Extragalactic Background Light Encyclopedia of Astronomy & Astrophysics eaa.iop.org Rebecca A Bernstein
... include both older populations at low redshift and young populations at high redshift. Finally, much of the stellar emission in the universe will be contribute to the far-IR background, both because the light from the earliest generations of stars (most distant stars) will be redshifted to longer wa ...
... include both older populations at low redshift and young populations at high redshift. Finally, much of the stellar emission in the universe will be contribute to the far-IR background, both because the light from the earliest generations of stars (most distant stars) will be redshifted to longer wa ...
ertan et al 11cesme
... AXP/SGRs. For the sources with weaker magnetic dipole fields, rin comes out of the light cylinder earlier than it does for the sources with stronger dipole fields. After this point, P remains almost constant because of decreasing efficiency of the disk torque [2]. As seen in Fig. 1, the model source ...
... AXP/SGRs. For the sources with weaker magnetic dipole fields, rin comes out of the light cylinder earlier than it does for the sources with stronger dipole fields. After this point, P remains almost constant because of decreasing efficiency of the disk torque [2]. As seen in Fig. 1, the model source ...
Discovery of Kilohertz Quasi-periodic Oscillations from 4U 1820
... pressure from the X-ray source may cause the inner disk to puff up into a torus. The vertical extent of this toroidal material may block our line of sight to the very innermost regions of the disk where the HF QPOs originate. However, the cutoff luminosity of LX 5 3.1 3 1037 ergs s21 only represents ...
... pressure from the X-ray source may cause the inner disk to puff up into a torus. The vertical extent of this toroidal material may block our line of sight to the very innermost regions of the disk where the HF QPOs originate. However, the cutoff luminosity of LX 5 3.1 3 1037 ergs s21 only represents ...
The importance of episodic accretion for low
... protostar. The disc becomes gravitationally unstable (first and second column) but fragmentation is damped by heating due to an accretion burst (third column); however, after this burst the disc cools sufficiently to undergo gravitational fragmentation; 2 low-mass stars form in the disc. ...
... protostar. The disc becomes gravitationally unstable (first and second column) but fragmentation is damped by heating due to an accretion burst (third column); however, after this burst the disc cools sufficiently to undergo gravitational fragmentation; 2 low-mass stars form in the disc. ...
Molecular Clouds and the Onset of Star Formation
... cloud cores. The clouds have been characterized as both clumpy and filamentary. The general properties on selected scales are listed in Table 2.1. In fact each type of structure exhibits a range of properties [335]. The clumpiness of a molecular cloud can be characterized by a so-called volume filli ...
... cloud cores. The clouds have been characterized as both clumpy and filamentary. The general properties on selected scales are listed in Table 2.1. In fact each type of structure exhibits a range of properties [335]. The clumpiness of a molecular cloud can be characterized by a so-called volume filli ...
Pleiades Mythology
... They believe that Mythic Mountain is actually the home of the Kachinas [Gods]. This mountain top is sacred. Being the home of the Kachina spirits it is the place where all of the large mythic beings they honor in their rituals land. "We come as clouds to bless the Hopi people" is a quote passed from ...
... They believe that Mythic Mountain is actually the home of the Kachinas [Gods]. This mountain top is sacred. Being the home of the Kachina spirits it is the place where all of the large mythic beings they honor in their rituals land. "We come as clouds to bless the Hopi people" is a quote passed from ...
PS1-10jh: The Disruption of a Main-Sequence Star of Near
... This means that a complete simulation of the full problem within a single simulation is very computationally expensive. Instead, we run two separate simulations that are each wellequipped to describe the behavior of the debris stream at two different epochs. To determine the fate of the debris liber ...
... This means that a complete simulation of the full problem within a single simulation is very computationally expensive. Instead, we run two separate simulations that are each wellequipped to describe the behavior of the debris stream at two different epochs. To determine the fate of the debris liber ...
Statistical properties of a sample of periodically variable B-type supergiants ⋆
... with M = 64 M⊙ and predicted irregular velocity and luminosity variations with time scales of 1 to 20 d. They also proposed that such massive stars undergo pulsationally-driven mass-loss. It is not clear how their result will change for stars in the mass range of 10 to 30 M⊙ , which is the transitio ...
... with M = 64 M⊙ and predicted irregular velocity and luminosity variations with time scales of 1 to 20 d. They also proposed that such massive stars undergo pulsationally-driven mass-loss. It is not clear how their result will change for stars in the mass range of 10 to 30 M⊙ , which is the transitio ...
On the elemental abundance and isotopic mixture of mercury in
... flow of excited particles in one direction while unexcited particles flow in the opposite direction. Since the collisional cross sections typically are larger for excited than unexcited atoms on account of their larger effective radius, the flow of excited particles is decelerated more efficiently by c ...
... flow of excited particles in one direction while unexcited particles flow in the opposite direction. Since the collisional cross sections typically are larger for excited than unexcited atoms on account of their larger effective radius, the flow of excited particles is decelerated more efficiently by c ...
preprint, pdf version - LESIA
... occultation campaigns. They usually have large apparent sizes (30 mas or more) and thus have a greater chance of a positive detection. In addition, theory indicates that larger TNOs are most likely to possess atmospheres (Elliot & Kern 2003). In the case of atmospheres, even negative occultation cho ...
... occultation campaigns. They usually have large apparent sizes (30 mas or more) and thus have a greater chance of a positive detection. In addition, theory indicates that larger TNOs are most likely to possess atmospheres (Elliot & Kern 2003). In the case of atmospheres, even negative occultation cho ...
Correlation Between Nitrogen and Oxygen Content in Planetary
... setting, we hypothesized that the amount of oxygen and nitrogen present in the nebulae will affect the shape of the nebulae as it forms. Based on the data collected in this experiment, it does appear as if this hypothesis is supported. It is important to address that oxygen and nitrogen were the two ...
... setting, we hypothesized that the amount of oxygen and nitrogen present in the nebulae will affect the shape of the nebulae as it forms. Based on the data collected in this experiment, it does appear as if this hypothesis is supported. It is important to address that oxygen and nitrogen were the two ...
Circumstellar dust shells around long-period variables
... Nevertheless, for our study we selected AFGL 3068 because it is the brightest and best studied specimen, having the highest known mass loss rate of any carbon rich AGB stars in the solar neighborhood. Also the data available on this source are particularly appropriate to our intended modeling. Final ...
... Nevertheless, for our study we selected AFGL 3068 because it is the brightest and best studied specimen, having the highest known mass loss rate of any carbon rich AGB stars in the solar neighborhood. Also the data available on this source are particularly appropriate to our intended modeling. Final ...
Collisions and Encounters of Stellar Systems
... between two such galaxies is Σ ≈ π(2R)2 . If the positions and velocities of the galaxies are uncorrelated, the rate at which an L! galaxy suffers collisions with similar galaxies is then expected to be of order nΣvp ≈ 10−6 Gyr−1 , so only about one galaxy in 105 would suffer a collision during the ...
... between two such galaxies is Σ ≈ π(2R)2 . If the positions and velocities of the galaxies are uncorrelated, the rate at which an L! galaxy suffers collisions with similar galaxies is then expected to be of order nΣvp ≈ 10−6 Gyr−1 , so only about one galaxy in 105 would suffer a collision during the ...
Influence of the Gould Belt on Interstellar Extinction
... objects, and the extinction for a typical large region of space can be determined as, say, 5.0m ± 0.5m , i.e., with an accuracy of 10%. An analytical model of extinction within the nearest kiloparsec with a relative accuracy higher than that of the model by Arenou et al. (1992) is unlikely to be po ...
... objects, and the extinction for a typical large region of space can be determined as, say, 5.0m ± 0.5m , i.e., with an accuracy of 10%. An analytical model of extinction within the nearest kiloparsec with a relative accuracy higher than that of the model by Arenou et al. (1992) is unlikely to be po ...
Radiative hydrodynamics simulations of red supergiant stars. III
... 5.6 ≤ V ≤ 20. These data along with multi-band and multiepoch photometric and spectrocopic data will allow to reconstruct the formation history, structure, and evolution of the Galaxy. Among all the objects that will be observed, late-type stars present granulation-related variability that is consid ...
... 5.6 ≤ V ≤ 20. These data along with multi-band and multiepoch photometric and spectrocopic data will allow to reconstruct the formation history, structure, and evolution of the Galaxy. Among all the objects that will be observed, late-type stars present granulation-related variability that is consid ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.