Is this one galaxy or two? Astronomer Art Hoag first asked this question when he chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark.
How Hoag’s Object formed remains unknown, although similar objects have been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished.
This image, taken by the Hubble Space Telescope in July 2001, revealed unprecedented details of Hoag’s Object. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o’clock) is yet another ring galaxy that likely lies far in the distance.
Originally published by Cosmos as A galactic doughnut
Cosmos
Curated content from the editorial staff at Cosmos Magazine.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.
