Project 9: Stellar Spectra: Temperature
... Emission spectrum: An emission line is characterized by excessive radiation at specific wavelengths. Emission lines are added to the continuum emission, so that they appear brighter. You can observe emission lines by looking at the cool gas (that caused absor ...
... Emission spectrum: An emission line is characterized by excessive radiation at specific wavelengths. Emission lines are added to the continuum emission, so that they appear brighter. You can observe emission lines by looking at the cool gas (that caused absor ...
jbrown_keck - Astronomy at Swarthmore College
... where they have burnt their hydrogen core. The resulting gravitational collapse provides the densities necessary to begin helium burning. The star begins to accumulate a carbon and oxygen core with helium and then hydrogen in shells around the core. Helium burning occurs in short phases when conditi ...
... where they have burnt their hydrogen core. The resulting gravitational collapse provides the densities necessary to begin helium burning. The star begins to accumulate a carbon and oxygen core with helium and then hydrogen in shells around the core. Helium burning occurs in short phases when conditi ...
their evolution, nucleosynthesis and dusty end
... 2. Differential rotation is considered and, following Endal & Sofia (1976,1978), the evolution of angular momentum (J) through the star is followed via a nonlinear diffusion equation (except at the inner border of the convective envelope, where we apply the same formalism of the chemical transport), ...
... 2. Differential rotation is considered and, following Endal & Sofia (1976,1978), the evolution of angular momentum (J) through the star is followed via a nonlinear diffusion equation (except at the inner border of the convective envelope, where we apply the same formalism of the chemical transport), ...
This is the Title - Astronomy at Swarthmore College
... where they have burnt their hydrogen core. The resulting gravitational collapse provides the densities necessary to begin helium burning. The star begins to accumulate a carbon and oxygen core with helium and then hydrogen in shells around the core. Helium burning occurs in short phases when conditi ...
... where they have burnt their hydrogen core. The resulting gravitational collapse provides the densities necessary to begin helium burning. The star begins to accumulate a carbon and oxygen core with helium and then hydrogen in shells around the core. Helium burning occurs in short phases when conditi ...
Stars Stellar Lifetimes Life cycles of low
... Pressure and gravity in balance Stars attempt to maintain equilibrium 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. W ...
... Pressure and gravity in balance Stars attempt to maintain equilibrium 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. W ...
Undergraduate Project in Physics Alon Grubshtein Guided by Prof. Eduardo Guendelman
... deuterium. If the temperature is too high, the deuterium does not survive. In fact, there is a narrow range of temperatures over which reactions are possible (around 109 degrees). At one hand, high temperatures are needed for a nucleus to come close enough for the nuclear forces to take over, and on ...
... deuterium. If the temperature is too high, the deuterium does not survive. In fact, there is a narrow range of temperatures over which reactions are possible (around 109 degrees). At one hand, high temperatures are needed for a nucleus to come close enough for the nuclear forces to take over, and on ...
here - SDSU Astronomy Department and Mount Laguna Observatory
... different sizes can appear to have the same angular sizes. ...
... different sizes can appear to have the same angular sizes. ...
Orbital Period Modulation in Chromospherically
... However we should bear in mind that the orbital period modulation should not be strictly periodic. The examples of the application are given in Table 1. The model proposed by Applegate takes the orbital period modulations in the active close binaries as a signature of stellar magnetic activity. The ...
... However we should bear in mind that the orbital period modulation should not be strictly periodic. The examples of the application are given in Table 1. The model proposed by Applegate takes the orbital period modulations in the active close binaries as a signature of stellar magnetic activity. The ...
Document
... – Take into account: – two p-p fusions per branch – weightings of each branch – 15 MeV per p-p fusion – Given number of fusions per m-3 calculated earlier, energy production rate ~ 120 Wm-3 ...
... – Take into account: – two p-p fusions per branch – weightings of each branch – 15 MeV per p-p fusion – Given number of fusions per m-3 calculated earlier, energy production rate ~ 120 Wm-3 ...
How much radioactive nickel does ASASSN
... zero-metallicity models in the helium-core mass range between 65 M⊙ and 135 M⊙. The initial corresponding mainsequence star mass ranges from 140 M⊙ to 260 M⊙. However, the evolutionary parameter space greatly exceeds this grid of very massive stars (Woosley & Heger 2015). There is no difficulty to p ...
... zero-metallicity models in the helium-core mass range between 65 M⊙ and 135 M⊙. The initial corresponding mainsequence star mass ranges from 140 M⊙ to 260 M⊙. However, the evolutionary parameter space greatly exceeds this grid of very massive stars (Woosley & Heger 2015). There is no difficulty to p ...
Can We Successfully Apply A Solar Thin-Flux
... The star must have an outer convection zone and a radiative core underneath. Parker instability sets in as the magnetic field grows. As the crests penetrate into the convection zone, the superadiabatic stratification accelerates the growth of the instability, a loop forms. The summit of the loop ...
... The star must have an outer convection zone and a radiative core underneath. Parker instability sets in as the magnetic field grows. As the crests penetrate into the convection zone, the superadiabatic stratification accelerates the growth of the instability, a loop forms. The summit of the loop ...
document
... larger than for Astrometry. (short periods favor RV, long periods favor Astrometry) • For the Sun the astrometric noise is ~0.5m/s and ~0.08uas at each epoch. (This noise becomes “random” for epochs separated by longer than ~ 1 week.) • Preliminary analysis of ~100 stars observed by Corot shows that ...
... larger than for Astrometry. (short periods favor RV, long periods favor Astrometry) • For the Sun the astrometric noise is ~0.5m/s and ~0.08uas at each epoch. (This noise becomes “random” for epochs separated by longer than ~ 1 week.) • Preliminary analysis of ~100 stars observed by Corot shows that ...
Document
... temperature would have to be 1.1x1010K. This is nearly four orders of magnitude higher than the minimum mean temperature of the Sun, 2x106K, we derived earlier. How can these two numbers be reconciled? First, one could argue that we only estimated the minimum mean temperature of the Sun. Detailed st ...
... temperature would have to be 1.1x1010K. This is nearly four orders of magnitude higher than the minimum mean temperature of the Sun, 2x106K, we derived earlier. How can these two numbers be reconciled? First, one could argue that we only estimated the minimum mean temperature of the Sun. Detailed st ...
The dance of elements in space: from clouds to planets
... When enough material has been accumulated in the central zone of the pre-stellar core, the gravitational force wins against the pressure and whatever other mechanism may have contrasted it, turbulence, magnetic fields... Nothing can prevent the storm to begin! Matter from the whole core rains freely ...
... When enough material has been accumulated in the central zone of the pre-stellar core, the gravitational force wins against the pressure and whatever other mechanism may have contrasted it, turbulence, magnetic fields... Nothing can prevent the storm to begin! Matter from the whole core rains freely ...
Turning AGN Microlensing From a Curiosity Into a Tool
... this is very hard to probe and has little effect on results • Disk structure at fixed wavelength – extensive prior theoretical studies show that microlensing data measures typical size rather than details of the surface brightness distribution – better to focus on size versus wavelength, black hole ...
... this is very hard to probe and has little effect on results • Disk structure at fixed wavelength – extensive prior theoretical studies show that microlensing data measures typical size rather than details of the surface brightness distribution – better to focus on size versus wavelength, black hole ...
Accretion Processes of Binaries of White Dwarfs
... Binarity of the central star system? • Severe mass loss rate through slow stellar wind from the giant. • Fast stellar wind from the white dwarf component • Collision of slow stellar wind and fast wind ...
... Binarity of the central star system? • Severe mass loss rate through slow stellar wind from the giant. • Fast stellar wind from the white dwarf component • Collision of slow stellar wind and fast wind ...
Testing the evolution of the DB white dwarf GD 358: first results of a
... central oxygen abundance and the shape of the C/O profile affect the pulsation pattern. M1 modified the code to include as free parameters any central oxygen mass fraction (X0 ) between 0 and 1 with resolution 1% and a fractional mass parameter (q). The GA fitting process explored different chemical p ...
... central oxygen abundance and the shape of the C/O profile affect the pulsation pattern. M1 modified the code to include as free parameters any central oxygen mass fraction (X0 ) between 0 and 1 with resolution 1% and a fractional mass parameter (q). The GA fitting process explored different chemical p ...
Genesis of the Heaviest Elements in the Milky Way Galaxy
... would expect to produce pockets of chemically inhomogeneous ISM material. Over time, such disparities in the total abundance levels would be minimized by mixing throughout the Galaxy. There is also a downward trend of [Eu/Fe] ratios at higher metallicities (Fig. 4). Early in the history of the Galax ...
... would expect to produce pockets of chemically inhomogeneous ISM material. Over time, such disparities in the total abundance levels would be minimized by mixing throughout the Galaxy. There is also a downward trend of [Eu/Fe] ratios at higher metallicities (Fig. 4). Early in the history of the Galax ...
The Kinematics of Star Formation: Theory and Observation in the
... cluster potential. These cores are therefore more likely to grow to become the most massive stars in the cluster. Competitive accretion therefore predicts that the most massive stars should form at the centres of the gravitational potential wells. Unfortunately observers cannot directly identify the ...
... cluster potential. These cores are therefore more likely to grow to become the most massive stars in the cluster. Competitive accretion therefore predicts that the most massive stars should form at the centres of the gravitational potential wells. Unfortunately observers cannot directly identify the ...
Lecture 2
... Since alm represent a deviation from the average temperature, their expectation value is zero, < alm > = 0 , and the quantity we want to calculate is the variance < |alm|2 > to get a prediction for the typical size of the alm. The isotropic nature of the random process shows up in the alm so that th ...
... Since alm represent a deviation from the average temperature, their expectation value is zero, < alm > = 0 , and the quantity we want to calculate is the variance < |alm|2 > to get a prediction for the typical size of the alm. The isotropic nature of the random process shows up in the alm so that th ...
Fluorine nucleosynthesis
... correlation. (See F/O vs C/O figure) * To disentangle the effects of galactic chemical evolution on F from stellar evolutionary effects, F and C abundances should be normalized by a species sensitive to galactic chemical evolution only and not to nucleosynthesis during the AGB. Iron-group species or ...
... correlation. (See F/O vs C/O figure) * To disentangle the effects of galactic chemical evolution on F from stellar evolutionary effects, F and C abundances should be normalized by a species sensitive to galactic chemical evolution only and not to nucleosynthesis during the AGB. Iron-group species or ...
Lecture 5: The Milky Way
... Tangential orbital speed V (km/sec) Thin-disc stars follow nearly circular orbits, with most of their motion being tangential. Halo stars are equally likely to follow prograde or retrograde orbits and cross the midplane with high speeds. ...
... Tangential orbital speed V (km/sec) Thin-disc stars follow nearly circular orbits, with most of their motion being tangential. Halo stars are equally likely to follow prograde or retrograde orbits and cross the midplane with high speeds. ...
File
... possibility at the end of its life to become a black hole that usually form at the center of the dying star where gravity starts to compress the star’s mass into one single point that there is no force that can prevent that point from collapsing on itself which forms a singularity that rips apart th ...
... possibility at the end of its life to become a black hole that usually form at the center of the dying star where gravity starts to compress the star’s mass into one single point that there is no force that can prevent that point from collapsing on itself which forms a singularity that rips apart th ...
Life (Briefly) Near a Supernova
... doomed star remain livable until shortly before the final disaster. Indeed, the collapse of the star's core does happen in milliseconds. However all supernovas are thought to occur in stars that have exhausted their initial hydrogen and gone on to fusion of heavier elements. Such stars would be in t ...
... doomed star remain livable until shortly before the final disaster. Indeed, the collapse of the star's core does happen in milliseconds. However all supernovas are thought to occur in stars that have exhausted their initial hydrogen and gone on to fusion of heavier elements. Such stars would be in t ...
Chapter 23 The Milky Way Galaxy
... • Subatomic particles? •Recall the solution to the “solar neutrino problem”, that neutrinos have a tiny bit of mass. Neutrinos turn out to be the most abundant particle in the universe (more than even photons). But falls short by an order of magnitude. A “weird subatomic particle” is the most (only? ...
... • Subatomic particles? •Recall the solution to the “solar neutrino problem”, that neutrinos have a tiny bit of mass. Neutrinos turn out to be the most abundant particle in the universe (more than even photons). But falls short by an order of magnitude. A “weird subatomic particle” is the most (only? ...
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.