Milky Way and Andromeda galaxy may not be on a collision course after all

The Milky Way and the Andromeda Galaxy may not collide in a few billion years after all; the probability of them missing each other is as high as 50 percent. This has been determined by an international research group using precise measurement data from the Hubble and Gaia space telescopes. Contrary to previous assumptions, the probability of the two galaxies colliding in the next five billion years is only 2 percent, they write.

Dozens of variables increase uncertainty

As research leader Till Sawala from the University of Helsinki explains, the new findings do not mean that previous calculations on the fate of the two galaxies were wrong. It's just that the much more comprehensive data now available allows us to explore many more possible scenarios. According to NASA, a total of 22 different variables were included that could influence the future orbits of the galaxies.

The team carried out around 100,000 simulations based on the measurement data to run through how the Milky Way and the Andromeda Galaxy are likely to move over the next 10 billion years. The previously predicted collision in five billion years is therefore quite unlikely. A collision is most likely in seven to eight billion years, but overall, it is just as likely that the two galaxies will miss each other completely.

Collision perhaps only later

However, the simulations have also indicated that the Milky Way and the neighboring Andromeda Galaxy will remain together even if they miss each other. A merger in the distant future is therefore possible. None of this is likely to have any consequences for the solar system: the Earth will become completely hostile to life in around a billion years, and the sun will burn out in five billion years. However, a galaxy collision would trigger a veritable explosion of star formation.

The study, which has now been published in the scientific journal Nature Astronomy, once again underlines the enduring value of the data collected by ESA's Gaia space telescope during its mission. Using a gigapixel camera, it continuously photographed the starry sky for more than ten years. As it moved around the sun with the Earth, the precise measurement data made it possible to determine the position of billions of stars with increasing accuracy thanks to the parallax measurement. In the spring, it had to be switched off due to a lack of fuel.

(mho)