Skip to comments.Astronomy Picture of the Day -- Hoag's Object: A Strange Ring Galaxy
Posted on 07/28/2013 1:57:51 AM PDT by SunkenCiv
Explanation: Is this one galaxy or two? This question came to light in 1950 when astronomer Art Hoag 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 now 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. The above photo taken by the Hubble Space Telescope in July 2001 revealed unprecedented details of Hoag's Object. More recent observations in radio waves indicate that Hoag's Object has not accreted a smaller galaxy in the past billion years. 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.
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Not seen one of these before.
Very neat and tidy...
“A splash in the cosmic pond”—Sagan describing ring galaxies. In a bulls-eye galaxy collision, there is an expanding shock front of star formation. Newly-formed but short-lived stars outshine the older ones by an order of tens of thousands, which is why only the expanding ring is readily visible.
What’s truly remarkable is that we are viewing this one from the “top”, from near one of the galactic poles, so it appears circular rather than elliptical. (Unless it is actually elliptical and we just have a luck viewing angle.) Note the guy in the background, at one O’clock who appears elliptical.
Thanks so much!
Also note it appears to be a bit red shifted as well. Assuming it’s the same size as the one in the foreground, it must be several times farther away.
The dark area is just the part that North Korea owns.