Submitted via IRC for SoyCow4408
How does our Milky Way galaxy get its spiral form?
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."
(Score: 1, Interesting) by Anonymous Coward on Friday December 20 2019, @07:59AM (8 children)
Ever watch a toilet flush? It's like that.
(Score: 0) by Anonymous Coward on Friday December 20 2019, @09:20AM (1 child)
No no no...
Ii's something weilding a cosmic spoon made of dark matter that's responsible..
The question is, as is it stirring the galactic soup, when will it be ready to drink?
Alternatively, if the soup bowl analogy doesn't do it for you, as any fule kno God is an Englishman, and he's vigourously stirring his galaxy sized cup of tea...extra Milky (way) as it were..
(Score: 0) by Anonymous Coward on Friday December 20 2019, @02:54PM
The Galactic Barista.
(Score: 0) by Anonymous Coward on Friday December 20 2019, @09:35AM
Dors that mean in the other hemisphere of universe/localgroup. The galaxies form arms the other direction?
(Score: 5, Interesting) by Coward, Anonymous on Friday December 20 2019, @09:35AM (4 children)
The textbooks claim that the spiral shapes of galaxies represent an equilibrium disk with superimposed density waves, which is important for follow-on claims about rotation curves and dark matter. The density wave theory comes out of some very mathematical papers whose validity is hard to judge. But like your example, all the spirals we know in daily life are associated with non-equilibrium processes.
The equilibrium claim seems to be mainly based on the estimate that stars have made many orbits around the galaxy. The number I remember for the sun is 50 or so, which doesn't seem particularly large.
(Score: 2, Informative) by Anonymous Coward on Friday December 20 2019, @02:37PM (1 child)
(Score: 2) by Coward, Anonymous on Friday December 20 2019, @10:11PM
Thanks for the correction.
(Score: 2) by bzipitidoo on Friday December 20 2019, @08:06PM (1 child)
But are galaxies in equilibrium? The supermassive black hole at the center could act much the same as the drain of a toilet.
(Score: 2) by Coward, Anonymous on Friday December 20 2019, @11:39PM
The equilibrium model applies to the non-core part of spiral galaxies, i.e. the arms. A black hole at the center could still slowly accumulate mass. According to my textbook (Binney & Tremaine: Galactic Dynamics), the spiral arms are not indicative of mass flow. They say:
But this explanation did require the invention of a whole new type of matter, so I'm not convinced.
(Score: 2) by legont on Friday December 20 2019, @02:46PM
https://earthsky.org/space/supermassive-black-hole-milky-way-galaxys-center-may-have-friend [earthsky.org]
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.