Astronomers have discovered one of the faintest galaxies ever found near the Andromeda Galaxy.
The tiny galaxy, called Andromeda XXXVI (And XXXVI), may be around 12.5 billion years old, making it one of the oldest known galaxies in our cosmic neighborhood.
The discovery gives scientists a rare chance to study what the universe was like not long after the Big Bang.
The findings were published in the journal Astronomy & Astrophysics.
The Andromeda Galaxy is about 2.5 million light-years from Earth. It is the closest large spiral galaxy to our own Milky Way. Like the Milky Way, Andromeda has many much smaller galaxies orbiting around it. These are called satellite galaxies because they are held in place by the gravity of the larger galaxy.
And XXXVI belongs to a special group known as ultra-faint dwarf galaxies. These are the smallest and dimmest galaxies ever discovered. They contain very few stars and produce only a tiny amount of light, making them extremely difficult to find.
Scientists believe these galaxies formed during the earliest days of the universe. Because they have changed very little over billions of years, they are often described as cosmic fossils. Studying them helps researchers learn how the first galaxies formed.
According to lead researcher Joanna Sakowska from the Instituto de Astrofísica de Andalucía in Spain, the new galaxy appears to be extremely old and contains very few heavy elements. Heavy elements, such as iron and oxygen, are created inside stars over time. A galaxy with very few of these elements suggests that it formed before many generations of stars had a chance to enrich the universe.
However, scientists say more observations are needed to confirm its exact age, distance, and chemical makeup. Powerful space telescopes, including the Hubble Space Telescope, could provide much more detailed information.
The discovery is also important because it may help solve a long-standing puzzle in astronomy.
The leading theory of the universe, called the Lambda Cold Dark Matter (ΛCDM) model, predicts that large galaxies like Andromeda should be surrounded by hundreds of tiny satellite galaxies.
Yet astronomers have only found around 40 satellites around Andromeda so far, and only about 15 of them are considered ultra-faint dwarf galaxies.
Researchers believe many more are still waiting to be discovered because they are simply too faint to detect with current surveys.
Co-author Isabel Santos-Santos from the Leibniz Institute for Astrophysics Potsdam said that every newly discovered ultra-faint galaxy helps scientists test ideas about how galaxies formed and better understand dark matter, the mysterious substance that makes up most of the matter in the universe but cannot be seen directly.
Interestingly, And XXXVI was first spotted by amateur astronomer Giuseppe Donatiello while studying images from the Pan-Andromeda Archaeological Survey. After the object was identified as a possible galaxy, professional astronomers used the Gran Telescopio Canarias, one of the world’s largest optical telescopes, to take much deeper images.
Even with this powerful telescope, the galaxy remained incredibly difficult to study. Researchers could identify only about 46 individual stars that belong to And XXXVI.
Although tiny and almost invisible, this faint galaxy could hold valuable clues about the birth of the first galaxies and the mysterious dark matter that shaped the early universe. Every new discovery like And XXXVI helps astronomers build a clearer picture of how our universe began more than 13 billion years ago.
