Investigate: Measure the Size of a Galaxy

Have you ever wondered how big a galaxy is? They contain millions to billions of stars but what does that really mean for size?

Reading about sizes in a book is one thing, but what if you could make an observation of a galaxy and then measure its size?

This activity will guide you through the process of how to do this. Use Go Observing to get your image of a galaxies, and use AstroLab to measure the size for yourself.

By the end of this resource you will:

  • Have used Go Observing to request an observation of a galaxy.
  • Have used AstroLab software to open and analyse your image.
  • Have measured the distance across the galaxy and converted the units to light years.

To complete this resource you will need:

  • To watch the video above
  • To watch the video on how to measure size using AstroLab.
  • To make sure you are logged in to the website (and registered).
  • A calculator (optional).


IT Equipment

  • Access to the internet (table or computer recommended).
  • Internet browser.