The researchers have investigated how ultraviolet light of a certain wavelength travels through the galaxies and found that the light often takes a detour before it reaches us. One effect of this is that the galaxies appear larger and more diffuse than they really are.

These are the first results of the LARS project (Lyman Alpha Reference Sample), where the Hubble Space Telescope (HST) has been used to study 14 nearby galaxies in detail to find out how the so-called “Lyα light” travels through the galaxies.

“We found that the Lyα light has a hard time finding its way out of the galaxies. In the cases where it does manage to get out, it happens as the light bounces off of clouds of neutral hydrogen. This bouncing makes the light travel farther and farther out, which makes the galaxies appear larger in Lyα light than in ordinary visible light”, says Luci Guaita, postdoctoral fellow at the Department of Astronomy, Stockholm University, who is working on the project.