The nearest galaxy, Andromeda, is approximately the same size as our Milky Way, rather than being two or three times larger as previously thought. This means that when the two galaxies merge in about 4 billion years, the Milky Way will not be completely “swallowed up” by Andromeda, as predicted by computer models.
According to a report in the Monthly Notices of the Royal Astronomical Society, a team led by astrophysicist Prajwal Kafle from the International Centre for Radio Astronomy Research (ICRAR) in Perth, Australia, has measured the mass of the Andromeda galaxy to be around 800 billion times that of the Sun.
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In comparison, the Milky Way has a mass of about 800-1,200 billion times that of the Sun. Based on this new information, the two galaxies, separated by about 2.5 million light-years, are roughly equivalent in size.
The Milky Way and Andromeda are the two largest galaxies in the so-called “Local Group,” a cluster of over 30 galaxies spanning 10 million light-years in diameter. Kafle states that this new knowledge completely changes our understanding of this group, and in the future, we may need to build new models to imagine what might happen when the two galaxies merge.
According to NASA, it seems that there won’t be a catastrophic collision of stars during the merger. However, they will be flung into different orbits, far from their previous positions. The models suggest that the solar system may be ejected further from the galactic center than it is now.
Previously, Andromeda was seen as the “giant” of the group, a potential threat to the survival of the Milky Way. It is the closest neighbor to our galaxy and one of the 10 galaxies visible to the naked eye from Earth.