Prepare your scantron: Please take a moment to mute your cell phone! Use a pencil, not a pen! Fill in your name and fill the bubbles under your name. LAST NAME FIRST, First name second Put your 4-digit code instead of “IDENTIFICATION NUMBER”. --- (The last 4 digits of your OleMiss ID.) Question # 1: answer A Question # 2: answer B Question # 3: answer A Setup: Reading assignment Chapter 14, pp. 464 – 485 Please take a moment to mute your cell phone!

Hydrogen (mainly) gas ball The Sun Sunspots An Average main sequence STAR Surface features: • sharp edge (photosphere) • sunspots • limb darkening (we see less deep down at the edge) Hydrogen (mainly) gas ball Hot surface (6000 C)

What’s inside? In core: 4 H -> He (> 1 million K) Radiation zone: heat transfer by radiation Convection zone: by convection (“boiling”) Photosphere: visible edge (6000 C)

Questions coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 4 The photosphere is A the name of all the hot parts of the Sun B the name of the visible edge of the Sun C the name of the central region of the Sun D the name of a type of camera used to photograph the Sun. E the name of a type of lens used to photograph the Sun. Next question coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 5 How hot is the photosphere? A 600 K B 6,000 K C 60,000 K D 600,000 K E 6,000,000 K Next question coming …

sec 10 9 11 13 14 8 12 7 2 1 3 4 6 5 15 17 26 25 27 28 30 29 16 24 19 18 23 20 22 21 Question 6 Why is the edge of the Sun darker than the middle? A Because the photosphere is colder at the edge of the Sun than in the middle. B Because of the blurring effect of Earth’s atmosphere. C Because we see deeper down in the middle of the Sun, where it is hotter. D Because light is absorbed on the long way to the edge of the Sun. E Because the middle of the Sun is closer to us than the edge.

Convection zone sticking out: granulation The Sun is “boiling”: Granules live ~ 10 min rising (hot) and sinking (“cold”) matter H image

Photosphere: “grainy” Granules explained Photosphere: “grainy” Hot gas up Cold gas down

Sunspots Undisturbed photosphere Penumbra Umbra (6000 K) (5000 K) “Cold spots” in the photosphere where convection is stopped by the magnetic field Penumbra (5000 K) Umbra (4000 K)

Sunspot details

What are sunspots? (1) Convection brings up magnetic field (2) Strong field stops convection (3) Spot cools off (only 4000 C)

Questions coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 7 Where in the Sun is heat being produced? A Everywhere inside the Sun. B Only in the core (close to the center). C Only in a narrow region close to the surface. D In most of the Sun except in the convective outside region. E Nowhere, because no more energy is being produced in the Sun now. It has been heated up once and it is only giving off its heat as it is cooling off. Next question coming …

sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22 Question 8 What are sunspots? A Regions on the Sun, hotter than the photosphere. B Regions on the Sun, composed of dark substances. C Regions on the Sun, colder than the photosphere. D Holes in the surface of the Sun where we see deep into the Sun. E Clouds floating over the photosphere. Next question coming …

sec 8 9 10 12 11 7 6 1 2 3 4 13 30 35 40 45 14 25 16 15 18 17 19 20 5 Question 9 Which of the following explains what granules are? A The strong heat from below causes cracks on the surface of the Sun. B Rising hot bubbles reach the surface and glow until they cool down and sink. C The magnetic field of the Sun makes gas glow when charged particles cross it. D Clouds float over the photosphere. E Asteroids keep falling into the Sun and burn up in the intense heat. Next question coming …

sec 8 9 10 12 11 7 6 1 2 3 4 13 30 35 40 45 14 25 16 15 18 17 19 20 5 Question 10 What causes the sunspots? A The magnetic fields of the Sun deflects sunlight from the spots, so they appear dark. B The magnetic field of the Sun channels dark substances into sunspots. C The magnetic field of the Sun stops hot bubbles of gas from rising, causing the region to cool off. D The gravity of the Sun heats up the gas, which burns quickly and the remaining ashes are dark. E The shadow of the Moon is cast on the Sun, covering dark regions.