Top 10
... technology, our vehicles, our society—would have to be completely incorrect, implying almost everything we base our modern lives on would not work as it does. ...
... technology, our vehicles, our society—would have to be completely incorrect, implying almost everything we base our modern lives on would not work as it does. ...
Stars and Star Patterns
... How many galaxies are there? How do scientists classify stars? What is the name of our galaxy? What type of galaxy is it? Describe our star, the sun. ...
... How many galaxies are there? How do scientists classify stars? What is the name of our galaxy? What type of galaxy is it? Describe our star, the sun. ...
Main-sequence stage Stellar lifetimes
... – No further nuclear fusion sources. Hence: – Core collapses in seconds; central T rises again; γ-rays photodissociate 56Fe into 4He nuclei, then into protons and electrons. – As densities rise, p + e– neutrons + neutrinos – Neutron-rich matter compresses to density ~ 1017 kg m–3 and stops further c ...
... – No further nuclear fusion sources. Hence: – Core collapses in seconds; central T rises again; γ-rays photodissociate 56Fe into 4He nuclei, then into protons and electrons. – As densities rise, p + e– neutrons + neutrinos – Neutron-rich matter compresses to density ~ 1017 kg m–3 and stops further c ...
Cosmic Rays and Plasma Astrophysics
... Nuclear burning in stellar interiors can proceed up to the production of 56Fe, which is the most stable of the heavy nuclei, having the peak binding energy per nucleon. Above this point, nuclear fusion is no longer energetically favorable. Heavier elements are thought to be produced only in supernov ...
... Nuclear burning in stellar interiors can proceed up to the production of 56Fe, which is the most stable of the heavy nuclei, having the peak binding energy per nucleon. Above this point, nuclear fusion is no longer energetically favorable. Heavier elements are thought to be produced only in supernov ...
Stellar evolution - Chandra X
... about them. X-ray data reveal extreme or violent conditions where gas has been heated to very high temperatures or particles have been accelerated to extremely high energies. These conditions can exist near collapsed objects such as white dwarfs, neutron stars, and black holes; in giant bubbles of h ...
... about them. X-ray data reveal extreme or violent conditions where gas has been heated to very high temperatures or particles have been accelerated to extremely high energies. These conditions can exist near collapsed objects such as white dwarfs, neutron stars, and black holes; in giant bubbles of h ...
PH607 – Galaxies 1
... stars in the cluster, at 200 million to 300 million years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they estimated the age of the Galaxy at 13.6 ± 0.8 billion years. ...
... stars in the cluster, at 200 million to 300 million years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they estimated the age of the Galaxy at 13.6 ± 0.8 billion years. ...
Life Cycle of Stars
... nuclei join to form helium nuclei through nuclear fusion, and a star is born. Nuclear fusion is the process by which lighter elements combine to form heavier elements. (For example, Hydrogen fuses to form Helium.) This process releases energy. When hydrogen beings to run low, the star becomes a red ...
... nuclei join to form helium nuclei through nuclear fusion, and a star is born. Nuclear fusion is the process by which lighter elements combine to form heavier elements. (For example, Hydrogen fuses to form Helium.) This process releases energy. When hydrogen beings to run low, the star becomes a red ...
n,n - Osaka University
... The r-process makes ~half the nuclides heavier than iron, and all nuclides heavier than 209Bi. It is thought to occur in ~second in the bubble just outside the nascent neutron star, in a hot n wind. The r-process requires a neutron density ~1020 cm-3 in order to have it go fast enough to circumvent ...
... The r-process makes ~half the nuclides heavier than iron, and all nuclides heavier than 209Bi. It is thought to occur in ~second in the bubble just outside the nascent neutron star, in a hot n wind. The r-process requires a neutron density ~1020 cm-3 in order to have it go fast enough to circumvent ...
sun.galaxy.notes
... Depending upon the stars initial mass or size, It will end up as either a neutron star or Black hole ...
... Depending upon the stars initial mass or size, It will end up as either a neutron star or Black hole ...
Dark matter in the Galactic Halo Rotation curve (i.e. the orbital
... 21 cm emission from hydrogen • for the outer Galaxy by looking at the velocity of star clusters relative to the Sun. (details of these methods are given in Section 2.3 of Sparke & Gallagher…) ...
... 21 cm emission from hydrogen • for the outer Galaxy by looking at the velocity of star clusters relative to the Sun. (details of these methods are given in Section 2.3 of Sparke & Gallagher…) ...
2.1 Hubble Space Telescope
... star formation billions of years after its galactic neighbours. Galaxies resembling I Zwicky 18’s youthful appearance are typically found only in the early Universe. Astronomers were thrilled that a newly-forming galaxy like I Zwicky 18 could be studied nearby to learn about galactic evolution, whic ...
... star formation billions of years after its galactic neighbours. Galaxies resembling I Zwicky 18’s youthful appearance are typically found only in the early Universe. Astronomers were thrilled that a newly-forming galaxy like I Zwicky 18 could be studied nearby to learn about galactic evolution, whic ...
PH607lec10
... stars in the cluster, at 200 million to 300 million years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they estimated the age of the Galaxy at 13.6 ± 0.8 billion years. ...
... stars in the cluster, at 200 million to 300 million years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they estimated the age of the Galaxy at 13.6 ± 0.8 billion years. ...
Neutron Density and Neutron Source Determination in Barium
... such as poor fitting of the continuum, poorly determined gf values or stellar parameters, a poor determination of the C 2 strength, or the presence of unknown blends. The latter source of error is the most likely in view of the cool nature of the star under study. In light of these uncertainties it ...
... such as poor fitting of the continuum, poorly determined gf values or stellar parameters, a poor determination of the C 2 strength, or the presence of unknown blends. The latter source of error is the most likely in view of the cool nature of the star under study. In light of these uncertainties it ...
positive charge and negative charge. Positive charge a
... As most of each atom is empty space, most alpha-particles go through the atoms in the thin foil un-deflected. However, as the nucleus is much smaller than the whole atom, a very small number of alpha-particles incidentally go near the nucleus, and are deflected significantly due to the Coulomb forc ...
... As most of each atom is empty space, most alpha-particles go through the atoms in the thin foil un-deflected. However, as the nucleus is much smaller than the whole atom, a very small number of alpha-particles incidentally go near the nucleus, and are deflected significantly due to the Coulomb forc ...
The Designed `Just So` Universe Dr. Walter L. Bradley Walter L
... levels on "energy ladder", then the particles will simply bounce off of each other rather than sticking together, or fusing. Hoyle (1970) predicted that the existence of the unknown resonance energy level for carbon, and it was subsequently found to exist. The fusion of helium and beryllium give a m ...
... levels on "energy ladder", then the particles will simply bounce off of each other rather than sticking together, or fusing. Hoyle (1970) predicted that the existence of the unknown resonance energy level for carbon, and it was subsequently found to exist. The fusion of helium and beryllium give a m ...
Stellar Lifetime - Madison Public Schools
... Making heavy elements • How do the plentiful elements heavier than iron form if fusion is an endothermic process at that point? ...
... Making heavy elements • How do the plentiful elements heavier than iron form if fusion is an endothermic process at that point? ...
The evolution of helium rich subdwarf B stars
... • It was realised early on that helium-rich subdwarfs do not evolve from helium-poor sdB stars (Groth et al. 1985) • sdB have nHe < 0.01 (Heber 1986) • sdB evolution takes ~108 yr (Caloi 1989) ...
... • It was realised early on that helium-rich subdwarfs do not evolve from helium-poor sdB stars (Groth et al. 1985) • sdB have nHe < 0.01 (Heber 1986) • sdB evolution takes ~108 yr (Caloi 1989) ...
Astronomy Astrophysics
... Furthermore, and perhaps even more importantly, individual age determinations are possible for these stars using long-lived radioactive isotopes, such as 232 Th (half-life 14.05 Gyr) or 238 U (4.468 Gyr). By comparing the abundance ratio of these elements relative to a stable r-process element of si ...
... Furthermore, and perhaps even more importantly, individual age determinations are possible for these stars using long-lived radioactive isotopes, such as 232 Th (half-life 14.05 Gyr) or 238 U (4.468 Gyr). By comparing the abundance ratio of these elements relative to a stable r-process element of si ...
The Hamburg/ESO R-process Enhanced Star survey (HERES)
... Furthermore, and perhaps even more importantly, individual age determinations are possible for these stars using long-lived radioactive isotopes, such as 232 Th (half-life 14.05 Gyr) or 238 U (4.468 Gyr). By comparing the abundance ratio of these elements relative to a stable r-process element of si ...
... Furthermore, and perhaps even more importantly, individual age determinations are possible for these stars using long-lived radioactive isotopes, such as 232 Th (half-life 14.05 Gyr) or 238 U (4.468 Gyr). By comparing the abundance ratio of these elements relative to a stable r-process element of si ...
Lecture 5: The Milky Way
... Combine evidence from “near field cosmology” with evidence from high redshift observations ...
... Combine evidence from “near field cosmology” with evidence from high redshift observations ...
What Is a Star
... billions of years. Our sun was born about 4.6 billion years ago. It is in the middle of its life cycle. It will live for at least another five billion years. ...
... billions of years. Our sun was born about 4.6 billion years ago. It is in the middle of its life cycle. It will live for at least another five billion years. ...
Stellar Evolution after the Main Sequence
... temperature very well, so as soon as the energy is released in one part of the core, it is transmitted throughout the core in seconds, producing a rapid heating of all of the He there. • The He burning accelerates like an explosion – the He Flash. • The new energy expands the core rapidly which in t ...
... temperature very well, so as soon as the energy is released in one part of the core, it is transmitted throughout the core in seconds, producing a rapid heating of all of the He there. • The He burning accelerates like an explosion – the He Flash. • The new energy expands the core rapidly which in t ...
Beyond solar system
... of? We haven’t spoken yet about their composition. Stars are made of high temperature gasses. Even though there are many kinds of stars, by analyzing the light that they emit, we know that they are composed mainly of hydrogen (70%) and helium (less than 30%), the most simple and abundant substances ...
... of? We haven’t spoken yet about their composition. Stars are made of high temperature gasses. Even though there are many kinds of stars, by analyzing the light that they emit, we know that they are composed mainly of hydrogen (70%) and helium (less than 30%), the most simple and abundant substances ...
The Origin, Evolution, and Fate of the Universe
... destroyed with equal efficiency. At the end of this time, when the Universe cooled to 1012 K, it is no longer hot enough to spontaneously produce protons and antiprotons. n ...
... destroyed with equal efficiency. At the end of this time, when the Universe cooled to 1012 K, it is no longer hot enough to spontaneously produce protons and antiprotons. n ...
Nucleosynthesis
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos.With the formation of stars, heavier nuclei were created from hydrogen and helium by stellar nucleosynthesis, a process that continues today. Some of these elements, particularly those lighter than iron, continue to be delivered to the interstellar medium when low mass stars eject their outer envelope before they collapse to form white dwarfs. The remains of their ejected mass form the planetary nebulae observable throughout our galaxy.Supernova nucleosynthesis within exploding stars by fusing carbon and oxygen is responsible for the abundances of elements between magnesium (atomic number 12) and nickel (atomic number 28). Supernova nucleosynthesis is also thought to be responsible for the creation of rarer elements heavier than iron and nickel, in the last few seconds of a type II supernova event. The synthesis of these heavier elements absorbs energy (endothermic) as they are created, from the energy produced during the supernova explosion. Some of those elements are created from the absorption of multiple neutrons (the R process) in the period of a few seconds during the explosion. The elements formed in supernovas include the heaviest elements known, such as the long-lived elements uranium and thorium.Cosmic ray spallation, caused when cosmic rays impact the interstellar medium and fragment larger atomic species, is a significant source of the lighter nuclei, particularly 3He, 9Be and 10,11B, that are not created by stellar nucleosynthesis.In addition to the fusion processes responsible for the growing abundances of elements in the universe, a few minor natural processes continue to produce very small numbers of new nuclides on Earth. These nuclides contribute little to their abundances, but may account for the presence of specific new nuclei. These nuclides are produced via radiogenesis (decay) of long-lived, heavy, primordial radionuclides such as uranium and thorium. Cosmic ray bombardment of elements on Earth also contribute to the presence of rare, short-lived atomic species called cosmogenic nuclides.