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OBSERVING THE UNIVERSE CHAPTER 4 STARS • STARS PRODUCE AND RADIATE ENERGY (“RADIANT ENERGY”) • THE ENERGY THAT THEY EMIT TRAVELS IN WAVES CALLED ELECTROMAGNETIC WAVES ELECTROMAGNETIC WAVES VS. MECHANICAL WAVES THE MAJOR DIFFERENCE BETWEEN MECHANICAL AND ELECTROMAGNETIC WAVES IS THAT MECHANICAL WAVES CAN ONLY MOVE THROUGH MATTER (WATER, LIQUID, GAS) AND ELECTROMAGNETIC WAVES CAN MOVE THROUGH MATTER OR THROUGH A VACUUM (SUCH AS SPACE) ELECTROMAGNETIC SPECTRUM THE ENTIRE RANGE OF RADIANT ENERGY CARRIED BY ELECTROMAGNETIC WAVES IS THE ELECTROMAGNETIC SPECTRUM A wave is classified by its wavelength LONG VS. SHORT WAVES • LONG WAVE LENGTHS = LOW FREQUENCIES AND LOW ENERGY • SHORT WAVE LENGTHS = HIGH FREQUENCIES AND HIGH ENERGY RADIANT ENERGY AND STARS • MOST STARS EMIT ENERGY IN ALL WAVELENGTHS • HOT STARS: SHORTER WAVES WITH HIGHER ENERGY • COOL STARS: LONGER WAVES WITH LOW ENERGY OUR SUN HAS A MEDIUM TEMPERATURE RANGE. THEREFORE, IT EMITS MOST OF ITS ENERGY IN THE FORM OF VISIBLE LIGHT. ELECTROMAGNETIC SPECTRUM FOLDABLE 1. LABEL THE OUTSIDE OF YOUR FLAPS WITH THE APPROPRIATE TYPE OF WAVE 2. PUT THE FOLLOWING CHARACTERISTICS UNDER THE APPROPRIATE WAVE: • SHORTEST WAVELENGTHS • LONGEST WAVELENGTHS • USED IN BROADCASTING • HIGHEST FREQUENCIES • LOWEST FREQUENCIES • WE CAN SEE IT! • TOO MUCH EXPOSURE CAN CAUSE CANCER • ENERGY IS GREAT ENOUGH TO DAMAGE OR KILL LIVING CELLS • INSECTS CAN SEE THIS • WHITE LIGHT CAN BE SEPARATED INTO RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO AND VIOLET • USED IN RADAR GUNS • USEFUL IN MEDICINE • WE FEEL THEM AS HEAT THE SPEED OF LIGHT ALL ELECTROMAGNETIC WAVES TRAVEL THROUGH SPACE AT A CONSTANT SPEED (THE SPEED OF LIGHT): 300,000 KM/S • REFLECTED LIGHT FROM THE MOON TAKES ABOUT 1 SECOND TO REACH EARTH • LIGHT FROM THE SUN TAKES ABOUT 8.3 MINUTES TO REACH EARTH • LIGHT FROM THE SUN TAKES ABOUT 40 MINUTES TO REACH JUPITER • SOME STARS ARE SO FAR AWAY THAT IT CAN TAKE MILLIONS OR BILLIONS OF YEARS FOR THEIR RADIANT ENERGY TO REACH EARTH (ASTRONOMERS CAN STUDY THOSE STARS TO KNOW WHAT THE UNIVERSE WAS LIKE A VERY LONG TIME AGO) TELESCOPES TELESCOPES ENABLE ASTRONOMERS TO OBSERVE MANY MORE STARS THAN THEY COULD WITH THEIR EYES BECAUSE THEY GATHER AND FOCUS LIGHT FROM OBJECTS IN SPACE EARTH BASED TELESCOPES 2 TYPES: 1.OPTICAL TELESCOPES: DETECTS AND COLLECTS VISIBLE LIGHT 2.RADIO TELESCOPES: DETECTS AND COLLECTS RADIO WAVES (AND SOME MICROWAVES) OPTICAL TELESCOPES 2 TYPES: 1. REFRACTING TELESCOPE: USES A CONVEX LENS TO CONCENTRATE LIGHT FROM A DISTANT OBJECT 2. REFLECTING TELESCOPE: USES A CURVED MIRROR TO CONCENTRATE LIGHT FROM A DISTANT OBJECT WHY ARE MOST OPTICAL TELESCOPES BUILT ON MOUNTAINS? RADIO TELESCOPES • A TELESCOPE THAT COLLECTS RADIO WAVES AND SOME MICROWAVES USING AN ANTENNA THAT LOOKS LIKE A TV SATELLITE DISH. • RADIO ANTENNA MUST BE LARGE. WHY? WHY ARE MOST RADIO TELESCOPES LOCATED IN DRY DESERTS? WHY DO WE ONLY HAVE TWO TYPES OF EARTH-BASED TELESCOPES? LIMITATIONS OF EARTH-BASED TELESCOPES • EARTH’S ATMOSPHERE NOT ONLY DISTORTS IMAGES, BUT ALSO ABSORBS SOME TYPES OF ELECTROMAGNETIC RADIATION. • ONLY VISIBLE LIGHT, RADIO WAVES, AND SOME MICROWAVES REACH EARTH’S SURFACE, THEREFORE, EARTH-BASED TELESCOPES ARE LIMITED TO COLLECTING THESE TYPES OF WAVES. • HOWEVER, TELESCOPES IN SPACE CAN COLLECT ENERGY AT ALL WAVELENGTHS! OPTICAL SPACE TELESCOPES • TELESCOPES THAT COLLECT VISIBLE LIGHT • CREATES BETTER IMAGES BECAUSE NO ATMOSPHERE • 1ST SPACE OPTICAL TELESCOPE: HUBBLE SPACE TELESCOPE (1990) - REFLECTING TELESCOPE THAT ORBITS EARTH SPACE TELESCOPES THAT USE OTHER WAVELENGTHS • THERE ARE OTHER SPACE TELESCOPES (OPERATED BY OTHER COUNTRIES) GAMMA RAYS, UV RAYS, X-RAY, AND INFRARED WAVELENGTHS. • IMAGES OF OBJECTS THAT COLLECT IN SPACE CAN BE CREATED BY A COMBINATION OF DATA FROM THESE DIFFERENT TYPES OF SPACE TELESCOPES. This image of the star Cassiopeia was made with a combination of optical, X-ray, and infrared data. SPITZER SPACE TELESCOPE • COLLECTS INFRARED WAVES • ORBITS THE SUN • USED TO VIEW YOUNG STARS AND PLANETS HIDDEN BY GAS AND DUST JAMES WEBB SPACE TELESCOPE • COLLECT INFRARED RADIATION • ORBITS THE SUN • SCHEDULED FOR LAUNCH IN 2018 • WILL BE USED TO DETECT GALAXIES THAT FORMED VERY EARLY IN THE HISTORY OF THE UNIVERSE