Spectral Analysis of Stars

Astronomy

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.