Galactic Spin Exclusion Principle

Spiral Galaxy Winds Backwards
By Jeremy Hsu
Staff Writer
posted: 10 January 2008
06:19 am ET

New discoveries in a strange spiral galaxy show it has a pair of arms winding backward compared to the typical direction for most galaxies.

"While the existence of a galaxy with a pair of 'backward' arms may seem like an inconvenient truth to many, our latest analysis indicates it is, nonetheless, a reality," said Gene Byrd, a University of Alabama astronomer.

Most spiral arms observed so far tend to trail in the wake of their galaxy's spin, meaning they wind in the direction opposite the rotation. The strange galaxy, known as NGC4622, lies 200 million light years away and has a large outer arm pair that winds clockwise.

Byrd and his colleagues analyzed a 2001 Hubble Space Telescope image of the galaxy and found a previously hidden inner pair of arms winding counter-clockwise. Whichever way the galaxy happens to rotate, one pair of arms ends up turning in the unusual direction.

Opposites attract.