The Sagittarius arm of our galaxy spirals out of the Milky Way’s middle, turning into a swooping stream of gas, covering tens of thousands of light-years.
That stream is lit up by the headlights of billions of stars, all appearing to move along the same curvy track. Currently, astronomers discovered an unusual trait to the galaxy – a “break” in the arm, slashing approximately perpendicularly through the spiral.
The unusual splinter is huge, spanning roughly 3,000 light-years. However, when you compare it to the sheer size of the Milky Way, which has a diameter of approximately 100,000 light-years, that splinter isn’t so impressive anymore, as it covers only 3% or so of the galaxy.
However, the newly discovered break is the first significant structure to be found interrupting the apparently uniform flow of the galaxy’s Sagittarius arm, a recently published study claims.
Robert Benjamin, the study’s co-author and astrophysicist of the University of Wisconsin-Whitewater, stated:
“This structure is a small piece of the Milky Way, but it could tell us something significant about the galaxy as a whole. Ultimately, this is a reminder that there are many uncertainties about the large-scale structure of the Milky Way, and we need to look at the details if we want to understand that bigger picture.”
Curiously, the astronomers had no clue that anything was wrong with the arm until they put data from recent star surveys side to side.
The discovery was made thanks to NASA’s Spitzer Space Telescope and the ESA’s Gaia satellite, as data from the two devices helped scientists determine the velocity and pitch angle of certain regions of the Sagittarius arm.
They discovered that the main arm presented a 12-degree pitch, while the section where the break is located had a 60-degree pitch.
Additionally, the numerous stars in the break appeared to be moving at a similar velocity and direction as one another, which may be proof that they formed at approximately the same time and have been impacted by similar gravitational forces.