Indian scientists spot Milky Way-like galaxy from 12 billion years ago

BBC:

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.