Cosmology: spiral galaxies formed by magnetism (Introduction)

by David Turell , Saturday, December 14, 2019, 20:03 (1807 days ago) @ dhw

Latest findings:

https://phys.org/news/2019-12-milky-galaxy-spiral.html

"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.

The M77 galaxy is located 47 million light years away in the constellation Cetus. It has a supermassive active black hole at its center that is twice as massive as the black hole at the heart of our Milky Way galaxy. The swirling arms are filled with dust, gas and areas of intense star formation called starbursts.

"SOFIA's infrared observations reveal what human eyes cannot: magnetic fields that closely follow the newborn-star-filled spiral arms. This supports the leading theory of how these arms are forced into their iconic shape known as "density wave theory." It states that dust, gas and stars in the arms are not fixed in place like blades on a fan. Instead, the material moves along the arms as gravity compresses it, like items on a conveyor belt.

"The magnetic field alignment stretches across the entire length of the massive, arms—approximately 24,000 light years across. This implies that the gravitational forces that created the galaxy's spiral shape are also compressing its magnetic field, supporting the density wave theory.

"'This is the first time we've seen magnetic fields aligned at such large scales with current star birth in the spiral arms," said Lopez-Rodriquez. "It's always exciting to have observational evidence like this from SOFIA that supports theories.'"

Comment: Making a giant spiral like the Milky Way is very complex, but its size and shape put the Earth in a very safe place two-thirds of the way out on the second arm.