Module 11.1.1: Galaxies: Morphology and the Hubble Sequence
... universe now, and their masses range from hundreds of million to maybe trillion solar masses, containing up to couple of hundred billion stars. [slide 3] The first thing that any empirical ...
... universe now, and their masses range from hundreds of million to maybe trillion solar masses, containing up to couple of hundred billion stars. [slide 3] The first thing that any empirical ...
UNIFYING THEORY OF LOW-ENERGY NUCLEAR REACTION AND
... identical Bose nuclei confined in a ion trap or an atomic cluster. Most recently, we have investigated the effect of a generalized particle momentum distribution derived by Galitskii and Yakimets (GY) [7] on nuclear reaction rates in plasma [8,9]. We have derived an approximate semi-analytical formu ...
... identical Bose nuclei confined in a ion trap or an atomic cluster. Most recently, we have investigated the effect of a generalized particle momentum distribution derived by Galitskii and Yakimets (GY) [7] on nuclear reaction rates in plasma [8,9]. We have derived an approximate semi-analytical formu ...
Galactic Evolution - Harvard-Smithsonian Center for Astrophysics
... than any stars now known. Such pure gas, lacking in C and O that normally help clouds to cool and condense, would have needed more mass to contract than stars typically now, >10 Gy after the bang. Without those heavy-element cooling agents, the earliest protostars would have retained much of their h ...
... than any stars now known. Such pure gas, lacking in C and O that normally help clouds to cool and condense, would have needed more mass to contract than stars typically now, >10 Gy after the bang. Without those heavy-element cooling agents, the earliest protostars would have retained much of their h ...
Thermodynamic properties of nuclear" pasta" in neutron star crusts
... electronic excitation energies. However, such temperature may have consequence to the structure of the Coulomb lattices involved. For example, the outer boundary of the crust is acutely controlled by the temperature because of the density dependence of the melting temperature of the bcc lattice [12] ...
... electronic excitation energies. However, such temperature may have consequence to the structure of the Coulomb lattices involved. For example, the outer boundary of the crust is acutely controlled by the temperature because of the density dependence of the melting temperature of the bcc lattice [12] ...
Lecture 12: Accretion
... The collisions of particles on intercepting orbits will heat the disk, which can then emit energy as EM radiation. To conserve energy, some particles must spiral inwards; but this requires angular momentum to be lost, so other particles must spiral outwards. Thus we may view an accretion disk as a w ...
... The collisions of particles on intercepting orbits will heat the disk, which can then emit energy as EM radiation. To conserve energy, some particles must spiral inwards; but this requires angular momentum to be lost, so other particles must spiral outwards. Thus we may view an accretion disk as a w ...
THE ORION NEBULA AND ITS ASSOCIATED POPULATION C. R. O
... was inconsistent with a spherically symmetric nebula and was used independently and essentially simultaneously by Balick et al. (1974) and Zuckerman (1973) to come up with today’s model. In a simple manner, the assumption of a thin emitting layer of radially decreasing density lying beyond the ioniz ...
... was inconsistent with a spherically symmetric nebula and was used independently and essentially simultaneously by Balick et al. (1974) and Zuckerman (1973) to come up with today’s model. In a simple manner, the assumption of a thin emitting layer of radially decreasing density lying beyond the ioniz ...
White Paper on Nuclear Astrophysics
... This white paper should also inform the nuclear physics community and funding agencies about the scientific directions and priorities of the field with the goal of providing input for the 2014 Long Range Plan. The answer of many questions in nuclear astrophysics can be found in the physics of nuclea ...
... This white paper should also inform the nuclear physics community and funding agencies about the scientific directions and priorities of the field with the goal of providing input for the 2014 Long Range Plan. The answer of many questions in nuclear astrophysics can be found in the physics of nuclea ...
A FUSE Survey of Coronal Forbidden Lines in Late
... but not detected. The Fe xviii feature, formed at log T ¼ 6:8 K, appears to be free of blends, whereas the Fe xix line can be corrupted by a C i multiplet. FUSE observations of these forbidden iron lines at spectral resolution =D 15; 000 provides the opportunity to study dynamics of hot coronal ...
... but not detected. The Fe xviii feature, formed at log T ¼ 6:8 K, appears to be free of blends, whereas the Fe xix line can be corrupted by a C i multiplet. FUSE observations of these forbidden iron lines at spectral resolution =D 15; 000 provides the opportunity to study dynamics of hot coronal ...
Clusters: age scales for stellar physics
... In order to define an age scale (or several), it is very important to keep in mind that we cannot make experiments except in very few situations and we rely on observations and theory. Thus, observational phenomena with very well defined ages, our anchors, are extremely important. As a matter of fac ...
... In order to define an age scale (or several), it is very important to keep in mind that we cannot make experiments except in very few situations and we rely on observations and theory. Thus, observational phenomena with very well defined ages, our anchors, are extremely important. As a matter of fac ...
Astronomy Astrophysics - Niels Bohr Institutet
... also recalibrated and redetermined the astrophysical parameters (T eff , Mv , and [Fe/H]) for all stars in our sample. Much effort has been devoted to the fundamental issue of determining reliable isochrone ages for as many stars as possible, and we believe that a rather more realistic assessment of t ...
... also recalibrated and redetermined the astrophysical parameters (T eff , Mv , and [Fe/H]) for all stars in our sample. Much effort has been devoted to the fundamental issue of determining reliable isochrone ages for as many stars as possible, and we believe that a rather more realistic assessment of t ...
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... Context. The mechanism by which supergiant (sg)B[e] stars support cool, dense dusty discs/tori and their physical relationship with other evolved, massive stars such as luminous blue variables is uncertain. Aims. In order to investigate both issues we have analysed the long term behaviour of the can ...
... Context. The mechanism by which supergiant (sg)B[e] stars support cool, dense dusty discs/tori and their physical relationship with other evolved, massive stars such as luminous blue variables is uncertain. Aims. In order to investigate both issues we have analysed the long term behaviour of the can ...
A Disintegrating Minor Planet Transiting a White Dwarf
... White dwarfs are the end state of most stars, including the Sun, after they exhaust their nuclear fuel. Between 1/4 and 1/2 of white dwarfs have elements heavier than helium in their atmospheres1,2, even though these elements should rapidly settle into the stellar interiors unless they are occasiona ...
... White dwarfs are the end state of most stars, including the Sun, after they exhaust their nuclear fuel. Between 1/4 and 1/2 of white dwarfs have elements heavier than helium in their atmospheres1,2, even though these elements should rapidly settle into the stellar interiors unless they are occasiona ...
Lokal fulltext - Chalmers Publication Library
... discs. Later, when the central star enters the main sequence, the evolution continues, albeit slower. At this time the stellar flux increases which clears its surroundings from most of the gas and dust and only planets of difference sizes, and rings of planetesimals, remains. These rings of planetes ...
... discs. Later, when the central star enters the main sequence, the evolution continues, albeit slower. At this time the stellar flux increases which clears its surroundings from most of the gas and dust and only planets of difference sizes, and rings of planetesimals, remains. These rings of planetes ...
A Star - Cloudy Nights
... When a star like our Sun uses up most of the fuel in its core, it shrugs off its outer layer and begins to shrink. The outer layer moves away, forming a sphere of material around the collapsing star and giving it a hazy round appearance in the sky. These objects are called planetary nebula, because ...
... When a star like our Sun uses up most of the fuel in its core, it shrugs off its outer layer and begins to shrink. The outer layer moves away, forming a sphere of material around the collapsing star and giving it a hazy round appearance in the sky. These objects are called planetary nebula, because ...
distribution and properties of a sample of massive young stars
... earliest stages of their evolution are therefore hidden behind many magnitudes of visual extinction, only observable at infrared (IR) and millimetre wavelengths. Moreover, massive stars are known to form exclusively in clusters (e.g. de Wit et al. 2004), which makes it difficult to attribute derived ...
... earliest stages of their evolution are therefore hidden behind many magnitudes of visual extinction, only observable at infrared (IR) and millimetre wavelengths. Moreover, massive stars are known to form exclusively in clusters (e.g. de Wit et al. 2004), which makes it difficult to attribute derived ...
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.