The ‘Little Lion’ Galaxy that Could Shed Light on the Early Universe

Astronomers just announced the discovery of the most metal-poor galaxy in the local universe, a bundle of stars located 30 million light years away in the constellation Leo Minor. The system goes by AGC 198691 in the official catalogue, but has been given the more memorable nickname Leoncino or “little lion” by the team that originally detected it using the Arecibo Legacy Fast ALFA (ALFALFA) radio survey project.

The system’s incredibly low metal content distinguishes it as an intriguing cosmic relic that can be used to reconstruct the conditions of the early universe. As opposed to sprawling, radiant, active galaxies like the Milky Way, packed with billions of stars and metal-rich stellar explosions, Leoncino contains only a few million dim stars and measures just 1,000 light years across, with the lowest luminosity of any galaxy of its type on record.

This is a very unusual configuration for the so-called “local” universe, which is an enormous expanse of space roughly covering the region within one billion light years of Earth. Indeed, new research into Leoncino published on Thursday in theAstrophysical Journal finds that the galaxy beats out the previous record-holder for the most metal-poor galaxy—discovered in 2005—by 29 percent.

"Finding the most metal-poor galaxy ever is exciting since it could help contribute to a quantitative test of the Big Bang," John J. Salzer, an astronomy professor at Indiana University and a co-author on the paper, said in a statement. "There are relatively few ways to explore conditions at the birth of the universe, but low-metal galaxies are among the most promising."

Salzer and his colleagues were able to measure Leoncino’s metal content by analyzing the spectrum of its stars with the Mayall Four-Meter Telescope and the Multiple Mirror Telescope, both of which are located in Arizona. The team hopes to follow up with further observations using even more sophisticated observatories, including the Hubble Space Telescope.

‘We're eager to continue to explore this mysterious galaxy,” Salzer said. “Low-metal-abundance galaxies are extremely rare, so we want to learn everything we can.