We are used to seeing them as spirals or ellipses. A bit like volleyballs or Frisbees. But ancient galaxies had very different shapes. Shapes like surfboards or pool fries.
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What astronomers call the Cosmic Evolution Early Release Science (CEERS) Survey aims to extract data provided by the James Webb Space Telescope (JWST), the galaxies that researchers believe existed as our universe between was 600 million and 6 billion years old.
The shape of the galaxies would reveal the quantum birth of the universe
And today, an analysis of all these images shows that these oldest galaxies in our universe most often appear flat and elongated. Between 50 and 80% of these galaxies are shaped like a surfboard or frying pan, such as those used for learning to swim in a swimming pool. Next are Frisbee-shaped galaxies. However, they become more common as we get closer to the end of the study boundaries that is closest to us. “Spherical” galaxies shaped like volleyballs appear to be both the most compact and least common galaxies.
What shape did our galaxy have at the beginning of the universe?
“It is surprising that galaxies that look like pool fries or surfboards are very common in the early universe. Because they are really rare in the nearby universe,” emphasizes Viraj Pandya, astronomer at Columbia University (USA), in a NASA press release. But the researchers point out that these galaxies are also less massive than the elliptical or spiral galaxies of our time. The sign that they are the precursors of larger galaxies like our Milky Way.
And what concrete idea do astronomers have today about what our galaxy might have looked like in this distant time? “Our best guess is that it looked more like a surfboard,” said Haowen Zhang, a researcher at the University of Arizona (US). By traveling through time, the theorists managed to get an idea of the mass of our Milky Way at that time. And it would conform to this particular shape.
New galaxy geometries to better understand their evolution
It is the data returned by the James Webb Space Telescope that made it possible to model the 3D geometry of all these galaxies. But astronomers emphasize that none of this would have been possible without decades of work already done thanks to the images captured by the Hubble Space Telescope. “There was already an excess of elongated galaxies,” recalls Marc Huertas-Company, researcher at the Institute for Astrophysics of the Canary Islands. The JWST provided a new wave of somewhat more precise evidence of their ubiquity. This reveals even more distant galaxies with similar geometries.
“It is exciting to identify additional categories for the earliest galaxies in the universe. But there is still a lot to analyze,” notes Kartheik Iyer, Hubble correspondent at Columbia University. Already, astronomers will be able to study the relationship between the shape of galaxies and their appearance and project their formation in much greater detail. With future samples of larger galaxies, they will be able to refine their conclusions and update models of galaxy evolution.