First axion bounds from a pulsating helium
... particles to dark matter is dependent on their mass (or coupling constant). However, the models do not provide information about the value of the axion mass, and therefore it has to be inferred from observations. In particular, stars can be employed to place constraints on the mass of the axion [8, ...
... particles to dark matter is dependent on their mass (or coupling constant). However, the models do not provide information about the value of the axion mass, and therefore it has to be inferred from observations. In particular, stars can be employed to place constraints on the mass of the axion [8, ...
The physics of neutron stars
... While the size of a neutron star mainly depends on the balance between gravity force and degenerate neutron pressure, white dwarfs resist gravitational squeezing due to the electron degeneracy pressure, and quark or strange stars resist it due to the pressure of matter composed of quarks not combine ...
... While the size of a neutron star mainly depends on the balance between gravity force and degenerate neutron pressure, white dwarfs resist gravitational squeezing due to the electron degeneracy pressure, and quark or strange stars resist it due to the pressure of matter composed of quarks not combine ...
Summary of Talks at Growing Black Holes 2004 in Garching
... to estimates of quasar lifetimes. At z < 2.5, SDSS clustering scale is about 7 Mpc. There is now preliminary, tentative evidence for correlation length to increase with redshift. Spectra of emission lines in high z quasars & Continuum shape consistent with lower z objects -> implication : rapid ch ...
... to estimates of quasar lifetimes. At z < 2.5, SDSS clustering scale is about 7 Mpc. There is now preliminary, tentative evidence for correlation length to increase with redshift. Spectra of emission lines in high z quasars & Continuum shape consistent with lower z objects -> implication : rapid ch ...
Blue horizontal branch stars in the Sloan Digital Sky Survey:
... BHB stars have very characteristic colors in the high-Galactic latitude stellar sample observed by the SDSS imaging survey, and photometric selection of candidate objects is straightforward. BHB stars are bluer in g − r than most halo stars because the halo main sequence turnoff lies at spectral typ ...
... BHB stars have very characteristic colors in the high-Galactic latitude stellar sample observed by the SDSS imaging survey, and photometric selection of candidate objects is straightforward. BHB stars are bluer in g − r than most halo stars because the halo main sequence turnoff lies at spectral typ ...
The chemical composition of IK Pegasi
... show that the mean metal abundance does not differ significantly from that of the Sun. Any anomalies are therefore subtle and are likely to be detected only at high-resolution. There have been relatively few abundance studies of IK Peg A. Cowley & Aikman (1980) extended the method of wavelength coin ...
... show that the mean metal abundance does not differ significantly from that of the Sun. Any anomalies are therefore subtle and are likely to be detected only at high-resolution. There have been relatively few abundance studies of IK Peg A. Cowley & Aikman (1980) extended the method of wavelength coin ...
Probing the Dark Matter Content of Local Group Dwarf Spheroidal
... solar masses. In this case, the numbers of dSphs might be consistent with CDM simulations. One of the key goals of our observations in Carina is to test in detail whether its properties are consistent with those of an object with a massive, extended dark halo. The shapes of the dark-matter density p ...
... solar masses. In this case, the numbers of dSphs might be consistent with CDM simulations. One of the key goals of our observations in Carina is to test in detail whether its properties are consistent with those of an object with a massive, extended dark halo. The shapes of the dark-matter density p ...
Molecular Cloud Evolution II. From cloud formation to the early
... (9.2 km s−1 , or a Mach number ∼ 1.22 in the unperturbed WNM). The collisions trigger a transition to the cold phase in the gas, and an overshoot to physical conditions typical of molecular clouds (MCs). Simultaneously, they generate turbulence in the resulting “cloud”, here defined as the gas at de ...
... (9.2 km s−1 , or a Mach number ∼ 1.22 in the unperturbed WNM). The collisions trigger a transition to the cold phase in the gas, and an overshoot to physical conditions typical of molecular clouds (MCs). Simultaneously, they generate turbulence in the resulting “cloud”, here defined as the gas at de ...
Manoel Couder
... I NSTITUTE FOR S TRUCTURE AND N UCLEAR A STROPHYSICS N UCLEAR S CIENCE LABORATORY 22Ne(a,n)25Mg ...
... I NSTITUTE FOR S TRUCTURE AND N UCLEAR A STROPHYSICS N UCLEAR S CIENCE LABORATORY 22Ne(a,n)25Mg ...
MEarth
... with precise infrared photometric monitoring as a large daynight temperature difference, while the detection of a small day-night difference would provide a strong case for the existence of a thick atmosphere. With the Spitzer Space Telescope and the James Webb Space Telescope (JWST), atmospheric ob ...
... with precise infrared photometric monitoring as a large daynight temperature difference, while the detection of a small day-night difference would provide a strong case for the existence of a thick atmosphere. With the Spitzer Space Telescope and the James Webb Space Telescope (JWST), atmospheric ob ...
are coronae of late-type stars made of solar-like structures? the x
... This work is dedicated to the solar-stellar connection, i.e., the close similarity of the Sun and late-type stars; in particular, this work shows that stellar coronae can be composed of X-ray–emitting structures similar to those present in the solar corona. To this end we use a large set of ROSAT PS ...
... This work is dedicated to the solar-stellar connection, i.e., the close similarity of the Sun and late-type stars; in particular, this work shows that stellar coronae can be composed of X-ray–emitting structures similar to those present in the solar corona. To this end we use a large set of ROSAT PS ...
Astronomy Astrophysics
... contribution to the detected variability can derive from Active Region Growth and Decay (ARGD). It is interesting to consider the possible effect of active regions’ evolution on spurious variations of the photometric period. Dobson et al. (1990), Donahue & Baliunas (1992) and Donahue (1993) have pro ...
... contribution to the detected variability can derive from Active Region Growth and Decay (ARGD). It is interesting to consider the possible effect of active regions’ evolution on spurious variations of the photometric period. Dobson et al. (1990), Donahue & Baliunas (1992) and Donahue (1993) have pro ...
The Milky Way - Faculty Web Pages
... Astronomers believe that gigantic spherical clusters of stars, called Globular Clusters, each with hundreds of thousands of stars, formed evenly around the center of the Milky Way many billions of years ago. These globular clusters are so large and bright that they can be seen from very far way – mu ...
... Astronomers believe that gigantic spherical clusters of stars, called Globular Clusters, each with hundreds of thousands of stars, formed evenly around the center of the Milky Way many billions of years ago. These globular clusters are so large and bright that they can be seen from very far way – mu ...
Determination of the distance to the Andromeda Galaxy using variable stars U
... position of each variable star. The scaling factor at the position of each variable star was obtained from the comparison with the DIA photometry of each PSF. For similar PSFs, the scaling factor can be obtained with an error of 0.3% or less. This process provided instrumental magnitudes for all the ...
... position of each variable star. The scaling factor at the position of each variable star was obtained from the comparison with the DIA photometry of each PSF. For similar PSFs, the scaling factor can be obtained with an error of 0.3% or less. This process provided instrumental magnitudes for all the ...
1. The catalogue structure
... correspondence with the figures from Dürer’s star charts in the Almagest. In fig. 2.9 we reproduce a page of the star catalogue from an edition of the Almagest that dates from 1551. In fig. 2.10 one sees a page from the Greek version of the Almagest that was written in the IX century ([1374], page 1 ...
... correspondence with the figures from Dürer’s star charts in the Almagest. In fig. 2.9 we reproduce a page of the star catalogue from an edition of the Almagest that dates from 1551. In fig. 2.10 one sees a page from the Greek version of the Almagest that was written in the IX century ([1374], page 1 ...
L7-Potentials-orbits
... These density distributions are similar to central regions of E’s and halos of galaxies in general If density falls as r-2 or faster, box orbits are replaced by boxlets box orbits about minor-axis arising from resonance between motion in x and y directions (Miralda-Escude & Schwarzchild 1989) Some i ...
... These density distributions are similar to central regions of E’s and halos of galaxies in general If density falls as r-2 or faster, box orbits are replaced by boxlets box orbits about minor-axis arising from resonance between motion in x and y directions (Miralda-Escude & Schwarzchild 1989) Some i ...
Selected topics in Nuclear Astrophysics
... the following topics: i) the nuclear aspects of the collapse of the inner core of massive stars once it has run out of its nuclear energy source and of the star’s explosion as a type II supernova; ii) the explosive nucleosynthesis occuring during this explosion which leads to the production of heavy ...
... the following topics: i) the nuclear aspects of the collapse of the inner core of massive stars once it has run out of its nuclear energy source and of the star’s explosion as a type II supernova; ii) the explosive nucleosynthesis occuring during this explosion which leads to the production of heavy ...
Angular Momentum Evolution of Young Low
... Similar results are seen in the 40-Ma clusters IC 4665 and NGC 2547, with the addition of very-low-mass stars that are faster rotators and exhibit a steep period-mass relationship. 4. Once on the early MS (0.1-0.6 Ga), a well-defined sequence of slow rotators starts to appear over the mass range 0.6 ...
... Similar results are seen in the 40-Ma clusters IC 4665 and NGC 2547, with the addition of very-low-mass stars that are faster rotators and exhibit a steep period-mass relationship. 4. Once on the early MS (0.1-0.6 Ga), a well-defined sequence of slow rotators starts to appear over the mass range 0.6 ...
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.