Star, light and distance
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Star, light and distance. Explain EMR and the properties of light. Understand the use of spectroscopes. KEY WORDS Luminosity Spectroscope Electromagnetic spectrum. Stars - classified by age, distance, and brightness Brightness ( luminosity ) of Stars

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Luminosity Spectroscope

Electromagnetic spectrum

  • Stars - classified by age, distance, and brightness

  • Brightness (luminosity) of Stars

  • There are two amounts (magnitudes) of brightness:

  • Apparent magnitude – brightness as we see it.

  • Absolute magnitude – actually brightness.

  • Sun has a high apparent magnitude, because it is so close.

  • Sun has an average absolute magnitude.

Star B looks brighter - apparent

Star B is closer to us than Star A.

- same Absolute magnitude.

The Sun is bigger than about 95% of stars.

  • Scientists use a spectroscope to analyse the light energy from stars.

  • Spectroscope - splits light up into a pattern of colours, like a rainbow.

Light is a type of energy called:

Electromagnetic Energy

The Electromagnetic Spectrum

  • Visible spectrum is the energy waves we can see.

  • Energy we cannot see:

  • ultraviolet, infrared, x-rays, microwaves, radiowaves, gamma rays.

  • Heated compounds give off a uniquespectrum.

  • By looking at the spectra for different stars, we can get some idea of what elements are present in them.

  • They can use the spectrum to determine in which direction a star is moving.

Types of Electromagnetic energy

Low energy High energy


Red light is low energy – cool

Blue is high energy - hot

Each gas in the star absorbs unique parts of the light energy as it is released.

The black lines in the spectrum show the elements that make up the gas surrounding the star.

Light from the sun through a spectroscope

Absorption lines of Helium