It was long believed that the shape of the Milky Way branched out into four arms, but scientists now believe it consists of only two armed spirals.
Written by Sean Thiessen | published
Scientists change the shape of the galaxy. Or at least they understand it. According to a report before Opportunity Space.comA team of researchers used data from sophisticated telescopes and other instruments to map the shape of the Milky Way, and came up with a theory that it is a two-armed spiral, in contrast to the previous belief that it has four arms.
The recent study determined that any galaxy is likely to be either elliptical, irregular, or spiral shaped. Spiral galaxies are the most common, and they usually have two main arms that branch off from the center and separate into smaller arms.
It has long been thought that the Milky Way is a strange exception to this common shape. Scientists previously assumed that our galaxy is a spiral with four main arms extending from a cluster of stars in the center.
Although many believe the Milky Way to be special in this respect, why it took this unique shape has remained a mystery. The new data indicates that the Milky Way may not be distinct at all. Astronomers from the Chinese Academy of Sciences at Purple Mountain and the National Astronomical Observatories studied data from multiple sources to build a new model of the galaxy.
The team measured the distances between about 200 stars in the Milky Way to create a map of the galaxy. They combined this data with measurements from the European Space Agency’s Gaia telescope. They focused the telescope’s readings on more than 1,000 galaxy clusters and 24,000 OB stars.
These large stars burn hot, bright, and fast, which means they move very little during their lives and are relatively easy to track. The team measured the motion of the stars with respect to Earth to help detail their new model of the galaxy. The theory the team came up with is that the Milky Way has a dense bar running through its center from which there are two main branches of arms.
At the edges of the galaxy are fragmented arms that are not connected to the dense star cluster at its centre. These fragmented arms are thought to be the result of galactic collisions deep in the Milky Way’s history. When our galaxy collided with another, or perhaps several others, the fragmentation that created the shape scientists are now determining would have occurred.
The team admits that this new model of the galaxy is incomplete. They will continue to add data from other sources and from the ongoing results of Gaia, which is expected to be active for at least another two years.
The methods that brought the research team to the spiral-armed model of the Milky Way could change the way scientists approach modeling galaxies across the board. Their process to determine galactic structure sheds new light on the shape of our galaxy and could continue to shed light on other people’s mysteries as well.
As scientists continue to solve the mysteries of space, our understanding of the universe and our galaxy evolves. The quest to map the galaxy is far from complete, but humanity is one step closer to understanding how the shape of our galaxy fits into the puzzle of the universe.
