Researchers using the Hubble Space Telescope took advantage of a naturally occurring zoom lens in space to capture an unprecedented quadruple image of an ancient supernova.
Between the supernova and the Earth-orbiting Hubble observatory lies a massive galaxy cluster whose gravity bends the path of the traveling photons. The existence of so-called "gravitational lenses" was proposed 100 years ago by physicist Albert Einstein. The first cosmic lens was discovered in 1979.
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"Einstein's theory of general relativity says that massive objects bend space and time. Light traveling close to massive objects will have their paths' bent," said astronomer Jennifer Lotz, with the Space Telescope Science Institute in Baltimore.
In addition to testing Einstein's theory of relativity, this type of curved light could be used to measure how fast the universe is expanding.
Astronomer Patrick Kelly, with the University of California Berkeley, and colleagues report this week about four different routes light from an ancient supernova took to reach the Hubble telescope after being deflected around an intervening elliptical galaxy. The phenomenon is known as an Einstein cross.
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"Basically, we get to see the supernova four times and measure the time delays between its arrival in the different images, hopefully learning something about the supernova and the kind of star it exploded from, as well as about the gravitational lenses," Kelly said in a statement.
The supernova will appear again in the next 10 years, as its light takes different paths around and through the gravitational lens.
The research is published in this week's Science.