Theory about Milky Way's formation challenged

Washington, Nov 22 : A new research has challenged the existing theory about the formation of galaxies like out own Milky Way.

The research, part of a multi-institutional project involving the University of Pittsburgh has challenged the longstanding theory that the bright extensions and rings surrounding galaxies are the remnants of smaller star clusters that struck a larger, primary galaxy, and then fragmented.

The research team was modeling disk galaxies for an unrelated astrological survey when they inadvertently discovered that stars in the main disk scattered when satellite galaxies, smaller galaxies surrounding larger ones, passed through.

The team's computer simulations of galaxy formation suggests that disk galaxies most likely began as flat, centralized star clusters.

Smaller galaxies collided with and tore through these disks billions of years ago, casting disk stars outward into the wild extensions present now; the bright center is the original formation.

In addition, vast bodies of dark matter, which is a low-density, high-gravity invisible mass thought to occupy nearly one-quarter of the Universe, swept through these disks and further pulled stars from the main disk.

The researchers' scenario largely applies to the formation of the rings and long flares of stars that surround such galaxies as the Milky Way, according to Andrew Zentner, a professor of physics and astronomy in Pitt's School of Arts and Sciences.

But, the model also presents a possible solution to how star spirals, the arcs of stars that radiate from the center of some disk galaxies, maintain their shape.

Spirals form as a result of any disturbance to the star disk, Zentner said.

However, the prolonged disturbance of a galaxy and dark matter expanse passing through a disk explains why the spirals seem to never recede.

"Our model suggests that a violent collision throws stars everywhere and continues moving through the disk, disturbing its structure," Zentner said.

"It also has been known for some time that for star spirals to develop and maintain their well-known form, there must be a prolonged disturbance. We show that large masses moving through a galaxy could provide that disturbance," he added.

ANI