When astronomers used the James Webb Telescope (JWST) to explore deep into the early universe, they made a serendipitous discovery: a galaxy that appears to be the Milky Way's ancient twin!
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In the new images, captured in light emitted just 1 billion years after the Big Bang, when the universe was about a quarter of its current age, the newly discovered galaxy appears fully formed, with a central mass of old stars, a vibrant disk of newborn stars, and two distinct spiral arms. Given its recognizable features and impressive size, the researchers have dubbed this galaxy the most distant Milky Way "twin" ever observed.
The detection of such a fully formed spiral galaxy so early in cosmic time adds to the many recent JWST discoveries that challenge our best theories of cosmology, which predict that galaxies of this size should take several billion years to form through a arduous series of mergers of smaller galaxies.
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A full description of the galaxy — named Zhúlóng, in honor of a mythical Chinese sun dragon whose eyes control the cycle of day and night — was published April 16 in the journal Astronomy & Astrophysics.
While Zhúlóng is undoubtedly older than our Milky Way, it could be mistaken for its "little" sibling. The new research estimates that Zhúlóng's star-forming disk is about 60,000 light-years across , compared to our Milky Way's 100,000 light-years , and contains about 100 billion solar masses, compared to our Milky Way's 1.5 trillion
However, Zhúlóng is by far the largest Milky Way-like galaxy to be detected so early in the history of the universe. It formed more than a billion years earlier than the similar spiral galaxy Ceers-2112, which JWST discovered in 2023, about 11.7 billion light-years from Earth.
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It didn’t take genealogical testing to find this long-lost twin of the Milky Way. Researchers discovered it by chance as part of PANORAMIC, a large-scale survey of billions of distant objects. The survey was conducted using JWST’s unique “pure parallel” mode — a method that allows the telescope to use two of its infrared instruments to observe two different regions of space at once.
Source: livescience
