A galaxy is a massive group of stars, star clusters, cosmic gas and dust, and dark matter, which is all gravitationally bound together. There are hundreds of billions of galaxies in the Universe, they come in all sorts of shapes and sizes but the three most common types are spiral galaxies, barred spiral galaxies and elliptical galaxies.
The galaxy in which our Solar System lies is called the Milky Way. Without this galaxy, life would likely not have flourished on Earth.
In this activity, students will learn about the different types of galaxies in the Universe in a fun art activity, while practising numeracy skills, too!
Barred-Spiral Galaxy Factsheet
Full Instructions
Learning Objectives
- Develop an understanding of the vast number and variety of galaxies in the Universe,
- Use numeracy skills to calculate the size of different galaxies and make a scale drawing of a galaxy.
Materials
- Printed Galaxy Factsheets, one page per student
- Black paper
- Glitter
- Glue
- Ruler
- Art materials (paint, pipe cleaners, fabric etc.)
- Optional: Calculator per student
Background Information
A galaxy is a massive group of stars, star clusters, interstellar gas and dust, and dark matter which is all gravitationally bound together. There are hundreds of billions of galaxies in the Universe, they come in all sorts of shapes and sizes but the three most common types are spiral galaxies, barred spiral galaxies and elliptical galaxies.
The most common type of galaxy is called a “spiral galaxy”. Spiral galaxies look like spirals, with long arms winding toward a bright bulge at the centre.
About 70% of the galaxies in the local Universe are spiral galaxies. Our own galaxy, the Milky Way, is a typical spiral galaxy.
Spiral Galaxy: Some spiral galaxies have arms that are wound tightly, while other galaxies have very loosely-wound arms. The arms of a spiral galaxy have lots of gas and dust, and they are often areas where new stars are constantly forming. The bulge of a spiral galaxy is composed primarily of old, red stars. Very little star formation goes on in the bulge.
Barred-spiral Galaxy: Barred spiral galaxies are spiral galaxies with a long bar in the middle, with spiral arms coming off the ends. Around two-thirds of all spiral galaxies are barred-spirals, including our galaxy, the Milky Way. Like spiral and elliptical galaxies, barred-spirals are thought to have a black hole lurking in their centres.
Elliptical galaxy: Elliptical galaxies are named after their shape (an ellipse is a stretched circle shape). Elliptical galaxies are made up of mostly old stars, and do not have much gas and dust. There is very little new star formation in these galaxies. Elliptical galaxies also come in many sizes. The largest galaxies we see are ellipticals, but, elliptical galaxies can also be small. About 60% of all galaxies are ellipticals.
Step-by-Step
1) Divide your class into pairs and assign each pair a class of galaxy: Spiral Galaxy, Barred-Spiral Galaxy or Elliptical Galaxy. Hand each pair the appropriate worksheet (they will only need the information sheet for the type of galaxy they are working on).
2) They will now read the description of their object on the worksheet.
3) Ask each pair to choose one of the three galaxies at the bottom of their sheet. The table provides information on the size of the galaxy and the scale they are to use.
4) Explain that 1:100 means they divide the size of their galaxy (in light years) by 100, 1:250 means they divide the size of their galaxy by 250 etc. You will find a table below that provides the correct size for each of the nine potential galaxies.
5) Ask the children to calculate the scale of their galaxy. The result will tell them the length of their galaxy in centimetres.
6) Explain that every centimetre represents the number of light years shown to the right of the colon in their ratio, e.g. 1:100 means 1cm: 100 ly.
7) Once they know the length of their galaxy, the children can begin to draw it. Ask them to lightly draw a line the length of their galaxy (as calculated in Step 5) on a piece of black paper.
8) Then with this line as reference, they can sketch their galaxy using a pencil. Make sure their galaxy is the right shape as described on their fact sheet.
9) The next step is to outline their galaxy with glue and sprinkle a generous helping of glitter to represent the many millions of stars in each galaxy.
10) From there the students can use a range of other materials to add the other features described on their worksheet, e.g. spiral arms, halo, bulge. This is a good opportunity to practise techniques you are currently teaching in Art, such as mosaic, texturing etc.
Bonus Exercise
Once each pair has completed their galactic artwork and it has dried properly, you can put all the galaxies together to create a famous Hubble Tuning Fork diagram. It makes a fantastic piece of wall art for your classroom! To do this follow the steps below.
1) Stick each galaxy in the correct place to form your own Tuning Fork, with the smallest galaxies on the left, working up to the largest on the right. (See image).
2) Finish the activity by asking your students if their galaxy is larger or smaller than the galaxy of the pair next to them.
Does this mean it is larger/smaller in real life? The answer is only for galaxies of the same class. This is because you can only compare the size of two models fairly if they use the same ratio.
3) Once their galaxy is dry, ask students to show and describe their galaxy, either to the class or in small groups. What is the name of their galaxy? What type of galaxy is it? What features of the galaxy have they included in their artwork?
Answer Table
| Galaxy Type | Galaxy Name | Galazy Size (cm) |
|---|---|---|
| Elliptical | Messier 60 | 17 |
| Elliptical | Messier 81 | 12 |
| Elliptical | Messier 49 | 24 |
| Spiral | Messier 74 | 18 |
| Spiral | Messier 81 | 20 |
| Spiral | Messier 88 | 22 |
| Barred-Spiral | Messier 66 | 19 |
| Barred-Spiral | Messier 108 | 18 |
| Barred-Spiral | NGC 1300 | 21 |
Conclusion
Now that your class is familiar with what a galaxy is and their existence in the Universe, use the robotic telescopes to take three pictures, one of each type of galaxy: spiral, barred spiral and elliptical.
Curriculum Links
Welsh National Curriculum KS2 Mathematics
“Calculate in a Variety of Ways” and “Investigate Patterns and Relationships”.