Studying the Universe

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Astronomy

Astronomy is the scientific study of space and the bodies in it

How do we study space?

The Nature of Light

Traveling in WavesLight is a form of electromagnetic energy that travels as a wave.

Different wavelengths different colors

The Visible Light SpectrumVisible light

combination of all colors of light

Visible Light Spectrum: Separate into colors.

Made of ROY G BIV

A World of ColorWhy do we see this Why do we see this red sweatshirt as red?red sweatshirt as red?

All colors hit it, with MOST colors absorbed. But red is reflected back to our eyes!

A World of ColorWhy are the leaves of plants green?

Why is my shirt black?

If I were wearing a white shirt, why would it be white?

Reflection

Light bounces back from an object at the Light bounces back from an object at the same angle at which it encounters a same angle at which it encounters a surfacesurface

RefractionRefraction

The change of direction of a ray of light, The change of direction of a ray of light, sound, etc in passing from one medium sound, etc in passing from one medium into another in which its wave velocity is into another in which its wave velocity is different. different.

Light is EnergyFrederick William Herschel (1738-1822)

Wanted to know if different colors had different temperatures.

Found there WAS a difference.

and something more …

Invisible ColorsExperiment showed a lot of heat where there was no light visible.

“Infrared” beyond red spectrumOther end of the spectrum “Ultraviolet”.

Electromagnetic Spectrum

All E.M. travels at the All E.M. travels at the speed of light: 186,000 speed of light: 186,000 miles/second.miles/second.

Stars give off electromagnetic energy that we can use to study them.

Lines in the SpectrumOne day, a scientist named Fraunhofer got some new, high purity prisms he ordered.

When he used the prisms to look at the Sun, he saw dark lines.

Lines in the SpectrumThat was until he figured out that those lines were really there and that he had just made an important discovery.

It turns out that when things heat up enough, they give off light.

Elemental Light When an element is heated, it produces a When an element is heated, it produces a unique color. This is how “neon” lights work.unique color. This is how “neon” lights work.

This unique color is caused by an equally unique spectra. For scientists, this acts like an elemental fingerprint.

Lines in the SpectrumWhen a pure element like hydrogen (or compound like water), is heated up, it gives of specific wavelengths (or colors) of light

Also, when light passes through a cold gas, (H2), it absorbs those same wavelengths (or colors).

Spectrum Types The color something is The color something is

represents the colors it represents the colors it is giving offis giving off

Emission SpectrumEmission Spectrum Represents the wave Represents the wave

lengths that the light lengths that the light source is putting outsource is putting out

Absorption SpectrumAbsorption Spectrum Represents the wave Represents the wave

lengths that are absorbed lengths that are absorbed by the light source by the light source

The SpectroscopeThe SpectroscopeHow do we learn about stars?Scientists use the visible spectrum of stars to

learn about themSpectroscopes: A tool that separates the

starlight into its visible spectrumWhat do spectroscopes tell us about a star?The elements in the star, temperature, gas

condition, magnetic field, and pressure