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
Absorption Spectrums
Absorption Spectrums