THE NUMBER OF HABITABLE PLANETS IN THE MILKY WAY
... of the HZ, respectively. They are explicit functions of the central star mass and the age of the corresponding planetary system [5]. In previous studies climatic constraints, e.g. the presence of liquid water at the planetary surface, have been used to assess the habitability of terrestrial planets ...
... of the HZ, respectively. They are explicit functions of the central star mass and the age of the corresponding planetary system [5]. In previous studies climatic constraints, e.g. the presence of liquid water at the planetary surface, have been used to assess the habitability of terrestrial planets ...
the 82nd arthur h. compton lecture series
... ➢ Type Ia SNe come from explosions of white dwarfs in binary systems and do not show signs of He, but strong Si absorption. ➢ Type II SNe show H in the spectra. Subtypes are IIP, IIn, IIL. ➢ Type Ib/c SNe have lost their H (Ib) and sometimes also He (Ic) envelopes. ➢ Most supernova light curves are ...
... ➢ Type Ia SNe come from explosions of white dwarfs in binary systems and do not show signs of He, but strong Si absorption. ➢ Type II SNe show H in the spectra. Subtypes are IIP, IIn, IIL. ➢ Type Ib/c SNe have lost their H (Ib) and sometimes also He (Ic) envelopes. ➢ Most supernova light curves are ...
2017 Maryland Regional
... supernova. This is the first documented case of a supernova candidate through white-dwarf merger.__ 23. __ The star, Mira, is thermally pulsing every 10,000 years, with each causing it to increase in luminosity and thus pulse stronger than the previous time.__ 24. __ The smaller companion on the lef ...
... supernova. This is the first documented case of a supernova candidate through white-dwarf merger.__ 23. __ The star, Mira, is thermally pulsing every 10,000 years, with each causing it to increase in luminosity and thus pulse stronger than the previous time.__ 24. __ The smaller companion on the lef ...
Sin título de diapositiva - Universitat de Barcelona
... The GAIA mission, the next ESA Cornerstone 6 (launch 2010- 2012), will create a precise three dimensional map of about one billion stars throughout our Galaxy and beyond. To reach the scientific goals, that is to quantify the dynamical, chemical and star formation evolution of the Milky Way, it is c ...
... The GAIA mission, the next ESA Cornerstone 6 (launch 2010- 2012), will create a precise three dimensional map of about one billion stars throughout our Galaxy and beyond. To reach the scientific goals, that is to quantify the dynamical, chemical and star formation evolution of the Milky Way, it is c ...
Slajd 1 - INFN-LNF
... Definition of a Be star (for the purpose of SPS calculations) The primary property of Be stars distinguishing them from other B stars is rapid rotation. All other properties (in particular, the presence of an excretion disc, which permits the efficient accretion on the compact companion) are the co ...
... Definition of a Be star (for the purpose of SPS calculations) The primary property of Be stars distinguishing them from other B stars is rapid rotation. All other properties (in particular, the presence of an excretion disc, which permits the efficient accretion on the compact companion) are the co ...
SHELL BURNING STARS: Red Giants and Red Supergiants
... composition. For example, the core may have no hydrogen, and mostly helium, while the envelope may be hydrogen rich. As a result, there is a nuclear burning shell at the bottom of the envelope; hydrogen burning shell in our example. The heat generated in the shell is diffusing out with radiation, an ...
... composition. For example, the core may have no hydrogen, and mostly helium, while the envelope may be hydrogen rich. As a result, there is a nuclear burning shell at the bottom of the envelope; hydrogen burning shell in our example. The heat generated in the shell is diffusing out with radiation, an ...
New Astrophysical Opportunities Exploiting Spatio-Temporal Optical Correlations
... have an expected size of 0.3 milli-arcsecond at the distance of NGC 1068 and resolving it would be a fantastic achievement. The nucleus has a visual magnitude of around 10m . Gamma-ray bursts and supernovae The energy, spectrum and delay between the spectrally-remote events and their inexplicable en ...
... have an expected size of 0.3 milli-arcsecond at the distance of NGC 1068 and resolving it would be a fantastic achievement. The nucleus has a visual magnitude of around 10m . Gamma-ray bursts and supernovae The energy, spectrum and delay between the spectrally-remote events and their inexplicable en ...
www.astro.caltech.edu
... New Classes of Burst While the majority of detected GRBs originate from massive stars, a smaller subset sees to have a completely different physical cause (Figure 2). The host galaxies of short-duration GRBs (those whose gamma-ray emission lasts for 2 seconds or less) observed with Keck have been lo ...
... New Classes of Burst While the majority of detected GRBs originate from massive stars, a smaller subset sees to have a completely different physical cause (Figure 2). The host galaxies of short-duration GRBs (those whose gamma-ray emission lasts for 2 seconds or less) observed with Keck have been lo ...
The Hα Balmer line as an effective temperature criterion
... Aims. We attempt to derive the true effective temperature of a star from the spectroscopic observation of its Hα Balmer line profile. Methods. The method is possible thanks to advances in two respects. First there have been progresses in the theoretical treatment of the broadening mechanisms of Hα. S ...
... Aims. We attempt to derive the true effective temperature of a star from the spectroscopic observation of its Hα Balmer line profile. Methods. The method is possible thanks to advances in two respects. First there have been progresses in the theoretical treatment of the broadening mechanisms of Hα. S ...
Hydrostatic equilibrium : no large scale acceleration of the same
... Opacity described by Opacity Distribution Function or Opacity Sampling NLTE represents, at its best, the interaction between matter and radiation NLTE is present – at some point – in every stellar atmosphere To have LTE, the net collisional rate in every atomic transition must be larger than the net ...
... Opacity described by Opacity Distribution Function or Opacity Sampling NLTE represents, at its best, the interaction between matter and radiation NLTE is present – at some point – in every stellar atmosphere To have LTE, the net collisional rate in every atomic transition must be larger than the net ...
The Interior of the Sun
... In the 1960’s it was discovered that sound waves are propagating in the Sun by Robert B. Leighton. About ten years later it was explained by Ulrich (1970) and Leibache and Stein in 1971. This has lead to the development of a new technique called helioseismology. The Sun is a ball of hot gas so its i ...
... In the 1960’s it was discovered that sound waves are propagating in the Sun by Robert B. Leighton. About ten years later it was explained by Ulrich (1970) and Leibache and Stein in 1971. This has lead to the development of a new technique called helioseismology. The Sun is a ball of hot gas so its i ...
The central star of the planetary nebula PB 8: a Wolf-Rayet
... A considerable fraction of the central stars of planetary nebulæ (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type ...
... A considerable fraction of the central stars of planetary nebulæ (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type ...
Brown Dwarfs - The University of Toledo
... Fusion begins, but degeneracy lowers temperature: transition object M ~ 0.075 M Fusion never becomes a significant source of energy: M < 0.07 M. BD is produced. ...
... Fusion begins, but degeneracy lowers temperature: transition object M ~ 0.075 M Fusion never becomes a significant source of energy: M < 0.07 M. BD is produced. ...
PX269 Galaxies The University of Warwick
... b) Assuming the Galactic disc has a radius of 20 kpc, a thickness of 300 pc, and it contains 1010 solar masses of hydrogen gas, estimate the average number density of hydrogen atoms in the interstellar medium. c) In what forms is this gas found? d) How might each form be detected? ...
... b) Assuming the Galactic disc has a radius of 20 kpc, a thickness of 300 pc, and it contains 1010 solar masses of hydrogen gas, estimate the average number density of hydrogen atoms in the interstellar medium. c) In what forms is this gas found? d) How might each form be detected? ...
Some observed properties of Dark Matter: a progress report on an
... Survival of cold local structures in UMi – plausibly an evolved star cluster -- requires cored mass distribution Kleyna etal 2003 [UMi] Kleyna etal 2004 [Sext] ...
... Survival of cold local structures in UMi – plausibly an evolved star cluster -- requires cored mass distribution Kleyna etal 2003 [UMi] Kleyna etal 2004 [Sext] ...
Unresolved Stellar Populations
... indices (e.g., J-K is sensitive to the metallicity-dependent AGB and/or RGB color). But this does not help much for a young SSP (for which the color of AGB and/or RGB also depends on the age). There are also other potential uncertainties: • For an SSP with mass < 106 M , the color may be subject to ...
... indices (e.g., J-K is sensitive to the metallicity-dependent AGB and/or RGB color). But this does not help much for a young SSP (for which the color of AGB and/or RGB also depends on the age). There are also other potential uncertainties: • For an SSP with mass < 106 M , the color may be subject to ...
Ch. 19 - Astro1010
... More than half the stars in the sky are double stars and are close enough to share matter when one goes Giant. The larger star goes giant 1st and dumps its extra mass to the smaller Main Sequence star until it is under the mass limit then it quietly goes to White Dwarf. When the now bloated 2nd star ...
... More than half the stars in the sky are double stars and are close enough to share matter when one goes Giant. The larger star goes giant 1st and dumps its extra mass to the smaller Main Sequence star until it is under the mass limit then it quietly goes to White Dwarf. When the now bloated 2nd star ...
Using Python to Study Rotational Velocity Distributions of Hot Stars
... The study of O and B stars is an important key to understanding how star formation occurs. When these stars are born, they have the greatest mass, temperature and rotation. Their mass can go from 2.5 up to 120 times the Solar mass, their temperatures ranging from 11,000 K up to 60,000 K, and rotatio ...
... The study of O and B stars is an important key to understanding how star formation occurs. When these stars are born, they have the greatest mass, temperature and rotation. Their mass can go from 2.5 up to 120 times the Solar mass, their temperatures ranging from 11,000 K up to 60,000 K, and rotatio ...
ppt - University of Arizona
... Spitzer photometry of a number of transiting systems (diamonds, TrES-1; square, HD 209458b) compared with theoretical models. Both figures from Fortney et al 2006 (ApJ, ...
... Spitzer photometry of a number of transiting systems (diamonds, TrES-1; square, HD 209458b) compared with theoretical models. Both figures from Fortney et al 2006 (ApJ, ...
this PDF file
... BD+48 740 is not the only Li-rich star exhibiting changes in radial velocities that might be interpreted as presence of stellar or low mass companion (planets or brown dwarfs). Among 17 red giant stars with enhanced Li abundance only a few do not show significant variations in radial velocities, whi ...
... BD+48 740 is not the only Li-rich star exhibiting changes in radial velocities that might be interpreted as presence of stellar or low mass companion (planets or brown dwarfs). Among 17 red giant stars with enhanced Li abundance only a few do not show significant variations in radial velocities, whi ...
Astronomy Chapter 16 – The Milky Way Galaxy A. Main Ideas 1
... into a thin layer in the disk ⇒ The gas in interstellar clouds has a composition similar to that of the Sun and other stars: about 71 % hydrogen and 27% helium with trace amounts of heavier elements • Interstellar Dust: Dimming and Reddening ⇒ Dimming and reddening result when light strikes a tiny p ...
... into a thin layer in the disk ⇒ The gas in interstellar clouds has a composition similar to that of the Sun and other stars: about 71 % hydrogen and 27% helium with trace amounts of heavier elements • Interstellar Dust: Dimming and Reddening ⇒ Dimming and reddening result when light strikes a tiny p ...
model
... (‘monolithic model’). No flows allowed (‘closed-box’) or, alternatively, assume that the gas accumulates either fast or slowly and the system has outflows (‘open model’) 2. Assume that the gas at t=0 is primordial (no metals) or, alternatively, assume that the gas at t=0 is pre-enriched by Pop III s ...
... (‘monolithic model’). No flows allowed (‘closed-box’) or, alternatively, assume that the gas accumulates either fast or slowly and the system has outflows (‘open model’) 2. Assume that the gas at t=0 is primordial (no metals) or, alternatively, assume that the gas at t=0 is pre-enriched by Pop III s ...
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.