In a remarkable achievement, Indian scientists have discovered a huge ancient galaxy called Alaknanda, which is similar to the Milky Way galaxy, where Earth is located. The discovery published in the European Journal of Astronomy and Astrophysics described Alaknanda as special because of its fully developed structure. The galaxy was discovered by researchers Rashi Jain and Yogesh Wadadekar at the Pune-based National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research (NCRA-TIFR) using the James Webb Space Telescope.
The galaxy was formed 12 billion years ago, which means it was formed when the universe was just 1.5 billion years old. According to the journal, galaxies formed so early are generally messy, small and unstable with no clear shape, but Alaknanda has classic spiral galaxies like the Milky Way with two clear, symmetric arms called a grand design spiral.
Speaking about the newly discovered galaxy, Professor Yogesh Wadadekar at the National Centre for Radio Astrophysics at the Tata Institute of Fundamental Research (NCRA-TIFR) announced the discovery of the galaxy and said that Alaknanda looked like a regular galaxy with a well-structured system. “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,” said Rashi Jain, a PhD student who led this research under Wadadekar’s supervision.
Revealing how the galaxy was named, Jain said, “Just as the Alaknanda is the sister river of the Mandakini river, which is also the Hindi name for our own Milky Way galaxy, we thought it fitting to name this distant spiral galaxy after the Alaknanda river”.
What sets Alaknanda apart from other galaxies?
Alaknanda is said to have formed at a time when the universe was 1.5 billion years old. The universe is currently 13.8 billion years old. According to Professor Wadadekar, galaxies the size of Alaknanda should take at least 3 billion years to form stable spiral arms. He added that the Milky Way took billions of years to form its spiral discs. The galaxy has two symmetrical arms emanating from a disc at the centre, wrapping around a bright central bulge.
Rashi Jain said, “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.”
The astronomers used the James Webb Space Telescope (JWST) to discover this Alaknanda galaxy, which is 12 billion light-years away and about 30,000 light-years wide. Rashi Jain termed the discovery of Alaknanda as surprising because it indicates that such complex and well-structured galaxies were forming much earlier in the universe than scientists expected.
When she old her supervisor Prof Wadadekar about the galaxy, he didn’t believe it at first. He said, “It’s astonishing how such a large galaxy with spiral arms could have existed just 1.5 billion years after the Big Bang.”
Until now, the science community believed that stable spiral galaxies, like the Milky Way, could only emerge several billion years after they had enough time to cool down and settle into well-formed disks. But Alaknanda has challenged this belief.
Jain spotted Alanknanda while going through the details of 70,000 celestial objects. “Only one there that was a grand design spiral galaxy, spanning approximately 30,000 light-years in diameter,” Jain said. “It’s massive, it’s one-third of the Milky Way in size, and has 10 billion stars,” Professor Wadadekar said. The astronomers also spotted new stars developing 20-30 times faster in Alaknanda than what is seen in the Milky Way. They are planning to seek access to the James Webb or the Alma observatory in Chile for follow-up research to learn more about Alaknanda.
As per Professor Wadadekar, this galaxy managed to assemble 10 billion times the mass of the Sun in stars and form a large spiral-shaped disk in just a few hundred million years. “Alaknanda reveals that the early Universe was capable of far more rapid galaxy assembly than we anticipated,” he added.
It is believed that there are a hundred billion galaxies in the universe, each containing billions of stars, many of them having planets. Many galaxies started forming just few million years after the Big Bang. At that time, the universe was chaotic and the galaxies were small with irregular shapes. However, the James Webb Space Telescope, which is much more powerfull than the Hubble, has now revealed that bigger and organised galaxied had started forming much earlier.
