Brazilian astronomers propose new model of our galaxy

Image of Messier 101, or the Pinwheel Galaxy, showing 'straight' arms. -NASA

The structure of nearby galaxies such as Andromeda is relatively straightforward to see. But the Milky Way presents an entirely different kind of challenge.

The map of the Milky Way has been redrawn several times since the first attempts in the 1950’s using radio telescopes to trace out the spiral arms of our home galaxy.

Brazilian astronomers have proposed a new model to explain the structure of our galaxy, the Milky Way. The new model suggests that our galaxy may have one more arm than previously thought and that these arms are more straight than curved.

The astronomers, led by Jacques Lepine at the University of Sao Paulo, used data from clouds of gas to develop their new proposed model.

Quote: Originally Posted by Jacques Lepine

“Basically, our results confirm the main aspects of the spiral structure revealed by the studies of HII regions,” said Levine and his team. “For instance if we move horizontally across the figure, to the right or to the left of the Galactic center, we find roughly 3 spiral arms on each side, like the previous works. There are departures from the pure logarithmic spirals, with segments of arms that are almost straight lines.”

In order to study the structure of the Milky Way, the astronomers studied spectra created by Carbon monosulphide clouds, contrary to the common method of analyzing spectra from clouds of ionized hydrogen. This method was used in hopes of producing an accurate 'face-on' map of our galaxy.

The postulated extra arm, if indeed actual, will increase the number of known arms from two to three. Previously, in 2008, the number was changed from four to two. This new arm is estimated to be about 30,000 light-years from the center of the Milky Way and is thought to have a "strong inward curvature".

The new model also suggests that our Solar System is in one of the straightest parts of an outer arm of our galaxy.

According to Lepine and his team of researchers: "Drawing a map of the Milky Way is a challenging task, since we only have an edge-on view of the galaxy in which we reside. ... We may not ever know exactly what our galaxy would look like when viewed from other worlds, but we’ll keep trying."