Rainbows from SpaceRainbows from Space

Astronomer’s ToolsAstronomer’s Tools

TelescopesTelescopes– On Earth or in Earth orbitOn Earth or in Earth orbit

CamerasCameras Prisms (spectroscope)Prisms (spectroscope) Photometer (measures Photometer (measures

brightness)brightness) ComputerComputer

Orion NebulaOrion Nebula

Crab NebulaCrab Nebula

Light from spaceLight from space

Because most objects in space Because most objects in space are too far away to visit, are too far away to visit, examining their light is the only examining their light is the only tool we have to explore them.tool we have to explore them.

Distance, temperature, Distance, temperature, composition, and motion details composition, and motion details are a few of the things we can are a few of the things we can deduce from their light. deduce from their light.

SpectroscopySpectroscopyA close up look at the color of lightA close up look at the color of light

White light is a White light is a mixture of all the mixture of all the colors.colors.

Isaac Newton Isaac Newton showed that a showed that a prism can show prism can show the colors that the colors that make up white make up white light.light.

Isaac Newtonborn: December 25, 1642 Woolsthorpe, England

died: March 20, 1727

White light is White light is composed of many composed of many colorscolors Newton passed Newton passed

sunlight through a sunlight through a piece of glass called a piece of glass called a PRISM, and produced PRISM, and produced colors.colors.

He called these colors He called these colors the spectrum, from the spectrum, from the word the word spectrespectre,, meaning ghost.meaning ghost.

RainbowRainbow A Rainbow is A Rainbow is

formed when formed when sunlight passes sunlight passes through through raindrops, which raindrops, which act like little act like little prisms.prisms.

SpectroscopeSpectroscope

Today Today astronomers use astronomers use very accurate very accurate prisms, called prisms, called spectroscopes, to spectroscopes, to find out about find out about objects in space.objects in space.

Personal SpectroscopePersonal Spectroscope

Astronomers’ Astronomers’ spectroscopes are spectroscopes are quite elaborate, but quite elaborate, but simple spectroscopes simple spectroscopes are cheap and easy to are cheap and easy to use.use.

Many spectroscopes Many spectroscopes use a grating, a piece use a grating, a piece of plastic or glass with of plastic or glass with thousands of lines thousands of lines scratched in it.scratched in it.

Observing SpectraObserving Spectra

Look at a white light bulb with the Look at a white light bulb with the diffraction grating and see the diffraction grating and see the

colors – like a colors – like a rraaiinnbbooww..

Glowing Gases Glowing Gases

View the gas tubes. View the gas tubes. Every glowing gas has Every glowing gas has

a unique pattern of a unique pattern of colors, like a colors, like a fingerprint is unique fingerprint is unique to a person.to a person.

Record the colors you Record the colors you see for each gassee for each gas

Gas Tube SpectraGas Tube Spectra

HydrogenHydrogen HeliumHelium NeonNeon OxygenOxygen MercuryMercury

Mystery GasMystery Gas

View the mystery gas and record View the mystery gas and record its pattern of colors.its pattern of colors.

Now refer to your drawings of the Now refer to your drawings of the other gasses and see if you can other gasses and see if you can recognize any of the line patterns.recognize any of the line patterns.

Can YOU tell what the gas in the Can YOU tell what the gas in the mystery tube is?mystery tube is?

PleiadesPleiades

Horsehead NebulaHorsehead Nebula

Bright and Dark Bright and Dark SpectraSpectra Clouds of glowing Clouds of glowing

gas show bright linesgas show bright lines

High pressure High pressure glowing gas shows glowing gas shows continuous colorscontinuous colors

Light from high Light from high pressure gas passing pressure gas passing through cooler gas through cooler gas gives dark linesgives dark lines

The Sun’s SpectrumThe Sun’s Spectrum

By passing sunlight By passing sunlight through a spectroscope through a spectroscope we can determine all of we can determine all of the chemical elements the chemical elements that make up the Sun.that make up the Sun.

What’s the Sun made What’s the Sun made of?of? By matching the dark lines in By matching the dark lines in

the Sun’s spectrum with lines the Sun’s spectrum with lines observed of elements in a observed of elements in a laboratory you can determine laboratory you can determine what elements are present.what elements are present.

Solar SpectrumSolar Spectrum

Doppler EffectDoppler Effect

Christian Doppler Christian Doppler first showed that first showed that when a source of when a source of light or sound is light or sound is coming towards you coming towards you or going away, the or going away, the color or pitch of the color or pitch of the light or sound is light or sound is raised or lowered.raised or lowered.

Christian Dopplerborn: 29 November 1803 Salzburg, Austria

died: March 17, 1853

SoundSound

When a source of When a source of sound is coming sound is coming toward the toward the observer, the pitch observer, the pitch of the sound is of the sound is raised.raised.

When a source of When a source of sound is going away sound is going away from the observer from the observer the pitch is lowered.the pitch is lowered.

Sound is a vibrationSound is a vibration

Sound vibrations travel through Sound vibrations travel through air like waves in the oceanair like waves in the ocean

Doppler Effect DemoDoppler Effect Demo

Sounder first comes toward you, Sounder first comes toward you, then moves away.then moves away.

The pitch will be higher when The pitch will be higher when coming toward you, and lower coming toward you, and lower going away.going away.

Sounder coming

toward you – higher pitch

Sounder movingaway from you –

lower pitch

Why?Why?

Sound vibrations Sound vibrations travel through air travel through air outward from the outward from the source.source.

When the sound When the sound source is moving source is moving the waves bunch the waves bunch up, or stretch out.up, or stretch out.

Low pitched Sound High pitched Sound

Observer herehears higher pitch

Observer herehears lower pitch

Doppler Effect on LightDoppler Effect on Light

If the line pattern If the line pattern is shifted to the is shifted to the blue end the blue end the source is coming source is coming towards us.towards us.

If shifted to the If shifted to the red end, it is red end, it is moving away.moving away.

Using the Doppler Effect Using the Doppler Effect to Detect an Unseen to Detect an Unseen PlanetPlanet If a star has a planet orbiting it, the If a star has a planet orbiting it, the

planet will tug on the star due to its planet will tug on the star due to its gravity.gravity.

As the planet orbits the star it will tug As the planet orbits the star it will tug first on one side of the star, then on the first on one side of the star, then on the other.other.

gravity

Lots of Planets FoundLots of Planets Found

The number of Extra-Solar planets The number of Extra-Solar planets discovered is now over 150 and discovered is now over 150 and growing every month.growing every month.

Artist’s Conception of 6-8 Artist’s Conception of 6-8 Earth Mass Planet Earth Mass Planet Orbiting Star Gliese 876Orbiting Star Gliese 876