TWO researchers from an astrophysics institute in Pune have discovered one of the most distant spiral galaxies ever observed - a massive, well-formed system that existed when the universe was just 1.5 billion years old. The finding adds to growing evidence that the early universe was more evolved than previously assumed, they said. Named ‘Alaknanda’ after a Himalayan river, the granddesign spiral galaxy challenges existing theories on how early complex galactic structures formed, the researchers said. “Finding such a wellformed spiral galaxy at this early epoch is quite unexpected.

 

It shows that sophisticated structures were being built much earlier than we thought possible,” one of the researchers said. Despite being present when the universe was only 10 per cent of its current age, Alaknanda appears strikingly similar to the Milky Way. The findings have been published in the European journal ‘Astronomy & Astrophysics’. Using NASA’s James Webb Space Telescope (JWST), researchers Rashi Jain and Yogesh Wadadekar from the Pune-based National Centre for Radio Astrophysics identified the galaxy. “Alaknanda lies at a redshift of about4,meaning its light has travelled more than 12 billion years to reach Earth,” Jain said. “We are seeing this galaxy as it appeared just 1.5 billion years after the Big Bang. Finding such a well-formed spiral galaxy at this early epoch is quite unexpected.

 

It shows that sophisticated structures were being built much earlier than we thought possible,” she said. Using JWST’s infrared sensitivity and resolution, the team found that Alaknanda contains roughly “10 billion times the mass of the Sun in stars” and is forming new stars at about 63 solar masses per year, nearly 20 to 30 times the Milky Way’s current rate, the researchers said in a release.

 

Before JWST, astronomers believed early galaxies were chaotic and clumpy,with stable spiral structures emerging only after several billion years, they said. Dominant models suggested that early galaxies were too “hot” and turbulent to form ordered disks capable of sustaining spiral arms, the release said. “Alaknanda tells a different story,” Wadadekar said. “This galaxy had to assemble 10 billion solar masses of stars and build a large disk with spiral arms in just a few hundred millionyears

 

That’s incredibly rapid by cosmic standards,”he said. Jain said the team chose the name Alaknanda - one of the two main head streams of the river Ganga - because of its connection to the Milky Way.