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Radiatively driven Rayleigh-Taylor instability candidates around a
... these features represent details of previously known morphology (Fujiyoshi et al. 2001). The 8−12 μm spectro-polarimetric studies have been used to show that the emission in this region is composed of both absorptive and emissive polarized components (Fujiyoshi et al. 2001). Also, significant line e ...
... these features represent details of previously known morphology (Fujiyoshi et al. 2001). The 8−12 μm spectro-polarimetric studies have been used to show that the emission in this region is composed of both absorptive and emissive polarized components (Fujiyoshi et al. 2001). Also, significant line e ...
an approach to effective temperature and surface gravity in post
... stars (0.8–8 M⊙ ) that have passed the asymtotic giant branch (AGB) and are on their way toward the planetary nebula (PN) phase. On the other hand, RV Tauri stars are very luminous and variable stars (MV ≈ −3 mag) with spectral types F, G and K which have an infrared excess attributed to the mass lo ...
... stars (0.8–8 M⊙ ) that have passed the asymtotic giant branch (AGB) and are on their way toward the planetary nebula (PN) phase. On the other hand, RV Tauri stars are very luminous and variable stars (MV ≈ −3 mag) with spectral types F, G and K which have an infrared excess attributed to the mass lo ...
A Detailed Spectroscopic and Photometric Analysis of DQ White
... π18.5 ±1.9 mas) whose measurements come from M. T. Ruiz (2005, private communication). Optical spectra for most of these stars have already been displayed in Figure 20 of BRL and Figure 6 of BLR, while the photometric data and parallax measurements can be found in Table 1 of both papers. Data acquis ...
... π18.5 ±1.9 mas) whose measurements come from M. T. Ruiz (2005, private communication). Optical spectra for most of these stars have already been displayed in Figure 20 of BRL and Figure 6 of BLR, while the photometric data and parallax measurements can be found in Table 1 of both papers. Data acquis ...
Determination of the position angle of stellar spin axes
... position angle of a large sample of stars and the required signalto-noise ratio (S/N). Spectro-astrometry concentrates on the spatial information contained in the spectrum by measuring the wavelength dependent position of the photocentre of an object. It is a powerful tool that allows us to reach su ...
... position angle of a large sample of stars and the required signalto-noise ratio (S/N). Spectro-astrometry concentrates on the spatial information contained in the spectrum by measuring the wavelength dependent position of the photocentre of an object. It is a powerful tool that allows us to reach su ...
Five New Extrasolar Planets
... Observatory. The lack of brightness variations in phase with the radial velocities supports planetary–reflex motion as the cause of the velocity variations. No transits were observed but their occurrence is not ruled out by our observations. Subject headings: planetary systems – stars: individual (HD ...
... Observatory. The lack of brightness variations in phase with the radial velocities supports planetary–reflex motion as the cause of the velocity variations. No transits were observed but their occurrence is not ruled out by our observations. Subject headings: planetary systems – stars: individual (HD ...
A MISALIGNED PROGRADE ORBIT FOR
... around both hot and cool stars will help to discriminate between these hypotheses. The vast majority of the measurements of spin–orbit misalignments of transiting exoplanets have come via radial velocity observations of the Rossiter–McLaughlin effect, where distortions in the stellar line profile du ...
... around both hot and cool stars will help to discriminate between these hypotheses. The vast majority of the measurements of spin–orbit misalignments of transiting exoplanets have come via radial velocity observations of the Rossiter–McLaughlin effect, where distortions in the stellar line profile du ...
PDF file
... Giant Molecular Clouds (GMCs). A GMC may give rise to one or more star complexes known as OB associations, first defined and recognized by Ambartsumian (1947) as young ...
... Giant Molecular Clouds (GMCs). A GMC may give rise to one or more star complexes known as OB associations, first defined and recognized by Ambartsumian (1947) as young ...
When Will Mankind Achieve “First Contact” with Extraterrestrial Life
... Another less expensive solution would be to launch telescopes into space that contain special star shades that could block out most of the home star’s light and allow the telescope to focus specifically on the light being emitted by the exoplanet itself. NASA has already designed such sun-block syst ...
... Another less expensive solution would be to launch telescopes into space that contain special star shades that could block out most of the home star’s light and allow the telescope to focus specifically on the light being emitted by the exoplanet itself. NASA has already designed such sun-block syst ...
A method for determining the V magnitude of asteroids from CCD
... It should be noted that Equation 3 will be different for different combinations of telescopes and CCD cameras and observers might wish to perform their own calculations. For the example here, the total SNR contribution to the error for the three reference stars and the asteroid (see Table 2) is ...
... It should be noted that Equation 3 will be different for different combinations of telescopes and CCD cameras and observers might wish to perform their own calculations. For the example here, the total SNR contribution to the error for the three reference stars and the asteroid (see Table 2) is ...
PDF only - at www.arxiv.org.
... Consider first a horizontal thread supported against gravity, the field Bh needed for support is then Bh ~ (4π Σ┴ g)1/2. For the above values this corresponds to Bh ~ 24 μG which is less than the equipartition value of 100 μG so energetically possible. By equipartition we mean that B2/8π=nkT and use ...
... Consider first a horizontal thread supported against gravity, the field Bh needed for support is then Bh ~ (4π Σ┴ g)1/2. For the above values this corresponds to Bh ~ 24 μG which is less than the equipartition value of 100 μG so energetically possible. By equipartition we mean that B2/8π=nkT and use ...
Elliptical galaxies
... of star formation at high redshifts (z ~ 5), followed by passive evolution of their stellar populations to the present day (Partridge & Peebles 1967; ...
... of star formation at high redshifts (z ~ 5), followed by passive evolution of their stellar populations to the present day (Partridge & Peebles 1967; ...
First detection of helium emissions in RR Lyrae⋆
... that a shock wave moving throughout the atmosphere during the rising light of each pulsation cycle can explain the presence of emission lines in the population II Cepheids. The first shock model was proposed by Whitney (1956), but the prediction of the occurrence of He I emission lines was discussed ...
... that a shock wave moving throughout the atmosphere during the rising light of each pulsation cycle can explain the presence of emission lines in the population II Cepheids. The first shock model was proposed by Whitney (1956), but the prediction of the occurrence of He I emission lines was discussed ...
PRESENT-DAY CLUSTER FORMATION
... Understanding the formation of bound clusters of stars evidently requires understanding the origin of the dense molecular clumps that produce them. Some clues concerning the large-scale processes responsible for the formation of these dense clumps and their embedded clusters can be obtained by exami ...
... Understanding the formation of bound clusters of stars evidently requires understanding the origin of the dense molecular clumps that produce them. Some clues concerning the large-scale processes responsible for the formation of these dense clumps and their embedded clusters can be obtained by exami ...
Introductory Astronomy
... at are its center • If “Nebulae” are other galaxies, must be far away, but “novae” in them are ~as bright as novae in our Galaxy • van Maanen: claimed to measure rotation of M31 • Nebulae “avoid” the Milky Way • Nebulae all appear to be moving away from us ...
... at are its center • If “Nebulae” are other galaxies, must be far away, but “novae” in them are ~as bright as novae in our Galaxy • van Maanen: claimed to measure rotation of M31 • Nebulae “avoid” the Milky Way • Nebulae all appear to be moving away from us ...
Large distance of epsilon Aurigae from interstellar
... The long-period (P = 27.1 years) peculiar eclipsing binary ε Aur, which has recently completed its 2 year-long primary eclipse, has perplexed astronomers for over a century. The eclipse arises from the transit of a huge, cool and opaque, disk across the face of the F0 Iab star. One of the principal ...
... The long-period (P = 27.1 years) peculiar eclipsing binary ε Aur, which has recently completed its 2 year-long primary eclipse, has perplexed astronomers for over a century. The eclipse arises from the transit of a huge, cool and opaque, disk across the face of the F0 Iab star. One of the principal ...
Turbulent Flow-Driven Molecular Cloud Formation: A Solution to the
... yet the ages of the stars produced by these clouds provide uniquely detailed constraints on cloud ages that are not obtainable in any other way (e.g., Hartmann et al. 1991; Feigelson 1996). Because of the importance of the stellar population ages, it is worth reviewing the situation in some detail, ...
... yet the ages of the stars produced by these clouds provide uniquely detailed constraints on cloud ages that are not obtainable in any other way (e.g., Hartmann et al. 1991; Feigelson 1996). Because of the importance of the stellar population ages, it is worth reviewing the situation in some detail, ...
Entropy Production of Stars
... variational principles proves to be important both for the foundation of nonequilibrium physics and for calculations: from heat-conduction problems to the solution of the Boltzmann equation [1–4]. It should be noted that the quantity of entropy production is convenient from the standpoint of theory ...
... variational principles proves to be important both for the foundation of nonequilibrium physics and for calculations: from heat-conduction problems to the solution of the Boltzmann equation [1–4]. It should be noted that the quantity of entropy production is convenient from the standpoint of theory ...
Neutron Stars - Lick Observatory
... Neutron stars are small compact stars with densities comparable to that inside nuclei, !0 = 2.8 × 1014 g cm!3, and radii R ! 10–15 km. They consist predominantly of NEUTRONS and a few percent of PROTONS and ELECTRONS. These huge neutron-rich ‘nuclei’ are bound by gravitation and require a minimum ne ...
... Neutron stars are small compact stars with densities comparable to that inside nuclei, !0 = 2.8 × 1014 g cm!3, and radii R ! 10–15 km. They consist predominantly of NEUTRONS and a few percent of PROTONS and ELECTRONS. These huge neutron-rich ‘nuclei’ are bound by gravitation and require a minimum ne ...
Giant molecular clouds: star factories
... tars are forming in our galaxy at a rate of between 1 and 4 solar masses of stars per year. In contrast to elliptical galaxies, which are largely devoid of star formation, star formation is still going on in spiral galaxies because of their reservoirs of molecular gas, the fuel for new stars. The di ...
... tars are forming in our galaxy at a rate of between 1 and 4 solar masses of stars per year. In contrast to elliptical galaxies, which are largely devoid of star formation, star formation is still going on in spiral galaxies because of their reservoirs of molecular gas, the fuel for new stars. The di ...
Theory of Motion of Matter on the Formation of Galaxy and Star
... As primordial galaxy nebula and primordial stellar nebula are vortex type, centrifugal effect makes dispersed matter unable to move rapidly towards nebula center. It produced relative motion between matter moving outwards primordial galaxy nebula center high density nuclear zone and dispersed matter ...
... As primordial galaxy nebula and primordial stellar nebula are vortex type, centrifugal effect makes dispersed matter unable to move rapidly towards nebula center. It produced relative motion between matter moving outwards primordial galaxy nebula center high density nuclear zone and dispersed matter ...
hal.archives-ouvertes.fr - HAL-ENS
... is centered on the star position whereas the strong red wing is found to the North-East of the star, and the weak blue wing to the South-West. KJ1996 interpret these CO profiles as resulting from three elements in the circumstellar shell: a very slowly expanding spherical wind (Vexp = 2.5 km s−1 ) a ...
... is centered on the star position whereas the strong red wing is found to the North-East of the star, and the weak blue wing to the South-West. KJ1996 interpret these CO profiles as resulting from three elements in the circumstellar shell: a very slowly expanding spherical wind (Vexp = 2.5 km s−1 ) a ...
Chemical Signatures in Dwarf Galaxies
... can come from H ii region emission lines, planetary nebulae, or supernova remnants, but mostly they come from stars. Since stars can live a very long time, for example, a 0.8 MA star born at the time of the Big Bang would only now be ascending the red giant branch, and, if, for the most part, its qu ...
... can come from H ii region emission lines, planetary nebulae, or supernova remnants, but mostly they come from stars. Since stars can live a very long time, for example, a 0.8 MA star born at the time of the Big Bang would only now be ascending the red giant branch, and, if, for the most part, its qu ...
Dynamical Instabilities in Extrasolar Planetary Systems Containing
... from the central star and later interacted dynamically (Rasio and Ford 1996). This could happen because their orbital radii evolved secularly at different rates (significant orbital migration is thought to have occurred in the outer Solar System; see Goldreich and Tremaine 1980, Malhotra 1995), brin ...
... from the central star and later interacted dynamically (Rasio and Ford 1996). This could happen because their orbital radii evolved secularly at different rates (significant orbital migration is thought to have occurred in the outer Solar System; see Goldreich and Tremaine 1980, Malhotra 1995), brin ...
View - ESA
... The first part of this report addresses the preliminary phase in which information about the Solar Neighborhood has been collected. This part has been particularly time consuming since the data sources are many and generally incomplete in several respects, making it necessary to merge information of ...
... The first part of this report addresses the preliminary phase in which information about the Solar Neighborhood has been collected. This part has been particularly time consuming since the data sources are many and generally incomplete in several respects, making it necessary to merge information of ...
Study of an unbiased sample of B stars observed with Hipparcos
... A caveat to place the supergiants in the HR diagram is that their temperature and luminosity are difficult to determine, especially by means of photometric data alone. Nevertheless, we have tried to derive these quantities for the 29 supergiants with α Cyg-type variability that resulted from both us ...
... A caveat to place the supergiants in the HR diagram is that their temperature and luminosity are difficult to determine, especially by means of photometric data alone. Nevertheless, we have tried to derive these quantities for the 29 supergiants with α Cyg-type variability that resulted from both us ...
Planetary nebula
![](https://commons.wikimedia.org/wiki/Special:FilePath/NGC6543.jpg?width=300)
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word ""nebula"" is Latin for mist or cloud and the term ""planetary nebula"" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, appearing as a bright coloured planetary nebula at several discrete visible wavelengths.Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances.In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.