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Fraser
2006-Aug-11, 03:58 PM
Astronomers have finally discovered an object that has long been theorized: an hourglass-shaped magnetic field in a star forming region. The field is located in the protostellar system NGC IRAS 4A, which is located about 980 light-years from Earth in the constellation Perseus. Theorists predicted that the magnetic fields of collapsing clouds of gas and dust would form this hourglass shape because of the competing forces of magnetism and gravity.

Read the full blog entry (http://www.universetoday.com/2006/08/11/hourglass-shaped-magnetic-field-discovered/)

iantresman
2006-Aug-11, 09:26 PM
Is the significance that an hourglass magnetic field has been discovered, or that one has been discovered in a star forming region?

Regards,
Ian Tresman

blueshift
2006-Aug-12, 05:12 PM
Is the significance that an hourglass magnetic field has been discovered, or that one has been discovered in a star forming region?

Regards,
Ian TresmanThe latter.

Cougar
2006-Aug-12, 09:42 PM
Is the significance that an hourglass magnetic field has been discovered, or that one has been discovered in a star forming region?
Well, I imagine a star-forming region is where one would look for a "system of two protostars," which is generating the field. (Even enlarged, the "hourglass" shape is a little tough to pick out. I wouldn't criticise an "artist's rendition" of this expected phenomenon....)



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.

I suppose such a huge mass IS going to be "rubbing against itself" from gravitational interactions, thus creating some nontrivial magnetic fields....

VanderL
2006-Aug-13, 08:35 AM
The original press release is
"Hourglass Figure" Points to Magnetic Field's Role in Star Formation. If I read the article correctly, the only "role" of the magnetic field is that it is overcome by gravity, producing the hourglass shape. For the record, if we assume the cloud is a plasma, Bennett- or Z-pinching also results in an hourglass shape.

Cheers.

iantresman
2006-Aug-13, 01:03 PM
Joseph Miquel Girart also has a short presentation on "Magnetic Field and Star Formation (http://www.oan.es/MFSF/PDF/girart.pdf)" (PDF) in which he says that "... magnetic fields may play a crucial role in the formation, evolution of interstellar clouds and in the formation of stars". And that seems to be about it.

The Science magazine of the article "Magnetic Fields in the Formation of Sun-Like Stars (http://www.sciencemag.org/cgi/content/abstract/313/5788/812)" notes that "The magnetic field is substantially more important than turbulence in the evolution of the system". This makes sense if the molecular cloud contains a significant amount of plasma.

An earlier paper by Girart, "Interferometric Mapping of Magnetic Fields in Star-forming Regions II. NGC2024 FIR5 (http://arxiv.org/abs/astro-ph/0110682)" (2001) describes part of the "hourglass shape" as a "pinch".

Regards,
Ian Tresman