June 24, 2012
Photographers: Alex Tudorica and David Muelheims
Summary Author: Alex Tudorica; Alex's Web site
This colorful image of the Crab Nebula, a vestige of a supernova in the constellation of Taurus first observed in 1054, was taken from the Argelander Institute for Astronomy in Bonn, Germany. Here, polarized light filtered at different angles was superimposed on a "normal" photograph of the Crab nebula. The red color comes from an arbitrary initial polarization angle, green color shows the nebula at an angle 45 degrees more than the initial polarization angle and blue light shows the nebula with the polarizing filter rotated by 90 degrees compared to the initial position. Polarized light enhances the contrast between a nebula and the background sky, or a bright nearby star, since the reflection of light on such objects partially polarizes them. Polarimetry is also useful for detecting exoplanets because even though starlight is unpolarized, starlight reflected by the atmosphere of a planet is in fact polarized. Image taken on December 15, 2011.
Photo details: Images taken with a 0.5m Cassegrain telescope; total exposure time of about 4 hours; SBIG STL 6303E camera; L, red, green, blue and Ha and OIII filters.