FYI.

This story is over 5 years old.

Tech

The Universe's Smallest Galaxies Gave Birth to Most of Its Stars

Unexpected results courtesy of the Hubble Space Telescope.
Image: NASA

Dwarf galaxies, as the name suggests, are among the smallest galaxies that exist, but that doesn’t mean they are uninteresting or unimportant. Quite the opposite, it turns out. New observations from NASA's Hubble Space Telescope have revealed that these small galaxies are some of the largest star-forming regions in the universe.

Stars are born inside the clouds of gas and dust that permeate most galaxies. Turbulence in these galactic clouds creates pockets with enough mass that the gas and dust begins collapsing on itself. As the material collapses, it heats up, forming a protostar. This protostar has enough mass and gravitational pull that it collects more gas and dust. Some will become part of the star and some might become planets orbiting around it. So with mass and gas density the key factors in galactic star formation, it should make sense that the largest galaxies with the most material formed the most stars in the Universe’s early year, right? Apparently not.

Advertisement

Scientists have been studying galaxies for decades to understand the correlation between a galaxy’s mass and its level of star formation. It’s part of unlocking the universe’s early years to understand how stars formed as galaxies grew and evolved 3.5 to 6 billion years after the Big Bang, the era of heavy star formation. The ultimate goal is a clear picture of the Universe’s early life, and where dwarf galaxies fit in is part of the question.

"We already suspected these kinds of galaxies would contribute to the early wave of star formation, but this is the first time we've been able to measure the effect they actually had," said  Hakim Atek of the École Polytechnique Fédérale de Lausanne in Switzerland. "They appear to have had a surprisingly huge role to play.”

This is the first time scientists have been able to study dwarf galaxies and their star forming power; previous studies have focused on medium and high mass galaxies. The new data comes from Hubble's Wide Field Camera 3 (WFC3), which scientists used to look at a sample of starburst galaxies in the young universe. Starburst galaxies, which scientists suspect are the result of a violent merging of galaxies, are those that make stars at a rate that scientists consider to be faster than normal.

Using WFC3 infrared eyes, astronomers have managed to calculate just how much low-mass dwarf galaxies contributed to star formation in our universe’s early life. It turns out they generated a substantial amount of the stars we have. ”These galaxies are forming stars so quickly they could actually double their entire mass of stars in only 150 million years, an incredibly short astronomical timescale," said Jean-Paul Kneib, also of the Swiss École Polytechnique. As a point of comparison, “normal,” larger mass galaxies need between 1 and 3 billion years to double their mass through star formation.

Understanding how dwarf galaxies have contributed to the star population of our galaxy is helping scientists gain a clearer understanding of the complex process of galactic evolution—how they merge, are consumed by their own stars, and see stars explode to leave behind supermassive black holes. The paper detailing this latest galactic discovery is available through the Astrophysical Journal online.