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Milky Way Will Collide With Andromeda Galaxy
Astronomers have always believed our galaxy may collide with its cosmic neighbour Andromeda - and now the doomsday scenario has been confirmed.
Nasa has spent years tracking the direction of the Andromeda galaxy through its Hubble Space telescope.
The US space agency confirmed its precise observations "remove any doubt that it is destined to collide and merge with the Milky Way".
But there is little point in panicking yet - the big crash will not happen for another four billion years.
And after the two finally meet it will then take another two billion years for them "to completely merge under the tug of gravity and reshape into a single elliptical galaxy similar to the kind commonly seen in the local universe," Nasa added.
The stars inside the galaxies will not collide, however, according to Nasa they will be "thrown into different orbits around the new galactic centre".
Scientists have estimated that Andromeda, also known as M31, is moving towards our galaxy at a speed of 250,000 miles (402,000kms) per hour - the same speed as it would take to travel from Earth to the Moon in an hour.
Andromeda, which is currently 2.5 million light-years away, was first spotted as "a little cloud" by the Persian astronomer Abd al Rahman al Sufi in 964.
For more than 100 years scientists have been trying to discover what direction of movement the galaxy was taking, and repeated observations over a five-to-seven year period from the Hubble telescope have finally allowed them to determine its course.
Gurtina Besla of Columbia University in New York said: "In the worst-case scenario simulation, M31 slams into the Milky Way head-on and the stars are all scattered into different orbits.
"The stellar populations of both galaxies are jostled, and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular orbits.
"The galaxies' cores merge, and the stars settle into randomised orbits to create an elliptical-shaped galaxy."