L7 - QUB Astrophysics Research Centre
... We aim to formulate the eqns of stellar structure so that they are independent of mass MS. Hence we will assume that the way in which a physical quantity (e.g. L ) varies from centre of star to surface is the same for all stars of all masses (only absolute L varies). Schematic illustration: ratio of ...
... We aim to formulate the eqns of stellar structure so that they are independent of mass MS. Hence we will assume that the way in which a physical quantity (e.g. L ) varies from centre of star to surface is the same for all stars of all masses (only absolute L varies). Schematic illustration: ratio of ...
LIGHT VS. DISTANCE
... the sky (It's like a lottery: a ticket for each square degree) You see a FLASH! and then there's not another till about a day has gone by (But that depends upon detector sensitivity) In just a moment they spew energy worth (That's pretty fast) A value we can't even fathom on Earth (It's really vast! ...
... the sky (It's like a lottery: a ticket for each square degree) You see a FLASH! and then there's not another till about a day has gone by (But that depends upon detector sensitivity) In just a moment they spew energy worth (That's pretty fast) A value we can't even fathom on Earth (It's really vast! ...
– 1 – 1. Star Formation At Low Metallicity 1.1.
... luminosity is low, and hence the timescale for cooling the protostellar interior (i.e. the Kelvin-Helmholtz time, given by the internal energy/L) is long. Thus the accreted material piles onto the star without further cooling, the protostar mass increases, and thus its interior temperature increases ...
... luminosity is low, and hence the timescale for cooling the protostellar interior (i.e. the Kelvin-Helmholtz time, given by the internal energy/L) is long. Thus the accreted material piles onto the star without further cooling, the protostar mass increases, and thus its interior temperature increases ...
Navigate without compass
... night, however, they are not always in the same place. The position of the stars in the sky depends on the time, date and geographical position (latitude and longitude). You probably have noticed how stars appear to move across the sky during the night. The reason for that is due to the Earth's rota ...
... night, however, they are not always in the same place. The position of the stars in the sky depends on the time, date and geographical position (latitude and longitude). You probably have noticed how stars appear to move across the sky during the night. The reason for that is due to the Earth's rota ...
Powerpoint Presentation (large file)
... increase in luminosity that we call a nova • The peak luminosity of a nova is only 10–4 of that observed in a supernova • Explosive helium fusion may occur in the surface layer of a companion neutron star • This produces a sudden increase in X-ray radiation, which we call a burster ...
... increase in luminosity that we call a nova • The peak luminosity of a nova is only 10–4 of that observed in a supernova • Explosive helium fusion may occur in the surface layer of a companion neutron star • This produces a sudden increase in X-ray radiation, which we call a burster ...
PART 3 Galaxies
... – Some stars follow unusual orbits in the galaxy – Not all Pop II stars are the same age – Model predicts that the first stars might not have been very massive, and should still be around! ...
... – Some stars follow unusual orbits in the galaxy – Not all Pop II stars are the same age – Model predicts that the first stars might not have been very massive, and should still be around! ...
Goal: To understand the HR diagram
... • Color = B-V = temperature • Since the top left stars on the main sequence die first the top left is always peeling off of the main sequence. • The position where there is turn off tells you the age of the cluster • The comparison of absolute to apparent magnitudes tells you the distance to the clu ...
... • Color = B-V = temperature • Since the top left stars on the main sequence die first the top left is always peeling off of the main sequence. • The position where there is turn off tells you the age of the cluster • The comparison of absolute to apparent magnitudes tells you the distance to the clu ...
Intro Astro PP
... • His systematic method was to name a star by using a letter or number followed by the Latin name of the constellation. ...
... • His systematic method was to name a star by using a letter or number followed by the Latin name of the constellation. ...
Lesson 13 - Oregon State University
... short lifetimes, now extinct • Population II stars (H, He, 1% heavier elements) • Population I stars (H, He, 2-5% heavier elements) Includes our sun. ...
... short lifetimes, now extinct • Population II stars (H, He, 1% heavier elements) • Population I stars (H, He, 2-5% heavier elements) Includes our sun. ...
Galactic Center problem sheet
... odel, R., and Straubmeier, C. (2005). The black hole at the center of the Milky Way. Gillessen, S., Eisenhauer, F., Trippe, S., Alexander, T., Genzel, R., Martins, F., and Ott, T. (2009). Monitoring Stellar Orbits Around the Massive Black Hole in the Galactic Center. ApJ, 692:1075–1109. Meyer, L., G ...
... odel, R., and Straubmeier, C. (2005). The black hole at the center of the Milky Way. Gillessen, S., Eisenhauer, F., Trippe, S., Alexander, T., Genzel, R., Martins, F., and Ott, T. (2009). Monitoring Stellar Orbits Around the Massive Black Hole in the Galactic Center. ApJ, 692:1075–1109. Meyer, L., G ...
Document
... • Electrons accelerate down the magnetic field lines toward the lower atmosphere, producing microwave emission • Electrons collide with ions, producing hard x-rays, white light emission from chromosphere • Chromospheric plasma heated to coronal temperatures, hot plasma flows up into the corona • Sho ...
... • Electrons accelerate down the magnetic field lines toward the lower atmosphere, producing microwave emission • Electrons collide with ions, producing hard x-rays, white light emission from chromosphere • Chromospheric plasma heated to coronal temperatures, hot plasma flows up into the corona • Sho ...
Radio Microwave Infrared Visible Speed in Vacuum 3.00 x 108 m s
... Terrain Pinpoint Fires Climate Changes Thermal Imaging Vegetation Health Soil Composition Warm Objects Planets Cooler Stars Nebulae Detect Faint Objects See into dust clouds See Altitude of Atmospheric Layers ...
... Terrain Pinpoint Fires Climate Changes Thermal Imaging Vegetation Health Soil Composition Warm Objects Planets Cooler Stars Nebulae Detect Faint Objects See into dust clouds See Altitude of Atmospheric Layers ...
Stellar models and stellar stability
... convective envelope is sensitive to the surface boundary conditions. This means that the structure also depends on the uncertain details of near-surface convection (see Sec. 4.5). A small change or uncertainty in T eff can have a large effect on the depth of the convective envelope! For small enough ...
... convective envelope is sensitive to the surface boundary conditions. This means that the structure also depends on the uncertain details of near-surface convection (see Sec. 4.5). A small change or uncertainty in T eff can have a large effect on the depth of the convective envelope! For small enough ...
High-Speed Ballistic Stellar Interlopers
... old. Only stars greater than 10 times the Sun’s mass have stellar winds throughout their entire lifetimes. But the objects observed by Hubble are not very massive, because they do not have glowing clouds of ionized gas around them. They are medium-sized stars that are a few to eight times more massi ...
... old. Only stars greater than 10 times the Sun’s mass have stellar winds throughout their entire lifetimes. But the objects observed by Hubble are not very massive, because they do not have glowing clouds of ionized gas around them. They are medium-sized stars that are a few to eight times more massi ...
01.05.10 Centuries-Old Star Mystery Coming to a Close For almost
... For almost two centuries, humans have looked up at a bright star called Epsilon Aurigae and watched with their own eyes as it seemed to disappear into the night sky, slowly fading before coming back to life again. Today, as another dimming of the system is underway, mysteries about the star persist ...
... For almost two centuries, humans have looked up at a bright star called Epsilon Aurigae and watched with their own eyes as it seemed to disappear into the night sky, slowly fading before coming back to life again. Today, as another dimming of the system is underway, mysteries about the star persist ...
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.