12C13C1414N21312C/13C3he43He/4He Sub-surface
... evolution of hot massive stars, they may cause observable phenomena at the stellar surface. The reason is that the zones are located very close to the photosphere for some mass interval (see below). Here, we will discuss which observed features in hot stars might be produced by these near surface co ...
... evolution of hot massive stars, they may cause observable phenomena at the stellar surface. The reason is that the zones are located very close to the photosphere for some mass interval (see below). Here, we will discuss which observed features in hot stars might be produced by these near surface co ...
Chapter 16--Properties of Stars
... its life with roughly the same chemical composition: About three-quarters of the star’s mass at birth is hydrogen, and about one-quarter is helium, with no more than about 2% consisting of elements heavier than helium. During most of any star’s life, the rate at which it generates energy depends on ...
... its life with roughly the same chemical composition: About three-quarters of the star’s mass at birth is hydrogen, and about one-quarter is helium, with no more than about 2% consisting of elements heavier than helium. During most of any star’s life, the rate at which it generates energy depends on ...
Abundances and possible diffusion of elements in M 67 stars⋆
... abundance trend in iron was found between the turn-off point and the red giants (Mucciarelli et al. 2011), possibly indicating that the more massive outer convection zones of more metal-rich stars suppress atomic diffusion. It is now important to find out to what extent such diffusion effects are also v ...
... abundance trend in iron was found between the turn-off point and the red giants (Mucciarelli et al. 2011), possibly indicating that the more massive outer convection zones of more metal-rich stars suppress atomic diffusion. It is now important to find out to what extent such diffusion effects are also v ...
Neon abundances - UCL Astrophysics Group
... observe any Ne i lines. Physical parameters of the stars in this study are given in Table 1. All observations were obtained with the Hamilton Echelle Spectrograph (HES; Vogt 1987) at the Lick Observatory, fed by the 0.6-m Coude Auxilliary Telescope (CAT), during four runs in 1994±1997. Further deta ...
... observe any Ne i lines. Physical parameters of the stars in this study are given in Table 1. All observations were obtained with the Hamilton Echelle Spectrograph (HES; Vogt 1987) at the Lick Observatory, fed by the 0.6-m Coude Auxilliary Telescope (CAT), during four runs in 1994±1997. Further deta ...
SRMP Stars Curriculum - American Museum of Natural History
... ACTIVITY: Stellar Temperature and Distance In this activity, students will be given two tables of data – one of nearby stars, and one of bright stars in our sky. There is some overlap in stars, but most of them are separate. The table includes each star’s name, spectral type, apparent and absolute m ...
... ACTIVITY: Stellar Temperature and Distance In this activity, students will be given two tables of data – one of nearby stars, and one of bright stars in our sky. There is some overlap in stars, but most of them are separate. The table includes each star’s name, spectral type, apparent and absolute m ...
Chemical abundances and winds of massive stars in M31: a B
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
1 Astrobiologically Interesting Stars within 10
... considerably larger detail, fully exploring the completeness of data for the nearest stars and thereby being able to be less based on statistical considerations. For very nearby stars, the Hipparcos parallaxes allow luminosity determinations with uncertainties under 2%, and the location of their CHZ ...
... considerably larger detail, fully exploring the completeness of data for the nearest stars and thereby being able to be less based on statistical considerations. For very nearby stars, the Hipparcos parallaxes allow luminosity determinations with uncertainties under 2%, and the location of their CHZ ...
Annual report 2004 - Département d`Astrophysique, Géophysique et
... We try to model Eri by fitting the four most significant, independent frequencies that are present in both the photometric and spectroscopic data. So far we encounter a puzzle : a non adiabatic analysis of the solutions best fitting the observed frequencies shows that these modes are not excited. We ...
... We try to model Eri by fitting the four most significant, independent frequencies that are present in both the photometric and spectroscopic data. So far we encounter a puzzle : a non adiabatic analysis of the solutions best fitting the observed frequencies shows that these modes are not excited. We ...
Protostellar/PMS Mass Infall Luminosity Problem
... Accretion sphere with Racc=8dx=400 AU (external accretion) ...
... Accretion sphere with Racc=8dx=400 AU (external accretion) ...
Rotation Periods and Relative Ages of Solar-Type Stars
... chromospheres of stars; starspots are greatest where magnetic fields are greatest. Hence, as starspots or inhomogeneities travel across the surface of a star, Ca II flux will reflect that movement (Donahue 1993). Ca II flux is thus used to observe rotation periods. The search for rotational signals ...
... chromospheres of stars; starspots are greatest where magnetic fields are greatest. Hence, as starspots or inhomogeneities travel across the surface of a star, Ca II flux will reflect that movement (Donahue 1993). Ca II flux is thus used to observe rotation periods. The search for rotational signals ...
Stellar radii from long-baseline interferometry
... The cool dwarfs 61 Cyg A and B are the nearest stars in the northern hemisphere. They are a visual binary pair with a very long orbital period (≈ 700 yrs). In 1838, 61 Cyg became the first star whose distance from Earth was estimated accurately (Bessel 1838), shortly before Procyon’s, and it is now k ...
... The cool dwarfs 61 Cyg A and B are the nearest stars in the northern hemisphere. They are a visual binary pair with a very long orbital period (≈ 700 yrs). In 1838, 61 Cyg became the first star whose distance from Earth was estimated accurately (Bessel 1838), shortly before Procyon’s, and it is now k ...
Chemical abundances and winds of massive stars in M31: a Btype
... versus 0.3 for HD 92809). Our study represents the first detailed, chemical model atmosphere analysis for either a B-type supergiant or a Wolf –Rayet (WR) star in Andromeda, and shows the potential of how such studies can provide new information on the chemical evolution of galaxies and the evolutio ...
... versus 0.3 for HD 92809). Our study represents the first detailed, chemical model atmosphere analysis for either a B-type supergiant or a Wolf –Rayet (WR) star in Andromeda, and shows the potential of how such studies can provide new information on the chemical evolution of galaxies and the evolutio ...
The empirical mass distribution of hot B subdwarfs
... is an indication that the majority of sdB stars, including the isolated ones, are indeed post-red giant stars. Moreover, the empirical mass distribution strongly peaking at ∼0.47 M suggests that, in most cases, helium ignition occurs in the stellar core through a He-flash. The peak at ∼0.47 M also ...
... is an indication that the majority of sdB stars, including the isolated ones, are indeed post-red giant stars. Moreover, the empirical mass distribution strongly peaking at ∼0.47 M suggests that, in most cases, helium ignition occurs in the stellar core through a He-flash. The peak at ∼0.47 M also ...
Sample pages 1 PDF
... astronomers researching the production and evolution of planetary nebulae. Stars that are only 45% of the Sun’s mass do not become AGB stars; rather they cross the horizontal branch of the H-R diagram and become C-O white dwarfs, which then gradually fade away after their hydrogen envelopes have bee ...
... astronomers researching the production and evolution of planetary nebulae. Stars that are only 45% of the Sun’s mass do not become AGB stars; rather they cross the horizontal branch of the H-R diagram and become C-O white dwarfs, which then gradually fade away after their hydrogen envelopes have bee ...
Seventh Week. - UNLV Physics
... • What are the life stages of a high-mass star? – They are similar to the life stages of a low-mass star. • How do high-mass stars make the elements necessary for life? – Higher masses produce higher core temperatures that enable fusion of heavier ...
... • What are the life stages of a high-mass star? – They are similar to the life stages of a low-mass star. • How do high-mass stars make the elements necessary for life? – Higher masses produce higher core temperatures that enable fusion of heavier ...
PDF Full-text
... the photodissociation rate for H2 O in exoplanets with solar-type and M dwarf host stars including the observed UV fluxes and Lyman-α corrected for interstellar absorption to evaluate the H2 O loss rate. At this time, however, there are very few disequilibrium chemistry calculations that include obs ...
... the photodissociation rate for H2 O in exoplanets with solar-type and M dwarf host stars including the observed UV fluxes and Lyman-α corrected for interstellar absorption to evaluate the H2 O loss rate. At this time, however, there are very few disequilibrium chemistry calculations that include obs ...
Star
A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Other stars are visible from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Once the hydrogen in the core of a star is nearly exhausted, almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime and, for some stars, by supernova nucleosynthesis when it explodes. Near the end of its life, a star can also contain degenerate matter. Astronomers can determine the mass, age, metallicity (chemical composition), and many other properties of a star by observing its motion through space, luminosity, and spectrum respectively. The total mass of a star is the principal determinant of its evolution and eventual fate. Other characteristics of a star, including diameter and temperature, change over its life, while the star's environment affects its rotation and movement. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung–Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, hydrogen becomes steadily converted into helium through nuclear fusion, releasing energy in the process. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, a star with at least 0.4 times the mass of the Sun expands to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of its matter into the interstellar environment, where it will contribute to the formation of a new generation of stars with a higher proportion of heavy elements. Meanwhile, the core becomes a stellar remnant: a white dwarf, a neutron star, or (if it is sufficiently massive) a black hole.Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.