Astronomers discover one of faintest, oldest galaxies near Andromeda

Astronomers have discovered one of the faintest known galaxies orbiting the Andromeda Galaxy, offering new insights into the early universe and the formation of the first galaxies.

The newly identified ultra-faint dwarf galaxy, named Andromeda XXXVI (And XXXVI), is estimated to be around 12.5 billion years old, making it one of the oldest known galaxies in the Milky Way's cosmic neighbourhood. The findings were published in the journal Astronomy & Astrophysics, Knowridge reports.

Located near the Andromeda Galaxy, about 2.5 million light-years from Earth, And XXXVI contains very few stars and emits only a small amount of light, making it extremely difficult to detect. Scientists believe such ultra-faint dwarf galaxies are "cosmic fossils" that have remained largely unchanged since the early universe.

Lead researcher Joanna Sakowska of Spain's Instituto de Astrofísica de Andalucía said the galaxy appears to contain very few heavy elements, suggesting it formed before multiple generations of stars enriched the universe with heavier chemical elements.

Researchers say further observations, including with the Hubble Space Telescope, are needed to confirm the galaxy's age, distance and chemical composition.

The discovery may also help address a longstanding question in astronomy. The leading cosmological model predicts that large galaxies such as Andromeda should be surrounded by hundreds of small satellite galaxies, yet only about 40 have been identified so far.

Co-author Isabel Santos-Santos of the Leibniz Institute for Astrophysics Potsdam said each newly discovered ultra-faint galaxy helps scientists better understand galaxy formation and the nature of dark matter.

And XXXVI was first identified by amateur astronomer Giuseppe Donatiello using survey images before being confirmed through follow-up observations with the Gran Telescopio Canarias, one of the world's largest optical telescopes. Researchers were able to identify only 46 stars belonging to the galaxy, underscoring its extremely faint nature.

By Sabina Mammadli