'Hourglass Figure' Points to Magnetic Field's Role in Star Formation

Aug 11, 2006
'Hourglass Figure' Points to Magnetic Field's Role in Star Formation
The protostellar system NGC 1333 IRAS 4A is the first textbook example of an hourglass-shaped magnetic field (shown by dashed red lines on this color-coded submillimeter image). The pear-shaped green and red region marks the locations of two still-forming stars. Gravity is pulling the gas and dust of this interstellar cloud clump inward, warping the magnetic field in the process. Taken with the Smithsonian's Submillimeter Array, this image is about 7 arcseconds on a side, which translates to a physical size of 2,700 astronomical units (using a distance to the system of 980 light-years). Image credit: J. Girart (CSIC-IEEC), R. Rao (ASIAA) and D. Marrone (CfA)

Long predicted by theory, the Smithsonian's Submillimeter Array has found the first conclusive evidence of an hourglass-shaped magnetic field in a star formation region. Measurements indicate that material in the interstellar cloud is dense enough to allow it to gravitationally collapse, warping the magnetic field in the process.

Astronomers Josep Girart (Institute of Space Studies of Catalonia, Spanish National Research Council), Ramprasad Rao (Institute of Astronomy and Astrophysics, Academia Sinica), and Dan Marrone (Harvard-Smithsonian Center for Astrophysics) studied the protostellar system designated NGC 1333 IRAS 4A. This system of two protostars is located approximately 980 light-years from Earth in the direction of the constellation Perseus.

They reported their findings in the August 11 issue of the journal Science.

"We selected this system because previous work had offered tantalizing hints of an hourglass-shaped magnetic field," explained Marrone. "The Submillimeter Array offered the resolution and sensitivity we needed to confirm it."

NGC 1333 IRAS 4A is part of the Perseus molecular cloud complex - a collection of gas and dust holding as much mass as 130,000 suns. This region is actively forming stars. Its proximity to Earth and young age make the Perseus complex an ideal laboratory for studying star formation.

'Hourglass Figure' Points to Magnetic Field's Role in Star Formation
The star-forming region NGC 1333 contains dozens of new stars like the Sun but less than 1 million years old. Spitzer's IRAC camera reveals those stars, as well as warm dust glowing red and bright green shock fronts in this color-coded infrared image. Its proximity to Earth and young age make NGC 1333 an ideal laboratory for studying low-mass star formation. Image credit: NASA/JPL-Caltech/R. Gutermuth & A. Porras (CfA)

Theorists predict that collapsing molecular cloud cores - the seeds of star formation - have to overcome the support provided by their magnetic field in order to form stars. In the process, the competition between gravity pulling inward and magnetic pressure pushing outward was expected to produce a warped, hourglass pattern to the magnetic field within these collapsed cores.

Using the Array, Marrone and his colleagues observed dust emission from IRAS 4A. Because the magnetic field aligns the dust grains in the cloud core, the team could measure the magnetic field's geometry and estimate its strength by measuring the polarization of the dust emission.

"With the special polarization capabilities of the SMA we see the shape of the field directly. This is the first textbook example of theoretically predicted magnetic structure," said Rao.

The data indicate that, in the case of IRAS 4A, magnetic pressure is more influential than turbulence in slowing star formation within the cloud core. The same likely is true for similar cloud cores elsewhere.

Despite the moderating influence of the magnetic field, IRAS 4A is dense enough for gravitational collapse to continue. Approximately a million years in the future, two sunlike stars will shine where only a dust-cloaked cocoon lies today.

The SMA is a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan. It is located atop Mauna Kea in Hawaii.

Source: Harvard-Smithsonian Center for Astrophysics

Explore further: New filter could advance terahertz data transmission

add to favorites email to friend print save as pdf

Related Stories

Sending a rocket through the northern lights

Feb 17, 2015

The combination of American electron clouds and Norwegian northern lights spells trouble for navigation and communication in the Northern regions. The ICI4 rocket will provide knowledge that can help us predict ...

The strange case of the missing dwarf

Feb 18, 2015

The new SPHERE instrument on ESO's Very Large Telescope has been used to search for a brown dwarf expected to be orbiting the unusual double star V471 Tauri. SPHERE has given astronomers the best look so ...

A close call of 0.8 light years

Feb 17, 2015

A group of astronomers from the US, Europe, Chile and South Africa have determined that 70,000 years ago a recently discovered dim star is likely to have passed through the solar system's distant cloud of ...

Image: Giant filament seen on the sun

Feb 12, 2015

A dark, snaking line across the lower half of the sun in this Feb. 10, 2015 image from NASA's Solar Dynamics Observatory (SDO) shows a filament of solar material hovering above the sun's surface. SDO shows ...

Recommended for you

New filter could advance terahertz data transmission

22 hours ago

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

23 hours ago

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

A new X-ray microscope for nanoscale imaging

Feb 27, 2015

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

Top-precision optical atomic clock starts ticking

Feb 26, 2015

A state-of-the-art optical atomic clock, collaboratively developed by scientists from the University of Warsaw, Jagiellonian University, and Nicolaus Copernicus University, is now "ticking away" at the National ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.