Weird line of galaxies may have been created by a cosmic bullet

A wierd line of dwarf galaxies may have been the end result of a bullet-like cosmic collision.

Michael Keim at Yale University and his colleagues used the Keck Observatory in Hawaii to check a distinctive path of 12 small and faint dwarf galaxies about 75 million gentle years from the Milky Way.

The orientation and velocity of the galaxies recommend they originated from a head-on collision between two of them, known as NGC 1052-DF2 and NGC 1052-DF4. The collision left gasoline in its wake, which finally clumped into teams of stars underneath gravity.

“They’re very unique,” says Keim. “It’s the only system like this that’s known.”

There is a comparable assortment of bigger galaxies known as the Bullet Cluster, so Keim and his colleagues have nicknamed this method the “bullet dwarf”.

The two galaxies are thought to have crashed into one another at 350 kilometres per second relative to one another about 9 billion years in the past. As they handed by way of each other, gasoline was ripped from every galaxy. “It’s unlikely that two stars will collide,” says Keim. “But that’s not true for clouds of gas.”

Curiously, every of the clumps of stars left behind from the collision is devoid of darkish matter. This may be very uncommon as most galaxies have a great amount of darkish matter, generally accounting for greater than 90 per cent of their complete mass.

Keim and his workforce suppose this may be as a result of whereas the gasoline was torn from the galaxies, darkish matter doesn’t work together with matter – and even itself – so it was unaffected.

That might refute various concepts for darkish matter that recommend our proof for its gravitational affect end result from a mismeasurement of how stars and galaxies behave. “This is saying dark matter is a particle, and it can become separated from a galaxy,” says Keim.