Astronomy
Spectral Analysis of Stars
Energy Through Space
• Energy is transmitted through space as
electromagnetic waves.
• The movement of these waves through
space supports the concept of the ‘Big
Bang’ ~ particles are still moving as a result
of a gigantic explosion from a small,
concentrated area.
• Electromagnetic Spectrum: The arrangement of
visible light by wavelength. (ROYGBIV)
• Angstrom: Very small measurement used to
measure the distance between wavelengths of EM
radiation.
• Radial Velocity: The speed of a wavelength
toward or away from radar.
• Doppler Shift: Change in frequency toward or
away from an object. [Red shift is away and blue
shift is toward]
• Radiation: The transfer of energy by waves.
• Absorption Spectrum: Spectrum of light waves as
they are received. (What we see)
• Radiation Spectrum: Spectrum of light waves as
they are transmitted.
• Vacuum: An area with little or no pressure (outer
space).
• Wavelength: Distance between wave crests.
• Frequency: Number of cycle that pass in a
specific period of time.
• Lambda: The frequency of a wavelength
• Spectral Periodic Table
What elements are in that star?
• We can determine which elements are
found in distant stars by using a
spectroscope to observe the wavelengths of
energy being transmitted from the star.
For example . . .
• Each element emits a
unique wavelength of
light.
• The colors of the
spectrum from long wave
to short wave are: Red,
Orange, Yellow, Green,
Blue, Indigo and Violet
[ROYGBIV]
– Long = Red
– Short = Violet
Different light = Different spectrum
• A light bulb will emit all
the colors of the
spectrum, whereas gas
tubes will only emit the
spectra of the specific
element.
• Elements can be
identified by their
unique, characteristic
spectra.
• As the frequency of
electromagnetic waves
increases, the
wavelength decreases.
[Inverse relationship]
• The width of the
visible light spectrum
is a very small portion
of the total spectrum.
• As we move across the spectrum from gamma
rays (short waves) to radio (long waves),
wavelength increases and frequency decreases.
Therefore, infrared waves are longer than visible
waves.
Balmer Absorption Lines
• Balmer Absorption lines are the accepted
values for spectral wavelengths.
• We can determine the radial velocity and
direction of wavelengths by comparing
them to the Balmer lines.
Spectral analysis determines several star
features:
1. Composition; Determined by distinguishing
the elements found within the star by
assessing the emitted wavelengths.
2. Radial Velocity; difference between actual
and accepted (Balmer) wavelength value x
speed of light divided by the accepted
(Balmer) value.
3. Direction of movement; Red shift/away or
blue shift/toward.