Stellar Lifetimes
... 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 ...
Hill Sphere
... heavy elements the first to accrete, or did the enrichment occur at later stages? Depending on this Jupiter and Saturn may have received very different amounts of planetesimals and may have formed either very rapidly (such as through the nebula instability mechanism) or more slowly (such as through ...
... heavy elements the first to accrete, or did the enrichment occur at later stages? Depending on this Jupiter and Saturn may have received very different amounts of planetesimals and may have formed either very rapidly (such as through the nebula instability mechanism) or more slowly (such as through ...
Refusing to Go Quietly: GRBs and Their Progenitors
... Advanced LIGO will be able to detect gravitational waves that stretch the length of the arms by a fraction of the size of a proton ...
... Advanced LIGO will be able to detect gravitational waves that stretch the length of the arms by a fraction of the size of a proton ...
Astronomers discovered what they thought was the first black hole
... and his colleagues say the system was born between 8.7 and 11.4 million years ago with two massive stars orbiting each other. The more massive star – the one that is now the black hole – was born at least 110 times heavier than the Sun, making it one of the most luminous stars in the galaxy. Its par ...
... and his colleagues say the system was born between 8.7 and 11.4 million years ago with two massive stars orbiting each other. The more massive star – the one that is now the black hole – was born at least 110 times heavier than the Sun, making it one of the most luminous stars in the galaxy. Its par ...
Rocky planetesimals as the origin of metals in DZ stars
... obvious pattern is seen, although there may be a higher density of DZA stars near the Galactic disc and perhaps also towards more modest speeds, but the former may be an observational bias due to diminished spectroscopic sensitivity. In any case, one should expect a correlation between these quantit ...
... obvious pattern is seen, although there may be a higher density of DZA stars near the Galactic disc and perhaps also towards more modest speeds, but the former may be an observational bias due to diminished spectroscopic sensitivity. In any case, one should expect a correlation between these quantit ...
SUMMARY OF KEY CONCEPTS: GALAXIES AND COSMOLOGY
... direction toward which our galaxy is moving, and cooler in the opposite direction. (2) If this is subtracted, there’s an even smaller pattern of ripples with hot and cool spots that are a few parts in 100,000 different from the mean temperature. These anisotropies are the seeds from which galaxies a ...
... direction toward which our galaxy is moving, and cooler in the opposite direction. (2) If this is subtracted, there’s an even smaller pattern of ripples with hot and cool spots that are a few parts in 100,000 different from the mean temperature. These anisotropies are the seeds from which galaxies a ...
Comparing stars - The Open University
... than the Sun, and appears bluish-white. It has the greatest apparent visual brightness (most negative apparent visual magnitude!) of any star in the night sky. This is, as we have seen, not because it is very luminous, but because it is both fairly luminous and rather close - at 2.63 pc it's the sev ...
... than the Sun, and appears bluish-white. It has the greatest apparent visual brightness (most negative apparent visual magnitude!) of any star in the night sky. This is, as we have seen, not because it is very luminous, but because it is both fairly luminous and rather close - at 2.63 pc it's the sev ...
Stellar evolution - Statistical Physics Group
... Typically evolutionary time scales are between loe and 10lo years. Despite this, studies of stellar evolution have progressed considerably. On the observational side, it has been realized that, although the classification of stars into groups with similar properties is very useful, these groups are ...
... Typically evolutionary time scales are between loe and 10lo years. Despite this, studies of stellar evolution have progressed considerably. On the observational side, it has been realized that, although the classification of stars into groups with similar properties is very useful, these groups are ...
Cygnus X-1
... hundredth of a second bursts. It is also been proven that Cygnus X-1 is smaller than the Earth. Strangely enough, Cygnus X-1 has a companion star called HDE 226868. HDE 226868 is a supergiant with a temperature around 31,000 K. After extremely close observations of HDE 226868, it appears that its sp ...
... hundredth of a second bursts. It is also been proven that Cygnus X-1 is smaller than the Earth. Strangely enough, Cygnus X-1 has a companion star called HDE 226868. HDE 226868 is a supergiant with a temperature around 31,000 K. After extremely close observations of HDE 226868, it appears that its sp ...
Essential Question
... 6. If a star has a low surface temperature and is considered very dim, where would you expect it to be located on the Herztsprung-Russell diagram? ...
... 6. If a star has a low surface temperature and is considered very dim, where would you expect it to be located on the Herztsprung-Russell diagram? ...
The Earth and Man In the Universe
... It has often been suggested that the stars are infinite in number and that the universe is therefore infinite in extent. But the latest investigations, telescopic as well as photographic, show that the proportion of increase in the number of the stars diminishes when the. lowest magnitudes are reach ...
... It has often been suggested that the stars are infinite in number and that the universe is therefore infinite in extent. But the latest investigations, telescopic as well as photographic, show that the proportion of increase in the number of the stars diminishes when the. lowest magnitudes are reach ...
E3 – Stellar distances
... Cepheid variables • At distances greater than Mpc, neither parallax nor spectroscopic parallax can be relied upon to measure the distance to a star. • When we observe another galaxy, all of the stars in that galaxy are approximately the same distance away from the earth. What we really need is a li ...
... Cepheid variables • At distances greater than Mpc, neither parallax nor spectroscopic parallax can be relied upon to measure the distance to a star. • When we observe another galaxy, all of the stars in that galaxy are approximately the same distance away from the earth. What we really need is a li ...
Kinesthetic Life Cycle of Stars
... star’s outer layers, which drift away into space. The core then contracts under its own gravity, forming a white dwarf. ...
... star’s outer layers, which drift away into space. The core then contracts under its own gravity, forming a white dwarf. ...
3 The lives of galaxies
... Dead stars leave behind compact remnants - white dwarfs, neutrons stars, and black holes. We know such objects exist in the disk of the Milky Way. Perhaps the halo of our Galaxy has large numbers of them ? Such hypothetical objects are known as “Massive Compact Halo Objects” or MACHOs. They might be ...
... Dead stars leave behind compact remnants - white dwarfs, neutrons stars, and black holes. We know such objects exist in the disk of the Milky Way. Perhaps the halo of our Galaxy has large numbers of them ? Such hypothetical objects are known as “Massive Compact Halo Objects” or MACHOs. They might be ...
Pulsars
... • From exclusion principle, each allowed energy state can be occupied by no more than two particles of opposite spin • Electrons in a White Dwarf occupy a small volume and have very well defined positions – hence from uncertainty principle, they have large momentum/energy and generate a high pressur ...
... • From exclusion principle, each allowed energy state can be occupied by no more than two particles of opposite spin • Electrons in a White Dwarf occupy a small volume and have very well defined positions – hence from uncertainty principle, they have large momentum/energy and generate a high pressur ...
Astronomy 1
... has little gas & dust. all the stars visible to the unaided eye from Earth belong to the Milky Way ...
... has little gas & dust. all the stars visible to the unaided eye from Earth belong to the Milky Way ...
The white dwarf cooling sequence of 47 Tucanae
... the sudden increase in photometric errors for stars with magnitudes larger than 25 mag. Thus, the reason for the observed break in the empirical curve must be related to either the way the observed data is handled or to an unknown observational bias. We explore these possibilities next. In Fig. 2 we ...
... the sudden increase in photometric errors for stars with magnitudes larger than 25 mag. Thus, the reason for the observed break in the empirical curve must be related to either the way the observed data is handled or to an unknown observational bias. We explore these possibilities next. In Fig. 2 we ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.