Star, light and distance

1. Star, light and distance

2. Explain EMR and the properties of light. • Understand the use of spectroscopes. KEY WORDS Luminosity Spectroscope Electromagnetic spectrum

3. 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.

4. Star B looks brighter - apparent Star B is closer to us than Star A. - same Absolute magnitude.

6. Colour and Temperature of Stars • Colour – shows much energy a star has. • Colder star glows red. • Hotter star glows bluish white or even blue. 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.

7. Light is a type of energy called: Electromagnetic Energy

8. 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.

9. Types of Electromagnetic energy Low energy High energy ROYGBIV Red light is low energy – cool Blue is high energy - hot

10. 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.

11. Light from the sun through a spectroscope Absorption lines of Helium