ASTR 121 The Sun

Estimate the amount of mass that is converted to energy when a proton combines with a deuterium nucleus to form tritium, 3He. Put your answer in terms of the atomic number (u)

0.005 u

Assume that the mass of the Sun is 75% hydrogen and that all of this mass could be converted to energy according to Einstein's equation E = mc2. How much total energy could the Sun generate? If m is in kg and c is in m/s, then E will be expressed in joules. (The mass of the Sun is given in Appendix E.)

1. 35 X 10^47 Joules

Every second, the Sun converts 4 million tons of matter to energy. How long will it take the Sun to reduce its mass by 1% (assume the mass of the Sun is 2 × 1030 kg)?

180 billion years

Use your answer from the previous problem to determine how much energy is released when a proton combines with a deuterium nucleus to produce tritium, 3He? u= 1.66 x 10-27 kg

7.47 X 10^-13 Joules

The most common element in the Sun is

Hydrogen

You are out on the beach, enjoying the warm sunshine with friends. As you glance up at the Sun (only briefly we hope), the part of the Sun that you can see directly is called its:

Photosphere

What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker?

Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath

Which statement about the Sun's rotation is TRUE? 1. The Sun rotates only at the equator, where the sunspots are found; the rest of the Sun does not rotate 2. Only the atmosphere of the Sun rotates, not the main body of the Sun 3. The Sun does not rotate; only planets rotate 4. The Sun rotates once a day 5. The Sun rotates at different rates at different latitudes on the Sun

The Sun rotates at different rates at different latitudes on the Sun

Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE: 1. When sunspots are at a minimum, we get the largest number of flares and prominences 2. The Sun's activity cycle shows absolutely no connection to its magnetic field 3. The number of sunspots gets larger and smaller over the course of 11 years 4. The Sun's activity cycle is directly connected to the number of earthquakes at the continental plate boundaries on Earth 5. Every 11 years sunspots completely cover the Sun, making its surface much darker

The number of sunspots gets larger and smaller over the course of 11 years

Which of the following statements about the Sun's photosphere is NOT TRUE? 1. The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward) 2. The photosphere is not a solid layer; if a spaceship (that could withstand the heat) fell through it, it wouldn't feel anything when reaching the photosphere 3. Through a telescope, the photosphere looks mottled or granulated 4. The photosphere is the layer where the Sun becomes opaque (you can't see through it) 5. The photosphere is much less dense than our Earth's atmosphere

The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward)

Which of the following is NOT a product of the first step in the p-p chain of nuclear fusion? 1. a form of helium 2. a form of hydrogen 3. a neutrino 4. a positron 5. a deuteron (nucleus of deuterium atom consists of a proton and a neutron)

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

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

a neutrino

Which of the following statements about the violent events on the Sun called flares is FALSE? 1. flares originate in the upper part of the corona, in the regions called coronal holes 2. flares happen more often during solar maximum, and sometimes during those periods, there can be several in one day 3. a flare can release energy equivalent to a million hydrogen bombs 4. astronomers think that flares are connected with sudden changes in the magnetic field of the Sun

astronomers think that flares are connected with sudden changes in the magnetic field of the Sun

Solar wind particles can be captured by the Earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for:

aurorae

The hotter region directly above the Sun's visible surface is called the

chromosphere

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

The hottest zone in the Sun is the

core

Which part of the Sun's atmosphere has the lowest density (number of atoms per unit volume)?

corona

Which part of the Sun's atmosphere is the hottest?

corona

Recently, some engineers and scientists have proposed building spaceships with enormous "sails" that catch the solar wind and use it to move the ship. What kinds of particles would be hitting this sail (i.e., what is the solar wind mostly made of):

electrons and protons

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

Which of the following is not part of some active regions on the Sun? 1. plages 2. prominences 3. flares 4. sunspots 5. granulation

granulation

The granulation pattern that astronomers have observed on the surface of the Sun tells us that:

hot material must be rising from the Sun's hotter interior

As astronomers have learned more about the structure of the Sun, they have found that it

is made entirely of hot gas

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

Astronomers now realize that active regions on the Sun are connected with

loops of magnetic field emerging from the surface of the Sun

Which of the following particles has the lowest mass?

neutrino

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 we use the light of atoms such as hydrogen and calcium to examine the Sun's outer layers, we can see bright "clouds" in the chromosphere right around the location of sunspots. These bright clouds are given the name:

plages

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 NOT one of the fundamental particles that we find inside atoms? 1. positrons 2. neutrons 3. electrons 4. protons 5. all four of the above are found in most atoms

positron

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 Sun's chromosphere contains many jet-like projections that stick up into the transition region. These spikes of gas are called:

spicules

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

What mechanisms do astronomers believe is responsible for making the Sun's outer atmosphere so much hotter than its photosphere?

the Sun's magnetic field interacting with the charged particles that make up the atmosphere

Which part of the Sun has the greatest density?

the core

As you go upwards from the Sun's photosphere,

the density (number of atoms in a unit volume) decreases

How do astronomers know how strong the magnetic field of the Sun is?

the measure the Zeeman effect (the splitting of spectral lines)

The Sun's photosphere is

the part of the Sun from which the light comes that we see when we look at the Sun with our eyes

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

the speed of light

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 strong 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

Sunspots are darker than the regions of the Sun around them because

they are cooler than the material around them (although still very hot compared to Earth temperatures)

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

two protons