Measuring magnetic fields

Apr 09, 2012
An optical image of the Pelican Nebula, a complex region forming young stars. New observations of a similar star forming region have determined the strength of its magnetic field. Credit: Martin Pugh

(Phys.org) -- Polarized light is a familiar phenomenon, as people who prefer polarized sunglasses can testify. The electric field in a beam of light can vibrate either left-right or up-down, and the scattering or reflection of light can result in the preferential absorption of one or the other of these two "polarizations." The majority of sunlight on Earth, for example, is preferentially polarized in one direction due to scattering in the atmosphere; that's what makes polarized sunglasses so effective.

Electromagnetic radiation from astrophysical sources can also be polarized. It often occurs because of selective scattering from elongated (possibly even needle-shaped) . When most of the grains in a volume have been oriented in the same direction by the region's magnetic field, the degree of polarization of will be significant. Astronomers are extremely interested in magnetic fields, which play a major - perhaps even a dominant - role in controlling the shapes and motions of clouds. Unfortunately, magnetic fields are very difficult to measure directly. Polarization observations, it turns out, offer a unique way to probe the magnetic fields.

SAO astronomer Paul Ho and two colleagues used the (SMA) to measure the polarization of millimeter wavelength light from a dusty region of particularly active star formation called W51e2, located about twenty two thousand light-years away from us. The SMA measures two properties of the scattered light: the angle of the vibration with respect to the cloud's contours, and the amount of polarization compared to the unpolarized light.

The scientists used this information, together with known features of the region, to develop a new and potentially wide-ranging scheme to determine magnetic field strengths in . With some general assumptions, they show that the field strength can derived from the angle the polarization makes with the radiation's intensity contours. In the case of W51e2, they conclude that the field's strength is relatively strong (about 65 times weaker that the Earth's magnetic field; they suspected as much - that's why they chose this object in the first place).

This new technique, if corroborated by other research, can be expanded and applied to many other objects and potentially revolutionize our understanding of this key physical component of the interstellar medium.

Explore further: A star's early chemistry shapes life-friendly atmospheres

Related Stories

A new way to measure Earth's magnetosphere

Jan 04, 2012

US researchers have demonstrated the potential use of a new way to measure properties of Earth's magnetosphere, the magnetic bubble that surrounds the planet.

Magnetic fields set the stage for the birth of new stars

Nov 16, 2011

(PhysOrg.com) -- Astronomers at the Max Planck Institute for Astronomy have, for the first time, measured the alignment of magnetic fields in gigantic clouds of gas and dust in a distant galaxy. Their results ...

Magnetic fields in interstellar clouds

Mar 25, 2011

(PhysOrg.com) -- Magnetic fields play an important role in the formation and evolution of stars, as they stretch around a hot medium like a rubber band and help to determine the flow of material onto or away ...

SDO helps measure magnetic fields on the sun's surface

Jan 20, 2012

(PhysOrg.com) -- Science nuggets are a collection of early science results, new research techniques, and instrument updates that further our attempt to understand the sun and the dynamic space weather system ...

Physicists rotate beams of light

Apr 05, 2011

Controlling the rotation of light – this amazing feat was accomplished at the Vienna University of Technology (TU Vienna), by means of a ultra thin semiconductor. This can be used to create a transistor ...

Recommended for you

Professional and amateur astronomers join forces

14 hours ago

(Phys.org) —Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time. These amateur astronomers devote hours ...

A star's early chemistry shapes life-friendly atmospheres

Apr 23, 2014

Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless ...

User comments : 0

More news stories

Habitable exoplanets are bad news for humanity

Last week, scientists announced the discovery of Kepler-186f, a planet 492 light years away in the Cygnus constellation. Kepler-186f is special because it marks the first planet almost exactly the same size as Earth ...

Professional and amateur astronomers join forces

(Phys.org) —Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time. These amateur astronomers devote hours ...

Kazakh satellite to be launched into orbit

Kazakhstan's first-ever Earth observation satellite is to be fired into orbit next week from the European spaceport in Kourou in French Guiana, launch company Arianespace said.

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Ocean microbes display remarkable genetic diversity

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...