Could these galaxies be merging?

Many users have reported images to us that appear to have more than one galaxy in the centre, which may or may not be combining together into one galaxy. They have been described by our citizen scientists as “merging”, “colliding”, “interacting”, “twins”, “knotted”, “melting” and “dancing”!

It’s very difficult to tell whether galaxies are really merging with one another, or whether they are just overlapping in our line of sight. If they are interacting, they can have odd shapes due to their gravitational influence on each other. They might be the same colour, and surrounded by one fuzzy cloud. But without looking carefully at all the data collected from the galaxies, we can’t easily tell just by looking at them on AstroQuest. So it’s best to separate these galaxies whenever you can.

To help you make these decisions, we have collected some examples and checked with the science team how to approach these types of galaxies on AstroQuest.

In some cases, the computer thinks there is one galaxy where you can see two. In general, the instructions for these are:

  • If there is a larger galaxy and a smaller one, colour in the larger one and use the star tool on the smaller one. Tick the merging galaxies box.
  • If they are the same size, colour in the one that’s closer to the central dot in the cross hairs, and use the star tool on the other one. Tick the merging galaxies box.
  • If they are the same size and you can’t tell which one is closer to the central dot, skip this one and select merging galaxies in the drop down list of reasons.

In other cases, the computer may have separated two galaxies, but you think they might be merging and you would prefer to cover them with one segment. But in these cases, you should side with the computer.

We have also included some examples of highly irregular galaxies that might be the result of mergers. These can be the trickiest of all!

One segment covering multiple galaxies

Click on the thumbnails to see the full image and advice from the science team.

Galaxies that could be considered one system

Click on the thumbnails to see the full image and advice from the science team.

Galaxies that the computer has gotten right

Click on the thumbnails to see the full image and advice from the science team.

Irregular/interacting galaxies that have been split up incorrectly

Click on the thumbnails to see the full image and advice from the science team.