Overview spherical accretion
... Taking the sounds speed a∞ to be comparable to the mean particle speed v∞ , then this is times the collisionless accretion rate (page 11) ! For typical ionised interstellar gas with a∞ ~ 10 km/s, the accretion rate is a factor 109 ...
... Taking the sounds speed a∞ to be comparable to the mean particle speed v∞ , then this is times the collisionless accretion rate (page 11) ! For typical ionised interstellar gas with a∞ ~ 10 km/s, the accretion rate is a factor 109 ...
HWWS 2010 - Monash University
... • Energy released from accretion material onto an object of mass M and radius R is • i.e. the (specific) power-to-mass ratio is just a function of radius… • Neutron stars are the most compact objects in the universe • And hence arguably have the highest power-to-weight ratio ...
... • Energy released from accretion material onto an object of mass M and radius R is • i.e. the (specific) power-to-mass ratio is just a function of radius… • Neutron stars are the most compact objects in the universe • And hence arguably have the highest power-to-weight ratio ...
Diapositive 1
... 2R cf. ~15 R observed). Spectral lines ~10% of total broadband flux & vary little observed variation (P = 10h & other) must be related to pulsations of the stellar core! (supported by sp analysis for WN8 stars by Haeffener & Hamann 2008). Delayed reaction of wind (sp lines) triggered by superpos ...
... 2R cf. ~15 R observed). Spectral lines ~10% of total broadband flux & vary little observed variation (P = 10h & other) must be related to pulsations of the stellar core! (supported by sp analysis for WN8 stars by Haeffener & Hamann 2008). Delayed reaction of wind (sp lines) triggered by superpos ...
LAB #3 - GEOCITIES.ws
... LAB. You will begin lab with a short quiz on these questions. What are Magnitudes? Because what we know about stars is due solely to our analysis of their light, it is very important to develop further the idea of stellar magnitude, or how bright a star is. When the Greeks scientist Hipparcos determ ...
... LAB. You will begin lab with a short quiz on these questions. What are Magnitudes? Because what we know about stars is due solely to our analysis of their light, it is very important to develop further the idea of stellar magnitude, or how bright a star is. When the Greeks scientist Hipparcos determ ...
The Components of a Spiral Galaxy
... bottom panel shows the galaxy mass function divided by color- the spirals are mostly blue (some S0s are red) (Cattaneo et al 2009)-" spirals tend to be less massive than ellipticals" the black solid line is the prediction from cold dark matter theory of the number density of halos vs mass- notice do ...
... bottom panel shows the galaxy mass function divided by color- the spirals are mostly blue (some S0s are red) (Cattaneo et al 2009)-" spirals tend to be less massive than ellipticals" the black solid line is the prediction from cold dark matter theory of the number density of halos vs mass- notice do ...
A 25 micron search for Vega-like disks around main
... To check the ISO results we have correlated the ISO fluxes with the predicted fluxes and found a tight correlation. However, the correlation is not along the line of unit slope but along a power law where the high fluxes (Fν > 1 Jy) are systematically underestimated and the lower fluxes (Fν < 300 mJ ...
... To check the ISO results we have correlated the ISO fluxes with the predicted fluxes and found a tight correlation. However, the correlation is not along the line of unit slope but along a power law where the high fluxes (Fν > 1 Jy) are systematically underestimated and the lower fluxes (Fν < 300 mJ ...
Why is the Sun very dense on the inside?
... a) Some stars are larger than others and therefore appear larger. b) Some stars are nearer than others and therefore appear larger. c) Photographs make brighter stars appear larger than fainter stars, although they should all be points of light. d) Sometimes what looks like a single star is actu ...
... a) Some stars are larger than others and therefore appear larger. b) Some stars are nearer than others and therefore appear larger. c) Photographs make brighter stars appear larger than fainter stars, although they should all be points of light. d) Sometimes what looks like a single star is actu ...
here - Stars `r` Us!
... 10% or so of matter in the universe is the familiar “baryonic” material, mostly locked in stars. Only about 1% of all matter is gaseous and distributed between the stars. And of this 1%, perhaps half is molecular. Therefore only about 0.5% of the total mass of the universe is composed of molecules. ...
... 10% or so of matter in the universe is the familiar “baryonic” material, mostly locked in stars. Only about 1% of all matter is gaseous and distributed between the stars. And of this 1%, perhaps half is molecular. Therefore only about 0.5% of the total mass of the universe is composed of molecules. ...
A method for determining the V magnitude of asteroids from CCD
... of comparison star data. The All-Sky Survey (TASS), for example, is calibrated against Tycho-2 stars.19 GUIDE states that ‘In most cases the precision provided by Tycho is much greater than all earlier catalogues. About the only case in which Tycho data would be ignored is if Hipparcos data is avail ...
... of comparison star data. The All-Sky Survey (TASS), for example, is calibrated against Tycho-2 stars.19 GUIDE states that ‘In most cases the precision provided by Tycho is much greater than all earlier catalogues. About the only case in which Tycho data would be ignored is if Hipparcos data is avail ...
Cooling neutron star in the Cassiopeia A supernova remnant
... carbon atmospheric model The emission – from entire star surface ! ...
... carbon atmospheric model The emission – from entire star surface ! ...
The extended structure of the dwarf irregular galaxy Sagittarius⋆⋆⋆
... radial range. The structure and kinematics of the neutral hydrogen provide additional and complementary information. It must be stressed that dwarf galaxies evolved in isolation should have preserved their pristine DM haloes virtually untouched, hence bearing fundamental information on their origina ...
... radial range. The structure and kinematics of the neutral hydrogen provide additional and complementary information. It must be stressed that dwarf galaxies evolved in isolation should have preserved their pristine DM haloes virtually untouched, hence bearing fundamental information on their origina ...
X-ray emission from supernova shock waves Tanja Kramer Nymark Department of Astronomy
... Type IIP supernovae is discussed. We estimate the mass loss rate of the progenitors of Type IIP supernovae, and find that a superwind phase is not required. VLT observations of the ring of SN 1987A show broad optical emission lines coming from a range of ionization stages, in particular optical coro ...
... Type IIP supernovae is discussed. We estimate the mass loss rate of the progenitors of Type IIP supernovae, and find that a superwind phase is not required. VLT observations of the ring of SN 1987A show broad optical emission lines coming from a range of ionization stages, in particular optical coro ...
Magnetic Fields in Stars
... Magnetism—the force that deflects the needle of a compass—and magnetic fields have been found in some hundreds of stars during the past 50 yr. Magnetic fields have been detected in T Tauri stars and other pre-mainsequence stars, several types of main sequence stars, white dwarfs and neutron stars. W ...
... Magnetism—the force that deflects the needle of a compass—and magnetic fields have been found in some hundreds of stars during the past 50 yr. Magnetic fields have been detected in T Tauri stars and other pre-mainsequence stars, several types of main sequence stars, white dwarfs and neutron stars. W ...
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.