The Milky Way is expected to collide with neighboring Andromeda galaxy in 4 billion years, the U.S. space agency NASA said Thursday in a statement.

Years of "extraordinarily precise observations" by NASA's Hubble Space Telescope tracking the motion of the Andromeda galaxy "remove any doubt that it is destined to collide and merge with the Milky Way," NASA said. "It will take four billion years before the strike."

Computer simulations derived from Hubble's data show that it will take an additional 2 billion years after the encounter for the interacting galaxies to completely merge and reshape into a single elliptical galaxy similar to the ones commonly seen in the universe.

Although the galaxies will plow into each other, stars inside each galaxy are so far apart that they will not collide with other stars during the encounter. However, the stars will be thrown into different orbits around the new galactic center. Simulations show that our solar system will probably be tossed much farther from the galactic core than it is today.

"It is likely the sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed," NASA said.

To make matters more complicated, Andromeda's small companion, the Triangulum galaxy, will join in the collision and perhaps later merge with the Andromeda/Milky Way pair.

Andromeda is now 2.5 million light-years away and is moving toward the Milky Way at a speed of around 250,000 miles (400,000 kilometers) per hour.

The universe is expanding with an accelerating pace, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them.

Hubble's deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.

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