Researchers have discovered that there are far more massive stars across the universe than previously thought, challenging current notions of how stars and galaxies evolved.
Astronomers Find More Massive Stars
A team of astronomers at European Southern Observatory has looked into the rapid formation of new stars in galaxies dating as far back as 10 billion years ago. They have found that starburst galaxies harbor a lot more massive stars, and many of them are a lot heavier than scientists deemed possible before.
Starburst galaxies, which are characterized by quick bouts of star birth at the beginning, form new stars at a rate of 100 times faster than the Milky Way. Details of the new study, which are published in the journal Nature, show they also produce massive stars seven times more than typical galaxies.
Massive stars have a shorter lifespan than intermediate stars. The sun, which is an intermediate star, is expected to live up to tens of billions of years before it cools down into a white dwarf. Massive stars, however, go out with a literal bang by exploding into supernovas and scattering star material and enormous amounts of energy into the surrounding space.
The newest discovery about the distribution of massive stars could potentially change the most fundamental parameters used by astronomers to study the formation and evolution of stars, planets, and the seed black holes that come together to form the supermassive black holes found at the center of galaxies.
Scientists may have to review and redefine previous notions about the rate of star formation, stellar masses, and the timescales of gas depletion and gas formation, among others, according to the researchers.
"Our findings lead us to question our understanding of cosmic history," says Rob Ivison, co-author of the study. "Astronomers building models of the universe must now go back to the drawing board, with yet more sophistication required."
Mapping Carbon Monoxide Signatures In Galaxies
Using the Atacama Large Millimeter/submillimeter Array telescope in Chile, the researchers were able to locate early galaxies that had a high concentration of massive stars.
They used a technique similar to radiocarbon dating, which involves measuring the different types of carbon monoxide in four distant starburst galaxies. They measured the ratio of two types of carbon monoxide, each containing different isotopes.
Oxygen-18 isotopes are associated with massive stars, while carbon-13 isotopes are more often found in stars with intermediate mass. When oxygen and carbon come together, they form carbon monoxide.
The researchers found that the ratio of oxygen-18 to carbon-13 is significantly higher in starburst galaxies than in typical galaxies like the Milky Way.
"There is a much higher proportion of massive stars within these starburst galaxies," says Donatella Romano, co-author of the study and astronomer from the INAF-Astrophysics and Space Science Observatory.
Massive Stars Close To Home
A separate team of researchers has found similar results closer to home. Earlier this year, a University of Oxford team peering through ESO's Very Large Telescope found a high number of massive stars in one of the Milky Way's satellite galaxies.
The team, headed by astronomer Fabian Schneider, discovered a huge population of massive stars in 30 Doradus, a region characterized by intense star formation in the Large Magellanic Cloud.
They also found that the stars had more mass than expected. In particular, 70 percent more than expected of the 800 stars included in the study were found to have above 60 solar masses.
The results of their research could push the maximum solar mass of newborn stars beyond the current limit of 150. They also estimate that some stars may even have a solar mass of 300 at birth.
For comparison, the sun has 1 solar mass, which is equivalent to 2 nonillion kilograms or 2 with 30 zeroes after it.
