Tutorial: Luminosity
... Luminosity (brightness) of a Star However, the “brightness” of a star decreases as one moves farther and farther away. If a sphere of radius d is drawn around the star, it should be clear that the energy/sec through the surface of this sphere is the same as the energy/sec emitted through the surfac ...
... Luminosity (brightness) of a Star However, the “brightness” of a star decreases as one moves farther and farther away. If a sphere of radius d is drawn around the star, it should be clear that the energy/sec through the surface of this sphere is the same as the energy/sec emitted through the surfac ...
Semin2012.2 - Institute of Astronomy
... The reasons for faster rotation in giants in symbiotic systems could be: - synchronization, if the time spent by the mass-losing star on the giant branch is longer than the synchronization time. In all symbiotic systems with orbital period Porb ≤ 100 years tidal interaction overcomes the angular mom ...
... The reasons for faster rotation in giants in symbiotic systems could be: - synchronization, if the time spent by the mass-losing star on the giant branch is longer than the synchronization time. In all symbiotic systems with orbital period Porb ≤ 100 years tidal interaction overcomes the angular mom ...
supernova remnants
... white dwarfs (8M) and the most massive stars that can exist. Supernova physics relates some of the most complicated physical processes from the explosion mechanisms to nucleosynthesis, radiation transport, and shock physics SNe Ia are the main producer of iron in the universe. Their progenitors hav ...
... white dwarfs (8M) and the most massive stars that can exist. Supernova physics relates some of the most complicated physical processes from the explosion mechanisms to nucleosynthesis, radiation transport, and shock physics SNe Ia are the main producer of iron in the universe. Their progenitors hav ...
TAP 704- 8: The ladder of astronomical distances
... Beyond the distance where individual stars could be seen in galaxies, the only hope was to make further dangerous assumptions, for example that galaxies of the same type are equally bright, or equal in size. Neither method is helped by the fact that galaxies are seen at all angles to the line of sig ...
... Beyond the distance where individual stars could be seen in galaxies, the only hope was to make further dangerous assumptions, for example that galaxies of the same type are equally bright, or equal in size. Neither method is helped by the fact that galaxies are seen at all angles to the line of sig ...
Chapter 26.2 notes
... Most stars are found along a diagonal band running from the bright hot stars on the upper left to the dim cool stars on the lower right. Astronomers call this diagonal band on the H-R diagram the main sequence. About 90% of all stars are found on the main sequence. The sun lies near the middle of th ...
... Most stars are found along a diagonal band running from the bright hot stars on the upper left to the dim cool stars on the lower right. Astronomers call this diagonal band on the H-R diagram the main sequence. About 90% of all stars are found on the main sequence. The sun lies near the middle of th ...
The Relative Ages of M5 and Pal 4/Eridanus from their
... NGC 1232 is located in the constellation Eridanus . The distance is about 100 million light-years. ...
... NGC 1232 is located in the constellation Eridanus . The distance is about 100 million light-years. ...
Lecture 6: Multiple stars
... Amongst Solartype stars the PMS binary fraction is around 100%, compared to about 60% for MS Gdwarfs. Massive stars have a binary fraction of about 100% (they must be young). Lowmass PMS stars may have a high binary fraction, but it is low (~40%) in the field, they may have an excess at ~10 ...
... Amongst Solartype stars the PMS binary fraction is around 100%, compared to about 60% for MS Gdwarfs. Massive stars have a binary fraction of about 100% (they must be young). Lowmass PMS stars may have a high binary fraction, but it is low (~40%) in the field, they may have an excess at ~10 ...
Temperatures of Stars
... not all stars with Teff = 5800 K are like the Sun other parameters include the chemical composition, more specifically the proportion of heavy elements with respect to hydrogen in astronomical jargon this parameter is called [Fe/H] for the Sun, [Fe/H] = 0. For a star with an abundance of iron and o ...
... not all stars with Teff = 5800 K are like the Sun other parameters include the chemical composition, more specifically the proportion of heavy elements with respect to hydrogen in astronomical jargon this parameter is called [Fe/H] for the Sun, [Fe/H] = 0. For a star with an abundance of iron and o ...
Order-of-Magnitude Physics – Solution Set 4
... and tcond ∼ 2 × 107 (Tcore /107 K) yr (easy way but not quite right: should get full credit anyway) . More correct way (also gets full credit): So the easy way above misses the fact that the electrons are degenerate and therefore most of them don’t participate in carrying heat. The only heat-carryin ...
... and tcond ∼ 2 × 107 (Tcore /107 K) yr (easy way but not quite right: should get full credit anyway) . More correct way (also gets full credit): So the easy way above misses the fact that the electrons are degenerate and therefore most of them don’t participate in carrying heat. The only heat-carryin ...
Measuring the Distances to the Stars: Parallax What sets the parallax limit? 1
... Measuring the Distances to the Stars: Parallax ...
... Measuring the Distances to the Stars: Parallax ...
The cooling of CO white dwarfs: influence of the internal chemical
... early thermally-pulsing AGB phase. After the ejection of the envelope, when the nuclear reactions are negligible at the edge of the degenerate core, the Ledoux criterion can be used and, therefore, the chemical profiles are Rayleigh-Taylor unstable and, consequently, will be rehomogeneized by convec ...
... early thermally-pulsing AGB phase. After the ejection of the envelope, when the nuclear reactions are negligible at the edge of the degenerate core, the Ledoux criterion can be used and, therefore, the chemical profiles are Rayleigh-Taylor unstable and, consequently, will be rehomogeneized by convec ...
A Supermassive Black Hole in the Andromeda Galaxy
... This goes wrong for 0.6 - 1 M white dwarfs: 1 - Interior to rh, most progenitors collide and get destroyed. If they succeed to merge, they get converted into progenitors of 1 M white dwarfs, even neglecting dynamical friction. Lower-mass white dwarfs are also irrelevant – their progenitors get de ...
... This goes wrong for 0.6 - 1 M white dwarfs: 1 - Interior to rh, most progenitors collide and get destroyed. If they succeed to merge, they get converted into progenitors of 1 M white dwarfs, even neglecting dynamical friction. Lower-mass white dwarfs are also irrelevant – their progenitors get de ...
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.