New research provides a first description of a well-defined elliptical-like core surrounded by two circular rings - a galaxy that appears to belong to a class of rarely observed, Hoag-type galaxies.
This work was done by scientists at the University of Minnesota Duluth and the North Carolina Museum of Natural Sciences.
"Less than 0.1% of all observed galaxies are Hoag-type galaxies," says Burcin Mutlu-Pakdil, lead author of a paper on this work and a graduate student at the Minnesota Institute for Astrophysics, University of Minnesota Twin Cities and University of Minnesota Duluth.
Hoag-type galaxies are round cores surrounded by a circular ring, with nothing visibly connecting them. The majority of observed galaxies are disc-shaped like our own Milky Way. Galaxies with unusual appearances give astronomers unique insights into how galaxies are formed and change.
The researchers collected multi-waveband images of the galaxy, which is only easily observable in the Southern Hemisphere, using a large diameter telescope in the Chilean mountains. These images were used to determine the ages of the two main features of the galaxy, the outer ring and the central body.
While the researchers found a blue and young (0.13 billion years) outer ring, surrounding a red and older (5.5 billion years) central core, they were surprised to uncover evidence for second inner ring around the central body.
To document this second ring, researchers took their images and subtracted out a model of the core. This allowed them to observe and measure the obscured, second inner ring structure.
"We've observed galaxies with a blue ring around a central red body before, the most well-known of these is Hoag's object.
However, the unique feature of this galaxy is what appears to be an older diffuse red inner ring," says Patrick Treuthardt, co-author of the study and an astrophysicist at the North Carolina Museum of Natural Sciences. ■
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