The invisible galaxy plunges into the Milky Way

A galaxy that humans cannot see collides with the Milky Way but it retains its shape.

Newscientist said, in 2008 astronomers discovered a cloud of matter with a mass equivalent to about a million suns colliding with the Milky Way. Now scientists have proved that the cloud is big enough to become a galaxy. It has a length of 11,000 light years, a width of 2,500 light years. When plunging into the cloud the galaxy moves at a speed of 240 km / s.

The cloud of hydrogen gas is not mixed into the Milky Way during the collision, although it is much smaller than the "rival". In addition, the cloud's orbit indicates that it once penetrated the Milky Way's physical perimeter about 70 million years ago.

Image of hydrogen cloud rushing into the Milky Way by telescope.Photo: Newscientist.

To preserve the shape after that piercing, the cloud must contain a large amount of matter to create a strong gravitational force. That gravitational force makes matter in the cloud not separate from each other, so that it does not tear after a stab. Calculations by Matthew Nichols and Joss Bland-Hawthorn - two scientists at the University of Sydney (Australia) - show that cloud mass was about 100 times that of today.

Leo Blitz, an astronomer from the University of California (USA), said that many similarly-mass galaxies exist near the Milky Way.

"Simulated models of galaxy formation show that a galaxy the size of the Milky Way must have about 100 smaller galaxies. But so far we have found some such galaxies in the "It's possible that the remaining galaxies are so dark that we don't see them. It's invisible galaxies," Blitz explained.

According to Sydney, last year the cloud was about 8,000 light-years from Earth. It is composed primarily of hydrogen gas.