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A new technique for measuring the mass of galaxies has been applied to our closest galactic neighbour - and it has found that the Andromeda galaxy is roughly the same size as the Milky Way, and not two to three times bigger as was previously thought.

This means, when the two galaxies merge in about 4 billion years' time, the Milky Way won't be fully consumed by the Andromeda galaxy as previous models suggested.

Led by astrophysicist Prajwal Kafle from the International Centre for Radio Astronomy Research, the team found that the mass of the Andromeda galaxy is around 800 billion times the mass of the Sun, a measurement also known as a solar mass.