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Magnetic fields dragged and twisted by young star’s dusty disk

Artist's concept of magnetic field lines (purple) being twisted as they are dragged inward toward a swirling, dusty disk surrounding a young protostar. Image via Bill Saxton, NRAO/AUI/NSF.
Artist’s concept of magnetic field lines (purple) being twisted as they’re dragged inward toward a dusty disk surrounding a very young star. Image via Bill Saxton, NRAO/AUI/NSF.

An international team of scientists has learned that material moving in a swirling, dusty disk around a very young protostar – called NGC1333 IRAS 4A, located some 750 light-years from Earth – has probably has dragged in and twisted magnetic fields from the region of space surrounding it. In these circumstances, magnetic fields can either keep the disks from forming, or help them grow. Since these disks contain the raw material for planets, the work has implications for the way solar systems form.

The astronomers observed the star – which is located in our sky in the direction of the constellation Perseus – in 2013 and 2014, using the Karl G. Jansky Very Large Array (VLA) radio telescope near Socorro, New Mexico.

They say this young star is one of two forming within a common large envelope of dust and gas.

Meanwhile, the inner dusty disk surrounding the star contains more than twice the mass of our sun. According to a statement from NRAO, the astronomers:

… measured the alignment, or polarization, of radio waves emitted by material, mostly dust, falling into a burgeoning disk orbiting the young star. The polarization information revealed the configuration of magnetic fields in this region near the star.

One of the scientists involved in the study, Leslie Looney, of the University of Illinois at Urbana-Champaign, explained:

The alignment of magnetic fields in this region near young stars is very important to the development of the disks that orbit them. Depending on its alignment, the magnetic field can either hinder the growth of the disk or help funnel material onto the disk, allowing it to grow.

The scientists said their observations also indicated that millimeter- to centimeter-sized particles are numerous in the disk surrounding the young star. These particles may be the raw materials for planets that will, presumably, ultimately form in the disk.

Since the protostar is only about 10,000 years old – very young in astronomical timescales – the discovery of the particles may mean that such grains form and grow quickly in the environment of a star still in the process of being born.

The scientists are reporting their results in the Astrophysical Journal Letters.

Bottom line: A dusty disk orbiting the protostar NGC1333 IRAS 4A has probably has dragged in and twisted magnetic fields from a larger star-forming envelope surrounding it. These disks contain the raw materials for planet formation. The magnetic fields can either help or hinder their growth. So this new research helps show how solar systems are born.


December 27, 2015
Science Wire

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