Stellar evolution - Statistical Physics Group
... main-sequence stars can be obtained without a very precise knowledge of the source of energy, but this no longer remains true when evolution is studied. Calculations of models of stars of uniform chemical composition soon showed that they could not explain the existence of the giant branch. Although ...
... main-sequence stars can be obtained without a very precise knowledge of the source of energy, but this no longer remains true when evolution is studied. Calculations of models of stars of uniform chemical composition soon showed that they could not explain the existence of the giant branch. Although ...
12C13C1414N21312C/13C3he43He/4He Sub-surface
... 2 × 10−6 M to 10−4 M . For sufficiently hot models, the helium convection zones can even vanish (Fig. 2, lower panel). Second, comparing the 20 M and the 60 M model at Z=0.02 demonstrates that the FeCZ becomes more prominent for higher luminosity. This is because the opacity is not substantially ...
... 2 × 10−6 M to 10−4 M . For sufficiently hot models, the helium convection zones can even vanish (Fig. 2, lower panel). Second, comparing the 20 M and the 60 M model at Z=0.02 demonstrates that the FeCZ becomes more prominent for higher luminosity. This is because the opacity is not substantially ...
ancient cultures 114 - Stellenbosch University
... approximately 1700 BCE (Bienkowski & Millard 2000: 40). The interest during this time, however, seems to be purely astrological; the texts all being what are known as “omen” texts. A standard series of these omen texts was finalised in approximately 1000 BCE, and was named Enuma Anu Enlil. By this t ...
... approximately 1700 BCE (Bienkowski & Millard 2000: 40). The interest during this time, however, seems to be purely astrological; the texts all being what are known as “omen” texts. A standard series of these omen texts was finalised in approximately 1000 BCE, and was named Enuma Anu Enlil. By this t ...
Chemical analysis of 24 dusty (pre-) main
... as a class in 1960 by Herbig, based on three observational criteria: the stars have spectral type A or earlier, display emission lines, and illuminate a bright reflection nebula in their immediate vicinity. Later on other observational criteria were proposed. Finkenzeller & Mundt (1984) mentioned th ...
... as a class in 1960 by Herbig, based on three observational criteria: the stars have spectral type A or earlier, display emission lines, and illuminate a bright reflection nebula in their immediate vicinity. Later on other observational criteria were proposed. Finkenzeller & Mundt (1984) mentioned th ...
Barium and europium abundances in cool dwarf stars and
... barium the Ba ii λ4554 line is significantly strengthened compared with the case of solar even-to-odd isotopic ratio 82: 18. In Paper I we showed this difference can be easily detected if it exists: for example, for the star BD 66◦ 268 with [Fe/H] = −2.2 it consists of 0.2 dex in terms of abundances ...
... barium the Ba ii λ4554 line is significantly strengthened compared with the case of solar even-to-odd isotopic ratio 82: 18. In Paper I we showed this difference can be easily detected if it exists: for example, for the star BD 66◦ 268 with [Fe/H] = −2.2 it consists of 0.2 dex in terms of abundances ...
Luminosities and mass-loss rates of SMC and LMC AGB stars and
... interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. Aims. To investigate the relation between mass loss, luminosity and p ...
... interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. Aims. To investigate the relation between mass loss, luminosity and p ...
ASTRONOMY AND ASTROPHYSICS Barium and europium
... at λ/∆λ ∼60000. Almost all the stars were observed at least twice with the signal-to-noise ratio of about 200 (Fuhrmann 1998, 2000) in the spectral range λ ≥ 4550 Åand with less S/N (∼ 50) in the range where the Eu II resonance line λ4129 is located. Our sample of 9 stars from Paper I with metallic ...
... at λ/∆λ ∼60000. Almost all the stars were observed at least twice with the signal-to-noise ratio of about 200 (Fuhrmann 1998, 2000) in the spectral range λ ≥ 4550 Åand with less S/N (∼ 50) in the range where the Eu II resonance line λ4129 is located. Our sample of 9 stars from Paper I with metallic ...
Carbon-enhanced metal-poor stars in dwarf galaxies
... log(L/L# ) < 4.0 (shown in Fig. 1 with red circles), are from high-resolution spectroscopic studies (see caption for references). Although less than 20 stars have been observed in these 4 systems, the overall frequency of CEMP-no stars is very high, and at [Fe/H]≤ −3, 5 out of 6 stars are CEMP-no st ...
... log(L/L# ) < 4.0 (shown in Fig. 1 with red circles), are from high-resolution spectroscopic studies (see caption for references). Although less than 20 stars have been observed in these 4 systems, the overall frequency of CEMP-no stars is very high, and at [Fe/H]≤ −3, 5 out of 6 stars are CEMP-no st ...
A Walk through the Southern Sky: A Guide to Stars and
... constellations and the stars within them. Clear instructions guide the user on how to gauge sizes and distances, and how to move easily between constellations. This new edition has been updated with additional mythology information, and a list of the planet positions up to 2016. Ancient myths and le ...
... constellations and the stars within them. Clear instructions guide the user on how to gauge sizes and distances, and how to move easily between constellations. This new edition has been updated with additional mythology information, and a list of the planet positions up to 2016. Ancient myths and le ...
Deep SDSS optical spectroscopy of distant halo stars I. Atmospheric
... Aims. We analyze a sample of tens of thousands of spectra of halo turnoff stars, obtained with the optical spectrographs of the Sloan Digital Sky Survey (SDSS), to characterize the stellar halo population “in situ” out to a distance of a few tens of kpc from the Sun. In this paper we describe the de ...
... Aims. We analyze a sample of tens of thousands of spectra of halo turnoff stars, obtained with the optical spectrographs of the Sloan Digital Sky Survey (SDSS), to characterize the stellar halo population “in situ” out to a distance of a few tens of kpc from the Sun. In this paper we describe the de ...
Element Segregation in Low Metallicity Stars and the Primordial
... which have been formed by nuclear reactions during the first minutes of the Universe. Together with deuterium, helium-3 and helium-4, its abundance is used as a constraint on the baryonic density of the Universe. The fact that the observed abundances of these four isotopes are consistent, within the ...
... which have been formed by nuclear reactions during the first minutes of the Universe. Together with deuterium, helium-3 and helium-4, its abundance is used as a constraint on the baryonic density of the Universe. The fact that the observed abundances of these four isotopes are consistent, within the ...
12-1 - Piscataway High School
... makes star images about 1 second of arc in diameter, and that makes it difficult to measure parallax from Earth’s surface. Even when astronomers average together many observations, they cannot measure parallax with an uncertainty smaller than about 0.002 arc second. If you measure a parallax of 0.02 ...
... makes star images about 1 second of arc in diameter, and that makes it difficult to measure parallax from Earth’s surface. Even when astronomers average together many observations, they cannot measure parallax with an uncertainty smaller than about 0.002 arc second. If you measure a parallax of 0.02 ...
Observational studies of stellar rotation
... period Prot . This technique has the advantage over spectroscopy of yielding a measurement of the stellar rotation rate that is free of geometric effects and is straighforwardly converted to angular velocity, Ω = 2π/Prot . However, this is at the expense of requiring intense photometric monitoring o ...
... period Prot . This technique has the advantage over spectroscopy of yielding a measurement of the stellar rotation rate that is free of geometric effects and is straighforwardly converted to angular velocity, Ω = 2π/Prot . However, this is at the expense of requiring intense photometric monitoring o ...
on the pms star hbc 498 and its associated nebulous stars1
... 1200 seconds was used for HBC 498, DL Ori/G2 and HBC 495, and of 2400 seconds for HBC 496. A total of 12 spectra with useful signal to noise (S/N) ratio were secured: four of HBC 498, three of HBC 495, two of DL Ori/G2, two of HBC 496 and one of the westernmost of the stars, DL Ori/D, observed here ...
... 1200 seconds was used for HBC 498, DL Ori/G2 and HBC 495, and of 2400 seconds for HBC 496. A total of 12 spectra with useful signal to noise (S/N) ratio were secured: four of HBC 498, three of HBC 495, two of DL Ori/G2, two of HBC 496 and one of the westernmost of the stars, DL Ori/D, observed here ...
The CCD Photometric Calibration Cookbook
... independent of each other and you can use just the ones appropriate for your purposes. It is also worth noting that astronomical photometry is a diverse subject. There are many different ways of making and reducing photometric observations. Observations can be made for very different types of progra ...
... independent of each other and you can use just the ones appropriate for your purposes. It is also worth noting that astronomical photometry is a diverse subject. There are many different ways of making and reducing photometric observations. Observations can be made for very different types of progra ...
Behavior of Li abundances in solar-analog stars
... Third, ALi in the Sun appears to be located nearly at the lowest end (i.e., an outlier) in the considerable spread exhibited by similar solar-type stars. This tendency has been seen in studies of “solar twins”. That is, while several stars are considered to have stellar parameters very close to thos ...
... Third, ALi in the Sun appears to be located nearly at the lowest end (i.e., an outlier) in the considerable spread exhibited by similar solar-type stars. This tendency has been seen in studies of “solar twins”. That is, while several stars are considered to have stellar parameters very close to thos ...
- StealthSkater
... These stars quite likely have planets. Indeed, one 'M' star (known as Barnard's star) is believed to almost certainly have at least one (and 2-or-3) Jupiter-sized planets. Peter Van de Kamp of the Sproul Observatory at Swarthmore College (PA) has watched Barnard's star for over 3 decades and is conv ...
... These stars quite likely have planets. Indeed, one 'M' star (known as Barnard's star) is believed to almost certainly have at least one (and 2-or-3) Jupiter-sized planets. Peter Van de Kamp of the Sproul Observatory at Swarthmore College (PA) has watched Barnard's star for over 3 decades and is conv ...
THE MONTHLY SKY GUIDE, SIXTH EDITION
... represent. Constellations are best thought of not as pictures in the sky but as a convenient way of locating celestial objects. ...
... represent. Constellations are best thought of not as pictures in the sky but as a convenient way of locating celestial objects. ...
Influence of the Gould Belt on Interstellar Extinction
... (2008a) but in the extinction, whose accuracy depends primarily on the accuracy of the multiband photometry used. Therefore, for this study, the stars with photometry less accurate than 0.05m at least in one of the Tycho-2 and 2MASS bands under consideration were excluded from our sample: BT , VT , ...
... (2008a) but in the extinction, whose accuracy depends primarily on the accuracy of the multiband photometry used. Therefore, for this study, the stars with photometry less accurate than 0.05m at least in one of the Tycho-2 and 2MASS bands under consideration were excluded from our sample: BT , VT , ...
Hunting for Substructure in the Milky Way
... direction of the North Galactic Pole. In order to conserve angular momentum, over time this orbit remains approximately circular. Astronomers measure the velocity and distances of stars to analyse the angular momentum, and from this they can determine how circular the orbit of each star is. In previ ...
... direction of the North Galactic Pole. In order to conserve angular momentum, over time this orbit remains approximately circular. Astronomers measure the velocity and distances of stars to analyse the angular momentum, and from this they can determine how circular the orbit of each star is. In previ ...
Chapter 1 The Discovery of Open Clusters - Willmann-Bell
... have the effect of attracting less massive stars close by, creating a globular cluster. He also suggested that open clusters (then called “irregular clusters”) were formed when a group of similarly massive stars happened to lie within a certain distance of each other causing their mutual gravitation ...
... have the effect of attracting less massive stars close by, creating a globular cluster. He also suggested that open clusters (then called “irregular clusters”) were formed when a group of similarly massive stars happened to lie within a certain distance of each other causing their mutual gravitation ...
Red supergiants and the past of Cygnus OB2
... makes them easily detectable in the near infrared, making them useful probes of star formation that occurred several tens of Myr ago. Aims. We investigate the past star formation history of Cygnus OB2, the nearest very massive OB association, using red supergiants as a probe. Our aim is to confirm t ...
... makes them easily detectable in the near infrared, making them useful probes of star formation that occurred several tens of Myr ago. Aims. We investigate the past star formation history of Cygnus OB2, the nearest very massive OB association, using red supergiants as a probe. Our aim is to confirm t ...
The cosmic origin of fluorine and sulphur
... When stars have formed new elements, these can either be locked up inside the star (or stellar remnant), or be expelled into space through different processes. ese expelled left-overs are then used as starting material for the formation of new stars and celestial bodies in the eternal cosmic cycle. ...
... When stars have formed new elements, these can either be locked up inside the star (or stellar remnant), or be expelled into space through different processes. ese expelled left-overs are then used as starting material for the formation of new stars and celestial bodies in the eternal cosmic cycle. ...
The connection between stellar activity cycles and magnetic field
... chromospheric observations. Therefore, it is useful to study activity cycles with chromospheric data in conjunction with the ZDI technique. There are now numerous stars that have been characterised by ZDI that also have a chromospherically determined cycle period in the literature. While a number of ...
... chromospheric observations. Therefore, it is useful to study activity cycles with chromospheric data in conjunction with the ZDI technique. There are now numerous stars that have been characterised by ZDI that also have a chromospherically determined cycle period in the literature. While a number of ...
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some of the more frequently quoted ones. Star catalogues were compiled by many different ancient peoples, including the Babylonians, Greeks, Chinese, Persians, and Arabs. Most modern catalogues are available in electronic format and can be freely downloaded from NASA's Astronomical Data Center.Completeness and accuracy is described by the weakest apparent magnitude V (largest number) and the accuracy of the positions.