There are a lot of steps involved in making new scientific discoveries. Most are pretty familiar and pretty boring. There is the proposing to look for something, getting the data, analyzing the data, and finally the writing of research papers on the results. In astronomy, we sometimes get an extra step, and that is the “oh my goodness, this is so pretty” stage. Today’s top story highlights just how oddly beautiful our universe can be.

The Hubble Space Telescope has recently worked on a survey designed to image and probe extreme environments and galaxy clusters. As part of this survey, myriad galaxies in the process of merging were imaged, and yesterday a collection of six of the best images were released.

Galaxies grow over time through mergers. Often, these mergers are between moderately sized galaxies like our Milky Way galaxy and smaller, so-called, dwarf galaxies that don’t disrupt a galaxy’s structure too much when they crash. This is like a car striking a bag of kitchen trash on the highway. Periodically, however, two similarly sized systems can come together, and like two cars crashing, nothing is the same afterward.

With car crashes, we have the ability to see the entirety of a crash, and we can use test tracks and crash dummies to experiment with what happens when cars of different sizes hit at different angles and different speeds. With galaxies, however, crashes can last for billions of years, and humanity hasn’t existed long enough to watch a merger from start to finish. 

Instead of watching specific crashes from start to end, we end up searching across the sky for all the different stages of different kinds of crashes. For instance, we might get lucky and find ten different mergers of spiral galaxies coming together at right angles, with each system being caught at a different moment in their crash, and by combining the data from all these systems, we can piece together a movie of what happens during a merger.

In these images, we see some of the universal characteristics of a merger. There are knots of blue light marking the locations of newly forming star clusters. When galaxies collide, giant clouds of gas can collapse, forming huge numbers of stars. We also see streamers of light reaching out from the systems. These are called tidal tails, and they are made of stars and gas that get pulled and pushed out of galaxies the systems interact.

Hubble’s new survey is one of the most extensive and highest resolution surveys to have been completed so far. Science papers are still being written, so we don’t know what new science is going to come. For now, all we have are these amazing images. This is one of my favorite stages in science actually: it’s the “oh my goodness, this is pretty and I have no idea what all these details mean!” exciting stage.

When we know more, we’ll bring it to you right here on the Daily Space. 

More Information

Hubble image release 

“Star cluster formation in the most extreme environments: insights from the HiPEEC survey,” A. Adamo et al., 2020 December, Monthly Notices of the Royal Astronomical Society