Offner’s
research will shed light on the processes inside star-forming regions
such as 30 Doradus, seen in this view from Hubble Space
Telescope. Credit: NASA/ESA/F. Paresce/R. O’Connell/WFC3 (Click image to
access download options from hubblesite.org). Hi-res images
Cloud Models
Models of two turbulent clouds without stars (left) and with stars
launching winds (right). The colors show gas speed: grey (6-10 km/s),
blue (12-25 km/s), and red (180-250 km/s). Credit: Stella Offner/UT
Austin
Magnetic Waves from a Young Star
Gas density and velocity (top) and magnetic field strength and magnetic
field lines (bottom) showing magnetic waves propagating ahead of the
wind shell. The left and right panels show different models. The waves
stand out when the surrounding gas is not turbulent. Credit: Stella
Offner/UT Austin
New research by Stella Offner, assistant professor of astronomy
at The University of Texas at Austin, finds that magnetic waves are an
important factor driving the process of star formation within the
enormous clouds that birth stars. Her research sheds light on the
processes that are responsible for setting the properties of stars,
which in turn affects the formation of planets orbiting them, and,
ultimately, life on those planets. The research is published in the
current issue of the journal Nature Astronomy.
Offner used a supercomputer to make models of the multitude of
processes happening inside a cloud where stars are forming, in an effort
to sort out which processes lead to which effects.
“These clouds are violent places,” Offner said. “It’s an extreme
environment with all kinds of different physics happening at once,”
including gravity and turbulence as well as radiation and winds from
forming stars (called stellar feedback). The fundamental question,
Offner said, is: “Why are the motions in these clouds so violent?”
Some astronomers attribute the observed motions to gravitational
collapse, while others attribute it to turbulence and stellar feedback.
Offner wanted to test these theories and study how stars shape their
birth environment, but it’s virtually impossible to use telescope
observations of these clouds to separate the influence of the various
processes, she said.
“That’s why we need computer models,” Offner explained.
After comparing models of clouds with gravity, magnetic fields, and stars, Offner noticed extra motions.
Her models showed that stellar winds interacting with the cloud
magnetic field generated energy and influenced gas at far greater
distances across the cloud than previously thought: These local magnetic
fields caused action at a distance.
“Think of the magnetic fields like rubber bands that stretch across
the cloud,” Offner said. “The winds push the field — it’s like rubber
bands being plucked. The waves outrun the wind and cause distant
motions.”
This research has implications for the tug-of-war between feedback —
that is, the effect that the newly formed star has on its environment —
and gravity on the scale of solar systems up to entire galaxies, Offner
said.
As for the next step, Offner says she plans to study this process on
larger scales, both in time and space. Her current study focused on one
area within star-forming clouds; she said future studies will study the
effects of magnetic fields and feedback on scales larger than a single
cloud.
Media Contact:
Rebecca Johnson, Communications Mgr.
McDonald Observatory
The University of Texas at Austin
512-475-6763
Science Contact:
Dr. Stella Offner, Asst. Professor
Department of Astronomy
The University of Texas at Austin
512-471-3853
Source: McDonald Observatory/News
