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Volcanism based on melting rocks (silicate volcanism) is long known on Earth and has also been found on Jupiter’s moon Io. Remnants of this type of volcanism have been identified also on other bodies in the solar system. Energy sources powered by accretion and the decay of radioactive isotopes seem to be dominant mainly inside larger bodies, which have enough volume to accumulate and retain this energy in significant amounts. On the other hand, the impact of tidal forces allows even tiny bodies to melt up and pass into the stage of cryovolcanism. The dependence of tidal heating on the size of the object is minor, but the masses of and the distances to accompanying bodies as well as the inner compositions of the heated body are central factors. Even though Io as an example of a body supporting silicate volcanism is striking, the physics of tidal forces might suggest a relatively high probability for cryovolcanism. This chapter aims at considering the parameters known and objects found so far in our solar system to give insights into where in our system and other planetary systems cryovolcanism might be expected.

Decades of observations and theoretical studies present intriguing results about black hole accretions: supermassive black holes (SMBHs), located in the centers of galaxies, are accreting similar to Galactic stellar-mass black hole systems (GBHs). This is the unified model of black hole accretion, which indicates active galactic nuclei (AGNs, the accreting SMBHs) are only the scaled-up version of galactic X-ray binaries (XRBs, the accreting GBHs). The analogy between AGNs and XRBs ensures us to determine AGN evolutions on cosmological timescales by simply studying the quick-playing Galactic systems, which is much easy in observation and modeling. X-ray emission is produced by the inner region of the accretion disk and corona, which is close to the black holes and provides the diagnostics of accretion strength. Meanwhile, radio emission is an indicator of the ejection process, which is another fundamental part of accreting black holes. Furthermore, accreting flows are also regulated by black hole masses and accretion rates/Eddington ratios. Therefore, the unified model of black hole accretion is the correlation between accretion and ejection process and black hole masses. In this chapter, we will review models concerning the unified model of black hole accretions and present recent updates in this area.

Enceladus has a subsurface ocean in the South Pole that has been inferred due to the presence of water vapor and other molecules like molecular hydrogen and ammonia detected by the Cassini mission from the ejection of material through the plumes in that region. The chemical composition of this ocean could give some information about the evolutionary stage of the icy moon if its components are found to be similar with the aqueous chemistry of the primitive oceans on Earth during glacial periods. Here we present a comparative geochemical analysis between the ocean of Enceladus and the aqueous composition of the oceans on Earth during the Snowball Event, in order to figure out if there are similar species, how the interaction of the metabolic processes between them works and if, in the future, those molecules could evolve making possible the emergence of life.

In this work, a theoretical model is developed for explanation of temporal evolution of extragalactic radio sources via beaming, orientation effects and asymmetries. Equation of the form D≈P±q1+z−m is used to account for the D ∼ P/z relation. Also, D≈D01+z−1+z1+z2 accounted properly for Ω0=1 cosmology than the Ω0=0 counterpart in linear size versus redshift of radio sources. Similarly, D=Dc1∓lnPPc1/2 model explained redshift-luminosity relationship of extragalactic radio sources. The results from the regression analyses are q = +0.003 (r = 0.04) for sources with z

Problems related to Big Bang because of the Doppler interpretation of cosmological redshift have not been resolved up to recent years. The “tired light” theory proposes an energy loss model that has its own limitations. Chen in 2020 and 2021 proposed to treat light propagation through the space just as a field problem involving electromagnetic waves and governed by the well-known nonlinear Schrödinger (NLS) equation. The space is not a vacuum and is sparsely populated with matters. Electromagnetic waves traveling through the space will undergo changes as predicted by the NLS equation involving a linear dispersion and a nonlinear self-phase focusing terms. Using the cosmological principle, the coefficients associated with these terms could be constants but extremely small in value. Special numerical methods have been developed and could be used to find both bright and dark soliton-like solutions for the NLS equation that are stable and could travel through the extremely long distance involved. These solutions clearly show the redshift is linearly proportional to distance traveled for both bright and dark solitons. The conclusion is that redshift (and blue shift) is an innate nature of light traveling through the space.