Amazing Simulation of Rising Stars Is Most Realistic

Image of the first complete STARFORGE simulation. Nicknamed the “Anvil of Creation”, a giant molecular cloud with individual star formation and extensive feedback, including protostar jets, radiation, stellar winds and core-collapse supernovae. Credit: Northwestern University / UT Austin

First high-resolution model to simulate an entire gas cloud where stars are born.

Team included Northwestern University astrophysicists have developed the most realistic, highest-resolution 3D simulation of star formation to date. The result is a visually stunning, mathematically driven marvel that allows viewers to float around a colorful gas cloud in 3D space while watching twinkling stars.

Called STARFORGE (Star Formation in Gas Environments), the computer framework is the first to simulate an entire gas cloud – 100 times more massive than before possible and full of vibrant colors – where stars are born.

It is also the first simulation to simultaneously model star formation, evolution, and dynamics, while calculating star feedback, including jets, radiation, wind, and nearby supernova activity. While other simulations have assimilated individual types of star feedback, STARFORGE puts them together to simulate how these various processes interact to influence star formation.

Using this beautiful virtual lab, the researchers aim to explore long-standing questions, including why star formation is slow and inefficient, what determines the mass of a star and why stars tend to form in clusters.

The researchers have already used STARFORGE to discover that protostar jets – rapid gas flows that accompany star formation – play a vital role in determining star mass. By calculating the exact mass of a star, researchers can then determine its brightness and internal mechanisms as well as make better predictions about its death.

Recently accepted by the Royal Astronomical Society’s Monthly Notices, an advanced copy of the manuscript detailing the research behind the new model appeared online on May 17, 2021. An accompanying journal, describing how jets affect star formation, was published in the same journal in February 2021.

“People have been simulating star formation for a few decades now, but STARFORGE is a quantitative leap in technology,” said northwest Michael Grudic, who co-led the work. “Other models could only simulate a tiny bit of the cloud forming stars – not the whole high-resolution cloud. Without seeing the overall picture, we are missing many factors that could influence the star’s outcome. “

“How stars form is a very central question in astrophysics,” said Claude-André Faucher-Giguère of the Northwest, a senior author in the study. “We’ve explored a very difficult question because of the range of physical processes. This new simulation will help us directly address fundamental questions that we couldn’t definitively answer before.”

Bipolar Jets

Image of STARFORGE simulation. A rotating gas core collapses, forming a central star, which launches bipolar jets along its poles as it feeds gas from the surrounding disk. The jets remove gas away from the core, limiting the amount the star can ultimately sharpen. Credit: Northwestern University / UT Austin

Grudic is a postdoctoral fellow at Northwestern Center for Interdisciplinary Research and Research in Astrophysics (CIERA). Faucher-Giguère is an associate professor of physics and astronomy at the Weinberg Arts and Sciences University of Northwestern University and a member of CIERA. Grudic co-led the work with Dávid Guszejnov, a postdoctoral fellow at the University of Texas at Austin.

From beginning to end, star formation lasts tens of millions of years. So even as astronomers observe the night sky to catch a glimpse of the process, they can only see a short snapshot.

“When we observe forming stars in any region, all we see are star-shaped places frozen in time,” Grudic said. “Stars also form in dust clouds, so they’re mostly hidden.”

For astrophysicists to see the full dynamic process of star formation, they must rely on simulations. To develop STARFORGE, the team incorporated computer code for multiple phenomena in physics, including gas dynamics, magnetic fields, gravity, heating and cooling, and stellar reaction processes. Sometimes for three months to perform one simulation, the model needs one of the largest supercomputers in the world, a facility supported by the National Science Foundation and operated by the Texas Advanced Computer Center.

The resulting simulation shows a mass of gas – tens to millions of times the sun – floating in the galaxy. As the gas cloud evolves, it forms structures that collapse and break into pieces that eventually form single stars. Once the stars form, they launch gas jets out of both poles, piercing the surrounding cloud. The process ends when there is no more gas left to form more stars.

Pouring jet fuel on modeling

STARFORGE has already helped the team discover a crucial new insight into star formation. When the researchers did the simulation without counting jets, the stars ended up being too big – 10 times the solar mass. After adding jets to the simulation, the masses of the stars became much more realistic – less than half the sun.

“Jets interrupt the flow of gas to the star,” Grudic said. “They’re basically blowing away gas that would end up in the star and increase its mass. People suspected this could happen, but, simulating the whole system, we have a strong understanding of how it works.”

STARFORGE Simulation

Image of the first complete STARFORGE simulation. Nicknamed the “Anvil of Creation”, a giant molecular cloud with individual star formation and extensive reaction, including protostar jets, radiation, stellar winds, and core-collapse supernovae. Credit: Northwestern University / UT Austin

In addition to understanding more about stars, Grudic and Faucher-Giguère believe that STARFORGE can help us learn more about the universe and even about ourselves.

“Understanding galactic formation depends on assumptions about star formation,” Grudic said. “If we can understand star formation, then we can understand galactic formation. And by understanding galactic formation, we can understand more about what the universe consists of. Understanding where we come from and how we are located in the universe ultimately depends on an understanding of the origins of stars. “

“Knowing the mass of a star tells us its brightness and also what nuclear reactions take place in it,” Faucher-Giguère said. “By doing so, we can learn more about the elements synthesized in stars, such as carbon and oxygen – elements that we also consist of.”

Reference: “STARFORGE: A comprehensive numerical regime of star formation and reactions” by Michael Y Grudic, David Guszejnov, Philip F Hopkins, Stella SR Offner and Claude-André Faucher-Giguére, 17 May 2021 Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093 / mnras / stab1347

The study was supported by the National Science Foundation and NASA.

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