Webb telescope identifies earliest known primitive galaxy formation

13:05

By: Dakir Madiha

Webb telescope identifies earliest known primitive galaxy formation

An international team of astronomers has used the James Webb Space Telescope to identify the oldest primitive star-forming galaxy ever observed, offering a rare glimpse into the universe just 800 million years after the Big Bang. The galaxy, known as LAP1-B, contains oxygen levels estimated at only 1/240th of those found in the Sun, making it the most chemically primitive galaxy ever characterized.

The findings, published on May 13 in Nature, place the galaxy at a redshift of 6.625 during the epoch of reionization, a period when the first stars and galaxies transformed the early universe. Researchers said the discovery provides the clearest direct connection yet between ancient galaxies and the ultra-faint dwarf galaxies that now orbit the Milky Way.

Because LAP1-B is extremely faint, researchers relied on gravitational lensing to study it. A massive foreground galaxy cluster known as MACS J0416 acted as a natural cosmic magnifier, amplifying the galaxy’s light by nearly 100 times. Scientists then used the Webb telescope’s near-infrared spectrograph for more than 30 hours to capture weak emission lines from hydrogen and oxygen gas inside the galaxy.

Researchers said the galaxy’s chemical makeup points to material produced by the universe’s first generation of stars. LAP1-B also displays an unusually high carbon-to-oxygen ratio that matches theoretical predictions linked to early stellar explosions. Its stellar mass is estimated at only 3,300 times that of the Sun, suggesting dark matter makes up most of the galaxy’s total mass.

Astronomers believe the object closely resembles ultra-faint dwarf galaxies found near the Milky Way, long considered possible “fossils” from the early universe because of their extremely low heavy-element content. Scientists said LAP1-B now provides the first direct observational bridge between those nearby relics and the first galaxies formed after the Big Bang.

The discovery is expected to deepen scientific understanding of how the first chemical elements emerged and how the universe’s earliest structures evolved. Researchers plan to continue using the Webb telescope to search for even older and more primitive galaxies in hopes of tracing cosmic history closer to the universe’s beginnings.