Saturday, January 29, 2011

Polar Ring Galaxies

Polar Ring Galaxies have a large ring of material perpendicular to the main galaxy. See also Polar Disk Galaxy found in Wall between Voids.
 Polar Ring  Galaxy NGC 4650A: A Disk of Red Stars Ringed By Dust, Gas, and More Stars

Another Void Model of Cosmic Acceleration

Supernovae observations published in 1998 surprisingly indicated that the expansion of the universe is accelerating - with the standard explanation being Dark Energy. A very different explanation for this acceleration is the possibility that we are near the center of a gigantic void in the distribution of galaxies. Many such Voids (smaller, but still mind-bogglingly large themselves) have been found. The preprint Reconciling the local void with the CMB elaborates on earlier proposals by relaxing the assumption that the Cosmic Microwave Background (CMB) is scale-invariant.
Here's an earlier blog post on this topic: Void Models of Cosmic Acceleration.