What threatens the Milky Way with a collision with the Andromeda galaxy

Our closest space neighbor, the Andromeda galaxy, is speeding towards the Milky Way at a speed of 400,000 km / h. But there is nothing to be afraid of – two galaxies will collide not earlier than in a few billion years.

Until recently, scientists believed that it was our galaxy that would suffer the most from the collision, because it is smaller than its neighbor. Now this is not so certain: recent research by the International Center for Radio Astronomy Research shows that Andromeda is actually not much heavier. In fact, the two galaxies are roughly the same size. This is stated in a study published in the Monthly Notices of the Royal Astronomical Society.

It is not easy to estimate even the approximate mass of a galaxy. The brightly glowing stars that make up the visible portion of this huge system actually contribute very little to the total mass of the galaxy. Most are black holes and dark matter, which are difficult to measure even with ultra-modern telescopes. To get around this factor, ICRAR scientists used a relatively new method for calculating the mass of Andromeda.


Using data from analyzes of very fast stars in the Andromeda galaxy detected by the William Herschel Telescope, the researchers were able to calculate the galaxy’s escape velocity. The exit speed in this case indicates how fast the object must move to completely leave the orbit of the galaxy. By working backwards from that number, the researchers were able to calculate the mass of Andromeda. They found that, compared with previous estimates, the mass of the galaxy is about the same as the mass of the Milky Way, that is, about 800 billion times the mass of the Sun. Considering this, in the distant future, our galaxy may be much more fortunate – perhaps, in the process of a catastrophic collision, the two space systems will merge together.

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