1. Tools of Modern Astronomy
Chapter 21 Section 1
Pages

2. Constellations
Patterns of stars in the sky
ORION- The Hunter

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

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

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

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

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

8. 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

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

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

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

12. 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,

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

14. Parts of a Spectroscope
Lens
Prism
Spectrum

15. 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.

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

17. 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.

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

19. 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.

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

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

22. 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

23. 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.

24. 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.

25. 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

26. Absorption Spectrums
Star A
Hydrogen
Helium
Sodium
Calcium

27. Absorption Spectrums
Star B
Hydrogen
Helium
Sodium
Calcium

28. Absorption Spectrums
Star C
Hydrogen
Helium
Sodium
Calcium