present
... although they saw the stars as pictures of gods and goddesses or of stories from their culture. Many peoples noticed that the planets, the moon, and comets moved through the sky in a different way than the stars. ...
... although they saw the stars as pictures of gods and goddesses or of stories from their culture. Many peoples noticed that the planets, the moon, and comets moved through the sky in a different way than the stars. ...
PowerPoint Presentation - Neutron stars, pulsars and black
... than 100 times per second (the first was spinning 640 times per second) threw the field for a loop. When some millisecond pulsars were discovered in old star clusters it was even more confusing. • Eventually it was determined that all millisecond pulsars were in close binary systems and were `spun u ...
... than 100 times per second (the first was spinning 640 times per second) threw the field for a loop. When some millisecond pulsars were discovered in old star clusters it was even more confusing. • Eventually it was determined that all millisecond pulsars were in close binary systems and were `spun u ...
Pulsating Stars: Stars that Breathe
... Zhevakin’s zones Regions of the stellar interior where increased opacity can provide the necessary valve mechanism to drive pulsations, were first identified by the Russian astronomer S. A. Zhevakin in the 1950s. These were partial ionisation zones , where part of the energy released during a layer’ ...
... Zhevakin’s zones Regions of the stellar interior where increased opacity can provide the necessary valve mechanism to drive pulsations, were first identified by the Russian astronomer S. A. Zhevakin in the 1950s. These were partial ionisation zones , where part of the energy released during a layer’ ...
Electromagnetic pulse from final gravitational stellar collapse
... the direct radiation phase, before the black hole forms. In this paper, we calculate the direct phase electromagnetic energy radiated by stellar objects that bounce and become stable neutron stars, and stellar objects so massive that they become black holes. In order to calculate the electromagnetic ...
... the direct radiation phase, before the black hole forms. In this paper, we calculate the direct phase electromagnetic energy radiated by stellar objects that bounce and become stable neutron stars, and stellar objects so massive that they become black holes. In order to calculate the electromagnetic ...
February 2004
... Mars is still in the evening sky in the north west, perhaps almost forgotten after its showing last August, it could be mistaken for a star like Betelgeuse, (it nearly was!) but it is still in a part of the sky where there are not many other bright objects. It showed a small disc in Michael’s 3 inch ...
... Mars is still in the evening sky in the north west, perhaps almost forgotten after its showing last August, it could be mistaken for a star like Betelgeuse, (it nearly was!) but it is still in a part of the sky where there are not many other bright objects. It showed a small disc in Michael’s 3 inch ...
Lecture 2. Thermal evolution and surface emission of
... prototypes of a different subpopulation of NSs born with low magnetic field (< few 1011 G) and relatively long spin periods (few tenths of a second). These NSs are relatively hot, and probably not very rare. Surprisingly, we do not see objects of this type in our vicinity. In the solar neighbourhood ...
... prototypes of a different subpopulation of NSs born with low magnetic field (< few 1011 G) and relatively long spin periods (few tenths of a second). These NSs are relatively hot, and probably not very rare. Surprisingly, we do not see objects of this type in our vicinity. In the solar neighbourhood ...
A Catalog of Blue Stragglers in Open Clusters
... Quality of the color-magnitude and color-color diagrams ...
... Quality of the color-magnitude and color-color diagrams ...
5. Star Formation and the Interstellar Medium in the Milky Way
... interstellar chemistry. Nonetheless, the great bulk of the relevant data come from heterodyne observations of rotational spectra at mm and sub-mm wavelengths. The high sensitivity, angular resolution, and mapping speed of the LMT will enable detailed investigations of the chemistry of interstellar m ...
... interstellar chemistry. Nonetheless, the great bulk of the relevant data come from heterodyne observations of rotational spectra at mm and sub-mm wavelengths. The high sensitivity, angular resolution, and mapping speed of the LMT will enable detailed investigations of the chemistry of interstellar m ...
Dark Matter: What is it?
... Strictly speaking, brown dwarfs are “dim matter”, not “dark matter”. A cold ...
... Strictly speaking, brown dwarfs are “dim matter”, not “dark matter”. A cold ...
Document
... in the sun is of order 1014 year (see next transparency) • The photosphere is thus representative of the originary solar material, since there was not enough time to mix it with the inner part of the sun, where nuclear reactions occurs and element abundances change. ...
... in the sun is of order 1014 year (see next transparency) • The photosphere is thus representative of the originary solar material, since there was not enough time to mix it with the inner part of the sun, where nuclear reactions occurs and element abundances change. ...
Lecture notes 17: Active Galaxies
... edge of the galaxy and compare it to the characteristic rotation speed of the Milky Way. 4. (a) The mass density of stars in the neighborhood of the Sun is approximately 0.05MS /pc3 . Assuming that the mass density is constant and that all of the stars are main sequence M stars, estimate the fracti ...
... edge of the galaxy and compare it to the characteristic rotation speed of the Milky Way. 4. (a) The mass density of stars in the neighborhood of the Sun is approximately 0.05MS /pc3 . Assuming that the mass density is constant and that all of the stars are main sequence M stars, estimate the fracti ...
A neutron star with a carbon atmosphere in the Cassiopeia A
... data were performed using an additional (temperature) component, for example, a second blackbody or atmosphere spectrum, which produced inferred R∞ of ≈ 0.2 and 2 km for blackbody fits or 0.4 and 11 km for H atmosphere fits.4 The high-temperature component has been interpreted as being due to a smal ...
... data were performed using an additional (temperature) component, for example, a second blackbody or atmosphere spectrum, which produced inferred R∞ of ≈ 0.2 and 2 km for blackbody fits or 0.4 and 11 km for H atmosphere fits.4 The high-temperature component has been interpreted as being due to a smal ...
Wind Opacity Issues
... plot cross section and some plot the radius of optical depth unity, R1. R1 is very similar to tau_star for large tau_star values, and they both depend on mass-loss rate, stellar radius, and wind velocity, in addition to the atomic opacity. This is important for comparisons between stars and even bet ...
... plot cross section and some plot the radius of optical depth unity, R1. R1 is very similar to tau_star for large tau_star values, and they both depend on mass-loss rate, stellar radius, and wind velocity, in addition to the atomic opacity. This is important for comparisons between stars and even bet ...
Fusion Reactors – a dream that can never come true
... The speed of the cluster increases drawing energy from inside. The increased speed increases the force towards its center, and so the galaxies require more kinetic energy to counter it, and this is drawn from inside the galaxy, and thus the process of internal energy changing into speed spreads to ...
... The speed of the cluster increases drawing energy from inside. The increased speed increases the force towards its center, and so the galaxies require more kinetic energy to counter it, and this is drawn from inside the galaxy, and thus the process of internal energy changing into speed spreads to ...
On the evolution and fate of supermassive stars
... Context. We study the evolution and fate of solar composition super-massive stars in the mass range 60 — 1000 M⊙ . Our study is relevant for very massive objects observed in young stellar complexes as well as for super-massive stars that could potentially form through runaway stellar collisions. Aim ...
... Context. We study the evolution and fate of solar composition super-massive stars in the mass range 60 — 1000 M⊙ . Our study is relevant for very massive objects observed in young stellar complexes as well as for super-massive stars that could potentially form through runaway stellar collisions. Aim ...
On the anomalous mass defect of strange stars in the Field
... defects characterized by energy excesses with respect to the energies they would have to be (stable) bound systems. Anomalous mass defects were interpreted in terms of a catastrophic additivity violation of the internal energy due to the very intense gravitational fields in the interior of such supe ...
... defects characterized by energy excesses with respect to the energies they would have to be (stable) bound systems. Anomalous mass defects were interpreted in terms of a catastrophic additivity violation of the internal energy due to the very intense gravitational fields in the interior of such supe ...
YREC: the Yale rotating stellar evolution code
... of the envelope (as determined by the local Schwarzschild criterion), the temperature gradient is evaluated according to the formalism of Stothers and Chin (1995), which is designed to describe superadiabatic convection. It is in this region that the peak of the highly superadiabatic transition laye ...
... of the envelope (as determined by the local Schwarzschild criterion), the temperature gradient is evaluated according to the formalism of Stothers and Chin (1995), which is designed to describe superadiabatic convection. It is in this region that the peak of the highly superadiabatic transition laye ...
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... consistent with a model where they are formed at high redshifts (z > 3, say) and evolve nearly passively since then ...
... consistent with a model where they are formed at high redshifts (z > 3, say) and evolve nearly passively since then ...
Dark matter, neutron stars and strange quark matter
... result of multiple WIMP annihilations over scales of several fm (typical size of a strangelet). A long-lived cluster may be formed from different small clusters with interdistance l on the diffusion time-scale, tdiff ∼ l/vdiff , before they decay over a mean lifetime, τ ∼ 10−10 − 10−5 s. This effect ...
... result of multiple WIMP annihilations over scales of several fm (typical size of a strangelet). A long-lived cluster may be formed from different small clusters with interdistance l on the diffusion time-scale, tdiff ∼ l/vdiff , before they decay over a mean lifetime, τ ∼ 10−10 − 10−5 s. This effect ...
A model of low-mass neutron stars with a quark core
... To study the functional dependence of the structural and integrated parameters of stellar configurations on the form of the equation of state for superdense matter, we have considered a large set of realistic equations of state that provide the coexistence of neutron matter with strange quark matter. ...
... To study the functional dependence of the structural and integrated parameters of stellar configurations on the form of the equation of state for superdense matter, we have considered a large set of realistic equations of state that provide the coexistence of neutron matter with strange quark matter. ...
Physics of Stars and the Measurement Data: Part III
... molecular gas. However assumed [4], that adsorbed hydrogen is ionized in some metals, such as T i, and it exists there in the form of gas of ”naked” nuclei. In this case, the free electrons of the metal matrix should form clouds around the bare nuclei of tritium. In accordance with the above calcula ...
... molecular gas. However assumed [4], that adsorbed hydrogen is ionized in some metals, such as T i, and it exists there in the form of gas of ”naked” nuclei. In this case, the free electrons of the metal matrix should form clouds around the bare nuclei of tritium. In accordance with the above calcula ...
The s-process in low metallicity stars - GSI
... I. I. Ivans (3, 4) F. Kaeppeler (5) Dipartimento di Fisica Generale , Università di Torino, 10125 Torino ( Italy) (2) Osservatorio Astronomico di Collurania – Teramo, 64100 (3)The Observatories of the Carnegie Institution of Washington, Pasadena, CA, (USA) (4)Princeton University Observatory, Prince ...
... I. I. Ivans (3, 4) F. Kaeppeler (5) Dipartimento di Fisica Generale , Università di Torino, 10125 Torino ( Italy) (2) Osservatorio Astronomico di Collurania – Teramo, 64100 (3)The Observatories of the Carnegie Institution of Washington, Pasadena, CA, (USA) (4)Princeton University Observatory, Prince ...
GOFER Module: Google Sky Please open Google Earth, then
... D. Hydra 34. Notice that Sirius is the brightest star in the sky, yet its absolute magnitude (measure of brightness) is -1.47. Therefore, what can we infer about brightness and absolute magnitude? A. Negative numbers are brighter stars, while high positive numbers are dimmer. B. Negative numbers are ...
... D. Hydra 34. Notice that Sirius is the brightest star in the sky, yet its absolute magnitude (measure of brightness) is -1.47. Therefore, what can we infer about brightness and absolute magnitude? A. Negative numbers are brighter stars, while high positive numbers are dimmer. B. Negative numbers are ...
1 The Milky Way
... At 21cm radio wavelength, we see emission from cold hydrogen gas. This is the raw material for making new stars. At somewhat higher radio frequency, we see radiation from many different molecules. These molecules exist in the the dense inner parts of gas clouds, and indicate where the next stars are ...
... At 21cm radio wavelength, we see emission from cold hydrogen gas. This is the raw material for making new stars. At somewhat higher radio frequency, we see radiation from many different molecules. These molecules exist in the the dense inner parts of gas clouds, and indicate where the next stars are ...
Main sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or ""dwarf"" stars.After a star has formed, it generates thermal energy in the dense core region through the nuclear fusion of hydrogen atoms into helium. During this stage of the star's lifetime, it is located along the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and other factors. All main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy generation in the core on the temperature and pressure helps to sustain this balance. Energy generated at the core makes its way to the surface and is radiated away at the photosphere. The energy is carried by either radiation or convection, with the latter occurring in regions with steeper temperature gradients, higher opacity or both.The main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. Stars below about 1.5 times the mass of the Sun (or 1.5 solar masses (M☉)) primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton–proton chain. Above this mass, in the upper main sequence, the nuclear fusion process mainly uses atoms of carbon, nitrogen and oxygen as intermediaries in the CNO cycle that produces helium from hydrogen atoms. Main-sequence stars with more than two solar masses undergo convection in their core regions, which acts to stir up the newly created helium and maintain the proportion of fuel needed for fusion to occur. Below this mass, stars have cores that are entirely radiative with convective zones near the surface. With decreasing stellar mass, the proportion of the star forming a convective envelope steadily increases, whereas main-sequence stars below 0.4 M☉ undergo convection throughout their mass. When core convection does not occur, a helium-rich core develops surrounded by an outer layer of hydrogen.In general, the more massive a star is, the shorter its lifespan on the main sequence. After the hydrogen fuel at the core has been consumed, the star evolves away from the main sequence on the HR diagram. The behavior of a star now depends on its mass, with stars below 0.23 M☉ becoming white dwarfs directly, whereas stars with up to ten solar masses pass through a red giant stage. More massive stars can explode as a supernova, or collapse directly into a black hole.