What you’re seeing here is an illusion. The light is real but the bizarre blue ring is a fake — an imposter created by a cosmic trick called gravitational lensing.
What’s more is that Earth is perfectly positioned in the universe to see this exact image. If there are alien astronomers out there in a distant galaxy, chances are good that they would not see this blue ring the same way we do.
That’s because it takes a special type of alignment to create the nearly complete ring shown here. This blue ring is a stunning example of what astrophysicists call an Einstein ring and was captured by the Hubble Space Telescope in 2011.
We can only see a ring like this if the two objects that create the ring are lined up one directly behind the other. In this case, a bright blue galaxy is floating in space behind the red galaxy at the center of the blue ring.
Normally, we would not be able to see the blue galaxy because the red galaxy would be blocking our view. But, we know from Einstein’s theory of general relativity that gravity warps the fabric of space and, therefore, the path along which light travels. And the larger the object, the stronger its gravitational pull, and the more it distorts the light that passes through the warped space.
When this happens, we see bizarre images like this blue ring. The process by which powerful gravitational fields bend light is called gravitational lensing because it not only distorts the image, it magnifies it. Watch how this works in the animation below:
There are numerous cases of gravitational lensing throughout the universe, but few are quite as spectacular as this Hubble image, shown below.
Below is an example of what gravitational lensing can do to objects when they’re not perfectly aligned. Notice all of the curved streaks of light in this Hubble image, which are the result of gravitational lensing.
Because gravitational lensing magnifies the light from distant objects, it has become a crucial tool that astrophysicists use to study objects that they might not otherwise see. This is important for understanding what the universe looked like in its early stages of evolution, just a couple billion years after the Big Bang.
We’re seeing the blue galaxy, whose light made the blue ring in the Hubble image, as it was just 3 billion years after the Big Bang — more than 10 billion years ago.
In addition to learning about the distant object whose light is being distorted, astrophysicists use gravitational lensing to learn about the object that is doing the distorting. In most cases it is either a massive galaxy or a cluster of galaxies.
Measuring how strongly an object’s image is magnified, astrophysicists can deduce the mass of the foreground galaxy or galaxy cluster. In the case of this beautiful Hubble image of a blue ring, the foreground galaxy is of a special class called Luminous Red Galaxies. The galaxy at the center of the blue ring is about ten times more massive than our home galaxy, the Milky Way.
This is just one of more than a dozen stunning finds from the Hubble’s 24 years of operation that have taught us about the universe we call home.
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