A cosmic mirage where a galaxy splits a distant quasar into four

Space · Published 30 October 2026 Swipe more like this →

In short: Look closely at the constellation Pegasus and you might see a celestial optical illusion. Known as Einstein's Cross, this phenomenon occurs when a massive foreground galaxy acts as a natural magnifying glass, warping the light of a quasar billions of light-years away into a distinct cross shape.

The phenomenon is technically known as gravitational lensing. It occurs when light from a distant source passes close to a massive foreground object. According to the principles of general relativity, the gravity of that foreground object bends the path of the light. In the specific case of G2237 + 0305, a galaxy located approximately 400 million light-years from Earth sits directly in front of a quasar situated about 8 billion light-years away. Because the galaxy is 20 times closer to us than the quasar, its gravitational field acts as a lens, creating multiple images of the same distant source.

The resulting visual is a striking arrangement of four bright outer images surrounding the diffuse central region of the foreground galaxy. A gap of merely 1.6 arcseconds exists between the top and bottom pictures. While four images are clearly visible, astronomers actually expect a faint fifth image to exist near the center of the galaxy, though it requires careful image processing to confirm its presence in high-resolution exposures like those from the Faint Object Camera on the Hubble Space Telescope.

Beyond its aesthetic beauty, Einstein's Cross serves as a vital laboratory for astrophysics. By measuring the relative positions and brightness of the four images, scientists can effectively "weigh" the foreground galaxy to understand its mass distribution. Furthermore, by measuring the time delays in brightness changes across the different lensed images, researchers can help determine the Hubble Constant—a fundamental value used to calculate the size and age of our universe.

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