Back then baby galaxies. Next, a Super-Mega Galactic Cluster?

Like basketball scouts who discovered a nimble, super-sized teen, astronomers using the James Webb Space Telescope recently reported identifying a small, captivating group of baby galaxies by the dawn of time. These galaxies, the scientists say, could grow into one of the largest conglomerates of mass in the universe, a massive cluster of thousands of galaxies and trillions of stars.

The seven galaxies they identified date from 13 billion years ago, just 650 million years after the Big Bang.

“This indeed could have been the most massive system in the entire universe at the time,” said Takahiro Morishita, an astronomer at the California Institute of Technology’s Infrared Processing and Analysis Center. He described the protocluster as the most distant and thus earliest such entity yet observed. Dr. Morishita was the lead author of a report on the discovery, which was published on Monday in The Astrophysical Journal Letters.

The scientists’ report is an outgrowth of a larger effort known as the Grism Lens-Amplified Survey from Space, organized by Tommaso Treu, an astronomer at the University of California, Los Angeles, to examine early scientific results from the Webb telescope. to collect.

The telescope was launched into orbit around the sun on Christmas Day in 2021. With its infrared detectors and booming 6.5-meter-wide primary mirror, it’s ideal for exploring the early years of the universe. As the universe expands, galaxies so far in space and time race away from Earth so fast that most of their visible light, and the information about it, is stretched into invisible infrared wavelengths, like receding sirens dropping in pitch.

In its first year, the Webb has already recovered a wealth of bright galaxies and large black holes that formed just a few hundred million years after the Big Bang.

The newest young galaxies had been detected over the years by the Hubble Space Telescope as red dots of light, only visible at such a great distance because they had been magnified by the space-warping gravity of Pandora’s Cluster, an intermediate cluster of galaxies in the constellation Sculptor.

Spectroscopic measurements with the Webb telescope confirmed that the seven dots were galaxies and were all equidistant from Earth. They span an area of ​​space 400,000 light-years across, or about one-sixth of the distance from here to the Milky Way’s closest cousin, the large spiral galaxy Andromeda.

“So our efforts to follow up on the previously known potential protocluster have finally paid off after nearly 10 years!” Dr. Morishita wrote.

According to calculations based on current models of the Universe, gravity will eventually contract these galaxies into a massive cluster of at least a trillion stars. “We can see these distant galaxies as little drops of water in different rivers, and we can see that eventually they will all become part of one big, mighty river,” said Benedetta Vulcani of Italy’s National Institute of Astrophysics and a member of the research group. .

The spectroscopic data allowed Dr. Morishita and colleagues also find that the stars populating some of these embryonic galaxies were surprisingly mature and contained significant amounts of elements, such as oxygen and iron, that should have been forged in the nuclear furnaces over generations. of past stars. Others among the young galaxies were more pristine. In theory, the very first stars in the universe would be composed of pure hydrogen and helium, the first elements to emerge from the Big Bang.

Some of these galaxies gave birth to stars at a prodigious rate, more than 10 times faster than the Milky Way, which is 10 to 100 times larger. Others in the young group produced barely one star per year, “which is an interesting diversity in a group of galaxies in this early epoch,” said Dr. Morishita.

All this adds to the suspicion among some cosmologists that the early universe produced stars, galaxies and black holes much faster than standard theory predicts. In an email, Dr. Morishita that there was no “crisis” in cosmology yet.

“The easier explanation,” he wrote, “is that our previous understanding of star formation and dust production in the early universe, which are complex phenomena, was incomplete.”