The Milky Way is still growing

New study finds that galaxies like the Milky Way are expanding at around 500 meters per second. The Milky Way is getting bigger as new stars form in its outer edges. The galaxy we live in, called the Milky Way, is a barred spiral galaxy, with a diameter of about 100,000 light years. Milky Way contains hundreds of billions of stars and a huge amount of gas and dust and the interaction between them determines the shape of our galaxy. However, the structure and shape of Milky Way are far from being simple. It is comprised of a disc in which stars, dust, and gas lie, while its two spiral arms stretch out from a central bar.

Milky Way is home to stars of different ages. Older stars dominate the bulge around the galactic center and the halo that surrounds the disc, while younger stars are found in the disc of the galaxy in which new stars continue to form. Some new stars are even found at the outer edge of the disc. Models of galaxy formation suggest that new stars will slowly increase the size of the galaxy they reside in and our galaxy is no exception to that. The problem is that we cannot precisely determine the shape of Milky Way. Because we live in the Milky Way, we cannot see our galaxy face-on or view it from above.

Astronomers often look at similar galaxies elsewhere to understand the nature of our own galaxy. To establish whether other spiral galaxies similar to the Milky Way really are getting bigger, researchers used both space and ground-based telescopes and closely observed stars at the end of the disc in the other galaxies.

Researchers measured the light predominantly originating from young blue stars and observed their vertical movement to figure out how long it will take for stars to move away from their point of origin and how they are contributing to the growth of their host galaxies. Based on calculations, they reveal that galaxies like the Milky Way are growing at around 500 meters per second. That’s fast enough to get from Liverpool to London in about twelve minutes.

Lead researcher Cristina Martínez-Lombilla from Instituto de Astrofísica de Canarias in Tenerife, Spain said, the Milky Way is pretty big already. But our work shows that at least the visible part of it is slowly increasing in size, as stars form on the galactic outskirts. It won't be quick, but if you could travel forward in time and look at the galaxy in 3 billion years' time it would be about 5% bigger than today.