Starting discussion suggestion 1:
Ask students if they have looked up at the stars. From the city if you are lucky, you’ll see some stars. If you can get out away from the city, you might see enough that there are too many to count. If you can, show images of the sky from the city and outside the city.
Each star is a sun like ours, but much further away. The light from the sun left the sun 8 minutes ago. Light from the next nearest star (Alpha Centauri) takes more than 4 years to reach us - it is 4 "light years" away from us. The light reaching us from some stars has been travelling for billions of years.
So seeing the light from stars shows how they used to look.
Starting discussion suggestion 2:
We explore and understand our Solar System by sending probes up in rockets, then guided to their destination with gravity assist. But to explore beyond the Solar System and back into the origins of our Universe we can only gather and interpret the light from stars.
Continuation of the lesson:
Telescopes can collect the light from far away stars, and spectroscopes in them can split the light into its colours, like a rainbow. The pattern of a spectrum can tell us what a star is made of, how stars change as they age and how fast and in what direction they are moving.
Large telescopes on earth can collect a lot of light, but the Hubble telescope orbiting earth gives the best images as the atmosphere does not wobble the light coming in. Soon the James Webb Telescope will replace Hubble and bring in a whole other batch of images that will allow us to discover new things about our Universe and its origins.
Make a spectroscope and look at the spectra of various light sources, to see how spectra can vary and be used to predict what kind of light sources we are looking at. Then look at the sun's spectra (best on a bright cloudy day).
When we look at the stars, they all have a continuous spectrum, like our sun.
The colours within each spectrum indicates the type of star.
All star spectra have dark Fraunhofer lines in them, which are formed as the gases in the star absorb some of the light emitted by the core of the star.
The position of the Frunhofer lines tells us what gases are in the star's atmosphere - what elements (or simply, "chemicals") the stars are made of.
With intermediates only:
The Fraunhofer lines can also be used to determine whether a star is moving towards us or moving away from us, and how fast.
Ask students to listen to the Doppler effect to hear how the frequency of sound waves changes with a moving object.
In the same way, the frequency of light (or the colour) changes if the star is moving towards or away from us, and so by looking how blue-shifted or red-shifted the Fraunhofer lines are, the speed and direction of a star can be deduced: http://en.wikipedia.org/wiki/Doppler_effect#mediaviewer/File:Redshift.svg
Continue lesson with all grades:
Use a hot bulb for students to detect another kind of light that is not visible: Infra Red (or heat).
Telescopes do not just detect visible light, but radiation of all wavelengths, including radio waves, microwaves, IR, UV and X-rays. The combination of all these wavelengths tells astronomers about cooler and hotter events in star birth, death and the life of galaxies. They get a tremendous amount of information, and then use filters to pick out the features that they want to study.
Use coloured filters to look at various composite images of nebulae, galaxies etc, to see how astronomers filter astronomical images to emphasize aspects of the image that they are studying.
Lesson for Kindergarteners:
Different kinds of light have different colours. Looked through scratched plastic to see the colours in different light sources, including sunlight.
When scientists look at stars they use tools that separate the colours to find out what the stars are made of. Different stars are different colours.
Coloured filters activity. How did your drawings change?
Scientists use filters to look at pictures of space to better see the part of the image they are interested in.