Dwarf Galaxy Mystery: Astronomers Shed Light On How The Smallest Galaxies Form Stars

An international team of researchers found new insights as to how dwarf galaxies form stars, shedding light into a long-standing mystery in astronomy.

Despite being the most abundant type of galaxy in the Universe, dwarf galaxies are difficult to detect because of their low luminosity, small size, and low mass. Compared to larger galaxies such as the Milky Way, dwarf galaxies have much fewer stars and, how they form stars remains to be one of the mysteries of the Universe that astronomers have been trying to understand.

For instance, the shape of the Phoenix dwarf galaxy suggests that it does not contain enough gas to form new stars but, observations have shown that it contains a significant number of young blue stars as well as a nearby cloud of gas, suggesting recent star formation.

"It is estimated that these dwarf galaxies stopped forming stars around 12 billion years ago," study lead Martin Rey of Lund University said in a news release from the Royal Astronomical Society. "Our study shows that this can be a temporary hiatus."

In the study, the researchers found that dwarf galaxies can actually remain dormant for billions of years before beginning to form new stars once again.

"The resumption of star formation is delayed by several billion years due to residual feedback from stellar winds and Type Ia supernovae," the researchers wrote.

Simply put, star formation in dwarf galaxies tend to halt as a result of certain processes in the Universe, such as ionization from strong light in newborn stars as well as supernova explosions. During this period of dormancy wherein, there is no ongoing star formation, the dwarf galaxies steadily accumulate gas. Eventually, the gas collapses and reignites star formation.

"This explains the observed star formation in existing faint dwarf galaxies, which has long puzzled astronomers," Rey said, also noting that further work to see how many such star-forming dwarf galaxies are out there is underway.

For the study, the researchers used high-resolution computer simulations that are said to be some of the most expensive that can be carried out.

The study was published in the Monthly Notices of the Royal Astronomical Society.