A composite image in radio and optical of NGC 4632. (J. English (U.Manitoba), with support of T. Jarrett (UCT) and the WALLABY team: ATNF/ASKAP:Suburu/Hyper Suprime Camera)
What we thought was a pretty normal spiral galaxy not far from the Milky Way has revealed a hidden surprise.
NGC 4632, some 56 million light-years away, is circled by a huge ring of gas that wraps around the galaxy at a highly inclined angle to its galactic plane. Why didn't we see it until now? It's invisible in most of the electromagnetic spectrum, appearing only when we stare at the sky with radio telescopes.
The discovery could put NGC 4632 in a class of extremely rare galaxies known as polar ring galaxies – but also suggests that these galaxies might not be as rare as we thought. Rather, NGC 4632 could mean that we've just been looking at them in the wrong light.
"The findings suggest that one to three per cent of nearby galaxies may have gaseous polar rings, which is much higher than suggested by optical telescopes. Polar ring galaxies might be more common than previously thought," says astrophysicist Nathan Deg of Queens University in Canada.
"While this is not the first time astronomers have observed polar ring galaxies, NGC 4632 is the first observed with ASKAP and there may be many more to come."
Polar ring galaxies are pretty much what they sound like: galaxies with a ring of material – dust, gas, and stars – that orbits around, or close to, the galaxy's poles; that is, perpendicular to the galactic plane. READ MORE...
