The three largest galaxies in our Local Group of Galaxies are our Milky Way along with the Andromeda and Triangulum galaxies.
The Triangulum galaxy is about 2.7 million light-years from our Milky Way.
The Triangulum galaxy’s diameter is about 60,000 light-years, or about 60% that of our Milky Way. 
It’s thought to contain some 40 billion stars.
In contrast, there are 100-400 billion stars in the Milky Way and a trillion stars in the Andromeda galaxy. It’s well known that the Andromeda galaxy is moving toward our Milky Way and that a collision between the two galaxies will occur some 4 billion years from now.
Around 6 billion years from now, the two galaxies will merge to form a single elliptical galaxy.
Meanwhile, the fate of the Triangulum galaxy isn’t known for certain.
It might participate in the collision between the Milky Way and Andromeda galaxies.
It might someday be torn apart and absorbed by the Andromeda galaxy or continue to orbit the merged galaxy.
It’s safe to say that the fate of these great galaxies is beyond human knowledge at this time!

Credits
Visualization: NASA, ESA, and F. Summers (STScI);
Simulation: NASA, ESA, G. Besla (Columbia University), and R. van der Marel (STScI)

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