Activity III: Calibrating Images
... just that it remains constant. For images of objects beyond our own galaxy, foreground stars are typically chosen. These are stars within our galaxy that are in the same line of sight to the further away object. If the observing conditions did not change from one night to the next, the reference sta ...
... just that it remains constant. For images of objects beyond our own galaxy, foreground stars are typically chosen. These are stars within our galaxy that are in the same line of sight to the further away object. If the observing conditions did not change from one night to the next, the reference sta ...
CHAPTER 1 The Formation and Structure of Stars
... • The thermal energy in clouds of gas causes them to resist collapse. – Temperature is a measure of the motion of the atoms or molecules in a material—in a hot gas, the atoms move more rapidly than do those in a cool gas. – Although the interstellar clouds are very cold, even at a temperature of onl ...
... • The thermal energy in clouds of gas causes them to resist collapse. – Temperature is a measure of the motion of the atoms or molecules in a material—in a hot gas, the atoms move more rapidly than do those in a cool gas. – Although the interstellar clouds are very cold, even at a temperature of onl ...
Stellar evolution - Statistical Physics Group
... hydrogen to helium supplies the star’s energy loss, is well understood and postmain-sequence evolution has been followed to the phase of helium burning or carbon burning at the centre of the star. I t is clear that it will only be a matter of time before these calculations are carried to a later sta ...
... hydrogen to helium supplies the star’s energy loss, is well understood and postmain-sequence evolution has been followed to the phase of helium burning or carbon burning at the centre of the star. I t is clear that it will only be a matter of time before these calculations are carried to a later sta ...
Why is the Sun very dense on the inside?
... Why do the hottest spectra (types O and B) show few absorption lines? ...
... Why do the hottest spectra (types O and B) show few absorption lines? ...
GammaRay Bursts, the Strongest Explosions in the Universe.
... Gamma‐ray bursts, GRBS, short and intense burst of low energy γ‐rays that arrive from random directions in the sky are possibly the most fascinating astronomical objects known today. GRBs are fascinating because they are the brightest objects in the sky corresponding t ...
... Gamma‐ray bursts, GRBS, short and intense burst of low energy γ‐rays that arrive from random directions in the sky are possibly the most fascinating astronomical objects known today. GRBs are fascinating because they are the brightest objects in the sky corresponding t ...
Stellar Lifetimes
... by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs out? © 2007 Pearson Education Inc., p ...
... by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs out? © 2007 Pearson Education Inc., p ...
Kinetic equilibrium of iron in the atmospheres of cool stars
... quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravities as determined by the Fe /Fe ionization equilibria are in agr ...
... quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravities as determined by the Fe /Fe ionization equilibria are in agr ...
The first photometric analysis of the overcontact binary MQ UMa with
... during their main sequence evolutionary stage. The formation and evolution of W UMa type binary systems are still unsolved problems in astrophysics. The most popular evolutionary scenario is that they are formed from initially detached systems via angular momentum loss (AML) by means of magnetic ste ...
... during their main sequence evolutionary stage. The formation and evolution of W UMa type binary systems are still unsolved problems in astrophysics. The most popular evolutionary scenario is that they are formed from initially detached systems via angular momentum loss (AML) by means of magnetic ste ...
Gravitational Waves and the Origin of Gravitation Abstract:
... But it may work if Magnetism dominates Gravitation (Hulse-Taylor Pulsar) The Quantum of Gravitational Radiation is the Neutrino, because Supernova Models indicate that 99% of the Gravitational Binding energy of a collapsing star is emitted in the form of Neutrinos’ Radiation. Since radiation is emit ...
... But it may work if Magnetism dominates Gravitation (Hulse-Taylor Pulsar) The Quantum of Gravitational Radiation is the Neutrino, because Supernova Models indicate that 99% of the Gravitational Binding energy of a collapsing star is emitted in the form of Neutrinos’ Radiation. Since radiation is emit ...
the first three thresholds - McGraw
... By the third century ce, as Christianity spread within the Roman Empire, a number of Christian theologians attempted to date the moment of creation. Their attempts were “scientific” insofar as they were based on evidence from the most authoritative written source they knew: the Bible. Using this sou ...
... By the third century ce, as Christianity spread within the Roman Empire, a number of Christian theologians attempted to date the moment of creation. Their attempts were “scientific” insofar as they were based on evidence from the most authoritative written source they knew: the Bible. Using this sou ...
VY Canis Majoris: The Astrophysical Basis of Its Luminosity
... photosphere or its surface directly. It has been known for some time that VY CMa’s absorption spectrum is significantly redshifted with respect to its systemic velocity (Humphreys 1975, Wallerstein 1977) due to scattering by dust (Herbig 1970, Kwok 1976, Van Blerkom & Van Blerkom 1978). Indeed, most ...
... photosphere or its surface directly. It has been known for some time that VY CMa’s absorption spectrum is significantly redshifted with respect to its systemic velocity (Humphreys 1975, Wallerstein 1977) due to scattering by dust (Herbig 1970, Kwok 1976, Van Blerkom & Van Blerkom 1978). Indeed, most ...
Measurements of Neutron Star Masses
... eating the phase structure of dense cold quark eventually squeezed out at densities near n0 (32). If so, beginning at about 0.1 n0, there matter (35) has yielded novel states of matter, Motivation 1. Nuclear equation of state. could be a continuous change of the dimenincluding color-superconducting ...
... eating the phase structure of dense cold quark eventually squeezed out at densities near n0 (32). If so, beginning at about 0.1 n0, there matter (35) has yielded novel states of matter, Motivation 1. Nuclear equation of state. could be a continuous change of the dimenincluding color-superconducting ...
The physics of white dwarfs
... found that there is a critical stellar mass above which stable degenerate dwarfs cannot exist (see the box on page 28). This was a major discovery, for the existence of this critical mass—now called the "Chandrasekhar limit," Mch. about 1.44MO—has profound consequences for the final stages of stella ...
... found that there is a critical stellar mass above which stable degenerate dwarfs cannot exist (see the box on page 28). This was a major discovery, for the existence of this critical mass—now called the "Chandrasekhar limit," Mch. about 1.44MO—has profound consequences for the final stages of stella ...
1. INTRODUCTION - Institut für Theoretische Astrophysik
... Ulmschneider, & Kalkofen 1985 ; Rammacher & Ulmschneider 1992) and therefore does not need to be described again in detail. The basic features of these computations include the following : 1. We adopt solutions of the one-dimensional hydrodynamic equations, which consist of the continuity equation, ...
... Ulmschneider, & Kalkofen 1985 ; Rammacher & Ulmschneider 1992) and therefore does not need to be described again in detail. The basic features of these computations include the following : 1. We adopt solutions of the one-dimensional hydrodynamic equations, which consist of the continuity equation, ...
The Physics of Star Formation: Understanding the Youngest Protostars
... observed envelope structures and cloud conditions; and iii) to explore whether higher mass protostars are assembled in a way fundamentally dierent from low mass ones. As illustrated in Figure 2, shocks propagating into a dense molecular medium can produce a wide variety of emission line diagnostics ...
... observed envelope structures and cloud conditions; and iii) to explore whether higher mass protostars are assembled in a way fundamentally dierent from low mass ones. As illustrated in Figure 2, shocks propagating into a dense molecular medium can produce a wide variety of emission line diagnostics ...
Type II supernova
A Type II supernova (plural: supernovae or supernovas) results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times, the mass of the Sun (M☉) for this type of explosion. It is distinguished from other types of supernovae by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.Stars generate energy by the nuclear fusion of elements. Unlike the Sun, massive stars possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium, albeit at increasingly higher temperatures and pressures, causing increasingly shorter stellar life spans. The degeneracy pressure of electrons and the energy generated by these fusion reactions are sufficient to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The star fuses increasingly higher mass elements, starting with hydrogen and then helium, progressing up through the periodic table until a core of iron and nickel is produced. Fusion of iron or nickel produces no net energy output, so no further fusion can take place, leaving the nickel-iron core inert. Due to the lack of energy output allowing outward pressure, equilibrium is broken.When the mass of the inert core exceeds the Chandrasekhar limit of about 1.4 M☉, electron degeneracy alone is no longer sufficient to counter gravity and maintain stellar equilibrium. A cataclysmic implosion takes place within seconds, in which the outer core reaches an inward velocity of up to 23% of the speed of light and the inner core reaches temperatures of up to 100 billion kelvin. Neutrons and neutrinos are formed via reversed beta-decay, releasing about 1046 joules (100 foes) in a ten-second burst. The collapse is halted by neutron degeneracy, causing the implosion to rebound and bounce outward. The energy of this expanding shock wave is sufficient to accelerate the surrounding stellar material to escape velocity, forming a supernova explosion, while the shock wave and extremely high temperature and pressure briefly allow for theproduction of elements heavier than iron. Depending on initial size of the star, the remnants of the core form a neutron star or a black hole. Because of the underlying mechanism, the resulting nova is also described as a core-collapse supernova.There exist several categories of Type II supernova explosions, which are categorized based on the resulting light curve—a graph of luminosity versus time—following the explosion. Type II-L supernovae show a steady (linear) decline of the light curve following the explosion, whereas Type II-P display a period of slower decline (a plateau) in their light curve followed by a normal decay. Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and (for Type Ic) helium. As a result, they appear to be lacking in these elements.