Kailash Chandra Sahu, an astronomer with the Space Telescope Science Institute, and colleagues used the Hubble Space Telescope to search among more than 5,000 stars for a precise and slight asymmetric alignment between two stars. This alignment, the researchers knew, would result in what is known as an “asymmetrical Einstein ring.” In an Einstein ring, a circle of light forms by one star passing in front of another from our vantage point. An asymmetrical Einstein ring occurs when these two stars are just offset. That arrangement, if they could find it, would allow them to determine the mass of the star in front.
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