CHAPTER 1 The Formation and Structure of Stars
... • Another source of shock waves may be the birth of very hot stars. – A massive star is so luminous and hot that it emits vast amounts of ultraviolet photons. – When such a star is born, the sudden blast of light, especially ultraviolet radiation, can ionize and drive away nearby gas—forming a shock ...
... • Another source of shock waves may be the birth of very hot stars. – A massive star is so luminous and hot that it emits vast amounts of ultraviolet photons. – When such a star is born, the sudden blast of light, especially ultraviolet radiation, can ionize and drive away nearby gas—forming a shock ...
WORD - Astrophysics
... A very large optical-infrared telescope will allow us to derive the important processes of galaxy formation and evolution in the full range of environments. Several complementary lines of attack are possible, directly connecting present-day Universe with the high redshift Universe, where the old sta ...
... A very large optical-infrared telescope will allow us to derive the important processes of galaxy formation and evolution in the full range of environments. Several complementary lines of attack are possible, directly connecting present-day Universe with the high redshift Universe, where the old sta ...
Comparing stars - The Open University
... be strongly excited, and partly because the colours are, in any case, rather weak. However, stellar colours can be emphasized photographically (as you will see in Figure 14). The H-R diagram can be represented in a number of different ways; the colour index of a star is a measure of its temperature ...
... be strongly excited, and partly because the colours are, in any case, rather weak. However, stellar colours can be emphasized photographically (as you will see in Figure 14). The H-R diagram can be represented in a number of different ways; the colour index of a star is a measure of its temperature ...
Supernovae - University of Texas Astronomy Home Page
... objects and jet-like structure in Section 5. All supernovae directly observed since 1604 (with the possible exception of Cas A), and hence all supernovae seen by modern astronomers, have been in other galaxies. Any single galaxy hosts a supernova only rarely. Supernovae occur roughly once per 100 ye ...
... objects and jet-like structure in Section 5. All supernovae directly observed since 1604 (with the possible exception of Cas A), and hence all supernovae seen by modern astronomers, have been in other galaxies. Any single galaxy hosts a supernova only rarely. Supernovae occur roughly once per 100 ye ...
Stars
... Stars attempt to maintain equilibrium by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs ...
... Stars attempt to maintain equilibrium by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs ...
Note - HKU Physics
... 5. The star is in local thermodynamic equilibrium (LTE). In other words, every microscopically large but macroscopically small region is very close to and hence can be well approximated by a region in thermodynamic equilibrium. Thus, it makes sense to talk about thermodynamic variables such as tempe ...
... 5. The star is in local thermodynamic equilibrium (LTE). In other words, every microscopically large but macroscopically small region is very close to and hence can be well approximated by a region in thermodynamic equilibrium. Thus, it makes sense to talk about thermodynamic variables such as tempe ...
star formation and galactic evolution
... their denser inner regions. By contrast, ionization simply evaporates even very dense clouds, and this destroys them very effectively at a rate that is not strongly sensitive to the cloud structure or density. Some of the ionized gas evaporated from star-forming clouds may stream away in ‘champagne ...
... their denser inner regions. By contrast, ionization simply evaporates even very dense clouds, and this destroys them very effectively at a rate that is not strongly sensitive to the cloud structure or density. Some of the ionized gas evaporated from star-forming clouds may stream away in ‘champagne ...
Magnetic fields in O-, B- and A-type stars on the main sequence
... time scales. For these stars with radiative envelopes, it is proven that the fields are remnants of an early phase of the star-life and one speaks of fossil fields (see Sect. 3.1.3). Over the past decade important progress has been achieved in the area of stellar magnetism. It is mainly due to the dev ...
... time scales. For these stars with radiative envelopes, it is proven that the fields are remnants of an early phase of the star-life and one speaks of fossil fields (see Sect. 3.1.3). Over the past decade important progress has been achieved in the area of stellar magnetism. It is mainly due to the dev ...
hwd_ewd_v3 - X-ray and Observational Astronomy Group
... The basis for understanding the nature of most stars is analysis of their optical spectra and classification according to the characteristics revealed. A number of physical processes can alter the atmospheric composition of a white dwarf as it cools. As noted by Schatzman4, the strong gravitational ...
... The basis for understanding the nature of most stars is analysis of their optical spectra and classification according to the characteristics revealed. A number of physical processes can alter the atmospheric composition of a white dwarf as it cools. As noted by Schatzman4, the strong gravitational ...
The accretion disk paradigm for young stars
... of a number of these objects, now known as YY Ori stars after their prototype, and had noticed the presence of red-displaced, highly variable absorption components in the Balmer lines of these objects, indicating infall velocity of up to 400 km/s. In these spectra the Balmer jump is clearly in emiss ...
... of a number of these objects, now known as YY Ori stars after their prototype, and had noticed the presence of red-displaced, highly variable absorption components in the Balmer lines of these objects, indicating infall velocity of up to 400 km/s. In these spectra the Balmer jump is clearly in emiss ...
AUGUSTE COMTE`S BLUNDER: AN ACCOUNT OF THE FIRST
... 1863). Less than three decades after Comte made his assertion, it was already shown to be incorrect, at least for the Sun. But the results for the solar spectrum were no more than qualitative and there was no theoretical understanding of how the absorption lines were formed. ...
... 1863). Less than three decades after Comte made his assertion, it was already shown to be incorrect, at least for the Sun. But the results for the solar spectrum were no more than qualitative and there was no theoretical understanding of how the absorption lines were formed. ...
5 Report of the Panel on Stars and Stellar Evolution
... PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION ...
... PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION ...
Export To Word
... Attention Young Astronomers, Thank you for completing your first set of stellar classification. We have added the information you have provided to our database. Since there are so many billions of stars, we have another set for you to classify. We need you to help classify this short list of 5 new s ...
... Attention Young Astronomers, Thank you for completing your first set of stellar classification. We have added the information you have provided to our database. Since there are so many billions of stars, we have another set for you to classify. We need you to help classify this short list of 5 new s ...
Astro 102 Practice Test 3
... d. a measure of the ease with which photons can pass through a gas. e. the temperature and density at which a gas will undergo thermonuclear fusion. 8. As a star begin to form the initial energy source is from a. nuclear fusion. b. nuclear fission. c. gravitational potential energy. d. magnetic fiel ...
... d. a measure of the ease with which photons can pass through a gas. e. the temperature and density at which a gas will undergo thermonuclear fusion. 8. As a star begin to form the initial energy source is from a. nuclear fusion. b. nuclear fission. c. gravitational potential energy. d. magnetic fiel ...
General Comments on Nebulae
... Planetary nebulae are shells of gas thrown out by some stars near the end of their lives. Our Sun will probably produce a planetary nebula in about 5 billion years. They have nothing at all to do with planets; the terminology was invented because they often look a little like planets in small telesc ...
... Planetary nebulae are shells of gas thrown out by some stars near the end of their lives. Our Sun will probably produce a planetary nebula in about 5 billion years. They have nothing at all to do with planets; the terminology was invented because they often look a little like planets in small telesc ...
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.