Baby Blue: IU Astronomers Say Little Blue Galaxy Could Illuminate Big Bang
Astronauts traveling at the speed of light would still take 30 years to reach AGC 198691, otherwise known as Leoncino, the "little lion" galaxy. Once arrived, they would find a cluster of stars described by scientists as "pristine," an intergalactic time capsule.
For some reason, the small, faint Leoncino contains the smallest amounts of metals in any galaxy ever discovered, a characteristic Indiana University astronomers say could offer scientists insight into theories about the Big Bang.
The findings appear this month in the Astrophysical Journal.
IU astronomy professor John Salzer, one of the study’s authors, explains that at the universe’s genesis, there were only two elements: hydrogen and helium. As stars age and die and regenerate, they create heavier and heavier elements of different types, referred to as "metals," in a process called stellar nucleosynthesis.
Less-evolved, metal-poor galaxies, then, can act as a glimpses into the deep past. Salzer says that’s what makes Leoncino of special interest.
“It’s as close to a direct measurement of the chemical abundance ratios of hydrogen to helium that was present at the early stages of the universe,” he says.
IU graduate student Alec Hirschauer was the first to discover the lack of metals in the galaxy—what scientists refer to as “metal abundance.” (Abundance is measured by studying the light stars emit with powerful tools called spectroscopes.)
“Because this galaxy is so metal-poor,” Hirschauer says, “it is our best specimen potentially for being able to study something in pretty good detail that is pretty representative of systems as they were after the Big Bang.”
Salzer says by looking at the properties of metal-poor galaxies, scientists can directly test theories posited about conditions in place during the first moments of the universe, thus strengthening and refining popular scientific models.
“Scientists as a group have an obligation to create theories,” says Salzer, “but [also] to verify them and hopefully, eventually allow people to reach a comfort zone.”
Because Leoncino is small and glows very dim, it took a special kind of telescope in Puerto Rico that measures radio waves, not visual light, to detect it.
Thanks to a number of recently-formed stars, Leoncino appears blue in color. It’s also relatively tiny, with a diameter about 100 times smaller than our own Milky Way.
Hirschauer, who initially checked out the galaxy cluster containing Leoncino as a favor for an astronomer friend, says he originally wrote the galaxy’s low metal abundance off as a research error, until Salzer, his advisor, encouraged him to take another look.
Hirschauer says the next step in the process is studying Leoncino’s relative abundance of helium. He also hopes the discovery will trigger more searching for additional well-hidden low-abundance systems.