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The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot , and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from ...
The Milky Way Galaxy [4] is only one of the billions of galaxies in the known universe. Galaxies are classified into spirals, [5] ellipticals, irregular, and peculiar. Sizes can range from only a few thousand stars (dwarf irregulars) to 10 13 stars in giant ellipticals. Elliptical galaxies are spherical or elliptical in appearance.
The interfaces between regions with sharp differences in rotation are believed to be efficient sites for the dynamo processes that generate the stellar magnetic field. There is also a complex interaction between a star's rotation distribution and its magnetic field, with the conversion of magnetic energy into kinetic energy modifying the ...
The interface between these two regions is where angular rotation gradients are strongest and thus where dynamo processes are expected to be most efficient. The inner differential rotation is one part of the mixing processes in stars, mixing the materials and the heat/energy of the stars.
The Sculptor Galaxy (NGC 253) is an example of a disc galaxy. A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies like the Milky Way and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous component (mostly composed of cool gas and dust).
When two galaxies collide, the material is pulled out in strands, allowing astronomers to determine which way the galaxies are moving. HI regions effectively absorb photons that are energetic enough to ionize hydrogen, which requires an energy of 13.6 electron volts .
The density wave theory also explains a number of other observations that have been made about spiral galaxies. For example, "the ordering of H I clouds and dust bands on the inner edges of spiral arms, the existence of young, massive stars and H II regions throughout the arms, and an abundance of old, red stars in the remainder of the disk".
This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies. Galactic astronomy should not be confused with galaxy formation and evolution , which is the general study of galaxies , their formation, structure, components, dynamics, interactions, and the range of forms they take.