The Electromagnetic Spectrum in our

Universe

Background info.

★Everything astronomers know about the universe comes from studying light from distant stars and nebula.

★The universe is full of energy, visible and invisible, all of these different energies are called electromagnetic radiation.

Background info.

★All these different energies are classified according to wavelength and frequency.

★This info. is displayed as the Electromagnetic Spectrum.

Background info.

How do we know this? Instruments detect

their presence.

Electromagnetic Spectrum

draw this

Sir Isaac Newton discovered that when light passes through a prism, the different colors of

light are broken up.

each color has its own wavelength

So...what’s a rainbow?

•Speed of light: 300,000 km/sec or 186,000 mi/sec

•Visible light only makes up a small part of different types of energy known as electromagnetic radiation

•Gamma waves and radio waves are different due to their wavelengths

long waves

short waves

Which have the highest energy?

•study of the properties of light that depend on its wavelength

•when the light of a star is studied there are spectral lines

•the spectral lines act as a “fingerprint” that helps to identify the elements inside the star (a star’s chemical composition)

Spectroscopy

Emission spectrum of Hydrogen, H

Emission spectrum of Iron, Fe

•optical telescopes, radio and x-ray telescopes are used to collect data

xray telescope

radio telescope

•The Doppler Effect is used to determine if a galaxy is moving away from or towards earth

The Expanding Universe

Compare red and blue visible Compare red and blue visible light...light...Does red have a long or short Does red have a long or short wavelength?wavelength?Does blue have a long or short Does blue have a long or short wavelength?wavelength?

Electromagnetic SpectrumElectromagnetic Spectrum

•Doppler Effect works with sound waves and light waves

the siren in front of the cop car has a high pitch, but behind the car it has a low pitch sound

If we could see the sound waves, what color would they be?

draw this

If a galaxy is moving toward If a galaxy is moving toward earth, is it earth, is it blueblue or or redred??

If a galaxy is moving away from If a galaxy is moving away from earth, is it earth, is it blueblue or or redred??

•1929 Edwin Hubble discovered that the universe is expanding

•galaxies are moving away because they appear red ( the waves are stretched out)

•most of the galaxies we see have a Red Shift

•Hubble’s Law: galaxies are moving away from earth at a speed that is proportional to their distance

Hubble’s LawHubble’s Law

•Distant galaxies are moving away Distant galaxies are moving away from each other faster than those that from each other faster than those that

are closer togetherare closer together

as the dough rises, raisins that were farther apart travel a greater distance in the same time as those that were closer together, raisins are like galaxies in an expanding universe

Review #1Which EM waves are long and stretched out?

๏radio waves

Review #2 What color waves are long and

stretched out?

๏red waves

Review #3Which EM waves are short and

squished?

๏gamma rays

Review #4What color waves are short and

squished?

๏violet waves

Review #5 What information is found by looking at the spectral lines from a star’s gases?

๏which elements are in the star (chemical composition)

Review #6 What is happening to the size of the universe?

๏universe is expanding

Review #7 What kind of shift is responsible for this?

๏Red shift

Review #8 What does Hubble’s Law explain?

๏galaxies are moving away at a speed that is proportional to their distance