“We have named it Alaknanda, after the Himalayan river,” Professor Yogesh Wadadekar at the National Centre for Radio
Astrophysics of the Tata Institute of Fundamental Research (NCRA-TIFR) in Pune said Tuesday while announcing the
Rashi Jain, a PhD student who led this research under Wadadekar’s guidance, said the discovery was a little unexpected.
“The galaxy looks remarkably similar to our own Milky Way despite being present when the universe was only 10 per cent
of its current age,” she said.
The discovery has been published in the leading European astronomy journal Astronomy and Astrophysics.
The striking thing about Alaknanda is its textbook spiral structure. The galaxy has two well-defined spiral arms
wrapping around a bright central bulge, spanning approximately 30,000 light-years in diameter. According to the current
understanding of scientists, the earliest formed galaxies did not have well-defined structures, were chaotic and clumpy,
extremely hot and turbulent. But Alaknanda is nothing like that.
“Finding such a well-formed spiral galaxy at this early epoch is quite unexpected. It tells us that sophisticated
structures were being built in our universe much earlier than we thought possible,” Jain said.
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The discovery was made using NASA’s James Webb Space Telescope (JWST), the most powerful piece of observation equipment
put into space. Launched in December 2021, JWST has already produced data that is redefining our understanding of the
universe. This includes spotting some of the oldest galaxies in the universe, those that were formed just a few hundred
million years after the Big Bang.
Jain explained the reason why the researchers decided to name it Alaknanda. “Alaknanda is a spiral galaxy located about
12 billion light years away and has a prominent grand design spiral structure just like our own galaxy, the Milky Way.
Just as Alaknanda is the sister river of Mandakini river, which is also the Hindi name for our own Milky Way galaxy, we
thought it fitting to name this distant sister after the Alaknanda river,” she said.
Jain said the discovery of Alaknanda adds to the growing body of evidence coming from JWST that the early universe was
more mature than previously thought.
Wadadekar told The Indian Express that the next step was to measure the kinematics of the gas and stars in Alaknanda
galaxy. “Depending on whether the motion is regular or chaotic, we will get some clues about the mechanism that resulted
in the formation of the spiral arms. Understanding whether Alaknanda’s disk is cold or hot will tell us which formation
mechanism created the spiral arms,” he said.
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The next set of studies would have to be done using data from JWST and the ALMA telescope based in Chile. “Further
studies would tell us whether galaxies like Alaknanda represent a different evolutionary pathway that existed in early
universe,” Wadadekar said.