Sidereal Messenger: Webb reveals Milky Way-like galaxies in the early Universe

An international group led by astronomers from the University of Texas at Austin (USA) found galaxies very similar to the Milky Way – with spiral arms and a central bar of stars – in deep images from the James Webb Space Telescope, showing that stars of this type were already well common 11 billion years ago.

It is yet another example of how the new space telescope, a partnership of space agencies in the USA (NASA), Europe (ESA) and Canada (CSA), even in its initial observations, begins to create a clearer picture of the evolution of the Young Universe, succeeding the famous Hubble in the mission to investigate the conditions prevailing in the cosmic past.

The work, accepted for publication in the journal Astrophysical Journal Letters, initially separated a sample of 348 ancient galaxies with a mass equal to or greater than ten billion suns and, of these, selected six to analyze more closely, due to the clarity with which they exposed the presence of spirals and a central bar. (It doesn’t hurt to remember that old is equivalent to deep, since light from distant stars takes a long time to travel from there to here, reflecting the state of the Universe billions of years ago.)

The six chosen for closer examination reflect ages between 8.4 billion and 11 billion years ago. One of them had even been previously observed by Hubble, but at the wavelengths at which the old telescope was capable of capturing it, it was nothing more than an indistinct blur. With Webb, and its infrared vision (for which the dust is transparent), it was possible to clearly notice its morphology, that is, its shape.

With this, it is definitively proven that the cosmos already had spiral galaxies similar to the Milky Way, in shape and size, just over 2 billion years after the Big Bang. It was something even predicted by some groups, but which still lacked solid confirmation in observations.

The finding is more in line with simulations of the Universe that suggest the rapid appearance of these characteristics and forms a consistent picture with everything else new that has been seen in recent times, with or without Webb, in the sense of demonstrating that the “adolescence” of the cosmos was fast. It is worth noting that the new telescope, in its first observations, broke distance records and detected galaxies that date back to when the Universe was 300 million years old, that is, 13.5 billion years ago.

The appearance of these structures, in particular a central bar of stars, helps to explain how the rapid growth of supermassive black holes in the hearts of these galaxies took place, since the bar helps to promote the flow of gas in the central direction, stimulating the rapid formation of new stars and feeding these mighty cosmic gluttons.

The next step in the research now is to look into a larger number of galaxies so that a statistical comparison can be made between the frequency of bars and spirals well delineated in the past and in the current Universe.

This column is published on Mondays in Folha Corrida.

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