Every galaxy is different, just like snowflakes, humans, and oak trees. While everyone is unique, we can understand them by looking at them in large numbers and looking for trends. 

For instance, snowflakes have different sizes and structures depending on temperature, moisture in the air, and even details like wind, and you’ll get similar – but not identical – snowflakes when conditions are the same. 

Growing conditions matter; children with better access to high-quality foods will grow taller and healthier, while those with contaminated water and poor nutrition will reflect these poor conditions in their bodies, and sometimes even in their minds. 

Even location matters, with oak trees growing to different sizes and shapes depending on if they are located on a windy cliff, in a crowded pine forest, or in beautiful isolation in a city park (more on that later). 

With galaxies, all these factors matter, and for the past seven years, the SAMI Survey at the four-meter Anglo-Australian Telescope has been taking detailed observations of galaxies in a wide range of circumstances to understand what factors literally shape them. This telescope is able to observe thirteen galaxies at a time, and the survey has just published its complete catalog of over three thousand galaxies.

According to lead author Scott Croom: The sheer size of the SAMI Survey lets us identify similarities as well as differences, so we can move closer to understanding the forces that affect the fortunes of galaxies over their very long lives.

These forces are the galaxy versions of nutrition and environment, and in this vast universe, galaxies occupy nearly countless different habitats. Croom continues: The nature of galaxies depends both on how massive they are and their environment. For example, they can be lonely in voids, or crowded into the dense heart of galactic clusters, or anywhere in between. The SAMI Survey shows how the internal structure of galaxies is related to their mass and environment at the same time, so we can understand how these things influence each other.

This catalog of 3,068 galaxies is published in the Monthly Notices of the Royal Astronomical Society. Since this is a data release, we know what the survey can tell us, but we don’t yet know what it has told us. Those papers are still to come, and when they do, we’ll bring them to you here on the Daily Space.

More Information

Astro3D press release

“The SAMI Galaxy Survey: the third and final data release,” Scott M Croom et al., 2021 February 1, Monthly Notices of Royal Astronomical Society