Magnetic Fields are crucial in shaping the Cradles of Massive Stars
Magnetic fields in massive dark clouds are strong enough to support the regions against collapse due to their own gravity. A study lead by researchers at the Max–Planck–Institut für Radioastronomie in Bonn, Germany, shows for the first time that high magnetization sets the stage for the formation of stars much more massive than the sun. This is demonstrated in observations of polarized dust emission from two of the most massive clouds in our Milky Way, the “Brick” and “Snake”. The results are published in this week’s issue of the “Astrophysical Journal”.
Stars much more massive than the Sun (with 8 solar masses or more)
live wild and die young. They spew out powerful stellar winds and
sometimes explode violently to end up as supernovae. Even their birth is
spectacular: massive stars form out of very dense and massive gaseous
cores that are deeply embedded within dark clouds of gas and dust. In
fact, the high mass of these cores has puzzled researchers for many
years: the cores should quickly collapse due to their own gravity and
destroy themselves before telescopes on Earth can detect them.
“For the first time we witness how magnetic fields thread a massive
cloud and help stabilize the region while it gets ready to form
high–mass stars” says Thushara Pillai from the Max–Planck–Institut für
Radioastronomie (MPIfR) in Bonn (Germany), the lead author of the study.
“The cloud would already be collapsing if there were no magnetic
support”, she adds. “In that case the young forming cores would never
become massive enough to form stars much larger than the Sun.”
It has long been suspected that magnetic fields help to support
clouds against collapse. But magnetic fields are elusive: it is
difficult to tease the weak signal from magnetic fields from the noise.
Every region has to be observed over several nights to finally achieve a
significant detection. The current study therefore only targets two
regions. The “Brick” is an unusually dense cloud that is as opaque as
its namesake. It resides just a few dozen light years away from the
Galactic Center Black Hole in a distance of about 26,000 light years.
The nickname of the “Snake” is inspired by its serpent–like shape. This
cloud is about 12,000 light years away from Earth. The team used
archival data from two telescopes on top of Mauna Kea (Hawaii, USA) to
conduct this research, the James Clerk Maxwell Telescope and the Caltech
Submillimeter Observatory.
The magnetic field geometry can be studied by observing the dust
particles aligned with the magnetic field. These grains emit polarized
radiation that can be detected with telescopes. The magnetic field lines
are constantly disturbed by random gas motions in the clouds. “You can
think of a guitar string being plucked”, suggests Paul Goldsmith, a team
member from the Jet Propulsion Laboratory at the California Institute
of Technology in Pasadena (California, USA). “On a stringed instrument
such as a guitar, the tension in the string tries to hold it straight.
In our clouds, the magnetic field tries to do this, and the degree of
straightness of the field lines is a measure of the magnetic field
strength.” Researchers Chandrasekhar and Fermi already suggested this
technique in 1953. But only recently have telescopes become sensitive
enough to conduct this experiment throughout the Milky Way.
This study opens a new chapter in research that started in the early
1980’s at the Effelsberg 100m–telescope of the MPIfR. First surveys of
dense gas near the center of the Milky Way revealed unusually massive
clouds, including the “Brick”. This discovery inspired several follow–up
studies, as co–author Jens Kauffmann from the MPIfR explains. “Two
years ago we successfully revealed for the first time the internal
structure of the Brick. We were surprised to find very little
substructure in this cloud: something seemed to stop the gas from
clumping up. Now we know that the strong magnetic field might do this.”
The team has now started a project that will observe many more such
clouds. This time the researchers will use MPIfR’s APEX telescope. “APEX
is currently the only telescope worldwide that is equipped to make
these observations”, concludes Thushara Pillai. “It is an exciting
possibility to use this observatory to explore more of our Galactic
backyard”.
The research team is comprised of Thushara Pillai, Jens Kauffmann and
Karl M. Menten (all MPIfR), moreover Jonathan C. Tan (University of
Florida), Paul F. Goldsmith (Jet Propulsion Laboratory, California
Institute of Technology), and Sean J. Carey (IPAC, California Institute
of Technology).
Original Paper
Magnetic Fields in High-mass Infrared Dark Clouds
T. Pillai, J. Kauffmann, J.C. Tan, P.F. Goldsmith, S.J. Carey, K.M. Menten, 2015, Astrophysical Journal Vol. 799
Links
- JCMT - James Clerk Maxwell Telescope, Mauna Kea, Hawaii
- CSO - Caltech Submillimeter Observatory, Mauna Kea, Hawaii
- Spitzer - NASA Spitzer Space Telescope
- Millimeter and Submillimeter Astronomy - Research Department at MPIfR
Contact
Dr. Thushara Pillai
Phone:+49 228 525-153
Email: tpillai@mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie, Bonn
Prof. Dr. Karl M. Menten
Direktor und Leiter der Forschungsabteilung "Millimeter- und Submillimeter-Astronomie"
Phone:+49 228 525-297
Email: kmenten@mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie, Bonn
Dr. Norbert Junkes
Presse- und Öffentlichkeitsarbeit
Phone:+49 228 525-399
Email: njunkes@mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie, Bonn
