Researchers have revealed through a new study of more than 20,000 merging galaxies that collision between two different sized galaxies causes the smaller one to stop making new stars. On the other hand, when two galaxies of similar sizes collide, the star production rate for both starts taking place at a much faster rate.

"When two 'giants' collide, they both increase their stellar birth rate, but when one galaxy significantly outweighs the other, the 'giant' begins rapidly forming new stars, whereas the 'dwarf' suddenly struggles to make any at all", said astrophysicist Dr. Luke Davies, from the UWA node of ICRAR.

Davies added that Andromeda, our nearest major galactic neighbor, is travelling ferociously at 400,000 kms per hour to hit the Milky Way. However, the collision between the two galaxies would not take place before another four billion years or so, said Davies.

Astronomers were earlier of the belief that birth of new stars takes place at a much faster rate after two galaxies smash into each other than if they remained separate.

However, researchers have now learnt that a galaxy's rate of producing stars largely depends on its size in this galactic car crash. Davies explained that when two different sized galaxies collide, the larger one takes away its smaller companion's gas, which is the fuel required by galaxies to form stars. Another possibility is larger galaxy prevents the smaller one from obtaining the new gas required to form more stars.