Bright 22 μm excess candidates from the wise all-sky
... Since the first discovery of a debris disk around Vega via excess IR, (Aumann et al. 1984), excess IR has been a useful tool in the search for debris disks. To date, many works have been conducted on the search for stars with excess IR emission. Most of the samples used in previous work were selecte ...
... Since the first discovery of a debris disk around Vega via excess IR, (Aumann et al. 1984), excess IR has been a useful tool in the search for debris disks. To date, many works have been conducted on the search for stars with excess IR emission. Most of the samples used in previous work were selecte ...
the fragmentation of magnetized, massive star-forming
... We obtain the dust opacities κ0P and κ0R from a piecewise-linear fit to the models of Semenov et al. (2003); see Cunningham et al. (2011) for the exact functional form. We solve the above equations using a new version of our astrophysical AMR code Orion, which allows us to simultaneously include the ...
... We obtain the dust opacities κ0P and κ0R from a piecewise-linear fit to the models of Semenov et al. (2003); see Cunningham et al. (2011) for the exact functional form. We solve the above equations using a new version of our astrophysical AMR code Orion, which allows us to simultaneously include the ...
Fluorine abundances in dwarf stars of the solar neighbourhood⋆
... Fluorine abundances were derived from an unblended line R9 (1−0) of the HF molecule at λ ∼ 2.3358 μm (Abia et al. 2009). We used the classical method of spectral synthesis in LTE for the abundance analysis. Theoretical spectra were computed with the TURBOSPECTRUM code (Alvarez & Plez 1998, and furth ...
... Fluorine abundances were derived from an unblended line R9 (1−0) of the HF molecule at λ ∼ 2.3358 μm (Abia et al. 2009). We used the classical method of spectral synthesis in LTE for the abundance analysis. Theoretical spectra were computed with the TURBOSPECTRUM code (Alvarez & Plez 1998, and furth ...
T
... The long-term precision of the instrument cannot be checked easily because it requires a long time base on one hand, and the knowledge of stable stellar sources on the other hand. Especially the latter point represents a new challenge since the intrinsic stability of the stars has never been studied ...
... The long-term precision of the instrument cannot be checked easily because it requires a long time base on one hand, and the knowledge of stable stellar sources on the other hand. Especially the latter point represents a new challenge since the intrinsic stability of the stars has never been studied ...
Luminosity
... • How does nuclear fusion occur in the Sun? – The core’s extreme temperature and density are just right for nuclear fusion of hydrogen to helium through the proton–proton chain. – Gravitational equilibrium acts as a thermostat to regulate the core temperature because fusion rate is very sensitive to ...
... • How does nuclear fusion occur in the Sun? – The core’s extreme temperature and density are just right for nuclear fusion of hydrogen to helium through the proton–proton chain. – Gravitational equilibrium acts as a thermostat to regulate the core temperature because fusion rate is very sensitive to ...
Spectroscopic Binaries - Thüringer Landessternwarte Tautenburg
... SBs requires to disentangle the effects due to orbital motion • The eclipse phases in EBs can be used to screen the surface of the eclipsed star spectroscopically for the structure of its surface velocity field (e.g. pulsation) or to determine the stellar parameters (rotation, RME). ...
... SBs requires to disentangle the effects due to orbital motion • The eclipse phases in EBs can be used to screen the surface of the eclipsed star spectroscopically for the structure of its surface velocity field (e.g. pulsation) or to determine the stellar parameters (rotation, RME). ...
A timeline of the universe
... consists primarily of bare hydrogen nuclei and free electrons. Stellar UV light maintains this ionization. These photons pack enough punch to tear electrons off any neutral hydrogen atoms that form by recombination. The current dominance of ionized hydrogen is one reason we can see so far with opti ...
... consists primarily of bare hydrogen nuclei and free electrons. Stellar UV light maintains this ionization. These photons pack enough punch to tear electrons off any neutral hydrogen atoms that form by recombination. The current dominance of ionized hydrogen is one reason we can see so far with opti ...
Pan-Planets: Searching for hot Jupiters around cool dwarfs⋆
... Since radial velocity surveys provide information about the planetary mass and transit surveys about radii, it is not trivial to compare these results directly. Furthermore, many RV surveys focus on metal-rich host stars which seem to have a higher rate of hot Jupiters (Dawson & Murray-Clay 2013). W ...
... Since radial velocity surveys provide information about the planetary mass and transit surveys about radii, it is not trivial to compare these results directly. Furthermore, many RV surveys focus on metal-rich host stars which seem to have a higher rate of hot Jupiters (Dawson & Murray-Clay 2013). W ...
Stellar Metamorphosis
... accretion/proto-planetary disk model for solar system formation because these stars should have already squeezed together to make one single star. According to the mainstream dogma solar systems have a central star which centralizes the majority of the material that forms the theorized disk surround ...
... accretion/proto-planetary disk model for solar system formation because these stars should have already squeezed together to make one single star. According to the mainstream dogma solar systems have a central star which centralizes the majority of the material that forms the theorized disk surround ...
The dark heart of the Milky Way
... to us on Earth. More massive black holes may form when certain dense stars of more than 25 solar masses use up their nuclear fuel. What can happen then is that the star explodes as a supernova while at the same time its core collapses into a black hole of some three to 10 solar masses. Then there ar ...
... to us on Earth. More massive black holes may form when certain dense stars of more than 25 solar masses use up their nuclear fuel. What can happen then is that the star explodes as a supernova while at the same time its core collapses into a black hole of some three to 10 solar masses. Then there ar ...
aaswinter06
... • Evidence for a hot, blue companion (B3 V) was discovered when V838 Mon cooled (10,11). The progenitor of the outbursting component has been estimated to be 1) a very massive (65 Msolar), hot (Teff ~ 50,000 K), evolved star such as a Wolf-Rayet star (7); or 2) a main sequence or pre-main sequence s ...
... • Evidence for a hot, blue companion (B3 V) was discovered when V838 Mon cooled (10,11). The progenitor of the outbursting component has been estimated to be 1) a very massive (65 Msolar), hot (Teff ~ 50,000 K), evolved star such as a Wolf-Rayet star (7); or 2) a main sequence or pre-main sequence s ...
doc - Pocket Stars
... Compass Indicates and changes which compass direction is shown at the top of the display. The yellow line indicates North. Click within the red circle and then drag the yellow line to point in the direction of North. Using this control, you can rotate the star chart 360°. ...
... Compass Indicates and changes which compass direction is shown at the top of the display. The yellow line indicates North. Click within the red circle and then drag the yellow line to point in the direction of North. Using this control, you can rotate the star chart 360°. ...
S-process in extremely metal-poor, low-mass stars
... the beginning of the thermally pulsating asymptotic giant branch (TP-AGB) phase. Similar to the occurrence of the PIE during the core He-flash, proton-rich material is dragged down into the He-burning zone during the development of a thermal runaway in the He-shell. After the ensuing dredge-up event ...
... the beginning of the thermally pulsating asymptotic giant branch (TP-AGB) phase. Similar to the occurrence of the PIE during the core He-flash, proton-rich material is dragged down into the He-burning zone during the development of a thermal runaway in the He-shell. After the ensuing dredge-up event ...
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.