Stellar Helium Burning in Other Universes: A
... energy of 8 Be (or twice that of 4 He) is of order 56 MeV, whereas we are interested in changes of order 0.1 – 1 MeV, so that (δEj )/Ej 1 is satisfied. More specifically, this deriviation is based on reference [14], which holds for relative changes as large as ∼ 10%. In this scheme, the pion mass ...
... energy of 8 Be (or twice that of 4 He) is of order 56 MeV, whereas we are interested in changes of order 0.1 – 1 MeV, so that (δEj )/Ej 1 is satisfied. More specifically, this deriviation is based on reference [14], which holds for relative changes as large as ∼ 10%. In this scheme, the pion mass ...
Searching for RR Lyrae Stars in M15
... of available low energy states is too small so many electrons are forced into higher energy states. This makes the electrons degenerate which make a significant contribution to the pressure due to their high energy states. Since this pressure arises from a quantum mechanical effect, it is unaffected ...
... of available low energy states is too small so many electrons are forced into higher energy states. This makes the electrons degenerate which make a significant contribution to the pressure due to their high energy states. Since this pressure arises from a quantum mechanical effect, it is unaffected ...
Origin and loss of nebula-captured hydrogen envelopes from `sub`
... 2.1 The XUV activity during the stellar saturation phase The evolution of the solar high-energy radiation has been studied in detail within the ‘Sun in Time’ programme (e.g. Ribas et al. 2005; Güdel 2007). At ages higher than about 0.1 Gyr, the activity of Sun-like stars decreases because of magnet ...
... 2.1 The XUV activity during the stellar saturation phase The evolution of the solar high-energy radiation has been studied in detail within the ‘Sun in Time’ programme (e.g. Ribas et al. 2005; Güdel 2007). At ages higher than about 0.1 Gyr, the activity of Sun-like stars decreases because of magnet ...
GRB EXPERIMENT
... (Duncan & Thompson 1992) • A neutron star undergoes vigorous convection in the first ~30 s after its formation • Coupled with rapid rotation (~1 ms period), this makes the neutron star a likely site for dynamo action • If the rotation period is less than the convective overturn time, magnetic field ...
... (Duncan & Thompson 1992) • A neutron star undergoes vigorous convection in the first ~30 s after its formation • Coupled with rapid rotation (~1 ms period), this makes the neutron star a likely site for dynamo action • If the rotation period is less than the convective overturn time, magnetic field ...
2012 NSS Phy 2-(E).
... of a star), it will appear as the “second sun” in the sky for a few weeks. Referring to the information given below, explain whether this is true or not by comparing the brightness of Betelgeuse in supernova explosion with that of the Sun. (3 marks) A star of similar mass as that of Betelgeuse gives ...
... of a star), it will appear as the “second sun” in the sky for a few weeks. Referring to the information given below, explain whether this is true or not by comparing the brightness of Betelgeuse in supernova explosion with that of the Sun. (3 marks) A star of similar mass as that of Betelgeuse gives ...
Chapter 1 Telescopes 1.1 Lenses
... This is why many more stars are seen using a telescope than using the unaided eye. The greater the diameter of the objective of a telescope, the greater the number of stars that can be seen. Planets and other astronomical objects in the solar system are magnified using a telescope (unlike stars whic ...
... This is why many more stars are seen using a telescope than using the unaided eye. The greater the diameter of the objective of a telescope, the greater the number of stars that can be seen. Planets and other astronomical objects in the solar system are magnified using a telescope (unlike stars whic ...
exemplars and commentary
... thought to be 10 billion years old and older than our galaxy. It must have been captured from elsewhere. Bernard’s star is travelling towards us at a very high speed. It will become closer to us than Proxima Centauri. Barnard’s star emits most of its radiation as infrared light and emits almost no u ...
... thought to be 10 billion years old and older than our galaxy. It must have been captured from elsewhere. Bernard’s star is travelling towards us at a very high speed. It will become closer to us than Proxima Centauri. Barnard’s star emits most of its radiation as infrared light and emits almost no u ...
Hot DQ White Dwarfs: Something Different
... stars in our Galaxy). Standard stellar evolution theory predicts that a typical white dwarf is composed of a core that encompasses more than 99 % of the mass of the star, surrounded by a thin envelope of helium (and hydrogen) that has survived the nuclear burning and mass loss phase. The core, which ...
... stars in our Galaxy). Standard stellar evolution theory predicts that a typical white dwarf is composed of a core that encompasses more than 99 % of the mass of the star, surrounded by a thin envelope of helium (and hydrogen) that has survived the nuclear burning and mass loss phase. The core, which ...
A timeline of the universe
... consists primarily of bare hydrogen nuclei and free electrons. Stellar UV light maintains this ionization. These photons pack enough punch to tear electrons off any neutral hydrogen atoms that form by recombination. The current dominance of ionized hydrogen is one reason we can see so far with opti ...
... consists primarily of bare hydrogen nuclei and free electrons. Stellar UV light maintains this ionization. These photons pack enough punch to tear electrons off any neutral hydrogen atoms that form by recombination. The current dominance of ionized hydrogen is one reason we can see so far with opti ...
Homework #3, AST 1002
... can't see enough material to explain the gravity that appears to hold them together. (c) Seyfert galaxies emit spectra having broad emission lines. The correct answer(s) is(are) ____________. 28. If Hubble's constant is 50 km/sec/Mpc, an object receding from us at the rate of 5000 km/sec would be __ ...
... can't see enough material to explain the gravity that appears to hold them together. (c) Seyfert galaxies emit spectra having broad emission lines. The correct answer(s) is(are) ____________. 28. If Hubble's constant is 50 km/sec/Mpc, an object receding from us at the rate of 5000 km/sec would be __ ...
Cygnus X-2, super-Eddington mass transfer, and pulsar binaries
... rapid Case B mass transfer may end with the donor on the Hayashi line, still retaining a large fraction of its original hydrogen envelope. However, there will be no long-lasting phase of mass transfer with the donor on the Hayashi line because the star starts shrinking with ignition of central heliu ...
... rapid Case B mass transfer may end with the donor on the Hayashi line, still retaining a large fraction of its original hydrogen envelope. However, there will be no long-lasting phase of mass transfer with the donor on the Hayashi line because the star starts shrinking with ignition of central heliu ...
High-Energy Astrophysics with Gamma
... contribution to the total steady distribution of the primary and secondary electrons and positrons is separately shown. The horizontal rectangle shows the region of electron kinetic energies where the steady distribution of secondary electrons is larger than that of the primary electrons. It is in t ...
... contribution to the total steady distribution of the primary and secondary electrons and positrons is separately shown. The horizontal rectangle shows the region of electron kinetic energies where the steady distribution of secondary electrons is larger than that of the primary electrons. It is in t ...
Bluffer`s Guide to Sirius
... that the star was moving slightly in a predictable manner. It was clear that Sirius was being tugged by the gravitational pull of another object, so there was something else orbiting Sirius, too faint to be seen. However, telescopes were increasing in size and in 1862 the companion was seen for the ...
... that the star was moving slightly in a predictable manner. It was clear that Sirius was being tugged by the gravitational pull of another object, so there was something else orbiting Sirius, too faint to be seen. However, telescopes were increasing in size and in 1862 the companion was seen for the ...
XRaySNR_sm - Gettysburg College
... default for the student, and should not be made available to them. In reality, multiobject spectroscopy is not possible with XMM-Newton. This feature is included simply as an aid to the instructor. To enable it, in the Spectra tab under Options/Multi-Object Spectrometer, click either “Enable after 1 ...
... default for the student, and should not be made available to them. In reality, multiobject spectroscopy is not possible with XMM-Newton. This feature is included simply as an aid to the instructor. To enable it, in the Spectra tab under Options/Multi-Object Spectrometer, click either “Enable after 1 ...
Module 4.1 - The Scale of the Universe [slide 1] We now turn to
... expands, but the temperature changes as well. So the radius changes, the temperature changes therefore, luminosity must change. If we observe stars spectroscopically, we can observe the velocity of the photo sphere. Come towards us and go away from us. So we can measure stellar temperatures using co ...
... expands, but the temperature changes as well. So the radius changes, the temperature changes therefore, luminosity must change. If we observe stars spectroscopically, we can observe the velocity of the photo sphere. Come towards us and go away from us. So we can measure stellar temperatures using co ...
Eclipsing Binary Stars as Astrophysical Laboratories
... to the left — backwards, but that’s just a historical accident. Every star has a place on the HertzsprungRussell diagram. In the upper right corner are giants and super giants, like Betelgeuse and Rigel, which are both in Orion, which is high in the sky right now. You can also see Polaris, a yellow ...
... to the left — backwards, but that’s just a historical accident. Every star has a place on the HertzsprungRussell diagram. In the upper right corner are giants and super giants, like Betelgeuse and Rigel, which are both in Orion, which is high in the sky right now. You can also see Polaris, a yellow ...
The DBV stars: Progress and problems
... ’whitedwarfs. There are at least two possible progenitors of DB white dwarfs: the PG 1159 stars and the interacting binary white dwarfs. Dehner & Kawaler (1995) show the seismological helium profile of PG 1159-035 can evolve into something similar to what Bradley & Winget (1994) derive for GD 358, b ...
... ’whitedwarfs. There are at least two possible progenitors of DB white dwarfs: the PG 1159 stars and the interacting binary white dwarfs. Dehner & Kawaler (1995) show the seismological helium profile of PG 1159-035 can evolve into something similar to what Bradley & Winget (1994) derive for GD 358, b ...
Student copy of notes - User Web Areas at the University of York
... Astronomers recognise two types based on their characteristic light curves; type I and type II supernovae. Let’s have a brief recap…If a main sequence star has a mass of over 8 times the mass of the Sun it is destined to be a type II supernova, such as SN1987A shown in the figure. The pressure produ ...
... Astronomers recognise two types based on their characteristic light curves; type I and type II supernovae. Let’s have a brief recap…If a main sequence star has a mass of over 8 times the mass of the Sun it is destined to be a type II supernova, such as SN1987A shown in the figure. The pressure produ ...
Homework Due
... Sun releases energy by fusing four hydrogen nuclei into one helium nucleus. Starting point is 4 protons. End point is 2 p + 2 n (a helium nucleus) + energy There are several steps required to make this happen. © 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley ...
... Sun releases energy by fusing four hydrogen nuclei into one helium nucleus. Starting point is 4 protons. End point is 2 p + 2 n (a helium nucleus) + energy There are several steps required to make this happen. © 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley ...
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.