When we look up at the night sky with our eyes, almost all of the bright spots we see twinkling are stars in our galaxy, the Milky Way. If the night is dark, we can also see faint spots of light. These are the galaxies closest to our own, the Andromeda Galaxy and the two Magellanic Clouds, although these are only visible from the southern hemisphere of our planet.

But how do we measure the distance to stars and galaxies if we can’t reach them? It seems complicated, doesn’t it? Astronomers have gradually discovered different methods that enable calculating the distances to objects in the Universe, from those that are closest to us, to those that are farther away and can only be seen using powerful telescopes.

Introduction

Do you want to know how we measure the distances to the stars in our galaxy? Do you want to know the shapes of galaxies and how to classify them? We encourage you to find out with PETeR in this Unit.

Download here the INTRODUCTION to this Didactic Unit.

Activities

Now we invite you to help us classify some galaxies that we have observed with the Liverpool Telescope. Can you measure their diameter?

• Download the ACTIVITY GUIDE.
• Download the images of the GALAXIES you are going to work with.
• Download this SPREADSHEET to write down your measurements.
• If you haven’t already done so, download the software (PeterSoft) to view and analyse the images.

Remember you can also obtain your own images of the planets in  “Quiero Observar” and make new measurements and investigations.

Activity Data

Concepts: Distances to nearby stars. Parallax. Small-angle approximation. Our galaxy: the Milky Way. Classification of galaxies.

Tools to learn to use: Filters and contrast in images.

Estimated time: 3 hours.

Authors: Oswaldo González, Nayra Rodríguez, Alfred Rosenberg, Inés Bonet.

Materials for educators: Teacher’s guide.