1. Electromagnetic Spectrum

2. Making Waves Waves begin with vibrations and transfer energy
There are two types of waves:
Compressional--such as sound waves, require a medium to transfer energy
Transverse--such as light waves, can travel through a vacuum (space)

3. Electromagnetic Wave
A transverse wave that transfers electric & magnetic waves.
It consists of vibrating electric & magnetic fields that move through space at the speed of light (300,000 km per second).
Produced by charged particles

4. Electromagnetic Waves

5. Electromagnetic waves cont.
Electromagnetic radiation: the energy transferred through space by EM waves
Travels through empty space
Doesn’t require a medium
This is why we can see the sun & stars

6. All electromagnetic waves travel at the same speed in a vacuum, but have DIFFERENT wavelengths & DIFFERENT frequencies.

7. Wavelength & Frequency
Frequency: number of wavelengths repeating during a unit of time
Wavelength: the distance between the crest of one wave & the crest of the next wave

8. Wavelength & Frequency
As wavelength decreases, the frequency INCREASES.
Waves with longest wavelengths = lowest frequency AND have less energy
Waves with shortest wavelengths=highest frequency AND more energy

9. Electromagnetic Spectrum
TgThe complete range of electromagnetic waves placed in order of increasing frequency
Made up of: radio waves, infrared rays, visible light, ultraviolet rays, X-rays & gamma rays

11. Radio Waves the longest wavelengths in the electromagnetic spectrum
used by radios, TV, cell phones

12. Microwaves shorter than radio waves but longer than infrared
used by microwave ovens, cell phones, tv, weather radar
transmits information over long distances

13. Radar Stands for “radio detection and ranging”
uses reflected radio waves to detect objects & measure their distance & speed
Used in police radar guns

14. Infrared between microwaves & visible light on the EMS
we experience this type of infrared radiation every day in the form of heat
Uses: remote controls, infrared imaging

15. Visible Light the only electromagnetic waves we can see
appear as the colors of the rainbow (ROY G BIV)
Have shorter wavelengths, higher frequency than infrared
Things that appear red = longest wavelength
Things that appear violet = shortest wavelength.
As the wavelengths decrease, other colors are visible
Visible light that appears white is a mixture of the other colors

17. Ultraviolet shorter wavelengths than visible light (carry more energy)
produced by the sun, blocked by the ozone
causes sunburns, skin cancer, damage eyes
Good use: vitamin D (for bones/teeth)

18. X-rays smaller wavelengths & higher energy than ultraviolet waves
the ozone blocks all x-rays from space
X-rays can go through most matter
Used by doctors to diagnose & treat health problems

19. Gamma Ray
the smallest wavelengths & the most energy of any other wave (highest frequency)
generated by radioactive atoms & in nuclear explosions
Most penetrating of all EM waves
used to kill cancerous cells (radiation)

20. Stars

21. Classifying Stars
Color and Temperature: color indicates surface temperature
Cooler stars appear RED.
Hot stars are BLUE & about 20,000 degrees C
Our sun is yellow & about 5,500 degrees C

22. Size of stars SStars can be small, medium or large.
Our Sun is a medium sized star.
Large stars are called super giants or giant stars. Ex. Betelgeuse

23. Classifying Stars
Chemical composition: most are about 73% H, 25% He, & 2% other
Spectrograph: a device that breaks light into colors and produces an image of the resulting spectrum.
Since different gases absorb different wavelengths, we can identify what gases are in a star.

24. Measurement
Light year: the distance that light travels in one year, about 9.5 trillion kilometers
Parallax: the apparent change in position of an object when you look at it from different places

25. How a star is born
Nebula: a large cloud of gas and dust spread out in an immense volume
Protostar: a contracting cloud of gas & dust with enough mass to form a star. Earliest stage of a star’s life.
Nebula: a large cloud of gas and dust spread out in an immense volume
Protostar: a contracting cloud of gas & dust with enough mass to form a star. Earliest stage of a star’s life.

26. Life Spans Low mass star: 200 billion years
Medium mass star: 10 billion years
Our sun is estimated to be 4.6 billion years
High mass star: 10 million years

27. Life Cycle of a medium sized star
Low/medium mass nebulaL/Med. Mass star
Red GiantPlanetary NebulaWhite DwarfBlack dwarf

28. Life cycle of a high mass star
High mass nebulaHigh mass starsupergiant
Supernovaneutron star OR black hole

30. Phases of Death
When stars begin to run out of fuel, the core shrinks and the outer portion expands
Eventually, the outer parts grow larger and drift out into space creating a planetary nebula.

31. Phases
White dwarf: the blue-white core of the star that is left behind
Supernova: results from an exploding supergiant and can form a nebula which has the potential for new stars

32. Phases
Neutron stars: the remains of a supergiant and can have a mass three times that of the sun but the size of a city
Pulsars: radio waves emitted by neutron stars that are spinning

33. Phases
Black hole: has gravity so strong that not even light can escape. These can be detected by other objects’reaction when near a black hole.

34. Galaxies and the Universe
Clusters of stars:
All the stars in a cluster formed from the same nebula at about the same time & the same distance from Earth.

35. Clusters 2 Types of clusters:
1. Open: disorganized, loose appearance contains no more than 1000 stars; a lot of bright super giants & lots of gas & dust

36. 2. Globular: large groupings of older stars; round & densely packed with stars; some may contain more than a million stars

37. Galaxies: enormous swarms of stars, gas, dust & dark matter held together by gravity
Our solar system is in the _________________ Galaxy.
The MWG is one of a billion galaxies in the universe (that have been observed)!!

38. Types of Galaxies
spiral: pinwheel shaped, young stars are found on the arms, older stars found in the nucleus Ex. Milky Way

39. 2. Elliptical: oldest & largest galaxies, smooth & oval shaped
3. Irregular: don’t have a distinct shape, may be young galaxies that haven’t formed or 2 gal. colliding

40. Milky Way Galaxy Contains more than 200 billion stars
About 100,000 light years wide
Sun orbits the galaxy’s core every 240 million years.

41. Origins of the Universe
3 common theories about the origin:
1. Steady state theory: the universe has always been the same & will NEVER change
Not a readily accepted theory based on scientific evidence
2. Oscillating Model: expansion of the Universe began & everything moved outward, but over time, expansion slowed & the matter moved back in (think of a slinky), then it repeated over and over

42. 3. BIG BANG THEORY: everything started with a BANG……
3. BIG BANG THEORY: everything started with a BANG……. Most widely accepted theory, matter clumped together to form H & He

44. Our Expanding Universe
The Doppler Shift explains how we are expanding:
If a star is moving towards Earth, the wavelengths are compressed & you see the spectrum BLUE.
If a star is moving away from Earth, the light wavelengths are stretched out & you see the spectrum in RED.

45. The Red Shift-Hubble Law
In 1929, Edwin Hubble published a paper about light from other galaxies.
All galaxies beyond the Local Group (our group of galaxies) show a red shift in their spectrum, this shows they are moving away from us.
The universe is EXPANDING!!!!

46. Dark Energy The universe is accelerating due to dark energy.
Dark energy: force causing the galaxies to be moving far apart at a faster rate

47. How long does it take for the light from stars to be visible here on Earth?
Other stars are so much farther away that it is convenient to express the distance to them in units of the distance traveled by light in one year. This unit is called a light year.
The next closest star to us is Proxima Centauri. This star is 4.3 light years away which means that light from it takes 4.3 years to reach us.
Our galaxy is about 100,000 light years across. This means that it can take tens of thousands of years for light from some stars in our galaxy to reach us.
For stars that we can see in nearby galaxies it can take millions of years. The farthest objects we can see are quasars. They are so distant that the light we see from them today left billions of years ago.

48. So when we look up at the stars we are looking back in time
So when we look up at the stars we are looking back in time. This is useful for astronomers because when we look at very distant objects we can see what the Universe was like a long time ago.

49. Future of the Universe 3 possibilities:
1. all stars will run out of fuel & burn out, the universe will be cold & dark
2. force of gravity will pull the galaxies back together (“Big Crunch”), all matter would be crushed into a black hole
3. universe will keep on EXPANDING

50. Age of our Universe About 13.7 billion years old
Scientists know this from measurements of how fast the galaxies are moving away from us AND cosmic background radiation (thermal energy leftover from the big bang)