The Milky Way is growing by 500 metres every second, say astronomers

New stars forming on the edge of the Milky Way, claim researchers

Spanish astronomers believe that the Milky Way may be going through a phase of rapid expansion after studying galaxies with similar traits.

Cristina Martínez-Lombilla, who is a researcher at the Instituto de Astrofísica de Canarias in Tenerife, made the claim at the European Week of Astronomy and Space Science in Liverpool today.

The scientists wanted to explore the evolution of spiral galaxies, which contain large amounts of flat stars, gas and dust that continually rotate.

According to the researchers, the Milky Way happens to be one of them. With a diameter of 100,000 light years, it is home to billions of stars that are packed with gas and dust, all of which interact within its gravitational force.

This type of interaction is responsible for determining a galaxy's shape, which can either be spiral, or elliptical or irregular. The Milky Way happens to be formed from a barred spiral structure, so its contents intermingle in a flat plane.

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

Most of the stars based in the Milky Way are relatively young in age, having emerged millions of years ago. In comparison, stars in other galaxies date back up to hundreds of billions of years.

Because these young stars are based at the disc of the Milky Way, lots more are beginning to form - meaning our galaxy is continuously expanding.

Unfortunately, tracing the star-forming regions of the Milky Way galaxy is not an easy task because we happen to live in it and therefore lack a proper perspective. As a result, scientists focus on other galaxies with similarities in order to learn more about the characteristics of our own.

In this particular study, Martínez-Lombilla and her colleagues used the ground-based SDSS telescope and two space-based telescopes to explore other galaxies.

With a combination of ground and space telescopes, the scientists were able to trace the colours and movements of expanding stars based in similar galaxies.

After measuring the light and vertical movement in these environments, the researchers were able to work out when the stars were born and the growth rate of these galaxies.

They then applied this data to the Milky Way, suggesting that it is expanding by 500 metres every second. Martínez-Lombilla called the research groundbreaking.

"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," she said.

"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."