Stars, Galaxies, and the Universe

1. Stars, Galaxies, and the Universe Chapter 21

2. How does distance affect an image? • Telescope- device that makes an object in the sky appear closer. • Revolutionized astronomy (study of space)- allowed them to see objects in space for first time. • Galileo made telescope famous seeing sun spots, Saturn’s rings, and Jupiter’s moons

3. Electromagnetic Radiation • There are waves of energy and light moving around us in the form of TV and radio transmissions, gamma radiation from space, and heat in the atmosphere. • The waves of energy are called electromagnetic (EM) because they have both electric and magnetic characteristics.

5. Electromagnetic Radiation • They are classified by the frequency of their wavelength, going from high to low frequency. • When a wave has a lot of energy, it could be a gamma ray or x-ray, and has high frequency. • If it has low frequency, it has less energy and could be a TV or radio wave.

7. http://video.pbs.org/video/2219781967/

8. DETECTING ENERGY • All types of EM radiation are useful to the world of science. Radio waves for example, They are used to carry communications from one point to another. • Astronomers listen to the radio waves of other galaxies to learn more about their stars. • Stars give off large amounts of EM radiation across the entire spectrum and we can study that radiation to learn more about the universe.

9. Space Measurement • Parallax- the apparent shift in position of an object when viewed from 2 separate positions • Seen if you look at a star when Earth is at two different points during its orbit around the sun

10. Scientists can measure the parallax of relatively close stars to determine their distance from Earth. • Knowing the angle that the star’s position changes and the size of the Earth’s orbit, we can calculate the distance of the star from Earth.

11. Classifying Stars • Color • Temperature • Size • Composition • Brightness

12. Star Properties • Color & temperature • white / Hot stars • Blue • Yellow, orange, • red / Cool stars

13. Star Properties • Size • neutron- smallest • white dwarf • medium • large • giant/ super giant

14. Composition Use a spectrograph(breaks light into colors and produces an image) to detect elements Gases in a star’s atmosphere absorb some of the wavelength of the light it produces Each Chemical element absorbs light Star Properties

15. Brightness • How a star appears from Earth depends on the distance and the actual brightness of the star • Actual brightness depends on size and temperature (absolute) • Distance depends on how bright it appears (apparent)

16. Star Magnitude (Brightness) • Two types of magnitude • Absolute • Apparent

17. Apparent magnitude brightness • Measure of the amount of light received on Earth from a star. • Brightness seen from Earth • Both apparent and received have a r

18. Absolute Magnitude Brightness • The brightness the star would have at a standard distance from Earth. • The total measure of the amount of light given off by a star. • Total= absolute

19. Light-year • The distance between stars and galaxies in the universe is so vast it would be too much to describe it in miles or kilometers—like measuring the distance from New York to Tokyo in inches! Instead, scientists use light-years to measure distances in space.

20. is actually a distance: the distance that light travels in one year. Light travels 186,000 miles per second which is equal to 300,000 km/s 9.5 trillion km/year Light-year

21. Space Measurement • Scientists can measure the parallax of relatively close stars to determine their distance from Earth. • Knowing the angle that the star’s position changes and the size of the Earth’s orbit, we can calculate the distance of the star from Earth.

22. Space Measurement • Parallax- the apparent shift or change in position of an object when you look from 2 different positions • Seen if you look at a star when Earth is at two different points during its orbit around the sun

23. if you stretch out your hand in front of you and look at your thumb while taking turns covering one eye and then the other, your thumb will appear to move back and forth. • Stars do the same thing, but our eyes are much too close to see the difference. • If we take a picture while on one side of Earth's orbit, and then take another when we get to the opposite side of the orbit, then we have a large enough distance that we can see the stars parallax, and determine how far away they really are.

24. Parallax

25. Classifying Stars • EjnarHertzsprung and Henry Russell graphed stars by temperature and absolute magnitude in a H-R diagram • Main Sequence • Dwarfs • Giants • (Pg 722)

27. Main sequence stars • 90% fall on the diagonal band of the H-R diagram • Stars in upper left of diagram graphs the hot, blue, bright stars • Stars in lower right are cool, red, dim stars • Stars in the middle are average, yellow stars like our sun

28. Dwarfs and giants • The 10% that fall outside the diagonal of the main sequence stars are dwarfs and giants

29. Fusion • The fusion of hydrogen in the core of star releases huge amounts of energy- atoms combine to form heavier atoms (2) HYDROGEN ATOMS SMASH and FUSE into HELIUM with a RELEASE of ENERGY

30. All stars begin as a nebula (large cloud of gas and dust spread out in large volume) A Star is Born

31. Nebula • A nebula is a cloud of dust and gas, composed primarily of hydrogen (97%) and helium (3%). Within a nebula, there are varying regions when gravity causes this dust and gas to “clump” together. As these “clumps” gather more atoms (mass), their gravitational attraction to other atoms increases, pulling more atoms into the “clump.”

32. Protostar- a contracting cloud of dust with enough mass to start formation of a star- fusion has not begun Protostar

33. A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion begins.

34. The evolution of low mass stars

35. High Mass Stars Evolution quicker and more violent Black hole form when supernova collapses to a point where no volume Recycling Matter Neutrons stars are collapsed core of supernovas; only neutrons exist in neutron star. Spinning neutron stars are –pulsars Core collapses violently and outer portion of star explodes Core heats up quickly

37. Black Holes http://coolcosmos.ipac.caltech.edu//cosmic_kids/AskKids/blackholes.shtml

38. Galaxies and the Universe

39. Clusters of stars • Open • Globular

40. Open- loose, disorganized appearance containing no more than 1000 stars

41. Globular- large groupings of older stars. Round and densely packed with stars. Some may contain more than a million stars

42. Galaxies • enormous swarms of stars, dust, gas, and dark matter held together by gravity. • The sun is one of about 100 billion stars in our own galaxy, called the Milky Way. If you think that’s incredible, imagine this: The Milky Way is just one of billions in the observable universe!

43. Spiral • Spiral galaxiesare shaped like disks and look like pinwheels from above. Young stars are found in the arms, and older stars are found in the central bulge, or nucleus

44. Elliptical galaxies • Elliptical galaxiesare the oldest and largest galaxies. They are smooth and oval and contain many old stars. There are many more elliptical galaxies in the universe than spiral galaxies

45. Irregular galaxies • Irregular galaxiesdon’t have a distinct shape and are not symmetrical like spiral or elliptical galaxies. They may be young galaxies that have not yet formed a symmetrical shape, or their irregular shape may be caused by two galaxies colliding.

46. The Universe within 50000 Light YearsThe Milky Way Galaxy

47. Clusters of galaxies are often collected in super clusters. • Our Milky Way is part of the Local Group and is part of the Virgo Super cluster, which contains several thousand galaxies.

48. Milky Way Galaxy • Classified as a normal spiral galaxy • Contains more than 200 billion stars • About 100,000 light years wide • Sun orbits galaxy’s core every 240 million years

49. Other planets around other stars? • http://www.nasa.gov/multimedia/videogallery/index.html?media_id=58885371

50. Origin of the Universe