Supermassive black holes (SMBHs) represent an important aspect of galaxy evolution theory that remains at the frontier of modern research. Like their stellar-mass versions, SMBHs have Schwarzschild radii, prevent light from escaping their event horizons and form accretion disks (ADs). Understanding SMBH origin and growth is of central importance in extragalactic astron- omy due to their connection with the evolution of galaxies (Kelly et al. 2010).
The stellar photosphere, the “surface of a star,” is defined as the layer of its atmosphere at an optical depth τλ = 2/3 for a given wavelength λ. But why exactly 2/3?
Among the pioneers of the idea of swirling vortices of gas being responsible for the formation of the solar system was Descartes (1644). In his treatise, he speculated that God sent clouds adrift which changed into comets and planets. Although lacking scientific detail, parallels can be observed with nebular hypotheses pro- posed almost a century later by Swedenborg (1734) and, later, Kant (1755) using Newtonian principles. The first to develop a model of the rotating gaseous nebula collapsing and evolving into a planetary system was, however, Laplace (1796) who did it in a rigorous mathematical way. Although recent history of cosmological theories includes many contrasting alternatives (Buffon 1745; Chamberlin 1901; Jeans 1928; Jeffreys 1929; Whipple 1948), scientific consensus appears to be emerging on how the solar system evolved into its current state.
Geomorphological, mineralogical and other evidence of the conditions favoring the existence of water on Mars in liquid phase is reviewed. This includes signatures of past and, possibly, present aqueous environments, such as the northern ocean, lacustrine environments, sedimentary and thermokarst landforms, glacial activity and water erosion features. Reviewed also are hydrous weathering processes, observed on surface remotely and also via analysis of Martian meteorites. Chemistry of Martian water is discussed: the triple point, salts and brines, as well as undercooled liquid interfacial and solid-state greenhouse effect melted waters that may still be present on Mars. Current understanding of the evolution of Martian hydrosphere over geological timescales is presented from early period to the present time, along with the discussion of alternative interpretations and possibilities of dry and wet Mars extremes.
The subject of the nature and origins of ultra-luminous X-ray sources (ULXs) remains at the frontier of modern research. Existing data allows to fit a wide range of interpretations, including those based on stellar-mass black holes (sMBHs) and intermediate-mass black holes (IMBHs), accretion-powered pulsars, microquasars, and so on. The research of the ULXs is of cosmological and astrophysical importance, as they may become evidence of the existence of IMBHs that may be intimately connected to the formation of first active galactic nuclei engines at z~6.4. Although more recent research favors ULX interpretation based on stellar origins, the presence of IMBHs cannot be ruled out completely. In particular, hyper-luminous X-ray sources (HLXs), which comprise the brightest subset of the ULXs with X-ray luminosities LX 1041 erg s−1, are considered to be the strongest cases for harboring black holes of that type. This report will overview some of the observations and general properties of ULXs and will serve as an introduction to the discussion on the underlying physical models. In addition to ULX models based on black holes of both types, alternative interpretations will be reviewed. Within the sMBH framework, in particular, the importance of interpreting short timescale variations of ULXs is emphasized as a good diagnostic for revealing the underlying super-Eddington emission mechanisms.
It is suggested that two distinct Population III classes may have existed: population III.1 and population III.2. The former, consisting of stars of ∼ 100M⊙, and possibly going as high as 500M⊙, is believed to be formed in dark matter halos at z ≈ 10–30 which corresponds to the times of 0.1–0.48 Gyr after the Big Bang (Rydberg et al. 2013).
I would like to discuss Jupiter’s energy balance, in particular the excess heat radiated by it to space and the amount of Kevin–Helmholtz contraction required to support our measurements.
The aims of this project are as following:
- Reduce multi-band (BVR) CCD data of the M 51, M 63, M 106 (NGC 4258) and NGC 4725 galaxies obtained via 0.8-m (30-inch) telescope at the McDonald Observatory (MDO) in Austin, TX.
- Prepare scientific and color-combined frames.
- Discuss differences and similarities of galactic features appearing in the images that depend on the wavelength and the galaxy type.
- Conduct preliminary surface photometry of galaxies.
Following (Zwicky 1937) we start with the virial theorem that relates the average kinetic energy ⟨K⟩ to the average gravitational potential energy ⟨U⟩ of bodies in a system (cluster, galaxy, etc) in the state of equilibrium: ⟨K⟩ = −1/2⟨U⟩, with brackets denoting an average value. We can measure radial velocities Vr of individual bodies in a system (of stars in a globular cluster or a galaxy, of galaxies in a cluster of galaxies) via spectroscopic means.
It is known that star formation occurs in regions where dense molecular clouds undergo gravitational collapse. While observations of cold dusty disks and envelopes require long wavelength detectors to penetrate through obscuring material—from mid-infrared to radio—it is preferred to observe stars in the range between ultraviolet and near-infrared range (Hartmann 2003).