2017 Div. C (High School) Astronomy Help Session
... • Maximum mass of a white dwarf is dictated by electron degeneracy pressure ~ 1.4 x Msun– the pressure below which the electrons are not pushed into the nucleus. This is called the Chandrasekhar limit • White dwarfs will take a long time to cool off but as they do, they will become red dwarfs and th ...
... • Maximum mass of a white dwarf is dictated by electron degeneracy pressure ~ 1.4 x Msun– the pressure below which the electrons are not pushed into the nucleus. This is called the Chandrasekhar limit • White dwarfs will take a long time to cool off but as they do, they will become red dwarfs and th ...
Chapter 15 Surveying the Stars
... sequence? – Normal stars that fuse H to He in their cores fall on the main sequence of an H-R diagram – A star’s mass determines its position along the main sequence (high-mass: luminous and blue; low-mass: faint and red) ...
... sequence? – Normal stars that fuse H to He in their cores fall on the main sequence of an H-R diagram – A star’s mass determines its position along the main sequence (high-mass: luminous and blue; low-mass: faint and red) ...
The Life Cycle of Spiral Arm Galaxies
... massive amount of matter (galactic cosmic rays), which are charged particles such as protons and pieces of atoms (ions). The charge particles released have near relativistic speeds. It is commonly tho ...
... massive amount of matter (galactic cosmic rays), which are charged particles such as protons and pieces of atoms (ions). The charge particles released have near relativistic speeds. It is commonly tho ...
Presidential
... The Observations on Accelerating Universe are intimately related to the Measurements on Exploding Stars, far away in Cosmos. This is linked to a great mystery in Cosmology Today, which is the possible Presence of a Dark Energy in the Universe. In Supernovae, the core collapses in less than a Second, ...
... The Observations on Accelerating Universe are intimately related to the Measurements on Exploding Stars, far away in Cosmos. This is linked to a great mystery in Cosmology Today, which is the possible Presence of a Dark Energy in the Universe. In Supernovae, the core collapses in less than a Second, ...
Solutions
... allowed the energy in the explosion to be released?) Type Ia: fusion of carbon to heavier elements Type II: gravitational potential energy released as the core collapses to a much smaller size Notes: That’s all that this problem needed. Many of you who got this also embellished your answer with a pa ...
... allowed the energy in the explosion to be released?) Type Ia: fusion of carbon to heavier elements Type II: gravitational potential energy released as the core collapses to a much smaller size Notes: That’s all that this problem needed. Many of you who got this also embellished your answer with a pa ...
"Cosmic furnaces"()
... cycle, first proposed by Nobel prize winner Hans Bethe in the late 1930s. This process requires a star to have at least a trace of 12C mixed in with the hydrogen. In this event, a 12C nucleus can absorb a proton to produce a nucleus of the nitrogen isotope 13N. Within a few minutes, the 13N nucleus ...
... cycle, first proposed by Nobel prize winner Hans Bethe in the late 1930s. This process requires a star to have at least a trace of 12C mixed in with the hydrogen. In this event, a 12C nucleus can absorb a proton to produce a nucleus of the nitrogen isotope 13N. Within a few minutes, the 13N nucleus ...
Analysis of Two Pulsating X-ray Sources
... Calculations and Interpretations: The acceleration due to gravity (g) on the surface of a star (according to Newton’s Universal Law of Gravitation) is given by g = (GM)/R2 where G = 6.67 X 10-11 Nm2/kg2, M=star’s mass and R = star’s radius Centripetal acceleration (ac) of an object on the surface o ...
... Calculations and Interpretations: The acceleration due to gravity (g) on the surface of a star (according to Newton’s Universal Law of Gravitation) is given by g = (GM)/R2 where G = 6.67 X 10-11 Nm2/kg2, M=star’s mass and R = star’s radius Centripetal acceleration (ac) of an object on the surface o ...
Synthetic color-magnitude diagrams: the ingredients
... The SFR and AMR are not independent, given that each generation of stars will inject in the interstellar medium – through SNe and mass-loss processes along the AGB and RGB stages – large quantities of gas chemically enriched by nuclear processes. ...
... The SFR and AMR are not independent, given that each generation of stars will inject in the interstellar medium – through SNe and mass-loss processes along the AGB and RGB stages – large quantities of gas chemically enriched by nuclear processes. ...
pkt 14 Astrophysics
... Nebula is an interstellar cloud of dust, hydrogen gas and plasma. It is the first stage of a star's cycle but it can also refer to the remains of a dying star (planetary nebula). Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some ...
... Nebula is an interstellar cloud of dust, hydrogen gas and plasma. It is the first stage of a star's cycle but it can also refer to the remains of a dying star (planetary nebula). Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some ...
Approaching a black hole
... What would happen IF we could observe directly the collapsing stellar core: ...
... What would happen IF we could observe directly the collapsing stellar core: ...
doc - Eu-Hou
... realize something: the furthest ones appear less bright than expected! At the same time, the two teams realized that only a Universe in accelerated expansion can explain this effect, and published their results in scientific papers. Their discovery implied that the Universe was filled by an energy t ...
... realize something: the furthest ones appear less bright than expected! At the same time, the two teams realized that only a Universe in accelerated expansion can explain this effect, and published their results in scientific papers. Their discovery implied that the Universe was filled by an energy t ...
Week 6
... has a radius 936 times that of the Sun and a surface temperature of 3500 K. What is the luminosity of this star? If Betelgeuse is 640 ly from Earth, what is the brightness of the light from Betelgeuse that reaches Earth? ...
... has a radius 936 times that of the Sun and a surface temperature of 3500 K. What is the luminosity of this star? If Betelgeuse is 640 ly from Earth, what is the brightness of the light from Betelgeuse that reaches Earth? ...
What is a white dwarf?
... Shrinkage of White Dwarfs • Quantum mechanics says that electrons in the same place cannot be in the same state • Adding mass to a white dwarf increases its gravity, forcing electrons into a smaller space • In order to avoid being in the same state in the same place some of the electrons need to mo ...
... Shrinkage of White Dwarfs • Quantum mechanics says that electrons in the same place cannot be in the same state • Adding mass to a white dwarf increases its gravity, forcing electrons into a smaller space • In order to avoid being in the same state in the same place some of the electrons need to mo ...
Type II supernova
A Type II supernova (plural: supernovae or supernovas) results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times, the mass of the Sun (M☉) for this type of explosion. It is distinguished from other types of supernovae by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.Stars generate energy by the nuclear fusion of elements. Unlike the Sun, massive stars possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium, albeit at increasingly higher temperatures and pressures, causing increasingly shorter stellar life spans. The degeneracy pressure of electrons and the energy generated by these fusion reactions are sufficient to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The star fuses increasingly higher mass elements, starting with hydrogen and then helium, progressing up through the periodic table until a core of iron and nickel is produced. Fusion of iron or nickel produces no net energy output, so no further fusion can take place, leaving the nickel-iron core inert. Due to the lack of energy output allowing outward pressure, equilibrium is broken.When the mass of the inert core exceeds the Chandrasekhar limit of about 1.4 M☉, electron degeneracy alone is no longer sufficient to counter gravity and maintain stellar equilibrium. A cataclysmic implosion takes place within seconds, in which the outer core reaches an inward velocity of up to 23% of the speed of light and the inner core reaches temperatures of up to 100 billion kelvin. Neutrons and neutrinos are formed via reversed beta-decay, releasing about 1046 joules (100 foes) in a ten-second burst. The collapse is halted by neutron degeneracy, causing the implosion to rebound and bounce outward. The energy of this expanding shock wave is sufficient to accelerate the surrounding stellar material to escape velocity, forming a supernova explosion, while the shock wave and extremely high temperature and pressure briefly allow for theproduction of elements heavier than iron. Depending on initial size of the star, the remnants of the core form a neutron star or a black hole. Because of the underlying mechanism, the resulting nova is also described as a core-collapse supernova.There exist several categories of Type II supernova explosions, which are categorized based on the resulting light curve—a graph of luminosity versus time—following the explosion. Type II-L supernovae show a steady (linear) decline of the light curve following the explosion, whereas Type II-P display a period of slower decline (a plateau) in their light curve followed by a normal decay. Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and (for Type Ic) helium. As a result, they appear to be lacking in these elements.