Milky Way may be getting bigger, study reports

New research shows that Milky Way-like galaxies steadily grow with time, shedding new light on our system.
By Joseph Scalise | Apr 04, 2018
Researchers at the Instituto de Astrofsica de Canarias have discovered evidence that the Milky Way is slowly getting bigger.

The Milky Way is a massive space. It measures 100,00 light years across and is home to several hundred billion stars. In addition, it is also a spiral shape. That meansit has a disc in the center -- which contains stars, dust, and gas -- and a series of arms that spiral outward. Our solar system rests in one such arm.

However, though scientists have spent a lot of time studying the galaxy, there is a lot they do not know about it. For example, while they have evidence that our galaxy has star-forming regions at the outer edge of its disc, nobody is sure if those steadily increase the Milky Way's overall size.

To shed light on that question, the team in the new research analyzed other spiral galaxies that are similar to the Milky Way. Using the SDSS telescope for optical data, and the two space telescopes GALEX and Spitzer for near-UV and near-infrared data, the team studied the color and motion of stars in other galaxies.

After measuring the light in the distant regions, the team calculated how long it would take stars to move from their birthplace. That then showed if their host galaxies grew in size.

Such calculations revealed that galaxies like the Milky Way grow at roughly 500 meters per second. As a result, it is likely our galaxy grows at a similar rate.

"The Milky Way is pretty big already," explained lead researcher Cristina Martnez-Lombilla, a researcher at the Instituto de Astrofsica de Canarias, according to"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 percent bigger than today."

As the Milky Way may one day collide with the neighboring Andromeda Galaxy, this growth may not matter in the future. However, the information is still important because it helps astronomers better understand how certain galaxies operate.

The new research will be presented in a talk at the European Week of Astronomy and Space Science in Liverpool.


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