Astronomers have discovered a huge reservoir of cold gas in one of the earliest known galaxies, providing new clues about how some galaxies grew so quickly after the Big Bang.
The galaxy, known as REBELS-25, is so far away that astronomers see it as it appeared about 700 million years after the birth of the universe.
Since the universe is now around 13.8 billion years old, this means scientists are looking back to a time when the cosmos was only about 5% of its current age.
The discovery was made by an international research team led by scientists from Leiden University.
Their findings were published in the journal Monthly Notices of the Royal Astronomical Society.
Galaxies grow by turning gas into stars. The most important ingredient for this process is cold molecular gas, which acts as the raw material for star formation.
Scientists had long suspected that some young galaxies contained enormous amounts of this gas, but until now they had never directly detected it at such a great distance.
To make the discovery, researchers used two powerful observatories. One was the U.S. National Science Foundation’s Very Large Array (VLA) in New Mexico, and the other was the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.
The VLA searched for faint radio signals produced by carbon monoxide molecules. These molecules are valuable because they act as markers for large clouds of molecular gas. The telescope detected a specific carbon monoxide signal coming from REBELS-25, making it the most distant detection of this type ever recorded.
The signal revealed that the galaxy already contained a massive supply of cold gas despite its young age. This suggests that REBELS-25 had plenty of fuel available to create new stars at an impressive rate.
ALMA provided additional observations that helped researchers estimate the gas’s temperature and density. Together, the data painted a detailed picture of the galaxy’s star-forming environment.
Detecting cold gas in such an ancient galaxy is not easy. One major challenge comes from the cosmic microwave background, or CMB, which is the faint leftover radiation from the Big Bang. In the early universe, the CMB was much brighter than it is today, making it harder to distinguish the weak signals emitted by cold gas clouds.
Despite this obstacle, the researchers successfully detected the gas, showing that modern radio telescopes can probe deep into a period known as the Epoch of Reionization. This was a crucial era when the first stars and galaxies transformed the universe from a dark, neutral place into the bright cosmos we see today.
The discovery helps explain how some galaxies became massive so quickly after the Big Bang. Instead of merely guessing how much star-forming fuel these galaxies contained, astronomers can now measure it directly.
Researchers believe REBELS-25 may be just the beginning. Future instruments, particularly the planned Next-Generation Very Large Array, will be far more powerful and will allow scientists to study many more young galaxies.
These observations could reveal how the first galaxies gathered gas, formed stars, and built the foundations of the modern universe.
Source: KSR.
