Astronomers in India say their discovery of a massive galaxy from when the Universe was only 1.5 billion years old challenges our understanding of how galaxies were formed in the early period after the Big Bang. Simply put, if the Universe is 13.8 billion years old, it means we're seeing a galaxy from 12 billion years ago when the cosmos was only one-tenth of its current age. Scientists say galaxies that formed so early were found to be mostly irregular in shape and chaotic. But when researchers Rashi Jain and Yogesh Wadadekar used James Webb Space Telescope (JWST) to peer into the Universe's early past, they spied a "fully-formed spiral galaxy — a massive, beautifully structured cosmic pinwheel". Their research was published in Astronomy and Astrophysics, a leading European journal, in November. "The galaxy looks remarkably similar to our own Milky Way, despite being present when the universe was only 10% of its current age," said Prof Wadadekar, adding that they've named it Alaknanda after a Himalayan river. The galaxy was spotted by Ms Jain, a PhD researcher at the Pune-based National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research (NCRA-TIFR) earlier this year. Ms Jain says she was "really excited" when she spotted the galaxy while poring over the data and images from James Webb, the $10bn telescope launched jointly by the US, European and Canadian space agencies in 2021. "I had been looking at details of 70,000 objects and there was only one there that was a grand design spiral galaxy, spanning approximately 30,000 light-years in diameter," she says. In simple words, it means that the galaxy had two symmetrical arms emanating from a disc at the centre, wrapping around a bright central bulge, she explains. "We could see the typical 'beads-on a-string' pattern which is like clusters of stars along the spiral arms, similar to what we see in nearby spiral galaxies today." When she told her supervisor Prof Wadadekar, his initial reaction was of disbelief. "It's astonishing how such a large galaxy with spiral arms could have existed just 1.5 billion years after the Big Bang," he told the BBC. "This galaxy had to assemble 10 billion solar masses of stars and simultaneously form a large disc with spiral arms in just a few hundred million years. That's incredibly rapid by cosmic standards," he said. According to Nasa, there are an estimated hundred billion galaxies and many began forming within millions of years of the Big Bang. Astronomers have long believed that the Universe at the time – a period known as cosmic dawn — was very chaotic and the galaxies were small and low in mass. "But this galaxy is a different beast," says Prof Wadadekar. "It's massive, it's one-third of the Milky Way in size, and has 10 billion stars. The galaxy is forming new stars at a rate that's roughly 20-30 times faster than our Milky Way's current star formation rate." Since James Webb began operations, astronomers have been finding newer, more distant galaxies. In images shared by Nasa in initial years, many looked like red blobs or a faint smudge. But in recent years, Webb has been discovering more sophisticated structures, including spiral galaxies — and the new galaxy's discovery adds to that pile of growing evidence that early Universe was much more creative. "Finding such a well-formed spiral galaxy so far back in time is a rare exception, but such exceptions challenge our understanding of the universe's early past and how galaxies formed and evolved," Ms Jain says. "This galaxy shows that Universe was much more mature early on and that sophisticated structures were being built in our universe much earlier than we thought possible," she adds. The information about the new galaxy, however, is from 12 billion years ago — the galaxy lies at a distance from where its light has travelled for that many years to reach us. "We can see into the past because the light has reached us. A galaxy's lifetime is so big that we can't see it from start to finish, so we do statistical studies," says Ms Jain. So is there a status update? What's happened to it? Is it still there – and in what shape and form? "When people ask me about where it is at present, I tell them wait for 12 billion years to see where it is now," says Prof Wadadekar. For the moment though, the researchers say they would apply to do follow-up observations with James Webb or the Alma observatory in Chile to understand how the newly discovered galaxy managed to create its spiral arms. Because the keys to our present and future, they say, lie in the past. — BBC
