Ring of the Week: Mayall's Object
“Love is a burning flame
And it makes a fiery ring
Bringing hurt to the heart’s desire
I fell in the ring of fire”
– Johnny Cash
Before I venture any deeper into the mysterious world of Ring Galaxies, I thought I would give a quick introduction to the archetypal ring galaxy – the “Collisional Ring”.
Collisional Rings are formed when a smaller galaxy crashes through the centre of a larger galaxy. Just as throwing a stone into a pond creates an outwardly moving circular wave, a gravitational density wave is generated at the point of impact throwing matter out into a ring shape. Most Collisional Ring galaxies manage to hold onto a nucleus in the centre of the ring but sometimes the disturbance is so large that the nucleus is completely destroyed. Thanks to the work of Zoo members I have so far found about 125 Collisional Rings in the Galaxy Zoo (and still searching…!) so we can safely say that Collisional Rings are quite a rare phenomenon.
It is incredibly rare to see the galaxy collision actually taking place so my Ring of the Week this week is a fantastic Collisional Ring seen just after impact. Nick-named ‘Mayall’s object’, this ring is located in the constellation of Ursa Major, approximately 450 million light-years away. The image on the left is the Galaxy Zoo image and on the right is an image of the same galaxy taken by the Hubble Space Telescope. You can clearly see the elongated “bullet” galaxy blasting through the disc, creating a huge raggedy ring of stars.
The Hubble image is part of a collection of 59 images of merging galaxies released on the occasion of its 18th anniversary on April 24, 2008. (NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University))