Astronomers have made a major breakthrough by directly detecting the gas that fueled star formation in some of the universe’s earliest galaxies.
The discovery offers a new way to understand how the first galaxies formed and evolved shortly after the Big Bang.
The universe began with the Big Bang about 13.8 billion years ago.
Over time, matter gradually gathered together to form the first galaxies. Inside these young galaxies, stars were born from huge clouds of cold, neutral gas.
Although this gas played a crucial role in building galaxies, it has been extremely difficult to observe directly, especially in galaxies that are very far away.
Modern telescopes such as the James Webb Space Telescope and the Hubble Space Telescope can capture stunning images of distant stars and hot gas.
However, they cannot directly detect the cold, neutral gas that acts as the raw material for star formation.
To solve this problem, an international team of researchers led by scientists from Chiba University turned to the Atacama Large Millimeter/submillimeter Array, better known as ALMA.
The powerful observatory specializes in detecting radio waves and can observe parts of the universe that are invisible to optical telescopes.
The researchers focused on a specific signal known as the [O I] 145-micrometer emission line. This signal is produced by neutral oxygen atoms and serves as a direct indicator of neutral gas.
Unlike other commonly used signals, which can come from several types of gas and are difficult to interpret, the [O I] signal provides a much clearer picture of the material that forms stars.
The team studied four ordinary star-forming galaxies that existed when the universe was only about 700 million to 800 million years old. Remarkably, they detected the [O I] signal in all four galaxies. This is the most distant direct detection of neutral gas ever achieved in typical star-forming galaxies.
The scientists also examined another signal called the [N II] emission line, which traces only ionized gas. Because this signal was weak or missing, the researchers concluded that most of the detected material was indeed neutral gas.
By combining the ALMA observations with data from the James Webb Space Telescope, they were able to investigate the physical and chemical properties of this gas in unprecedented detail.
Their analysis showed that these early galaxies contained very dense gas, similar to that found in modern starburst galaxies, which produce stars at extremely high rates. However, the radiation inside these young galaxies appeared somewhat less intense.
This suggests that the first galaxies were compact, crowded environments where stars formed efficiently.
The researchers say their work opens a new window into studying the “fuel” that powered star formation in the early universe. By extending these observations to more galaxies, they hope to piece together a clearer picture of how galaxies, including our own Milky Way, came to exist.
Source: KSR.
