Magnetic field of the skeletal bone of the Milky Way – the G47 filament

(ORDO NEWS) — The formation of new stars in our Milky Way galaxy takes place inside long, dense filaments of gas and dust that stretch along the spiral arms.

Called “bones” because they outline the densest “skeletal” helical structures, these filaments are at least 50 times longer than they are wide, and share the same motion of all internal objects along the length of the filament.

Although most of the physical properties of these “bones” are known to scientists, the characteristics of magnetic fields remain rather poorly understood.

These fields play an important role in preventing the gravitational collapse of gas and dust clouds into new stars or in the transport of material along the “bone” into the cores with the formation of new stars.

Magnetic fields in space are difficult to measure. The most popular method is based on observations of the emission of non-spherical dust particles, which orient their short axes along the direction of the field, as a result of which the infrared radiation emitted by them acquires a polarization with a predominance of the polarization direction perpendicular to the direction of the field lines.

Measuring this weak polarization signal and then calculating the field strength and direction has only recently become more accessible to scientists, with the introduction of the Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne HAWC+ instrument and its 2.5-meter telescope.

In the new work, astronomers led by Ian Stephens of the Harvard-Smithsonian Center for Astrophysics used the HAWC+ polarization map to get a detailed picture of the Milky Way’s G47.06+0.26 bone.

This filament is 190 light years long and about five light years wide. The mass of the structure is estimated at 28,000 solar masses, while the typical dust temperature is 18 Kelvin. The Spitzer Space Telescope’s IRAC camera previously helped map the “bones” to identify star-forming regions along the length of the filament.

Astronomers have determined in which zones along the length of the “bone” the magnetic field is able to keep gas from gravitational collapse with the formation of stars, as well as areas where the magnetic field is not strong enough for this.

They also mapped low-density areas where the field has a more complex shape. These results will help scientists analyze the evolutionary processes taking place in our Milky Way galaxy.

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