Slide sem título - Instituto de Física / UFRJ
... (9.2X1011 g/cm3) to 5X103 MeV/fm3 (9.2X1015 g/cm3). We can see in fig. 1 that both the total mass and radius of the stars are increased by the presence of charge. Fig. 2 shows how much charge these stars can have. Table 1 shows these results for the maximum mass configuration [4]. ...
... (9.2X1011 g/cm3) to 5X103 MeV/fm3 (9.2X1015 g/cm3). We can see in fig. 1 that both the total mass and radius of the stars are increased by the presence of charge. Fig. 2 shows how much charge these stars can have. Table 1 shows these results for the maximum mass configuration [4]. ...
The Physics of Massive Star Formation
... clumps with Entire clumps have M ~ 1000 M, vir ≈ 1 no competitive accretion If clumps undergo global collapse, stagnation points form with low mass, velocities where stars stay after accreting cores (Bonnell & Bate 2006), (although these may not fragment at all) CA can occur only if clumps are c ...
... clumps with Entire clumps have M ~ 1000 M, vir ≈ 1 no competitive accretion If clumps undergo global collapse, stagnation points form with low mass, velocities where stars stay after accreting cores (Bonnell & Bate 2006), (although these may not fragment at all) CA can occur only if clumps are c ...
Stars and Light
... cooler brown dwarf stars. These stars have such low masses, < 0.08 M⊙, that no fusion occurs inside. Spectral class M include the most massive brown dwarfs. • Need extra spectral types: L, T, Y • L is hottest, Y is coolest (down to ~300K) • Note Y brown dwarfs were discovered only this year and are ...
... cooler brown dwarf stars. These stars have such low masses, < 0.08 M⊙, that no fusion occurs inside. Spectral class M include the most massive brown dwarfs. • Need extra spectral types: L, T, Y • L is hottest, Y is coolest (down to ~300K) • Note Y brown dwarfs were discovered only this year and are ...
PPT
... 1. Absolute Photometry: fν/Fν = (R/D)2 ; need Fν(Teff, log g, composition, B, …) Need the distance D! Also need to know what fraction of the stellar surface radiates! The Magnificent Seven: seven soft X-ray sources with a ‘stellar’ spectrum and a distance estimate ...
... 1. Absolute Photometry: fν/Fν = (R/D)2 ; need Fν(Teff, log g, composition, B, …) Need the distance D! Also need to know what fraction of the stellar surface radiates! The Magnificent Seven: seven soft X-ray sources with a ‘stellar’ spectrum and a distance estimate ...
Orion
... Why does Mintaka appear so dim given that it is very luminous? Which stars are main sequence stars? Rigel is a true supergiant, blazing white-hot star of intense brilliance and dazzling beauty. Its surface temperature is about 12,000 K and its energy output exceeds that of our Sun by a factor of ma ...
... Why does Mintaka appear so dim given that it is very luminous? Which stars are main sequence stars? Rigel is a true supergiant, blazing white-hot star of intense brilliance and dazzling beauty. Its surface temperature is about 12,000 K and its energy output exceeds that of our Sun by a factor of ma ...
Goal: To understand how Saturn formed and what its core is
... Evolution to Hot Jupiter • As the planet moves in it is closer to material that was previously too close. • It is also now larger and will eat that material as well. • This will produce a run away effect that only ends when the gas giant either gets very close to the star or the protostar turns int ...
... Evolution to Hot Jupiter • As the planet moves in it is closer to material that was previously too close. • It is also now larger and will eat that material as well. • This will produce a run away effect that only ends when the gas giant either gets very close to the star or the protostar turns int ...
Lecture5
... Tc ≥ ~ 107 K for stars like the sun (- compare with the surface temperature Ts = 5800 K). H and He (main composition) all ionized at such high T. Note: Thermonuclear reactions (e.g., H-burning) take place only in the central high T core. ...
... Tc ≥ ~ 107 K for stars like the sun (- compare with the surface temperature Ts = 5800 K). H and He (main composition) all ionized at such high T. Note: Thermonuclear reactions (e.g., H-burning) take place only in the central high T core. ...
112501. r-process beam neutron
... nucleosynthesis. Weak rates in this mass region are not well understood: GT strength distributions first-forbidden contribution Fröhlich et al., PRL 96 (2006) ...
... nucleosynthesis. Weak rates in this mass region are not well understood: GT strength distributions first-forbidden contribution Fröhlich et al., PRL 96 (2006) ...
Lecture 24 - Empyrean Quest Publishers
... How bright (L in watts)? Luminosity at the source is determined from apparent brightness and distance (d). Apparent magnitude (old way). We can see about 1,000 stars in Northern Hemisphere with naked eye. Hipparchus rated them from 1 to 6. A '1' is 2.52 x brighter than a '2', etc. Range in brightnes ...
... How bright (L in watts)? Luminosity at the source is determined from apparent brightness and distance (d). Apparent magnitude (old way). We can see about 1,000 stars in Northern Hemisphere with naked eye. Hipparchus rated them from 1 to 6. A '1' is 2.52 x brighter than a '2', etc. Range in brightnes ...
Standard EPS Shell Presentation
... Describe how the composition and size of planets is related to their formation and proximity to the sun. Identify the structure of the Milky Way Galaxy and the location of our solar system within the galaxy. Explain how astronomers measure the distance to stars and ...
... Describe how the composition and size of planets is related to their formation and proximity to the sun. Identify the structure of the Milky Way Galaxy and the location of our solar system within the galaxy. Explain how astronomers measure the distance to stars and ...
SETI: First Considerations (PowerPoint)
... Numbers of Stars The Milky Way is forming about one new star a year, and an ‘average’ star (like the Sun) might last about ten billion years. In the ‘steady state,’ there will be at least several billion radiating stars out there. Stars much more massive than the Sun burn up their fuel very quickly, ...
... Numbers of Stars The Milky Way is forming about one new star a year, and an ‘average’ star (like the Sun) might last about ten billion years. In the ‘steady state,’ there will be at least several billion radiating stars out there. Stars much more massive than the Sun burn up their fuel very quickly, ...
HEA_Accretion_2003_04
... R~10,000km so nuclear burning more efficient by factor of ~50. • Accretion still important process however - nuclear burning on surface => nova ...
... R~10,000km so nuclear burning more efficient by factor of ~50. • Accretion still important process however - nuclear burning on surface => nova ...
The Sun has been stable for 4 billion years.
... Main sequence stars produce energy by fusing hydrogen into helium in their centers. The radius, temperature, luminosity, and lifetime of a main sequence star are determined by its mass. Pressure balance A star is an immense ball of gas. The pressure at any point is equal to the total weight of the g ...
... Main sequence stars produce energy by fusing hydrogen into helium in their centers. The radius, temperature, luminosity, and lifetime of a main sequence star are determined by its mass. Pressure balance A star is an immense ball of gas. The pressure at any point is equal to the total weight of the g ...
Chapter 09 - The Independent School
... Example: Star Radii Polaris has just about the same spectral type (and thus surface temperature) as our sun, but it is 10,000 times brighter than our sun. ...
... Example: Star Radii Polaris has just about the same spectral type (and thus surface temperature) as our sun, but it is 10,000 times brighter than our sun. ...
O star
... spectral type and the luminosity class of a star from its spectrum. This is extraordinarily valuable, as it means that, just from the spectrum of a star, one can plot it in on the H-R diagram. BUT: if you can plot a star on the H-R diagram, you know its absolute magnitude! And if you know its absolu ...
... spectral type and the luminosity class of a star from its spectrum. This is extraordinarily valuable, as it means that, just from the spectrum of a star, one can plot it in on the H-R diagram. BUT: if you can plot a star on the H-R diagram, you know its absolute magnitude! And if you know its absolu ...
Nova
... Binaries in this stage of mass transfer are called semi-detached binaries, because only one of the stars is actually in contact with its Roche surface. The subsequent flow of gas between the stars is called the gas stream or mass transfer stream. During Roche lobe overflow, mass transfer feeds gas p ...
... Binaries in this stage of mass transfer are called semi-detached binaries, because only one of the stars is actually in contact with its Roche surface. The subsequent flow of gas between the stars is called the gas stream or mass transfer stream. During Roche lobe overflow, mass transfer feeds gas p ...
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
... where vr is the radial velocity. (b) Assume that the original cloud had a mass of 1M� and a radius of 0.5 pc. If the collapse is halted at a radius of approximately 100 AU, find the initial angular velocity of the cloud. What was the original rotational velocity (in cm s−1 ) of the edge of the cloud? ...
... where vr is the radial velocity. (b) Assume that the original cloud had a mass of 1M� and a radius of 0.5 pc. If the collapse is halted at a radius of approximately 100 AU, find the initial angular velocity of the cloud. What was the original rotational velocity (in cm s−1 ) of the edge of the cloud? ...
MSci Astrophysics 210PHY412 - Queen's University Belfast
... Heat is convected by rising elements which are hotter than their surroundings and falling elements which are cooler. Suppose the element differs by T from its surroundings, because an element is always in pressure balance with its surroundings, it has energy content per kg which differs from surrou ...
... Heat is convected by rising elements which are hotter than their surroundings and falling elements which are cooler. Suppose the element differs by T from its surroundings, because an element is always in pressure balance with its surroundings, it has energy content per kg which differs from surrou ...
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.