Although star formation is one of the most fundamental processes of astrophysics, there is no widely accepted theory of star formation, despite decades of intensive work from both observers and theorists. The primary reason for this is the large set of interconnected, complex physical processes, including gravity, turbulence, magnetic fields, chemistry and radiation. Furthermore, these processes interact in a non-linear way that also create interactions between vastly different scales, e.g. feedback from massive stars affecting their parent star-forming cloud. Thus, in order to understand star formation it is vital to investigate the role each physical process plays and how it modifies the outcome.
A simulated star-forming region where massive stars destroy their parent cloud. Image credit: STARFORGE.
“Stars are the atoms of the galaxy. Their mass distribution dictates whether planets will be born and if life could develop,” said Dr. Stella Offner, an astronomer in the Department of Astronomy at the University of Texas at Austin.
“Every subfield of astronomy depends on the mass distribution of stars — what we call the initial mass function (IMF) — which has proved challenging for scientists to be able to model correctly.”
Stars much bigger than our Sun are rare, making up only 1% of newborn stars. And, for every one of these stars, there are up to 10 Sun-like stars and 30 dwarf stars.
Previous observations found that these ratios (i.e., the IMF) are nearly universal in the Milky Way and its satellites, for both newly formed star clusters and for those that are billions of years old. This is the mystery of the IMF; in theory, it should vary dramatically.
“For a long time, we have been asking why,” said Dr. Dávid Guszejnov, a postdoctoral researcher in the Department of Astronomy at the University of Texas at Austin and leader of the STARFORGE (STAR FORmation in Gaseous Environments) project.
“Our simulations followed stars from birth to the natural endpoint of their formation to solve this mystery.”
The STARFORGE project was completed on two of the most powerful supercomputers in the world: Frontera and Stampede2.
One of the greatest challenges in studying star formation is the enormous dynamic range of the problem, an example of which is stellar feedback: where individual stars can affect their parent clouds, which are 100 million times larger than they are.
“Even the largest supercomputer and best code could not cover the entire dynamic range, but Frontera and Stampede2 supercomputers are powerful enough that we can capture a sufficient amount to identify individual stars forming in the simulation,” Dr. Guszejnov said.
“These simulations are the first to follow the formation of individual stars in a collapsing giant cloud while also capturing how these newly formed stars interact with their surroundings by giving off light and shedding mass via jets and winds, a phenomenon referred to as stellar feedback.”
“We have discovered that star formation is a self-regulating process,” he added.
“Stars that form in wildly different environments have a similar IMF, because stellar feedback, which opposes gravity, also acts differently, pushing stellar masses toward the same mass distribution.”
The team’s findings will be published in the Monthly Notices of the Royal Astronomical Society.
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Dávid Guszejnov et al. 2022. Effects of the environment and feedback physics on the initial mass function of stars in the STARFORGE simulations. MNRAS, in press; arXiv: 2205.10413
Source link: https://www.sci.news/astronomy/initial-mass-function-11072.html
