The Milky Way’s neighbouring galaxy, Andromeda, was formed
in a colossal crash between two smaller star systems no
more than three billion years ago when Earth already
existed, researchers said Wednesday.
Calculating the birth date of the galaxy has been a major
challenge for astrophysicists given the vast age gap between
the different stars it is made up of.
For the latest study, French and Chinese researchers led by
Paris Observatory astronomer Francois Hammer used “the most
powerful available computers in France” to crunch about a
terabyte of data—the equivalent of two million 500-kilobyte
This allowed them to zoom in on “the physical mechanisms of
the Andromeda formation, so lifting the veil on its origin,”
the observatory said in a statement.
The results were published in the Monthly Notices of the
Royal Astronomical Society.
Previous research had noted one major difference between our
own galaxy and Andromeda—long considered twin clusters, the
team pointed out.
In Andromeda, certain stars orbit erratically while in the
Milky Way, all stars observe a simple rotation
around the galaxy’s centre.
The star agitation was due to the galaxy’s “recent”
formation, the team said.
The data showed that between seven and 10 billion years ago,
two galaxies—one four times more massive than the other—found
themselves on a collision course.
The team simulated both precursor galaxies‘ trajectories and calculated that they
fused between 1.8 billion and three billion years ago to
Two reconstructions of the event can be seen below:
Stream of stars in Andromeda satellite galaxy shows cosmic