By tracking the star clusters within those arms, astronomers can piece together a picture of the galaxy as a whole.
"Spiral arms are like traffic jams in that the gas and stars crowd together and move more slowly in the arms. As material passes through the dense spiral arms, it is compressed and this triggers more star formation," Denilso Camargo, lead author of the paper from the Federal University of Rio Grande, said in a statement.
Camargo and his team used NASA's Wide-field Infrared Survey Explorer, or WISE. WISE uses infrared to cut through the dense gas of the galaxy, allowing researchers to spot far-off star clusters. Because most star clusters are formed within the arms of our galaxy -- and spend awhile there before spreading out -- star cluster location can be used to chart the framework of the galaxy.
Researchers are still learning from its data, but WISE isn't actually looking for stars anymore. In 2011, the spacecraft completed its second complete scan of the sky, and thereby its mission objective, and was put into hibernation mode. WISE was turned back on in 2013 (with the snazzy new name NEOWISE) but now it works to help NASA detect hazardous near-Earth objects.