Astronomers have discovered a previously undetected feature of our Milky Way galaxy – a group of young stars and star-forming gas clouds protruding from one of the galaxy’s iconic spiral arms “like a splinter poking out from a plank of wood.” With each subsequent discovery, we’re slowly unraveling the secrets of the universe and learning more about how we came to be.
The structure is said to extend roughly 3,000 light-years out from the Sagittarius Arm, and was discovered using NASA’s (now retired) Spitzer Space Telescope along with data from the European Space Agency’s Gaia mission. It features four nebulae: the Eagle Nebula, the Omega Nebula, the Trifid Nebula and the Lagoon Nebula.
Michael Kuhn, an astrophysicist at Caltech and lead author of the study, said a key property of spiral arms is how tightly they wind around a galaxy. “Most models of the Milky Way suggest that the Sagittarius Arm forms a spiral that has a pitch angle of about 12 degrees, but the structure we examined really stands out at an angle of nearly 60 degrees.”
The structure itself, sometimes known as a spur or feather, isn’t all that unique as they have been spotted in other spiral galaxies. But making key discoveries like this about the Milky Way is especially tough considering Earth’s position inside the galaxy (in the Orion Arm). “It’s akin to standing in the middle of Times Square and trying to draw a map of the island of Manhattan,” NASA noted in its write up.
Another of the paper’s co-authors, Robert Benjamin, said the discovery is a reminder that there are many uncertainties about the large-scale structure of the Milky Way. “This structure is a small piece of the Milky Way, but it could tell us something significant about the galaxy as a whole,” he added.
The team’s paper can be read in the international journal Astronomy & Astrophysics.