Chapter 9

Question 1

Star

Answer 1

A glowing ball of gas held together by its own gravity and powered by nuclear fusion in its core

Question 2

Photosphere

Answer 2

The visible surface of the Sun, lying just above the uppermost layer of the Sun’s interior and just below the chromosphere.

Question 3

Chromosphere

Answer 3

The Sun’s lower atmosphere, lying just above the visible atmosphere.

Question 4

Transition zone

Answer 4

The region of rapid temperature increases that separates the Sun’s chromosphere from the corona.

Question 5

Corona

Answer 5

The tenuous outer atmosphere of the Sun, which lies just above the chromosphere and, at great distances, turns into the solar wind.

Question 6

Solar windAn outward flow of fast-moving charged particles from the Sun.

Question 7

Convection zone

Answer 7

Region of the Sun’s interior, lying just below the surface, where the material of the Sun is in constant convection motion. This region extends into the solar interior in a depth of about 20,000 km

Question 8

Radiation zone

Answer 8

Region of the Sun’s interior where extremely high temperatures guarantee that the gas is completely ionized. Photons only occasionally interact with electrons and travel through this region with relative ease.

Question 9

Core

Answer 9

The central region of any planet or star.

Question 10

Standard solar model

Answer 10

A self-consistent picture of the Sun, developed by incorporating the important physical processes that are believed to be important in determining the Sun’s internal structure into a computer program. The results of the program are then compared with observations of the Sun, and modifications are made to the model. The standard solar model, which enjoys widespread acceptance, is the result of this process.

Question 11

Hydrostatic equilibrium

Answer 11

Condition in a star or other fluid body in which gravity’s inward pull is exactly balanced by internal forces due to pressure.

Question 12

Helioseismology

Answer 12

The study of conditions far below the Sun’s surface through the analysis of internal “sound” waves that repeatedly cross the solar interior.

Question 13

Granulation

Answer 13

Mottled appearance of the solar surface caused by rising (hot) and falling (cool) material in convective cells just below the photosphere.

Question 14

Supergranulation

Answer 14

Large-scale flow pattern on the surface of the Sun, consisting of cells measuring up to 30,000 km across, believed to be the imprint of large convection cells deep in the solar interior.

Question 15

Solar activity

Answer 15

Unpredictable, often violent events on or near the solar surface, associated with magnetic phenomena on the Sun.

Question 16

Sunspot

Answer 16

An Earth-sized dark blemish found in the surface of the Sun. The dark color of the sunspot indicates that it is a region of lower temperature than its surroundings.

Question 17

Polarity

Answer 17

A measure of the direction of the solar magnetic field in a sunspot. Conventionally, lines coming out of the surface are labeled “S”, while those going into the surface are labeled “N.”

Question 18

Sunspot cycle

Answer 18

The fairly regular pattern that the number and distribution of sunspots follows, in which the average number of spots reaches a maximum every 11 or so years, then falls off to almost zero.

Question 19

Solar cycle

Answer 19

The 22-year period that is needed for both the average number of spots and the Sun’s magnetic polarity to repeat themselves. The Sun’s polarity reverses on each new 11-year sunspot cycle.

Question 20

Active region

Answer 20

Region of the photosphere of the Sun surrounding a sunspot group, which can erupt violently and unpredictably. During sunspot maximum, the number of active regions is also a maximum.

Question 21

Prominence

Answer 21

Loop or sheet of glowing gas ejected from an active region on the solar surface that then moves through the inner parts of the corona under

Question 22

Flares

Answer 22

Explosive event occurring in or near an active region on the Sun

Question 23

Coronal holes

Answer 23

Vast regions of the Sun’s atmosphere where the density of matter is about 10 times lower than average. The gas there streams freely into space at high speeds, escaping the Sun completely.

Question 24

Nuclear fusion

Answer 24

Mechanism of energy generation in the core of the Sun, in which light nuclei are combined, or fused, into heavier ones, releasing energy in the process.

Nucleus 1 + Nucleus 2 -> nucleus 3 + energy

Question 25

Law of conversation of mass and energy

Answer 25

A fundamental law of modern physics that states that the sum of mass and energy must always remain constant in any physical process. In fusion reactions, the lost mass is converted into energy, primarily in the form of electromagnetic radiation.

Question 26

Strong nuclear force

Answer 26

Short-range force responsible for binding atomic nuclei together. The strongest of the four fundamental forces of nature.

Question 28

Deuteron

Answer 28

An isotope of hydrogen in which a neutron is bound to the proton in the nucleus. Often called " heavy hydrogen" because of the extra mass of the neutron.

Question 29

Positron

Answer 29

Atomic particle with properties identical to those of a negatively charged electron, except for its positive charge. This positron is the anti-particle of the electron. Positrons and electrons annihilate one another when they meet, producing pure energy in the form of gamma rays.

Question 30

Neutrino

Answer 30

Virtually massless and chargeless particle that are one of the products of fusion reactions in the Sun. Neutrinos move at close to the speed of light and interact with matter hardly at all.

Question 31

Weak nuclear force

Answer 31

Short-range force, Weaker than both electromagnetism and the strong force, but much stronger than gravity; responsible for certain nuclear reactions and radioactive decays.

Question 32

Proton-proton chain

Answer 32

The chain of fusion reactions, leading from hydrogen to helium, that powers main-sequence stars

Question 33

Neutrino problem

Answer 33

Virtually massless and chargeless particle that is one of the products of fusion reactions in the Sun. Neutrinos move at close to the speed of light and interact with matter hardly at all.

Question 34

Neutrino oscillations

Answer 34

Possible solution to the solar neutrino problem, in which the neutrino has a very tiny mass. In this case, the correct number of neutrinos can be produced in the solar core, but on their way to Earth some can "oscillate," or become transformed into other particles, and thus go undetected.