Astronomers are turning to some of the smallest galaxies in the universe to answer one of the biggest questions in science: what was the universe like shortly after the Big Bang?
A new study published in Monthly Notices of the Royal Astronomical Society suggests that ultra-faint dwarf galaxies — tiny galaxies orbiting our Milky Way — may hold important clues about the early universe and how galaxies first formed.
These small galaxies are often described as “cosmic fossils” because they have changed very little over billions of years. By studying them, scientists hope to learn what conditions were like when the universe was still very young.
The research team created an unusually large and detailed set of computer simulations to study these faint galaxies. The work was led by scientists from the Oskar Klein Centre in Stockholm, together with researchers from Durham University and the University of Hawaii.
Ultra-faint dwarf galaxies are incredibly small compared to the Milky Way. Some are more than a million times less massive than our galaxy. Because they are so tiny and fragile, they have been very difficult for scientists to model accurately in the past.
The new simulations allowed researchers to see more clearly how these galaxies formed and evolved over time.
The scientists compared the process to farming. Just as crops depend heavily on weather conditions, tiny galaxies depend strongly on the “climate” of the early universe. Factors such as radiation levels in the young universe could decide whether a small dark matter halo successfully formed stars or remained dark and empty.
The team studied two different versions of what the universe may have been like less than 500 million years after the Big Bang. They then looked at how those early conditions affected galaxies more than 13 billion years later.
They discovered that ultra-faint dwarf galaxies are extremely sensitive to these early conditions. Larger galaxies like the Milky Way were much less affected.
In some cases, small differences in the early universe determined whether a dwarf galaxy became visible with stars or stayed as a dark matter halo with no stars at all.
This finding is exciting because new telescopes may soon discover many more of these tiny galaxies. The Vera C. Rubin Observatory, which is expected to begin major observations soon, could help astronomers create the most complete map ever made of small galaxies surrounding the Milky Way.
Scientists believe these observations could provide a new way to study the universe’s infancy — something that is normally very difficult because the earliest galaxies are so distant and faint.
The study is also important because recent observations from the James Webb Space Telescope have revealed surprisingly massive and bright galaxies in the early universe, challenging some existing theories about galaxy formation.
Running the simulations was a massive task. The project took more than six months on the COSMA 8 supercomputer and generated around 300 terabytes of data. Researchers even had to redesign older data-processing methods to handle such huge amounts of information.
In the future, scientists hope these simulations will also help answer other mysteries, including the nature of dark matter and where the universe’s very first stars may still be hiding today.
Source: Royal Astronomical Society.
