Tools of Modern Astronomy Chapter 21 Section 1 Pages 716-718

Constellations Patterns of stars in the sky ORION- The Hunter

Electromagnetic Radiation ER- Electromagnetic Waves Travel in the form of waves. These waves can travel through empty space.

Electromagnetic Spectrum ER waves travel at 300,000km per second The speed of light The lengths of the waves determine the type Wavelength

Which of the following has the longest wavelength? A. Radio Waves B. Visible C. Ultraviolet D. Gamma Rays

The Sun Emits electromagnetic radiation of all types. How can the radiation emitted by the sun travel through space and reach Earth?

Electromagnetic Spectrum The various types of ER waves arranged on a continuum

What is Visible Light? A form of electromagnetic radiation that you can see. A form of energy that travels in waves like: Radio waves X-rays Visible light

Which color has the shortest wavelength? A. Red B. Orange C. Yellow D. Green E. Blue F. Violet

Spectrum (Prisms) when light is passed through a prism The light is bent into the visible spectrum

Spectrum Visible Light Made of various colors, each with a different wavelength. These are the colors seen in a rainbow,

Spectrum Visible Light Made of various colors, each with a different wavelength. (Red, Orange, Yellow, Green, Blue, Violet) These are the colors seen in a rainbow,

Spectroscope Uses a prism to split the light gathered by a telescope into a spectrum. (roygbv)

Parts of a Spectroscope Lens Prism Spectrum

Three types of Spectra Three different types Continuous Spectrum Emission Spectrum Absorption Spectrum Allow astronomers to figure out what elements make up the atmospheres of stars and planets.

Continuous Spectrum Unbroken band of colors Shows that the source is emitting all visible wavelengths.

Emissions Spectrum A series of unevenly spaced lines of different colors and brightness. The bright lines show that the source is emitting light of certain wavelengths.

Emission Spectrum Produced by glowing gases. Every element has a unique emission spectrum Allows scientists to determine the elements in objects.

Absorption Spectrum A continuous spectrum crossed by dark lines Lines form when light from a glowing object passes through a cooler gas. The gas absorbs the wavelengths.

Absorption Spectrum The colors absorbed are the same that the gas would emit. Absorption Spectrum for Hydrogen Emission Spectrum for Hydrogen

Which spectrum would you expect to see produced by glowing gasses? A. Visible B. Emission Spectrum C. Continuous Spectrum D. Absorption Spectrum

Which spectrum would you expect to see if you were studying the gasses on another planet? A. Visible B. Emission Spectrum C. Continuous Spectrum D. Absorption Spectrum

Chemical Composition Chemical elements in a star’s atmosphere absorb light from the star. Each element absorbs a different wavelength. Each absorbed wavelength is shown as a dark line on a spectrum.

Chemical Composition It acts like a finger print each element has a unique set of lines. By comparing the star’s spectrum to the known spectrums of different elements, astronomers can determine the elements present.

Temperatures Most stars have a chemical composition similar to the sun. 73% H, 25%He and 2% other elements. Stars at different temps produce different line spectrums. If the star is at about 10,000˚C it produces a very strong spectral lines for H. If the hydrogen line is not strong, it means the star is cooler than 10,000˚C

Absorption Spectrums Star A Hydrogen Helium Sodium Calcium

Absorption Spectrums Star B Hydrogen Helium Sodium Calcium

Absorption Spectrums Star C Hydrogen Helium Sodium Calcium