A head-on collision between two galaxies only 30 million light-years away has produced a ring of intense star formation – like the Cartwheel Galaxy but 40 times closer to Earth. The ring arises when two galaxies of similar mass collide so that the smaller one moves towards the centre of the larger one along the latter’s smaller axis, as if towards the bullseye of a target. The collision compresses the galactic gas, triggering star formation in a ring.
This image, taken with the UK Schmidt Telescope in Australia by a team led by Prof. Quentin Parker at the University of Hong-Kong and Prof. Albert Zijlstra at the University of Manchester, shows Hα emission from gaseous hydrogen. Only about 20 such complete rings are known.
The structure – dubbed Kathryn’s Wheel – lies behind a dense star field, close to a very bright foreground star, and is in an area with few other galaxies, making the odds of a collision low. Prof. Parker said: “Not only is this system visually stunning, but it’s close enough to be an ideal target for detailed study.” The research is published in Monthly Notices of the Royal Astronomical Society. (Ivan Bojicic/the scientific team)
This image is published in the October 2015 issue of Astronomy & Geophysics.