Tuesday, July 23, 2024

Back then, baby galaxies. Next, a supermassive galaxy cluster?


Like basketball explorers spotting a lithe, tall teenager, astronomers using the James Webb Space Telescope recently reported that they identified a small and captivating group of young galaxies near the dawn of time. Scientists say these galaxies could grow into one of the largest clusters of mass in the universe, a massive collection of thousands of galaxies and trillions of stars.

The seven galaxies they identified date back to a moment 13 billion years ago, just 650 million years after the Big Bang.

“This may indeed be the most massive system in the entire universe at that time,” said Takahiro Morishita, an astronomer at Caltech’s Center for Infrared Processing and Analysis. He described the primary cluster as the outermost, and therefore the closest, entity ever observed. Dr. Morishita was the lead author of a report published on this discovery Monday in Astrophysical Journal Letters.

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

The telescope was launched into orbit around the sun on Christmas Day in 2021. With its infrared detectors and booming 21-foot-wide main mirror, it’s perfect for checking out the early years of the universe. As the universe expands, very distant galaxies in space and time are racing away from Earth so quickly that most of the visible light and information about them has spilled over into invisible infrared wavelengths, like sirens dropping in pitch.

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In its first year, the Web has already recovered a bounty of bright galaxies and the massive black holes that formed only a few hundred million years after the Big Bang.

The Hubble Space Telescope has discovered the youngest of the young galaxies over the years as red points of light, visible at such a great distance only because they are magnified by the space-twisting gravity of the Pandora Cluster, a nested group of galaxies in the constellation. sculptor.

Spectroscopic measurements using the Webb telescope confirmed that the seven points were galaxies and were all equally far from Earth. It occupies a swath of space 400,000 light-years across, or about one-sixth the distance from here to the Milky Way’s closest relative, the great spiral galaxy Andromeda.

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

According to calculations based on prevailing models of the universe, gravity will eventually pull these galaxies together into a massive cluster containing at least a trillion stars. said Benedetta Volcani of the National Institute of Astrophysics in Italy and a member of the research group.

The spectral data also allowed Dr. Morishita and his colleagues to determine that the stars inhabiting some of these embryonic galaxies were surprisingly mature, containing large amounts of elements such as oxygen and iron, which must have been formed in nuclear furnaces for generations. from the previous stars. Other galaxies among the smaller galaxies were much purer. Theoretically, the first stars in the universe were composed of pure hydrogen and helium, the first elements to emerge from the Big Bang.

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Some of these galaxies were stars being born at an astonishing rate, 10 times faster than the Milky Way, which is 10 to 100 times its size. Others in the young group were barely generating one star per year, said Dr. Morishita, “an interesting diversity in a group of galaxies in this early era.”

All this increases the suspicions of some cosmologists that the early universe was producing stars, galaxies and black holes much faster than standard theory predicts. In an email, Dr. Morishita said there is still no “crisis” in cosmology.

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