@let@token Stellar Oscillations: Pulsations of Stars Throughout the
... We analyze the stability of g-modes in white dwarfs with hydrogen envelopes. All relevant physical processes take place in the outer layer of hydrogen-rich material, which consists of a radiative layer overlaid by a convective envelope. The radiative layer contributes to mode damping, because its op ...
... We analyze the stability of g-modes in white dwarfs with hydrogen envelopes. All relevant physical processes take place in the outer layer of hydrogen-rich material, which consists of a radiative layer overlaid by a convective envelope. The radiative layer contributes to mode damping, because its op ...
classifying stars
... The brightness of a star depends on its size, temperature and distance from the earth. Some stars appear brighter to us on earth because they are much closer than others, astronomers call this apparent magnitude (HOW BRIGHT A STAR APPEARS.) However, if astronomers could take two stars and place them ...
... The brightness of a star depends on its size, temperature and distance from the earth. Some stars appear brighter to us on earth because they are much closer than others, astronomers call this apparent magnitude (HOW BRIGHT A STAR APPEARS.) However, if astronomers could take two stars and place them ...
The DBV stars: Progress and problems
... essentially unchanged. Other values, such as the seismological parallax also changed; the best parallax distance is now about 45 pc, and logg = 7.95. Provencal et al. (1995) find a slightly hotter temperature of 27,000 K. Depending on the carbon mass fraction in the core, I will probably be able to ...
... essentially unchanged. Other values, such as the seismological parallax also changed; the best parallax distance is now about 45 pc, and logg = 7.95. Provencal et al. (1995) find a slightly hotter temperature of 27,000 K. Depending on the carbon mass fraction in the core, I will probably be able to ...
White Dwarf Stars - Stellar Physics Department
... H for magnetic white dwarfs that do show any detectable polarization. P for polarized magnetic white dwarfs. V for variable white dwarfs. And finally to complete the classification, a temperature index can follow their spectral classification. This index is defined as θ = 50400/Teff . Therefore, a w ...
... H for magnetic white dwarfs that do show any detectable polarization. P for polarized magnetic white dwarfs. V for variable white dwarfs. And finally to complete the classification, a temperature index can follow their spectral classification. This index is defined as θ = 50400/Teff . Therefore, a w ...
Lecture18
... Off the main sequence Some stars hot but faint, or cool but very bright: Stars not on the main sequence: giants and super-giants, white dwarfs (all late phases in a star’s lifetime). “Luminosity class” used to distinguish a red main sequence (e.g. M5V) from a red supergiant (M5I). Sizes of stars va ...
... Off the main sequence Some stars hot but faint, or cool but very bright: Stars not on the main sequence: giants and super-giants, white dwarfs (all late phases in a star’s lifetime). “Luminosity class” used to distinguish a red main sequence (e.g. M5V) from a red supergiant (M5I). Sizes of stars va ...
Chapter 19 Stars Galaxies and the Universe
... How Do Stars Age? Stars do not remain the same forever. Like living things, stars go through a life cycle from birth to death. The actual life cycle of a star depends on its size. An average star, such as the sun, goes through four stages during its life. A star enters the first stage of its life cy ...
... How Do Stars Age? Stars do not remain the same forever. Like living things, stars go through a life cycle from birth to death. The actual life cycle of a star depends on its size. An average star, such as the sun, goes through four stages during its life. A star enters the first stage of its life cy ...
black hole
... Expansion into a Giant When the temperature of the surrounding hydrogen becomes high enough, hydrogen fusion begins in a spherical layer—called a shell—surrounding the exhausted core of the star. Like a grass fire burning outward from an exhausted campfire, the hydrogen-fusion shell creeps outw ...
... Expansion into a Giant When the temperature of the surrounding hydrogen becomes high enough, hydrogen fusion begins in a spherical layer—called a shell—surrounding the exhausted core of the star. Like a grass fire burning outward from an exhausted campfire, the hydrogen-fusion shell creeps outw ...
The figure below shows what scientists over 1000 years ago thought
... The Sun will spend most of its life cycle as a main sequence star. This is the stable period of the Sun’s life cycle. What happens to cause the stable period in the life cycle of a star to end? ...
... The Sun will spend most of its life cycle as a main sequence star. This is the stable period of the Sun’s life cycle. What happens to cause the stable period in the life cycle of a star to end? ...
Main-Sequence Stars and the Sun
... There is a wide variation in the mass of stars. The smallest stars have masses of about 0:08 MSun . Objects less massive than this never begin hydrogen fusion, and so are never technically considered stars. Objects just below the cutoff often emit energy produced by gravitational collapse, and are ca ...
... There is a wide variation in the mass of stars. The smallest stars have masses of about 0:08 MSun . Objects less massive than this never begin hydrogen fusion, and so are never technically considered stars. Objects just below the cutoff often emit energy produced by gravitational collapse, and are ca ...
Recent science results from VLTI commissioning
... but ~30 x 106 L at outburst (2nd brightest object in sky) • Super hot: 15-40 x 103 K • Super active: survivor of 1843 eruption that created the homunculus and expelled ~ 2-3M at up to 800 km/s • Current rate of mass loss 0.3-3 x 10-3 M/yr • Central object is not viewed directly but is obscured by ...
... but ~30 x 106 L at outburst (2nd brightest object in sky) • Super hot: 15-40 x 103 K • Super active: survivor of 1843 eruption that created the homunculus and expelled ~ 2-3M at up to 800 km/s • Current rate of mass loss 0.3-3 x 10-3 M/yr • Central object is not viewed directly but is obscured by ...
Asteroseismic constraints on Asymmetric Dark Matter: Light particles
... for which astrometric observations are also available, for example stars observed by both Kepler and Hipparcos [52]. Thus, the ideal candidate is an object with highly constrained fundamental properties and a large number of detected oscillation modes. Binary stars are also very interesting since so ...
... for which astrometric observations are also available, for example stars observed by both Kepler and Hipparcos [52]. Thus, the ideal candidate is an object with highly constrained fundamental properties and a large number of detected oscillation modes. Binary stars are also very interesting since so ...
Precision age indicators that exploit chemically peculiar stars
... Tracing stellar population age by integrated light is a mainstay of galaxy evolution interpretation. Somewhat ambiguously, yet still of great value, blue photometric colors generally indicate galaxies with ongoing star formation, while red colors indicate galaxies that have not formed significant nu ...
... Tracing stellar population age by integrated light is a mainstay of galaxy evolution interpretation. Somewhat ambiguously, yet still of great value, blue photometric colors generally indicate galaxies with ongoing star formation, while red colors indicate galaxies that have not formed significant nu ...
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.