It wasn’t until telescope design and the ability to capture photographic images had developed that astronomers came to the conclusion that galaxies exist outside our own Milky Way. Before that time, these fuzzy objects, or nebulae, were simply in a class of objects that were “not galaxies.” With the improved magnification and resolution provided by telescopes of the early 1920s, the first thing astronomers noticed were patterns in the shape of these objects. Let’s see what we can find out by observing galaxy images from the SDSS. To do this, we are going to use a citizen science project tool called Galaxy Zoo Navigator.
Classifying Galaxies by Shape in Galaxy Zoo Navigator
The Sloan Digital Sky Survey images are used in the citizen science projected called Galaxy Zoo. As part of this project, anyone can assist scientists to analyze astronomical images from the SDSS. The first thing you will need is a Zooniverse Account.
• Go to Galaxy Zoo.
• Click on the icon in the upper left to reveal the login header.
• Follow the instructions to create account.
For this exploration your instructor has set up a separate group within the Galaxy Zoo using a tool called Navigator at the bottom of the Galaxy Zoo page.
You are now ready to classify galaxies based upon their shapes. The Galaxy Zoo scientists have set up a series of easy-to-answer questions about what you see. Help is available any time you need examples or clarifications about the questions. The Galaxy Zoo has provided some important documents to assist you and your instructor get the most out of the Navigator tool. The student documents are available below.
– Student Guide to the Galaxy Zoo – provides help getting started.
– Student Guide to Navigator – instructions for the Navigator tool and and introduction to the graphing tool that you will use later in this exploration.
– Student Guide to Navigator Graphing Tool – detailed information about the information available with Galaxy Zoo images and how to view that information using the graphing tool.
– Zookeeping – provides a detailed example of the classification questions.
– Galaxy Zoo and Navigator Teacher’s Guide – This document contains important information about setting up and using the Galaxy Zoo Navigator tool with groups of students.
Keep Track of What You Observe
While you are classifying galaxies in Navigator, you have two important tasks:
• Record what you observe about the type of questions you are asked in the Navigator tool.
• Save at least twelve galaxies to your Favourites that you think are good examples of the variety of galaxy shapes you observed during your session. It will be easier if you choose galaxies from SDSS only.
Analyze Your Classifications
Your instructor will let you know when it is time to move on. The next step is to look at your classification data using the Navigator Graphing tool.
• Return to your group page.
• Click Graph Data.
• Construct a graph that shows the distribution of how bright the galaxy appears in the sky (apparent brightness) for smooth galaxies and galaxies with features. Remember that our measure of brightness (magnitude) runs backward. The smaller the number, the brighter the object. See Preflight – Magnitude for more information. What conclusions can you draw?
• Compare your group’s data to classifications made by all citizen scientists contributing to Galaxy Zoo. Make a new graph if necessary.
Organize Your Favourites
Return to your Favourites under the Profile link at the top of any Galaxy Zoo page. Hopefully, you have been able to save a variety of galaxy images. Your goal for this section is to create your own organization diagram for your collection. Sort and order them in any way you like. You can do this by saving snapshots of each of your galaxies using a snipping tool or by printing a black and white (inverted) image of your galaxies and then arranging them on a large piece of paper. The video below can help you access inverted images from the SDSS.
When you are finished, share your work with others in your group and explain your reasoning. Once done with that step, continue this activity with an exploration of how astronomers in the past first organized their galaxy images.