Scientists solves astronomy mystery

In a new research, scientists have solved the longstanding astronomy mystery of how massive stars form without blowing away the clouds of gas and dust that feed their growth.

The research, by Lawrence Livermore National Laboratory, University of California, Santa Cruz and UC Berkeley, has shown how a massive star can grow despite outward-flowing radiation pressure that exceeds the gravitational force pulling material inward.

Using 3-D radiation hydrodynamics simulations, the group, which includes Livermore’s Richard Klein, who also is an adjunct professor at UC Berkeley, and his LLNL post doc Andrew Cunningham, unexpectedly discovered that these massive stars also tend to occur in binary or multiple star systems.

Richard Klein, an adjunct professor at UC Berkeley said: “Originally, we were just exploring the physics of massive star formation. As we were looking at the physics, we found that gravitational instabilities cause companion stars to form around massive stars.

Logically, we thought the massive amounts of radiation pressure would stop the star in its tracks from growing any larger. But instead, gravitational instabilities channeled gas onto the star system through disks and filaments, sort of like fingers, that self-shield against the radiation, while allowing the radiation to escape through optically thin bubbles.

Massive stars produce so much light that the radiation pressure they exert on the gas and dust around them is stronger than their gravitational attraction, a circumstance that has long been expected to prevent them from growing by accretion.

Mark Krumholz, lead author and an assistant professor of astronomy and astrophysics at the UC Santa Cruz said: “We didn’t set out to solve that question, so it was a nice side benefit of the study. The main finding is that radiation pressure does not limit the growth of massive stars. The team spent years developing complex computer codes for simulating the processes of star formation.

Combined with advances in computer technology, their latest code (called ORION) enabled them to run a detailed 3-D simulation of the collapse of an enormous interstellar gas cloud to form a massive star.