ph507rev1
... about 1012 stars in our Galaxy. Space observations made by the European Space Agency with the Hipparcos mission (1989-1993) accurately determined the parallaxes of many more stars. Though a poor orbit limited its usefulness, Hipparcos was expected to achieve a precision of about 0.002”. It actually ...
... about 1012 stars in our Galaxy. Space observations made by the European Space Agency with the Hipparcos mission (1989-1993) accurately determined the parallaxes of many more stars. Though a poor orbit limited its usefulness, Hipparcos was expected to achieve a precision of about 0.002”. It actually ...
Introduc on to the Fundamental Astrophysics Course
... Being more specific … Stellar Evolu)on • Stellar evolu)on is the process by which a star undergoes a sequence of radical changes during its life)me. • Depending on the mass of the star, this lif ...
... Being more specific … Stellar Evolu)on • Stellar evolu)on is the process by which a star undergoes a sequence of radical changes during its life)me. • Depending on the mass of the star, this lif ...
Circumstellar
... In post RSG evolution, these stars will enter a region (6000-9000 K) of increased dynamical instability, high mass loss, increasing opacity – deJager’s “yellow void” HST/STIS spatially resolved spectroscopy – Halpha – uniform outflow, nearly spherical distribution Wind is optically thick variation ...
... In post RSG evolution, these stars will enter a region (6000-9000 K) of increased dynamical instability, high mass loss, increasing opacity – deJager’s “yellow void” HST/STIS spatially resolved spectroscopy – Halpha – uniform outflow, nearly spherical distribution Wind is optically thick variation ...
The empirical mass distribution of hot B subdwarfs
... expel almost entirely the red giant envelope. The He-core flash could also happen after some delay, when the star has already left the RGB. Indeed, this is an alternative and somewhat forgotten idea that stars that never quite reach the “standard” He ignition at the RGB tip can achieve a delayed He- ...
... expel almost entirely the red giant envelope. The He-core flash could also happen after some delay, when the star has already left the RGB. Indeed, this is an alternative and somewhat forgotten idea that stars that never quite reach the “standard” He ignition at the RGB tip can achieve a delayed He- ...
astrophysics - Collegiate Quiz Bowl Packet
... 14. Of the 26 brightest stars in the sky, it has the largest absolute magnitude of –8.1, due to it being over 1000 light years away. Also known as Algebar, it is a triple star system, but the other two can only be viewed with telescopes. This star ranks seventh behind Capella in visual brightness. I ...
... 14. Of the 26 brightest stars in the sky, it has the largest absolute magnitude of –8.1, due to it being over 1000 light years away. Also known as Algebar, it is a triple star system, but the other two can only be viewed with telescopes. This star ranks seventh behind Capella in visual brightness. I ...
“Breakthroughs” of the 20th Century
... ordered in two ways. All the breakthroughs suggested by all the respondents were considered, even though some respondents put forward fewer than the ten requested. First choices were given ten points, second choices nine, third choices eight and so on. List 1 shows the results using the Eurovision S ...
... ordered in two ways. All the breakthroughs suggested by all the respondents were considered, even though some respondents put forward fewer than the ten requested. First choices were given ten points, second choices nine, third choices eight and so on. List 1 shows the results using the Eurovision S ...
From Black Holes to Cosmology : The Universe in the
... solar masses. They are among the most powerful cosmic phenomena, releasing more energy within seconds than stars like the sun produce in billions of years. They terminate the lives of massive stars, giving birth to neutron stars or stellar-mass black holes, and are responsible for the production of ...
... solar masses. They are among the most powerful cosmic phenomena, releasing more energy within seconds than stars like the sun produce in billions of years. They terminate the lives of massive stars, giving birth to neutron stars or stellar-mass black holes, and are responsible for the production of ...
the evolutionary radial distributions of h2 density within spiral and
... SFRs. The lines in color correspond to the lowest star-forming efficiencies which maintain a higher density than in cases where stars are formed more efficiently (black lines). The distributions are close to exponential in the external regions but are flatter at the inner regions, as is in fact obse ...
... SFRs. The lines in color correspond to the lowest star-forming efficiencies which maintain a higher density than in cases where stars are formed more efficiently (black lines). The distributions are close to exponential in the external regions but are flatter at the inner regions, as is in fact obse ...
Dark matter
... Out to the edge of its visible disk, the Milky Way Galaxy contains: 200 billion solar masses, but only 20 billion solar luminosities. ...
... Out to the edge of its visible disk, the Milky Way Galaxy contains: 200 billion solar masses, but only 20 billion solar luminosities. ...
Figure 1. Map showing the region of the Fourth Quadrant selected
... Bate & Zinnecker 1998). On the other hand, by adding turbulence to an accretion model, McKee & Tan (2003) have shown that massive stars can still form by accretion. More generally, the new “turbulent” models for star formation may explain the low star formation efficiency and turbulence observed acr ...
... Bate & Zinnecker 1998). On the other hand, by adding turbulence to an accretion model, McKee & Tan (2003) have shown that massive stars can still form by accretion. More generally, the new “turbulent” models for star formation may explain the low star formation efficiency and turbulence observed acr ...
Physics of Galaxies 2016 Exercises with solutions – Batch II
... of EW(Hα) as predicted by the Yggdrasil model (Zackrisson et al. 2011, ApJ, 740. 13). As seen in Figure 2, EW(Hα) decreases with the age of the population. What is the physics behind this? The Hα emission line itself is a recombination line that forms in the photoionized gas surrounding young, hot s ...
... of EW(Hα) as predicted by the Yggdrasil model (Zackrisson et al. 2011, ApJ, 740. 13). As seen in Figure 2, EW(Hα) decreases with the age of the population. What is the physics behind this? The Hα emission line itself is a recombination line that forms in the photoionized gas surrounding young, hot s ...
Habitability of super-Earth planets around main
... forms during the phase of slowly increasing stellar luminosity, we would limit the mass range of host stars of potentially lifebearing planets to a maximum of about 1.3 M⊙. In Table 1, we also list the stellar effective temperatures, which are a steep monotonic function of the stellar mass. Note tha ...
... forms during the phase of slowly increasing stellar luminosity, we would limit the mass range of host stars of potentially lifebearing planets to a maximum of about 1.3 M⊙. In Table 1, we also list the stellar effective temperatures, which are a steep monotonic function of the stellar mass. Note tha ...
Three Coordinate Systems
... as a time going east – 0 to 24 hours is 360o “Prime meridian” – point where sun is located at the vernal equinox (spring) (called vernal equinoctial colure) ...
... as a time going east – 0 to 24 hours is 360o “Prime meridian” – point where sun is located at the vernal equinox (spring) (called vernal equinoctial colure) ...
Stellar Population Modeling of Galaxies in Nearby Groups
... We construct synthetic Hess diagrams from theoretical stellar isochrones. Each isochrone describes magnitudes and colors of a stellar population with a particular age and metallicity. All the sample of the synthetic diagrams covers a wide range of ages and metallicities. We take into account the dis ...
... We construct synthetic Hess diagrams from theoretical stellar isochrones. Each isochrone describes magnitudes and colors of a stellar population with a particular age and metallicity. All the sample of the synthetic diagrams covers a wide range of ages and metallicities. We take into account the dis ...
Three Coordinate Systems
... as a time going east – 0 to 24 hours is 360o “Prime meridian” – point where sun is located at the vernal equinox (spring) (called vernal equinoctial colure) ...
... as a time going east – 0 to 24 hours is 360o “Prime meridian” – point where sun is located at the vernal equinox (spring) (called vernal equinoctial colure) ...
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.