ELECTROMAGENTIC RADIATION

ELECTROMAGNETIC RADIATION IS A FORM OF ENERGY. IT CAN BEHAVE AS PARTICLES OR WAVES. SOMETIMES, WE USE THE TERM “LIGHT” WHEN WE ARE TALKING ABOUT ELECTROMAGNETIC RADIATION. LIGHT IS GENERALLY USED TO DESCRIBE THE ELECTROMAGENTIC RADIATION THAT THE HUMAN EYE CAN SEE. THE TYPE OF RADIATION IS CHARACTERIZED BY ITS WAVELENGTH.

Wavelength = Frequency  c 

VISIBLE LIGHT GOES FROM 400 TO 700 NANOMETERS (nm) 1 nm = meter

THE HUMAN EYE IS VERY LIMITED IN WHAT IT CAN SEE. WE ONLY SEE THIS NARROW LITTLE BAND OF THE ELECTROMAGNETIC SPECTURM. 400 TO 700 nm

THE ENERGY OF ELECTROMAGENTIC RADIATION IS INVERSELY PROPORTIONAL TO ITS WAVELENGHT. THE ENERGY OF A PHOTON IS GIVEN BY: E = h  hc  where h = boltzman constant THIS MEANS THAT THE SHORTER THE WAVELENGTH, THE MORE ENERGETIC THE RADIATION. WHAT DOES THIS MEAN FOR ASTRONOMERS?

IMAGINE IF WE WERE TRYING TO LOOK AT A BASEBALL GAME, AND VISIBLE LIGHT WOULD ALLOW US TO SEE ONLY A VERY SMALL SECTION OF THE BALL PARK. IT WOULD BE VERY DIFFICULT TO TELL MUCH ABOUT THE GAME OF BASEBALL.

IF OTHER WAVELENGTHS WOULD ALLOW US TO SEE OTHER SECTIONS, WE COULD PUT THE INFORMATION TOGETHER TO TELL WHAT A BALLPARK LOOKED LIKE.

DIFFERENT EVENTS INVOLVE DIFFERENT ENERGIES. IF ASTRONOMERS CAN SEE AT DIFFERENT WAVELENGTHS IN ADDITION TO VISIBLE LIGHT, THEY CAN LEARN A GREAT DEAL MORE ABOUT THE NATURE OF THE UNIVERSE. EXAMPLES: SUPER NOVA INVOLVE VERY HIGH ENERGIES – THESE CAN RELEASE GAMMA RAYS. DEATHS OF RED GIANTS AND THE PLANETARY NEBULA THAT RESULT CAN RESULT IN RELEASE OF X-RAYS.

LOW TEMPERATURE OBJECTS SUCH AS BROWN DWARF STARS COULD BE SEEN WITH INFRARED RADIATION. THE BACKGROUND RADIATION FROM THE BIG BANG HAS RED-SHIFTED TO MICROWAVE RADIATION. RADIO WAVELENGTH RADIATION WOULD BE EMITTED AS THERMAL RADIATION FROM PLANETS AND FROM RAPID ROTATION OF NEUTRON STARS. Cool Cosmos

ALL SKY VIEW FROM GLAST (GAMMA RAY LARGE AREA SPACE TELESCOPE) - RECENTLY RENAMED THE FERMI GAMMA RAY SPACE TELESCOPE. Gamma rays are 5 million times more energetic than dental x-rays.

IF WE CAN’T SEE RADIATION OTHER THAN VISIBLE, HOW DO WE VISUALIZE WHAT TELESCOPES IN OTHER RANGES OF THE SPECTRUM ARE SEEING. WE USE “FALSE COLOR”. BLACK AND WHITE DETECTOR IMAGE FALSE COLOR IMAGE WITH RED, GREEN, AND BLUE REPRESENTING X-RAYS OF INCREASING ENERGY

ETA CARINAE COMPOSITE PHOTO. ETA CARINAE IS A STAR 100 TO 150 TIMES MORE MASSIVE THAN OUR SUN AND IS IN UNSTABLE EQUILIBRIUM. THE BLUE IS HUBBLE OPTICAL IMAGE AND THE ORANGE AND RED IS CHANDRA X-RAY DATA.

ANT NEBULA – MZ3 - COMPOSITE

X-RAY IMAGE OPTICAL IMAGE