Exploring the Universe

1. Exploring the Universe

2. I.) Properties of Stars • Color and Temperature • A star’s color indicates that temperature of its surface • Hottest stars (surface temps above 30,000K) appear blue(*Hotter objects glow w/light that is more intense & has shorter wavelengths) • Milder stars (surface temps between 5,000-6,000K) appear yellow • Relatively cool stars (surface temps ~3,000K) appear red

4. Hertzsprung-Russell Diagram: a graph of the surface temperature (or color) and absolute brightness of a sample of stars • H-R diagrams are used to estimate the sizes of stars and their distances, and to infer how stars change over time • Horizontal axis=surfacetemperature • Vertical axis=absolutebrightness

5. H-R Diagram

7. Brightness of a Star • The actual “brightness” of a star depends upon 3 things: actual size of the star, temperature, and distance from Earth

8. Main-Sequence Stars • Mainsequence: A line or sequence in an H-R diagram where most stars spend 90% of their life. • A diagonal band running from the bright, hot stars on the upperleft to the dim, cool stars on the lowerright • Example: The Sun lies in the main sequence

9. Giants and Dwarfs a. Very bright stars in upper right of H-R diagram are known as supergiants • Very large (100 to 1000 times the diameter of the sun) • Just below the supergiants are the giants • Below the main sequence are the whitedwarfs, which are the small, dense remains of a low- or medium-mass star

10. Energy From Stars • Energy moves through the layers of a star by combination of convection, conduction, and radiation • Convection: rising hot gas moves upward, away from the star’s center, and cooler, denser gas sinks toward the center

12. Radiation occurs when energy radiates out from the star in the form of light • Travels at the speed of light • Light from Sun takes 8 minutes to reach Earth • Light and heat both travel this way from a star

13. II.) Life Cycle of Stars • How Stars Form • Nebula: a large cloud of dust & gas in interstellar space • Composed of mainly hydrogen gas • Gravity pulls the small pieces of dust to clump together & form a protostar

16. Nuclear Fusion Rewind • Fusion:the process in which smaller nuclei fuse together at extremely high temperatures and release energy(occurs in stars like the sun) • Light nuclei combine to form heavy nuclei ( hydrogen actively fuses into helium gas) • In nuclear fusion, tremendous amounts of energy can be produced from very small amounts of mass

17. Fusion Reaction . 2H + 3 H  4He + 1n 1 1 2 0

18. Nuclear fusion begins to take control over the gravity and the star begins to stabilize • Fusion reactions in the core produce an outward force that balances the inward force of gravity • Cool fusion clip

19. What force is responsible for causing interstellar material to condense and form our sun? • GRAVITY

21. Adult Stars • Most stars spend 90% of their life in mainsequence • Once achieving nuclear fusion, stars radiate energy into space

22. The Death of a Star • When the hydrogen fuel has run out & fusion can no longer continue, the star collapses because the forces are no longer balanced • Core collapses because of its own gravity & then rebounds with a shock wave that violently blows the star’s outer layers away from the core

23. The path a star takes in its life cycle depends on its size/mass

24. LARGE MASS STARS : Results in huge, bright explosion called a supernova • Supernova produce heavier elements up to the element iron.

25. The path a star takes in its life cycle depends on its size/mass

26. Star Life Cycle • Cool Star Video

27. Some Definitions • Universe- the sum of all space, matter, & energy that exists, that has existed in the past, & that will exist in the future • -everything physical that exists in space & time • Galaxy- a collection of stars, dust, & gas bound together by gravity • Solar System- the sun & all of the planets & other bodies that travel around it.

28. Big Bang Theory • The Big Bang Theory states that all matter and energy in the universe was compressed into an extremely small volume that 10 to 20 billion years ago exploded and began expanding in all directions

29. Big Bang Theory • Believed it took millions of years for the universe to “cool” because of the chaotic explosion • After 1 million years it is believed the first hydrogen atom formed and fusion began • Therefore, stars (like our sun) could form

30. III.) Evidence for Big Bang: Expanding Universe • Hubble’s Law • Edwin Hubble used observations of spectral lines from other galaxies to conclude that the universe is expanding • Lines shifted toward the red end of the visible light spectrum • http://www.youtube.com/watch?v=FhfnqboacV0 • http://www.youtube.com/watch?v=3kw4id0NvJ0&NR=1&feature=fvwp

31. Redshift: the apparent shift toward longer wavelengths of light caused when a luminous object moves away from the observer • Red shift showed that nearly all galaxies are getting fartheraway from Earth • Blueshift: an apparent shift toward shorter wavelengths of light caused when a luminous object moves towards the observer

32. Electromagnetic Spectrum

33. Evidence for the Bang • Redshift, and cosmicbackgroundradiation • Cosmicbackgroundradiation: steady, but very dim signals in the form of microwaves that are emitted all over the sky • Scientists believe that these microwaves are the remains of the radiation produced during the Big Bang • Cosmic Background Radiation

34. 4. What is the future of our universe? • It all depends on the mass of our universe • One of 3 things can happen: • Universe can continue to expand • Universe can stop expanding and remain constant • Universe can collapse in on itself (“Big Crunch”)

35. What causes the moon to “shine?” • It’s actually a reflection of the sun’s light off the surface. As the moon revolves around Earth, the illuminated portion of the side of the moon facing Earth changes. • ck to the earth.

36. Moon • The moon is able to be illuminated due to the sun’s light reflecting off of its surface

37. http://www.sumanasinc.com/webcontent/animations/content/moonphase.htmlhttp://www.sumanasinc.com/webcontent/animations/content/moonphase.html

38. http://www.youtube.com/watch?v=XMyqPxFh5Zw

39. http://www.youtube.com/watch?v=nXseTWTZlks&feature=related • http://www.youtube.com/watch?v=wHxcWSiD_4E

42. The Milky Way- our galaxy is a spiral galaxy