How to Shape a Spiral Galaxy

Posted: December 10, 2019 by oldbrew in Astrophysics, Electro-magnetism, Gravity, research

Spiral galaxy NGC 5457 aka the Pinwheel Galaxy [image credit: European Space Agency & NASA]


No mention of electricity here, although it’s required to create the magnetism: ‘The magnetic behavior of a material depends on its structure, particularly its electron configuration’ – Wikipedia. We’re told these electromagnetic forces stretch for 24,000 light years in one galaxy, but understanding them is still in its infancy.

New observations from SOFIA are shedding light on how spiral-shaped galaxies, like our own Milky Way, get their iconic shape, says NASA.

Our Milky Way galaxy has an elegant spiral shape with long arms filled with stars, but exactly how it took this form has long puzzled scientists. New observations of another galaxy are shedding light on how spiral-shaped galaxies like our own get their iconic shape.

Magnetic fields play a strong role in shaping these galaxies, according to research from the Stratospheric Observatory for Infrared Astronomy, or SOFIA.

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.

“Magnetic fields are invisible, but they may influence the evolution of a galaxy,” said 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.”

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.

The results are published in the Astrophysical Journal.

Full article here.
– – –
Harvard-Smithsonian Center for Astrophysics: What ionized the universe? [2019]

Quote: The sparsely distributed hot gas that exists in the space between galaxies, the intergalactic medium, is ionized. The question is, how?
. . .
The result…suggests that a serious reconsideration of the ionizing budget of the intergalactic medium of the universe is needed.

Comments
  1. JB says:

    The reason these blokes don’t understand it is they refuse to accept the pioneering research earlier investigators produced explaining the mechanisms. Aflvén, Arp,and Scott, to name a few. Tardy duplication seems to be modern astronomy and physics MO.

  2. Gamecock says:

    ‘Our Milky Way galaxy has an elegant spiral shape with long arms filled with stars, but exactly how it took this form has long puzzled scientists.’

    ‘This implies that the gravitational forces that created the galaxy’s spiral shape’

    Carl Sagan told us it was gravity. Galaxies passing in the night distorted each other’s shape. The most fascinating thing was that stars in the galaxies never collided; a galaxy could pass thru another and there would be no impacts, as the stars are actually vast distances apart – light years – even though they appear close to us.

  3. oldbrew says:

    ‘Instead, the material moves along the arms as gravity compresses it, like items on a conveyor belt.’

    Where is the supposed gravity coming from to do that? Gravity from the galactic core would want to pull material towards itself.

  4. Coeur de Lion says:

    It looks like drag on a rotation to me. But drag in what?

  5. Tom Abbott says:

    From the article: “The magnetic field alignment stretches across the entire length of the massive, arms — approximately 24,000 light years across.”

    I’m trying to figure out how a magnetic field communicates from one side of a galaxy to the other. Or does it? The speed of light has to be considered.

    How is there a coherent magnetic field across a galaxy thousands of lightyears wide?

  6. oldbrew says:

    M77: We report the first detection of galactic spiral structure by means of thermal emission from magnetically aligned dust grains.
    . . .
    The observations can be fit with a logarithmic spiral model.
    https://arxiv.org/abs/1907.06648

  7. oldbrew says:

    Tom Abbott says:
    December 12, 2019 at 2:03 am (Edit)

    How is there a coherent magnetic field across a galaxy thousands of lightyears wide?
    – – –
    Good question. Something has to be holding galaxies together, otherwise they wouldn’t exist.

    Same for solar systems on the small scale.

  8. Gamecock says:

    Gravity answers all questions.

    It applies even down to the star level. Fusion is trying to blow the stars apart; gravity is holding them together.

    Magnetic fields ARE important. Earth is shielded by its field. But there is no reason to believe that magnetic fields play a significant role in the shaping of the galaxies. What we see is consistent with gravity.

    ‘Magnetic fields play a strong role in shaping these galaxies, according to research from the Stratospheric Observatory for Infrared Astronomy, or SOFIA.’

    Gross speculation.

    ‘The magnetic field alignment stretches across the entire length of the massive, arms — approximately 24,000 light years across.’

    Maybe. At this point, it’s no more than a theory. An extraordinary claim. I’m waiting for the extraordinary evidence.

  9. oldbrew says:

    We have disc-shaped galaxies and solar systems, which rotate. All the bodies in them also rotate.

    Gravity doesn’t explain rotation.

  10. Gamecock says:

    It doesn’t need to. Gravity explains why the rotation is contained. Momentum plus gravity equals orbit.

  11. oldbrew says:

    The ‘Heron’ galaxy…

    Image of the interacting galaxy pair NGC 5394/5

    https://phys.org/news/2019-12-image-galactic-ngc.html