Star Types and luminosity Do not write what is in yellow

1. Star Types and luminosityDo not write what is in yellow

2. Sun Facts and Figures (DO NOT WRITE) • Distance from Earth= 1 AU 1AU = 150,000,000 km (93 million miles) • Diameter = 1.4 x 106 km (870000miles) 1 million Earth’s could fit inside the sun! • Mass= 2 x 1030 kg (333333x Earth’s mass) 99.8% the mass of the Solar System • Density = 1400 kg/m3 90% of the mass is found in interior half • Color = yellow (due to surface temperature)

5. Definitions • Sun: Star at the center of our solar system. Also another name for any star. • Luminosity: measures how bright a star would be in relation to the sun if all stars were the same distance from the observer • Nuclear fusion: the combining of the nuclei of smaller elements to form the nuclei of larger elements with some mass being converted into energy- this is how the sun produces energy

6. Definitions • Sunspots: a darker region of the sun’s visible surface; increased number of sunspots are related to an increase in electromagnetic energy emitted from the sun • Galaxy: the large groupings of millions or billions of stars and other forms of mass held together by gravitation

7. Stefan-Boltzmann Law(Energy directly proportional to temperature) • As stars get hotter, their energy output increases quickly! (hot stars burn “fast”) • A star 10 x’s hotter than Sun has 10,000 times more energy output (will “die” quicker) • Our sun burns “slowly” 9 billion years total (4.5 billions years left to go!)

8. Info. • The sun is the nearest star to the Earth • The Hertzsprung-Russel diagram (H-R diagram) on page 15 of the ESRT arranges groups of stars by color and luminosity • Color is an indication of temperature • The H-R diagram is basically the life cycle of an average star, like our sun

9. Stars may follow different paths in this cycle • Life cycle may take billions of years • Some stars created soon after the Big Bang may still exist

11. Star Types- Main Sequence • A broad band where 90% of studied stars are located • Majority of a star’s life span • The luminosity increases from red to blue-white, which is related to an increase in star size and higher temperatures • Our sun is a main sequence star of yellow color • Red Dwarf: smallest and coolest very common

12. Giant Stars • Rare red, orange, and yellow stars commonly seen at night because of their large size and high luminosity • Low temperature stars • Represent the late stage in the evolution of medium to small-size main sequence stars

13. Super Giants • Super giant stars can be up to 1000 times larger than the diameter of the sun • Late stage of evolution • Usually explode in what is called a supernova • Blue super giants are the brightest and exhibit the highest temperature

15. White Dwarfs • Not always white • Small (around the size of Earth) • Hot on the surface, low in luminosity • Represent last stage of low to medium mass stars

16. Black Dwarf • When a white dwarf cools and no longer emits much electromagnetic energy • “Dead” star

17. Sunspot Cycle11 year cycle - not always consistent (2001 last maximum) • Temporary storms that are a little cooler and dimmer than the normal surface of the sun • Always appear within 30º of the solar equator • Possible link to Earth’s climate • Rotation of the spots show that the sun rotates on its axis every 27 days • Often occur in pairs

18. Photosphere with Sun Spots

19. Underneath the Spot Hot gas is prevented from entering region by twisted magnetic field lines, thus region becomes cooler http://umbra.nascom.nasa.gov

20. Little Ice Age

21. The Solar Atmosphere • The Chromosphere • The middle layer (has red-ish color) • Temperatures average 28,000 °C (cooler than corona but hotter than photosphere) • Only visible during a total eclipse

22. Chromosphere

23. The Solar Atmosphere • Photosphere (sphere of light) • Outer layer of interior/Lower layer of atmosphere (the surface) • Visible part of sun (what we see!) • Looks boring! (But is boiling!) • Closer look- granules • Bubbles from convection zone • Temperature about 6000° C

24. The edge of the Sun

25. Other activity about the Sun • Prominences • Loops of ionized gas (plasma) bent by magnetic fields • May last up to three months • Flares - much violent than prominences • Eruptions on the lasting 5 to 10 min • Includes coronal mass ejections (500 to 1000 km/s) • Can disrupt communications and electricity • Cause more aurorae and can disable satellites • All these phenomenon happen in active regions on the Sun, which vary in position. • We don’t understand the details for the formations of these structures

26. Prominences

27. Photosphere with Prominence Photosphere with Prominence

28. Solar Flares

29. Solar Wind A continuous stream of high-energy particles from the corona. Solar flares will sometimes increase the speed of the solar wind and cause interference with radio communications here on Earth.

30. The Energy coming from the Sun is called Solar Wind.com comes out from the Sun is called the solar wind.

31. Movies • Birth of the Sun • Life Cycle of Stars • NASA

32. A star differs from a planet in that a star • Has a fixed orbit • Is self-luminous • Revolves about the sun • Shines by reflected light

33. Using page 15 of the ESRT… • A main sequence star is 1000 times more luminous than the sun. The temperature is likely to be most nearly • 3000 degrees Celsius • 5000 degrees Celsius • 12000 degrees Celsius • 25000 degrees Celsius

34. A giant star has a luminosity of 300. Its color is most likely to be • yellow-red • Black • White • Blue-white

35. A white dwarf star has a temperature of 13000 degrees Celsius. What is the probably luminosity of the star? • 100 • 10 • 0.1 • 0.01