USRA: How Does Our Milky Way Galaxy Get Its Spiral Form?

[bystander]

How Does Our Milky Way Galaxy Get Its Spiral Form?
Universities Space Research Association | 2019 Dec 13

Magnetic fields in NGC 1086, or M77, are shown as streamlines over a visible light and X-ray composite image of the galaxy from the Hubble Space Telescope, the Nuclear Spectroscopic Array, and the Sloan Digital Sky Survey. The magnetic fields align along the entire length of the massive spiral arms — 24,000 light years across (0.8 kiloparsecs) — implying that the gravitational forces that created the galaxy’s shape are also compressing the its magnetic field. This supports the leading theory of how the spiral arms are forced into their iconic shape known as “density wave theory.” SOFIA studied the galaxy using far-infrared light (89 microns) to reveal facets of its magnetic fields that previous observations using visible and radio telescopes could not detect. Credits: NASA/SOFIA; NASA/JPL-Caltech/Roma Tre Univ.

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A question that has long puzzled scientists is how our Milky Way galaxy which has an elegant spiral shape with long arms, took this form.

Universities Space Research Association today announced that new observations of another galaxy are shedding light on how spiral-shaped galaxies like our own get their iconic shape.

According to research from the Stratospheric Observatory for Infrared Astronomy (SOFIA), magnetic fields play a strong role in shaping these galaxies. “Magnetic fields are invisible, but they may influence the evolution of a galaxy,” said Dr. Enrique Lopez-Rodriguez, a Universities Space Research Association scientist at the SOFIA Science Center at NASA’s Ames Research Center in California’s Silicon Valley. “We have a pretty good understanding of how gravity affects galactic structures, but we’re just starting to learn the role magnetic fields play.”

Magnetic fields in the spiral galaxy are aligned with the spiral arms across the entire galaxy — more than 24,000 light years across. The magnetic field alignment with the star formation implies that the gravitational forces that created the galaxy’s spiral shape is also compressing the magnetic field. The alignment supports the leading theory of how the arms are forced into their spiral shape known as “density wave theory.”

Scientists measured magnetic fields along the spiral arms of the galaxy called NGC 1068, or M77. The fields are shown as streamlines that closely follow the circling arms. ...

How to Shape a Spiral Galaxy
NASA | Ames | SOFIA | 2019 Dec 10

SOFIA/HAWC+ Traces the Magnetic Fields in NGC 1068 ~ E. Lopez-Rodriguez et al (HAWC+ Science Team)

• arXiv.org > astro-ph > arXiv:1907.06648 > 15 Jul 2019 (v1), 15 Nov 2019 (v2)