The Layers of a Star

2. The Layers of a Star • The corona is the wide, outermost layer of a Sun’s atmosphere – (AL) • Thechromosphereis the orange-red layer of the Sun’s atmosphere, between the photosphere and the corona – (AL) • The convection zone region above the radiative zone of the Sun where hot gas moves up toward the surface and cooler gas moves deeper into the interior( IL) • __________is the wide, outermost layer of a Sun’s atmosphere – (AL) The photosphere is the apparent surface of a Sun’s atmosphere (AL) • The radiative zone is a shell of cooler hydrogen above a Sun’s core (IL) • Thecore is where fusion takes place and hydrogen is converted into helium. (IL)

3. Changing features of the Sun • The photosphere has sunspots, which are areas of strong magnetic activity that are dark because they are cooler than the rest of the photosphere. • A prominence, is a cloud of gas that loops into the corona. They occur where magnetic fields connecting sunspots soar into the outer atmosphere. • A(n) flare is a bright, violent eruption that can last for minutes or hours. • Huge bubbles of gas ejected from the corona are called coronal mass ejections. They occasionally cause radio blackouts or malfunctions in an orbiting satellite. • Electrically charged particles that flow out in all directions from the corona are called the solar wind.

4. The Sun’s Changing Features Solar wind Sunspots prominences Flares

5. Star Colors and Temperature • Blue Stars – the hottest stars • White - intermediate • Yellow - intermediate • Orange – intermediate star • Red – the coolest stars

6. Types of Stars Protostar - a new star formed when nuclear fusion takes place in the core of a nebula, causing gas to begin glowing Main Sequence – A star that is that is fusing hydrogen into helium. Red giant - When a star begins to cool after its main sequence period, it expands outward a puffs up into a giant star with a red glow. All stars go through the red giant phase before they die. Supergiant - Stars that are bigger than giants. As stars get older they begin to burn helium, the fuel burns hotter, so the star bulges out farther than normal. Supernova – An enormous explosion that destroys a star

7. Hertzsprung-Russell Diagram According to the Hertzsprung-Russell Diagram the Sun is a yellow main sequence star. Sun

8. Life and Death of Stars • Black holes are object whose gravity is so great that no light can escape • A nebula is a cloud of gas and dust, where stars form • A Neutron star is a dense core of neutrons that remains after a supernova • A supernova is an enormous explosion that destroys a star • A white dwarf is a hot, dense, slowly cooling sphere of carbon

9. Life Cycle of Low Mass Stars A. Nebula B. protostar C. Main sequence star D. Red giant E. Planetary Nebula F. Outer layers have blown away G. White dwarf forms

10. Life Cycle of Medium Mass and Super Massive Stars A. Planetary Nebula B. protostar C. Main sequence star D. a supergiant red star. E. Supernova F. Neutron star G. Black Hole

11. Galaxies are huge collections of stars The universe contains hundreds of billions of galaxies and each galaxy contains hundreds of billions of stars.

12. Spiral Galaxies are large, containing hundreds of billions to trillions of stars. Most of the stars are in a central bulge which has mostly old stars and few nebulae, making it the brightest part of the galaxy. The surrounding spiral arm disk contains younger stars and much gas and dust in nebulae that obscures light and makes it less bright.

13. Elliptical galaxies are much brighter than spirals because they contain only old stars and no nebulae to block their light. They are large galaxies and are shaped like an egg.

14. Irregular Galaxies tend to be smaller, dimmer and can be in any shape. They tend to have a much smaller number of stars.