Observations of galaxies similar to the Milky Way suggest that our galaxy will still grow in the distant future. The researchers calculated that the Milky Way is growing at the speed of 500 meters per second.
According to Cristina Martínez-Lombilla, a Ph.D. student at the Instituto de Astrofísica de Canarias de Tenerife in Spain and her collaborators, the Milky Way could get even bigger in the future. She presented her work in a lecture at the European Week of Astronomy and Space Science in Liverpool.
The solar system is located in one of the arms of the disc of a barred spiral galaxy which we call the Milky Way. The latter has a diameter of about 100,000 light-years and is made up of hundreds of billions of stars with enormous amounts of gas and dust all intertwined and interacting by the force of gravity.
The nature of this interaction determines the shape of a galaxy, which can be spiral, elliptical or irregular. As a barred spiral galaxy, the Milky Way consists of a disk in which stars, dust, and gas are mostly in a flat plane with arms extending from the central bar.
In the disk of the Milky Way, there are stars of different periods. The massive, warm blue stars are very bright and have a relatively short lifespan of several million years while lower-mass stars eventually become redder and much weaker and can live for hundreds of billions of years . The youngest short-lived stars are mostly found in the disk of the galaxy where new stars continue to form while the older stars dominate in the bulge around the galactic center and in the halo surrounding the disk.
Some star-forming regions are on the outer edge of the disk and galaxy formation patterns predict that the new stars will slowly increase the size of the galaxy in which they reside. A problem in establishing the shape of the Milky Way is that we live inside it, so astronomers look at galaxies similar to ours to make a picture of our own.
Martínez-Lombilla and his colleagues sought to establish whether other galactic galaxies similar to the Milky Way are expanding and if so, what does this mean for our own galaxy. She and her team used the ground-based SDSS telescope for optical data and the two GALEX and Spitzer space telescopes for near-UV and near-infrared data to examine in detail the colors and motions of stars at the end of the disc in the other galaxies.
The researchers measured light in these areas, mostly from young blue stars, and measured their vertical movement to determine the time needed to move away from their birthplaces and how their host galaxies grew in size. On this basis, they calculated that galaxies like the Milky Way are growing at about 500 meters per second.
“The Milky Way is already quite large, but our work shows that the visible part of the Milky Way is slowly increasing in size as new stars are formed on the periphery of the galaxy,” comments Mrs. Martínez-Lombilla. “If you could travel forward in time and look at the galaxy in 3 billion years, then it will have increased by 5% compared to today,” she added.