Indian scientists discover galaxy similar to Milky Way from 12 billion years ago

Researchers in India have identified a massive galaxy dating back to a time when the Universe was merely 1.5 billion years old, offering new insights that challenge existing theories of early galaxy formation. Considering the Universe is about 13.8 billion years old, this observation captures a galaxy as it existed 12 billion years ago, when the cosmos was just a fraction of its current age.

Most galaxies from this early era were thought to be small, irregular, and chaotic. However, scientists Rashi Jain and Yogesh Wadadekar, using the James Webb Space Telescope (JWST), have spotted a "fully-formed spiral galaxy," resembling a structured cosmic pinwheel. Their study was published in the journal Astronomy and Astrophysics in November.

Prof. Wadadekar noted, "The galaxy bears a striking resemblance to the Milky Way, even though it existed when the Universe was only 10% of its current age." The galaxy has been named Alaknanda, after a river in the Himalayas.

The discovery was made by Ms. Jain, a PhD student at the National Centre for Radio Astrophysics, part of the Tata Institute of Fundamental Research in Pune. She described her excitement upon finding the galaxy while analyzing data from the $10 billion JWST, launched in 2021. Out of around 70,000 objects examined, only one stood out as a grand-design spiral galaxy, approximately 30,000 light-years across.

The galaxy features two symmetric spiral arms extending from a central disc and wrapping around a bright core. Clusters of stars form a "beads-on-a-string" pattern along the arms, reminiscent of spiral galaxies observed in the nearby Universe today.

Prof. Wadadekar admitted initial disbelief at the finding. "It is remarkable that such a large spiral galaxy could exist just 1.5 billion years after the Big Bang. It had to form 10 billion solar masses of stars and build a large disc with spiral arms in just a few hundred million years, which is incredibly fast in cosmic terms."

NASA estimates there are roughly 100 billion galaxies, with many forming within millions of years after the Big Bang. Early Universe conditions, known as cosmic dawn, were considered chaotic, with galaxies small and low in mass. "But this galaxy is exceptional," said Prof. Wadadekar. "It is about one-third the size of the Milky Way, hosts 10 billion stars, and is producing new stars at 20-30 times the Milky Ways current rate."

Since the start of JWST operations, astronomers have been discovering increasingly distant and structured galaxies. Initial images revealed faint smudges or red blobs, but more recent observations show complex formations, including spiral galaxies. Alaknanda adds further evidence that the early Universe was capable of creating sophisticated structures.

Ms. Jain remarked, "Finding such a well-formed spiral galaxy so early is rare but forces us to rethink how galaxies evolved. This shows the Universe developed advanced structures far sooner than previously believed." She added that the galaxy is observed as it existed 12 billion years ago, its light taking that long to reach us.

When asked about its current state, Prof. Wadadekar humorously replied, "We will have to wait 12 billion years to see where it is now." The team plans to conduct follow-up observations with JWST and the Alma Observatory in Chile to understand how the galaxy developed its spiral arms, which could unlock secrets of cosmic evolution.

Analysis: A New Chapter in Galaxy Formation Theories

The discovery of the Alaknanda galaxy, observed at a time when the Universe was only 1.5 billion years old, challenges the prevailing theories on the formation of early galaxies. Previously, the general consensus held that galaxies in the early Universe were small, irregular, and lacked the structure seen in present-day galaxies. The identification of a massive, fully-formed spiral galaxy so early in cosmic history forces us to reconsider our understanding of galactic evolution.

Alaknanda, resembling the Milky Way with its distinct spiral arms and central disc, is a significant anomaly in the early Universe. Its existence raises the question of how such a structured galaxy could form so rapidly, with 10 billion solar masses and a large disc built in just a few hundred million years—an incredibly short time on cosmological scales. Prof. Wadadekar’s comment about the galaxy's rapid formation highlights the need for new models to explain these phenomena.

This discovery suggests that the conditions of the early Universe may have been more conducive to the formation of organized galaxies than previously thought. As scientists continue to analyze this and other similar findings, it is becoming increasingly clear that the early cosmos may have had the capacity for sophisticated galaxy formation, challenging our prior assumptions about the chaotic nature of cosmic dawn.

In conclusion, Alaknanda represents a breakthrough in our understanding of galaxy formation. With follow-up observations planned, astronomers are eager to uncover more about how such galaxies developed, potentially unlocking new insights into the evolution of the Universe itself.

Sources:

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