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Physics Galaxy was founded as an online learning portal by Ashish Arora. [2] It was founded as an initiative to coach students for free especially for those in rural areas, who cannot afford expensive coaching facilities. Later in 2011, a YouTube channel of the same name was founded. [3] [4]
Eris is a computer simulation of the Milky Way galaxy's physics. [1] It was done by astrophysicists from the Institute for Theoretical Physics at the University of Zurich, Switzerland and University of California, Santa Cruz. [2]
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".
Velocity dispersion (y-axis) plotted against absolute magnitude (x-axis) for a sample of elliptical galaxies, with the Faber–Jackson relation shown in blue.. The Faber–Jackson relation provided the first empirical power-law relation between the luminosity and the central stellar velocity dispersion of elliptical galaxy, and was presented by the astronomers Sandra M. Faber and Robert Earl ...
Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newton's second law to account for observed properties of galaxies.Its primary motivation is to explain galaxy rotation curves without invoking dark matter, and is one of the most well-known theories of this class.
And inside such a typical galaxy the dynamical friction and accretion on stellar black holes over a 10-Gyr Hubble time change the black hole's velocity and mass by only an insignificant fraction % if the black hole makes up less than 0.1% of the total galaxy mass N M ⊙ ∼ 10 6 − 11 M ⊙ {\displaystyle NM_{\odot }\sim 10^{6-11}M_{\odot }} .
The reason is that these galaxy formation models predict a large number of mergers. If disk galaxies merge with another galaxy of comparable mass (at least 15 percent of its mass) the merger will likely destroy, or at a minimum greatly disrupt the disk, and the resulting galaxy is not expected to be a disk galaxy (see next section).
The galaxy also contains a dynamically significant magnetic field, meaning that the dynamics are governed by the equations of compressible magnetohydrodynamics. In many cases, the electrical conductivity is large enough for the ideal MHD equations to be a good approximation, but this is not true in star forming regions where the gas density is ...