hot atmosphere of the Sun (where it can happen faster), not deep inside (where fusion is slow).
there are an enormous number of protons inside the Sun, and some of them will fuse much sooner than the average.
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: not being produced by the Sun because our star's nuclear fusion period has ended. being converted to antimatter in the core of the Sun and being destroyed as they hit matter. changing course before they reach the Earth as they hit other neutrinos in space. turning into a different type of neutrino in a neutrino oscillation.
turning into a different type of neutrino in a neutrino oscillation.
Which of the following statements about antimatter is true ? antimatter cannot be made in laboratories; we have tried but it just can't be done. antimatter only exists in Earth laboratories; it cannot be made in stars. when a particle of matter and the corresponding particle of antimatter meet, they become pure energy. antimatter is only a theory, we have no evidence that it exists.
when a particle of matter and the corresponding particle of antimatter meet, they become pure energy.
