Double Einstein Ring Found
A few days ago, during the cool-kids camp, HubbleSite released this image:
Image Credit: HubbleSite
This is a very interesting image. On the left, the bright blob in the center surrounded by rings is a galaxy and the gravitational field from that galaxy is warping the light of two more galaxies directly behind it (causing the rings).
The image on the right is a zoomed in version with the central galaxy removed.
Gravity from the central blob is bending the light from the distant galaxies aligned directly behind it into a ring much like a lens bends light as it enters it. This is known as gravitational lensing.
The animation at right is one I found on wikipedia. This isn’t what’s going on in the Hubble image, but it does demonstrate how gravity can bend light into rings.
In the above Hubble image, there are two rings, a thick, bright one with a fainter, somewhat broken one just outside it. It doesn’t look like it, but those rings are galaxies, and if that center blob wasn’t there, they’d be more recognizable.
Apparently, this is the first time TWO concentric rings like this have been found. It’s a product of a lucky alignment, the background galaxies lensed by the foreground galaxy happen to be directly behind the foreground galaxy, making these rings concentric.
The massive foreground galaxy is almost perfectly aligned in the sky with two background galaxies at different distances. The foreground galaxy is 3 billion light-years away. The inner ring and outer ring are comprised of multiple images of two galaxies at a distance of 6 billion and approximately 11 billion light-years. (Full Release)
This effect has much to do with the work I’m doing on the Dark Energy Survey. Our camera is designed to look at a very large area of the sky (3 degrees at a time) and we will tile these images to cover 5000 square degrees of the South Galactic Cap.
One of the things we’ll be getting are statistics on lensing of galaxies like this one. It turns out that the fraction of dark energy in the universe can be inferred by looking at large numbers of gravitational lenses and seeing where they are and how they are distributed (among other things).
BTW, I’m not totally sure why they’re called Einstein Rings, I imagine it’s because Einstein first predicted they should be there. I prefer gravitational lens, of which a ring is a special case.
Rick Fienberg, the editor of Sky and Telescope had a good post about this too.
Gravitational lens animation credit: wikipedia
Einstein Rings Diagram Credit: Jodrell Bank Observatory
Technorati Tags: cosmology, dark energy, gravitational lensing, hubble space telescope, hubblesite
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POSTED IN: Astronomy Porn, cosmology
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