Galaxy Zoo: Clump Scout

What are clumps?

Clumps are big, bright regions in galaxies where stars are being formed more quickly than usual. They can be anywhere from ten light-years across to over a thousand, and come in a wide range of shapes, colors and properties.

What's the goal of the Clump Scout project?

We're trying to identify all of the clumps in the Sloan Digital Sky Survey (SDSS), which has images of hundreds of thousands of nearby galaxies. We know some of these galaxies have clumps, but we don't know which or how many.

Why are they called "clumps"?

When mid-20th century scientists found a new type of galaxy with bright spots scattered around it, they didn't know quite what to make of them. Astronomers decided to call these galaxies "clumpy" in order to distinguish them from their smoother-looking counterparts. From there, the bright spots themselves became known as "clumps", and the name stuck.

Why are clumps worth studying?

Galaxies in the early universe used to be brimming with clumps, but today, there are very few. Their vanishing act raises many questions: Why did clumps form in the first place, and what happened to make them stop? By learning more about clumps, we're trying to understand how galaxies and the universe as a whole have changed over time.

We can also use clumps to test existing theories about how galaxies work. For example, some theories predict that galaxies are stable enough for clumps to live for billions of years; others predict that galaxies are less stable, and clumps are constantly being ripped apart and reformed. We can test both of these theories, and others like them, by finding real clumps to study.

What if I'm not sure if something is a clump or not?

There are a few resources to help you decide. If you click Need some help with this task?, you'll see some examples of what we're looking for. You can also read the Field Guide on the far right-hand side of the page at any time, which has many more examples of different situations and how to deal with them.

If you're still not sure if something is a clump or not, you can use the Unusual Clump Marker to mark it. We use this to identify objects that might be clumps, but are odd or different in some way.

After I submit my marks, what happens to them?

The first step is that marks are "aggregated". This means we take all of the marks made by all of the volunteers who classified the image and group them into clusters. If a cluster of marks fell near the same spot, we consider that spot a clump. We rely on crowd agreement, so spots with lots of marks nearby are designated as clumps, while stray clicks and spots without very few marks tend to be ignored.

Once we're certain that people's marks agree, we retire the image and it is no longer shown to users. The locations of its clumps become official scientific data.

Why can't a computer do this?

Identifying clumps may seem easy to us, but computers have a lot more trouble. The reason for this is that clumps appear in images that are full of extraneous information. Computers have to sift through other galaxies in the background, bright stars in the foreground, and the complexities of the subject galaxy itself before they can isolate clumps from all these competing signals. For computers to get better, they need to learn from real examples of clumpy galaxies, and that means we need to find some first!

Human volunteers are also better at drawing attention to clumps that are interesting, unexpected, or just plain weird. Based on your feedback, we can go back and examine these clumps in more detail. This is how citizen scientists in Galaxy Zoo project discovered Green Peas, an entirely new class of galaxy we weren't expecting.

Why are some of the clumps simulated?

In order to know how good our findings are, we need to know if anything was left out. It could be that some clumps are invisible because they're too faint or they blend into the background. To help us understand this, some images contain simulated clumps with properties we've chosen ourselves. If citizen scientists spot a simulated clump, it tells us they probably also spotted real clumps with properties like it. On the other hand, if no volunteers find a simulated clump, we'll know that clumps like it probably can't be found by this project.