The galaxy called M106 has been keeping astronomers up nights for about 45 years. Two starry arms spiral out from the nucleus. But radio and X ray images first taken in the early 1960s revealed two additional, ghostly arms. Astronomers knew that the so-called anomalous arms were mostly gas, and totally perplexing.
Now researchers from the University of Maryland think they’ve put their finger on those arms. By analyzing data from multiple observatories worldwide, the astronomers have confirmed suspicions that the ghostly arms are regions of gas heated by shock waves.
Two distinct jets of particles are constantly emitted from the core of the galaxy, blasting away some 30 degrees off kilter from the plane of the galaxy. The jets nevertheless manage to heat some gas near their path in the galactic disc, but also generate shock waves that further heat the gas, to millions of degrees. The jet-heated gas winds up looking like additional spiral arms radiating outside the visible spectrum. The explanation appears in the May 10th issue of the Astrophysical Journal.