Who developed the density wave theory?
The density-wave theory of spiral structure in disk galaxies was proposed in the mid 1960s by C.C. Lin and Frank Shu (Lin & Shu 1964; Bertin & Lin 1995; Shu 2016).
What is the density wave theory for spiral arm galaxies?
The spiral arms in a spiral galaxy are explained by the spiral density wave theorem, which states that they are regions of increased density moving slowly through space.
What causes spiral density waves?
The first is that spiral arms are really indications of density waves (slowly moving regions of higher density) in the disk of the galaxy. The second is that the spiral structure is generated by self-sustaining star formation, coupled with the differential rotation of the galaxy.
What do density waves do?
“Most spiral arms in galaxies are density waves, which are compression waves (like sound) that travel through the disk and cause a piling-up of stars and gas at the crest.
What is a density wave in astronomy?
One of the more successful models developed to explain the origin of spiral arms in galaxies is the density wave model. It is particularly good in describing the formation of the spiral structure we see in grand design spirals.
What does Hubble’s law tell us?
Hubble’s law, which says simply that a galaxy’s velocity (or as is sometimes plotted, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe. If the universe is static and unchanging, there should be no correlation between distance and velocity.
What does density wave theory predict?
The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy’s image. The reason is that stars are born in the density wave but move out of it as they age.
What causes spiral arms in galaxies?
This indicates that the arms are the result of a persistent pattern of stars rather than particular stars causing the structures. That pattern is caused by a density (pressure) wave that spirals from the edge of the disk to the center and back out again, creating the visible spiral arms of the galaxy.
What is the difference between a galactic merger and galactic cannibalism?
Key concepts and summary When galaxies of comparable size collide and coalesce we call it a merger, but when a small galaxy is swallowed by a much larger one, we use the term galactic cannibalism.
What is a density wave in physics?
[′den·səd·ē ‚wāv] (physics) A sound wave or other type of material wave which causes the density of the matter through which it passes to alternately rise above and drop below its mean value.
Is Milky Way a spiral galaxy?
The Milky Way is a huge collection of stars, dust and gas. It’s called a spiral galaxy because if you could view it from the top or bottom, it would look like a spinning pinwheel. The Sun is located on one of the spiral arms, about 25,000 light-years away from the center of the galaxy.