Chapter 28.1Electromagnetic

Spectrum

Scientists learn about the Universe by collecting Wave- Energy from the Electromagnetic Spectrum

The Electromagnetic- Spectrum is a continuum depicting the full range of

Electromagnetic Radiation,

with the longest wavelength at one

end, and the shortest at the other.

Electromagnetic Radiation is energy in the form of a Wave, resulting from the motion of electric charges and the magnetic fields that they produce.

Electromagnetic Spectrum

Visible Light

IncreasingWavelength

IncreasingEnergy

Objects in space emit energy in several different Frequencies and Wavelengths.

Wavelength

The Wavelength of a Wave

The wavelength of each color of light is different

Red Light Blue Light

Frequency Frequency

The Spectroscope and the Visible Spectrum

When light passes through a prism and out again, they are refracted, or bent, forming a band called the Visible Spectrum.

Stars emit light that falls within the visible spectrum.

Scientists use an instrument called a Spectroscope to separate this starlight into its colors so that it can be studied.

Spectroscopes break light into three different types.

• Continuous Spectrum

• Emission Spectrum

• Absorption Spectrum

                                                        Each element gives a unique spectrum. The position of the lines relative to one another changes from element to element and, as it turns out, from molecule to molecule. In essence, the emission spectrum is a fingerprint of the element/molecule that generates it.

By studying these different spectra, and comparing the emission/absorption spectra of stars to those of gaseous elements in a lab, astronomers can determine the types of elements that make up the atmospheres of the stars that emitted the light.

Emission Spectrum of Hydrogen

Absorption Spectrum of Hydrogen

Solar Spectrum

The Doppler Effect

Scientists use Spectral Analysis to not only determine what gases are present in stars, but also how they are moving relative to the Earth.

This is possible because of a phenomenon called the Doppler Effect.

Let’s look at some examples of the Doppler Effect that you have all experienced.

Person APerson B

Fire Engine at Rest

Fire Engine moving to the right, and toward Person B

Waves stretched Waves compressed

The Doppler Effect also applies to Light.

Bright Line Spectrum

Dark Line Spectrum

Because of Doppler Shift, scientists have determined that

our Universe is expanding

Scientists have even been able to use Doppler Shift to detect

the “wobble” of Stars with orbiting massive planets.

Galaxy moving away-Light shifted toward Red.

Galaxy moving toward -Light shifted toward Blue.

Stars emit energy in wavelengths that include…

1. Visible Light

2. Infrared3. Ultraviolet

4. X-Rays 5. Gamma Rays.

X-Ray Black Holes

UV

H Alpha

Gamma X-Ray

The Sun “viewed” through different wavelengths

M82 IR M82 Optical

M82 RadioM82 X-Ray

Astronomer view Space through different types of

Telescopes

Optical Telescopes

1. Telescopes gather far more light than the unaided eye can gather.

2. Telescopes magnify images.

Refracting Telescope

Refracting Telescope- Uses two lenses.

The Lense, at the front of the tube, gathers light.

The Eyepiece magnifies the image collected by the lense. (limited in size by tendency of large lenses to bend)

Reflecting Telescope- Uses one large lense to gather and focus light, then reflect the image to a small mirror, then to an eyepiece on the side. Since the lense is supported, reflecting telescopes can be much larger.

Reflecting Telescope

Reflector Scopes

Galaxy viewed through Optical wavelengths

Radio Telescopes

(technical term for really big satellite dishes)

Used to detect energy waves given off at frequencies lower than visible light.

Lovell Radio Telescope

Cambridge Radio Telescope

Aricebo Radio Telescope

Galaxy viewed through Radio wavelengths

Other Types of Telescopes

COBE (Cosmic Background Explorer)

Cosmic Background Radiation From Big Bang

Milky Way Galactic Center

Compton Gamma Ray Telescope

ASCAASCA

ASCA X-Ray Pulsar

ASCA X-Ray Black Hole

“Pillars of Creation” Photographed by the Hubble Telescope

(shown left)

IRAS Infrared Observatory

IR Man!

Infrared Milky Way Galactic Plain