Astronomers have captured the images of the most distant dying stars or supernovas ever observed, using a new technique that could provide new insights into the formation of the earliest galaxies. A supernova exploding stars occur when a massive star more than 50 times the mass of the Sun dies in a powerful bright explosion after it ran out of nuclear fuel and could no longer support its own weight.

The new technique used to find it could reveal tens of thousands of other ancient supernovae, tracing out how the universe became seeded over time with heavy elements. Light from the exploding stars, or supernovae, began its journey to Earth 11 billion years ago, not long after the "Big Bang" that created the cosmos. The next furthest large supernova known is six billion light years away. Professor Jeff Cooke, lead researcher on the study and an astronomer at the University of California, Irvine, found four supernovae, including the two distant objects, after analysing images from the Canada-France-Hawaii Telescope in Hawaii. "Using this method, we should be able to see objects much farther away and therefore much farther back in time, and actually see some of the first stars that ever lived," Cooke told New Scientist.

Cooke, who has analysed just a fifth of the survey data, expects more ancient supernovae to be found in the project. In distant galaxies, even the biggest supernovas are too faint to be detected using this method and, until now, astronomers have been confined to looking in the Milky Way and its neighbouring galaxies. By analysing the light from early supernovas, astronomers can determine the chemical elements present in the gases being ejected from the star. Comparing these results with the chemical composition of galaxies today can help to determine the age of galaxies such as the Milky Way. According to the new research, which is reported in the journal Nature, the new technique involves blending together pictures taken over the course of a year, and comparing them with image compilations from other years. "If you stack all of those images into one big pile, then you can reach deeper and see fainter objects. It's like in photography when you open the shutter for a long time. You'll collect more light with a longer exposure," Cooke said. He said the universe is about 13.7 billion years old, "so really we are seeing some of the first stars ever formed".

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