Lesson 3 3 The Sun Lesson 3 What

Lesson 3. 3: The Sun

Lesson 3: • What is the structure of the sun? • What features can you see on the sun?

What Is the Structure of the Sun? • No solid surface – ¾ of sun’s mass is hydrogen – ¼ of sun’s mass is helium • Has an interior and an atmosphere • Interior is made up of the: – Core – Radiation zone – Convection zone

The Sun’s Interior: The Core • Core: central region of the sun – An enormous amount of energy is produced here through nuclear fusion • Nuclear fusion: when hydrogen atoms join to form helium

The Sun’s Interior: The Radiation Zone • Energy produced in the sun’s core moves outward through the radiation zone • Radiation zone: a region of very tightly packed gas where energy moves mainly in the form of electromagnetic radiation – Is extremely dense; energy can take more than 100, 000 years to move through this zone

The Sun’s Interior: The Convection Zone • Convection zone: the outermost layer of the sun’s interior – Hot gases rise from the bottom of the convection zone and cool as they approach the top – Cooler gases sink, forming loops of gas that move energy toward the sun’s surface (convection currents)

The Sun’s Atmosphere • Stretches far into space • Layers become less dense the farther they are from the radiation zone • Mostly composed of hydrogen and helium • Includes the: – Photosphere – Chromosphere – Corona

The Sun’s Atmosphere: The Photosphere • Photosphere: the inner layer of the sun’s atmosphere – Considered to be the surface layer of the sun • Sun does not have a solid surface, although the gases of the photosphere are thick enough to be visible • When you look at an image of the sun, you see the photosphere

The Sun’s Atmosphere: The Chromosphere • Chromosphere: the middle layer of the sun’s atmosphere; means “color sphere” – The reddish glow visible around the photosphere at the start and end of a total eclipse

The Sun’s Atmosphere: The Corona • Corona: the outer layer that looks like a white halo around the sun; means “crown” – Extends into space for millions of kilometers – Gradually thins into streams of electrically charged particles called the solar wind

What Features Can You See on the Sun? • Using special telescopes to study the sun, scientists have spotted features like: – Sunspots – Prominences – Solar flares

Sunspots • Sunspots: dark areas on the sun’s surface; caused by areas of gas on the sun’s surface that are cooler than the gases around them – Often look small, but they can be larger than Earth – Number of sunspots varies in a regular cycle, with the most sunspots appearing about once every 11 years Sunspots

Prominences • Prominences: huge loops of gas; often link different parts of sunspot regions Prominences

Solar Flares • Solar flares: eruptions that occur when the loops in sunspot regions suddenly connect, releasing large amounts of magnetic energy – The energy heats gas on the sun to millions of degrees Celsius, causing the gas to erupt into solar flares

Solar Wind • Made up of electrical particles from the sun • Solar flares can increase the solar wind, meaning that more particles reach earth’s upper atmosphere • Earth’s atmosphere usually blocks these particles, except near the North and South poles – There, they create powerful electric currents that cause gas molecules in the atmosphere to glow, creating the auroras – They can also cause magnetic storms