Unit 3 Lesson 3 The Sun Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 3 Lesson 3 The Sun Florida Benchmarks SC.8.E.5.3 Distinguish the hierarchical relationships between planets and other astronomical bodies relative to solar system, galaxy, and universe, including distance, size, and composition. SC.8.E.5.6 Create models of solar properties including: rotation, structure of the Sun, convection, sunspots, solar flares, and prominences. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Unit 3 Lesson 3 The Sun Florida Benchmarks MA.6.A.3.6 Construct and analyze tables, graphs, and equations to describe linear functions and other simple relations using both common language and algebraic notation. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Here Comes the Sun What do we know about the sun? Unit 3 Lesson 3 The Sun Here Comes the Sun What do we know about the sun? The sun is a hot ball of gas composed mostly of the elements hydrogen and helium. The sun formed about 4.6 billion years ago. Of the light emitted from the sun, 41 percent is visible light, 9 percent is ultraviolet light, and 50 percent is infrared radiation. Without the sun, there would be no life on Earth. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What is the structure of the sun? Unit 3 Lesson 3 The Sun What is the structure of the sun? The sun is a spherical body with a layered atmosphere and an interior composed of layers. Energy is produced in the core (or middle) of the sun and is transported to the surface through the radiative zone and the convective zone. The sun’s atmosphere has three layers: the photosphere, the chromosphere, and the corona. Copyright © Houghton Mifflin Harcourt Publishing Company 5

What is the structure of the sun? Unit 3 Lesson 3 The Sun What is the structure of the sun? The sun’s surface is the photosphere. Energy escapes the sun from this layer. The middle layer of the sun’s atmosphere is the chromosphere, and its temperature rises with distance from the photosphere. The sun’s outer atmosphere is the corona, which extends millions of kilometers into space. Copyright © Houghton Mifflin Harcourt Publishing Company 6

What is the structure of the sun? Unit 3 Lesson 3 The Sun What is the structure of the sun? Copyright © Houghton Mifflin Harcourt Publishing Company 7

Let’s Get Together How does the sun produce energy? Unit 3 Lesson 3 The Sun Let’s Get Together How does the sun produce energy? Matter can change into energy according to the equation E = mc², where E is energy, m is mass, and c is the speed of light. The sun generates energy through the process of nuclear fusion. Nuclear fusion is the process by which two or more low-mass atomic nuclei fuse to form another, heavier nucleus. Copyright © Houghton Mifflin Harcourt Publishing Company 8

How does the sun produce energy? Unit 3 Lesson 3 The Sun How does the sun produce energy? Nuclear fusion takes place in the core of stars. In stars with core temperatures similar to the sun’s, the fusion process starts with the fusion of two hydrogen nuclei. In older stars with hotter cores, helium fuses into carbon. Copyright © Houghton Mifflin Harcourt Publishing Company 9

How does the sun produce energy? Unit 3 Lesson 3 The Sun How does the sun produce energy? In the sun’s core, hydrogen nuclei sometimes fuse to form a helium nucleus in a three-step process. In the first step, two protons collide to form a nucleus of deuterium, which has one proton and one neutron. Deuterium is a form of hydrogen. Next, a deuterium nucleus collides with another proton to form a variety of helium called helium-3. Copyright © Houghton Mifflin Harcourt Publishing Company 10

How does the sun produce energy? Unit 3 Lesson 3 The Sun How does the sun produce energy? Next, a deuterium nucleus collides with another proton to form a variety of helium called helium-3. In the third step, two helium-3 nuclei collide and form a helium-4 nucleus that has two protons and two neutrons. Two protons are released. Copyright © Houghton Mifflin Harcourt Publishing Company 11

How does the sun produce energy? Unit 3 Lesson 3 The Sun How does the sun produce energy? The entire chain of fusion reactions requires six hydrogen nuclei and results in one helium nucleus and two hydrogen nuclei. Approximately 1038 collisions between hydrogen nuclei take place in the sun’s core every second. These reactions keep the sun shining. Copyright © Houghton Mifflin Harcourt Publishing Company 12

Mixing It Up How is energy transferred to the sun’s surface? Unit 3 Lesson 3 The Sun Mixing It Up How is energy transferred to the sun’s surface? Energy is transferred to the sun’s surface by two different processes. Energy is transferred from the sun’s core through the radiative zone by radiation. Energy is transferred from the top of the radiative zone through the convective zone to the photosphere by convection. Copyright © Houghton Mifflin Harcourt Publishing Company 13

How is energy transferred to the sun’s surface? Unit 3 Lesson 3 The Sun How is energy transferred to the sun’s surface? Energy travels through the radiative zone in the form of electromagnetic waves. The radiative zone is densely packed with particles such as hydrogen, helium, and free electrons. Electromagnetic waves are repeatedly absorbed and re-emitted by particles until they reach the top of the radiative zone. Copyright © Houghton Mifflin Harcourt Publishing Company 14

How is energy transferred to the sun’s surface? Unit 3 Lesson 3 The Sun How is energy transferred to the sun’s surface? In the convective zone, energy is transferred by the movement of matter. Hot gases rise to the surface of the sun, cool, and then sink back into the convective zone. This process, called convection, takes place in convection cells, which form granules on the sun’s surface. Copyright © Houghton Mifflin Harcourt Publishing Company 15

Unit 3 Lesson 3 The Sun How does the sun rotate? Because it is a giant ball of gas, the sun rotates faster at its equator than it does at higher latitudes. This kind of rotation is called differential rotation. Copyright © Houghton Mifflin Harcourt Publishing Company 16

Unit 3 Lesson 3 The Sun How does the sun rotate? Near the equator, the sun rotates once in about 25 days, but at the poles it rotates once in about 35 days. The sun’s interior does not rotate in the same way as the surface. The sun’s core and radiative zone rotate together, at the same speed. Copyright © Houghton Mifflin Harcourt Publishing Company 17

How does the sun rotate? At which point does the sun rotate fastest? Unit 3 Lesson 3 The Sun How does the sun rotate? At which point does the sun rotate fastest? Copyright © Houghton Mifflin Harcourt Publishing Company 18

The Ring of Fire What is solar activity? Unit 3 Lesson 3 The Sun The Ring of Fire What is solar activity? Solar activity refers to variations in the appearance or energy output of the sun. Solar activity on the sun’s surface includes sunspots, solar flares, and prominences. Copyright © Houghton Mifflin Harcourt Publishing Company 19

Unit 3 Lesson 3 The Sun What is solar activity? Dark areas that form on the surface of the sun are called sunspots. They are about 1,500 °C cooler than the areas that surround them. Sunspots range in width from a few hundred kilometers to 10 to 15 times the diameter of Earth. Sunspot activity occurs on average in 11-year cycles, in which the activity increases and then decreases. Copyright © Houghton Mifflin Harcourt Publishing Company 20

Unit 3 Lesson 3 The Sun What is solar activity? A solar flare is an explosive release of energy that can extend outward as far as the sun’s outer atmosphere. During a solar flare, the sun ejects large numbers of high-energy particles, along with radiation from across the entire electromagnetic spectrum. Temperatures within solar flares reach millions of degrees Celsius. Copyright © Houghton Mifflin Harcourt Publishing Company 21

Unit 3 Lesson 3 The Sun What is solar activity? Huge loops of relatively cool gas that extend from the photosphere thousands of kilometers into the outer atmosphere are called prominences. Several objects the size of Earth could fit inside a loop of a prominence. Prominences generally last from several hours to a day, but some can last for several months. Copyright © Houghton Mifflin Harcourt Publishing Company 22

What is the structure of the sun? Unit 3 Lesson 3 The Sun What is the structure of the sun? Copyright © Houghton Mifflin Harcourt Publishing Company 23