In about 4.5 billion years, the Milky Way and Andromeda galaxies will collide with each other, resulting in a much larger galaxy. While that huge period of time is also the age of our own solar system, there’s no telling if humanity will live for another 4.5 billion years.
But in one peculiar way, Andromeda is already touching our galaxy. Actually, the two gigantic gas halos of the two galaxies are intersecting with each other, according to new research involving the Hubble Space Telescope.
Andromeda’s halo extends out 1.3 million light-years
This allows the halo of Andromeda to intersect the one of our Milky Way galaxy.
Samantha Berek, who is co-investigator of the new study and also an undergraduate student at Yale University, brings precious info about the halo of gas:
This reservoir of gas contains fuel for future star formation within the galaxy, as well as outflows from events such as supernovae. It’s full of clues regarding the past and future evolution of the galaxy, and we’re finally able to study it in great detail in our closest galactic neighbor.
While Andromeda’s halo has two layers of gas that form distinct shells, the lead author Nicolas Lehner explains that the inner shell is far more complex and dynamic. Lehner further explains:
The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.
Andromeda (aka Messier 31, M31, or NGC 224) is harboring about one trillion stars, which is much more than our own galaxy. Milky Way has only between 100 billion and 200 billion stars. However, Andromeda is also much bigger than the Milky Way: our neighboring galaxy has 220,000 light-years in diameter, compared to only 100,000 light-years that the Milky Way measures.
The new study was published in The Astrophysical Journal.