Australia's Chief Scientist

Try this: Star power

This activity shows you how to make a star projector. You will be able to make the constellation Scorpius shine on your ceiling and walls.

This activity is from CSIRO’s free weekly e-newsletter Science by Email.  Each issue includes science news, a hands-on activity to do at home, a quiz and more. Visit to subscribe. Want more hands-on activities? Visit CSIRO’s DIY Science pages and the Science by Email activity archive

Warning: This activity requires the use of a sharp compass. Be careful not to prick yourself.

You will need

  • torch
  • printer
  • paper
  • cardboard
  • pencil
  • tape
  • scissors
  • compass
  • mailing tube*

*These are the type of tubes you would use to mail a poster.

What to do

1. Place your torch on a piece of cardboard with the light facing the desk. Trace a circle around the face of the torch.
2. Cut out the circle and fold it in half. Cut a small semicircle out of the cardboard along the fold. It should be less than a centimetre wide. When you open it back out, it should look like a round hole in the centre of the circle.

Cut out a circle the size of the face of your torch. Fold it in half to cut a hole in the centre.

3. Tape the cardboard over the face of the torch. We also taped around the clear edges of the torch to minimise the light spilling out of the sides.

Tape the circle to your torch. You may also need to tape any gaps.

4. Print off the template, preferably onto cardboard.

5. Take the caps off the end of the mailing tube.

6. Place the end of the mailing tube over the template so that all the black dots are covered up. Trace a circle around the outside of the tube.
7. Use the compass to poke through the template where the black dots are. Wiggle the compass around at the larger dots to make a larger hole.

Cut out the template to the correct size and punch holes in it where the dots are.

8. Use tape to fix the template onto the end of the tube. Make sure that the side with the printing is facing outward.

Tape the template to the tube.

9. Find somewhere dark and shine the torch through the tube at the ceiling or wall. You may need to move closer or further away from the wall to see the stars at their finest.

Shine the torch through the tube and onto the wall or ceiling.

What’s happening?

A constellation is a group of stars that make up a picture in the sky.  Although the stars form a pattern in the sky from Earth, they may not be related at all. The stars in a constellation can be hundreds of light years apart.

The story of the constellation Scorpius is based on ancient Greek mythology. Scorpius was a scorpion sent to kill Orion, the great hunter. The two constellations are on the opposite sides of the sky. Orion sets as Scorpius rises, symbolising the fall of the hunter.

If you can, head outside to see if you can find Scorpius in the night sky. The brightest star in Scorpius is called Antares. You may be able to see it glowing slightly red. It is a red supergiant star with a diameter about 800 times that of our sun. Red supergiant stars are the largest stars in the universe, but do not necessarily have the greatest mass.


Light pollution is artificial light from streetlights, shopping centres, and other outdoor lighting. It makes the night sky brighter and the stars more difficult to see.

Later this year, as part of National Science Week, Australians will be asked to take part in the Big Aussie Star Hunt (BASH). Part of this project includes a light pollution survey.

All you need to do for the survey is count the stars you can see in Scorpius. The more stars you see, the less light pollution there is. List your observations on the website to contribute towards making a light pollution map of Australia. This map will help show where we can save energy and help the environment.

BASH will also show you how to find other constellations, teach you how to find south using the stars and help you find out more about Indigenous astronomy.

BASH is a project initiated by CSIRO and coordinated by the ABC. Visit the BASH website for more information.

Try another Science by Email activity using astronomy
Timing the stars
Make a telescope

More information

Australian Aboriginal constellations
Build a planisphere
CSIRO’s Australia Telescope National Facility

This article is an initiative by CSIRO Education