Jaká kritéria jsou vhodná ke klasifikaci hvězd horní části hlavní
... like temperature, surface gravity and chemical composition, but also give us a crucial piece of information needed to identify larger celestial systems and structures, for instance determining the radial velocity or the rate of rotation. However, to gain this information, we need to classify the sta ...
... like temperature, surface gravity and chemical composition, but also give us a crucial piece of information needed to identify larger celestial systems and structures, for instance determining the radial velocity or the rate of rotation. However, to gain this information, we need to classify the sta ...
The Big Bang and Stellar Evolution
... whether on earth or in space, cannot push itself into balls. Once together, a star maintains its gravity quite well, but there is no way for nature to produce one. Getting it together in the first place is the problem. Gas floating in a vacuum cannot form itself into stars. Once a star exists, it w ...
... whether on earth or in space, cannot push itself into balls. Once together, a star maintains its gravity quite well, but there is no way for nature to produce one. Getting it together in the first place is the problem. Gas floating in a vacuum cannot form itself into stars. Once a star exists, it w ...
Get ready for quiz # 7
... The irregular galaxies have a wide variety of shapes. These galaxies appear to be undergoing interactions with other galaxies. ...
... The irregular galaxies have a wide variety of shapes. These galaxies appear to be undergoing interactions with other galaxies. ...
Optical studies of an ultraluminous X-ray source: NGC1313 X-2 Jifeng Liu
... ultraluminous X-ray sources • ULXs are non-nuclear X-ray point sources with Lx > 2 X 1039 erg/s, i.e., more luminous than the Eddington luminosity for stellar mass black holes, and could be intermediate mass black holes of 30 - 105 Ms ...
... ultraluminous X-ray sources • ULXs are non-nuclear X-ray point sources with Lx > 2 X 1039 erg/s, i.e., more luminous than the Eddington luminosity for stellar mass black holes, and could be intermediate mass black holes of 30 - 105 Ms ...
SMA Observations of AB Aur
... The ring-like structure is most likely due to enhancement of the disk surface density. The NE part of the dust disk might have a larger dust spectral index than the SW part. ...
... The ring-like structure is most likely due to enhancement of the disk surface density. The NE part of the dust disk might have a larger dust spectral index than the SW part. ...
Carbon monoxide in clouds at low metallicity in the dwarf irregular
... where stars form, but it has never been detected in galaxies in which the oxygen abundance relative to hydrogen is less than 20 per cent of that of the Sun, even though such ‘low-metallicity’ galaxies often form stars. This raises the question of whether stars can form in dense gas without molecules ...
... where stars form, but it has never been detected in galaxies in which the oxygen abundance relative to hydrogen is less than 20 per cent of that of the Sun, even though such ‘low-metallicity’ galaxies often form stars. This raises the question of whether stars can form in dense gas without molecules ...
RHIC - HIM
... Binding energy from Color Coulomb & 4-point interaction is enough to make massless bound states ...
... Binding energy from Color Coulomb & 4-point interaction is enough to make massless bound states ...
The Chandra Orion Ultradeep Project Eric Feigelson
... But none of these variations coincide with X-ray flares ...
... But none of these variations coincide with X-ray flares ...
mass transfer in close, rapidly accreting protobinaries
... not well determined, due to low statistics and complex selection biases, there appears to be a significant population of very close binaries. The WR 20a system, the most massive binary known, has a separation of only 0.25 AU (Bonanos et al. 2004; Rauw et al. 2005). The semimajor axis of the massive ...
... not well determined, due to low statistics and complex selection biases, there appears to be a significant population of very close binaries. The WR 20a system, the most massive binary known, has a separation of only 0.25 AU (Bonanos et al. 2004; Rauw et al. 2005). The semimajor axis of the massive ...
Astronomy Astrophysics - Utrecht University Repository
... over the 5 years of observations. The size of the symbols corresponds to the RE -band amplitude of variability during the period of EROS II observations. The figure shows that the stars are distributed on an increasingly wider range of ∆R with increasing near-IR excess. This suggests that the maximu ...
... over the 5 years of observations. The size of the symbols corresponds to the RE -band amplitude of variability during the period of EROS II observations. The figure shows that the stars are distributed on an increasingly wider range of ∆R with increasing near-IR excess. This suggests that the maximu ...
Thermal emission and internal heating processes in millisecond
... • Observed UV emission of PSR J0437-4715 may be due to rotochemical heating • The same emission can be used to constrain |dG/dt|: – competitive with best existing constraints if fast cooling processes could be ruled out ...
... • Observed UV emission of PSR J0437-4715 may be due to rotochemical heating • The same emission can be used to constrain |dG/dt|: – competitive with best existing constraints if fast cooling processes could be ruled out ...
Mechanical and thermodynamical properties of matter in strong
... more complex situations and its study in stars mimics other fields and possible alterations in the gravitational field. The important quantity in knowing how much electric charge a star can support is the ratio of the mass m to the charge q of the main fundamental constituents of the star [9]. For n ...
... more complex situations and its study in stars mimics other fields and possible alterations in the gravitational field. The important quantity in knowing how much electric charge a star can support is the ratio of the mass m to the charge q of the main fundamental constituents of the star [9]. For n ...
THE HOBBY-EBERLY TELESCOPE CHEMICAL ABUNDANCES OF
... chain reactions. These nucleosynthesis reactions make it indeed possible for a star to self-enrich its atmosphere with Li, but only for a very short period of time before the freshly produced Li burns again. The enrichment can be quite extreme, however, with Li abundances sometimes 1Y2 dex higher th ...
... chain reactions. These nucleosynthesis reactions make it indeed possible for a star to self-enrich its atmosphere with Li, but only for a very short period of time before the freshly produced Li burns again. The enrichment can be quite extreme, however, with Li abundances sometimes 1Y2 dex higher th ...
Models for GRBs and diverse transients
... like SN 1998bw. To form a disk around a 3 M1 black hole in the collapsar model requires at least 2!1016 cm2 sK1. With less rotation, a supernova might still be possible, and even some sort of low-energy transient, but for j(1015 cm2 sK1, some other means besides rotation must be found to blow up the ...
... like SN 1998bw. To form a disk around a 3 M1 black hole in the collapsar model requires at least 2!1016 cm2 sK1. With less rotation, a supernova might still be possible, and even some sort of low-energy transient, but for j(1015 cm2 sK1, some other means besides rotation must be found to blow up the ...
WASP-12b: THE HOTTEST TRANSITING
... 7.5 pixel radius aperture, were performed on all the stars in the frame using DAOPHOT (Stetson 1987) run under IRAF.16 The differential photometry was derived from seven, nonvariable comparison stars within the field which had V < 14 magnitude and J – H colors similar to the target star. For each of ...
... 7.5 pixel radius aperture, were performed on all the stars in the frame using DAOPHOT (Stetson 1987) run under IRAF.16 The differential photometry was derived from seven, nonvariable comparison stars within the field which had V < 14 magnitude and J – H colors similar to the target star. For each of ...
The Age and Stellar Parameters of the Procyon Binary System
... Procyon B was first detected visually at the end of the 19th century by Schaeberle (1896), and was historically one of the first white dwarfs to be discovered. Even early estimates of the mass (MB ) of the white dwarf component, such as that by Strand (1951), showed that it is much closer to the mea ...
... Procyon B was first detected visually at the end of the 19th century by Schaeberle (1896), and was historically one of the first white dwarfs to be discovered. Even early estimates of the mass (MB ) of the white dwarf component, such as that by Strand (1951), showed that it is much closer to the mea ...
The potential of the variable DA white dwarf G117–B15A as
... interacting massive particles. This was recognized early by several authors (see, for instance Raffelt, 1996). There is, however, another important reason for this: white dwarfs are well studied stellar objects since the relative simplicity of the physics governing their evolution at moderately high ...
... interacting massive particles. This was recognized early by several authors (see, for instance Raffelt, 1996). There is, however, another important reason for this: white dwarfs are well studied stellar objects since the relative simplicity of the physics governing their evolution at moderately high ...
The Milky Way Galaxy - d_smith.lhseducators.com
... km/second around the galaxy’s center. The sun takes 1000 years to move 1 light year, or it takes 280 million years to orbit the nucleus of the galaxy once. The galaxy has only made about 50 complete rotations since the universe ...
... km/second around the galaxy’s center. The sun takes 1000 years to move 1 light year, or it takes 280 million years to orbit the nucleus of the galaxy once. The galaxy has only made about 50 complete rotations since the universe ...
Summary of recent research activities
... be ‘primordial’ galaxies, in the sense of having started forming stars only a few hundred Myr ago. In this respect, I Zw 18 is still considered the best candidate, since it has the lowest oxygen abundance among galaxies in the local Universe (∼ 1/50 solar; Searle & Sargent 1972, ApJ 173, 25); howeve ...
... be ‘primordial’ galaxies, in the sense of having started forming stars only a few hundred Myr ago. In this respect, I Zw 18 is still considered the best candidate, since it has the lowest oxygen abundance among galaxies in the local Universe (∼ 1/50 solar; Searle & Sargent 1972, ApJ 173, 25); howeve ...
Sources of Stellar Energy and the Theory of the Internal Constitution
... The results obtained, taken altogether, permit calculation of the physical conditions in the internal constitution of stars, proceeding from their observational characteristics L, M , and R. For instance, the temperature obtained for the centre of the Sun is about 6 million degrees. This is not enou ...
... The results obtained, taken altogether, permit calculation of the physical conditions in the internal constitution of stars, proceeding from their observational characteristics L, M , and R. For instance, the temperature obtained for the centre of the Sun is about 6 million degrees. This is not enou ...
A Detailed Spectroscopic and Photometric Analysis of DQ White
... The first sample used for this study is drawn from the BRL and BLR analyses, which include 21 DQ stars. From this we exclude those objects that have carbon features only in the ultraviolet (WD 0038+555, WD 0806−661), missing or bad optical spectra (WD 1708−147, WD 2254+076), and uncertain photometri ...
... The first sample used for this study is drawn from the BRL and BLR analyses, which include 21 DQ stars. From this we exclude those objects that have carbon features only in the ultraviolet (WD 0038+555, WD 0806−661), missing or bad optical spectra (WD 1708−147, WD 2254+076), and uncertain photometri ...
Observational Astronomy - Lecture 10 Galaxies
... They come in a wide variety of shapes, but there are two main types: Spiral galaxies, which are blue in color because they are still forming stars. Elliptical galaxies, which are no longer forming many stars and are therefore red in color. The star formation rate of the universe peaked long ago and ...
... They come in a wide variety of shapes, but there are two main types: Spiral galaxies, which are blue in color because they are still forming stars. Elliptical galaxies, which are no longer forming many stars and are therefore red in color. The star formation rate of the universe peaked long ago and ...
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.