Surprising image provides new tool for studying a galaxy

An international group of astronomers, including George Heald (ASTRON / University of Groningen), has found a surprising and useful new probe of galactic magnetic fields. While studying gas halos around nearby galaxies, they were surprised when detailed studies with the National Science Foundation's Karl G. Jansky Very Large Array (VLA) showed that one of their subjects is not a single galaxy, but rather two, nearly perfectly superimposed on the sky to masquerade as one. The discovery allowed them to use the alignment to learn otherwise-unobtainable facts about the nearer galaxy.

As part of a study of 35 galaxies, the astronomers observed one called UGC 10288, a spiral galaxy more than 100 million light-years distant that appears edge-on as seen from Earth. Their multiple VLA observations in 2011 and 2012 produced the best radio-telescope images of that galaxy ever made. The detailed images surprisingly revealed a more-distant galaxy, with strong radio emission, almost directly behind UGC 10288. In previous images, the two galaxies had been blended together. Alignment of a foreground galaxy with such a strongly- emitting background galaxy with extended jets probably is the first such alignment found, the astronomers said.

The background galaxy is nearly 7 billion light-years from Earth.