Gas giants in hot water: inhibiting giant planet
... In Section 2, I estimate the temperature of embedded star clusters, and in Section 3 I estimate their protoplanetary disc temperatures. I then compare the relative importance of cluster irradiation and (1) host star irradiation in passive discs, and (2) accretion power in active discs. Generically, ...
... In Section 2, I estimate the temperature of embedded star clusters, and in Section 3 I estimate their protoplanetary disc temperatures. I then compare the relative importance of cluster irradiation and (1) host star irradiation in passive discs, and (2) accretion power in active discs. Generically, ...
The Dynamics of White Dwarfs, Black Holes and Stellar Cusps
... relationship between the mass and kinematics of white dwarfs is demonstrated, whereby high- ...
... relationship between the mass and kinematics of white dwarfs is demonstrated, whereby high- ...
Chapter 1
... As was mentioned earlier, the main source of ionization for producing strong emission lines in star-forming galaxies is very massive stars. However, our knowledge about these massive stars is limited because direct observations of them often cannot be carried out as these stars are often heavily ens ...
... As was mentioned earlier, the main source of ionization for producing strong emission lines in star-forming galaxies is very massive stars. However, our knowledge about these massive stars is limited because direct observations of them often cannot be carried out as these stars are often heavily ens ...
SN 2006gy: DISCOVERY OF THE MOST LUMINOUS
... peak visual magnitude of about 22, it is the most luminous supernova ever recorded. Its very slow rise to maximum took 70 days, and it stayed brighter than 21 mag for about 100 days. It is not yet clear what powers the enormous luminosity and the total radiated energy of 1051 erg, but we argue t ...
... peak visual magnitude of about 22, it is the most luminous supernova ever recorded. Its very slow rise to maximum took 70 days, and it stayed brighter than 21 mag for about 100 days. It is not yet clear what powers the enormous luminosity and the total radiated energy of 1051 erg, but we argue t ...
Chemical composition of B-type supergiants in the OB8, OB10
... of the Si IV lines being marginal. Indeed a later spectral-type, such as B2Ia, would also be compatible with the data. OB78-277 and OB78-478: These two M31 targets are considered together as they have similar spectra, corresponding to spectral types of B1-2Ia. Indeed both spectra match well that of ...
... of the Si IV lines being marginal. Indeed a later spectral-type, such as B2Ia, would also be compatible with the data. OB78-277 and OB78-478: These two M31 targets are considered together as they have similar spectra, corresponding to spectral types of B1-2Ia. Indeed both spectra match well that of ...
UNIT 4 - Galaxies XIV. The Milky Way A. Structure
... recent observations suggest that most, if not all, Quasars reside in a host galaxy ...
... recent observations suggest that most, if not all, Quasars reside in a host galaxy ...
Microlensing - Caltech Astronomy
... bulge is greater than initially predicted by Galactic models, favoring a barred structure for the Galaxy. The distribution of timescales is consistent with most of the lenses being low-mass stars as expected and can provide constraints on the stellar mass function at low masses. (ii) Towards the Mag ...
... bulge is greater than initially predicted by Galactic models, favoring a barred structure for the Galaxy. The distribution of timescales is consistent with most of the lenses being low-mass stars as expected and can provide constraints on the stellar mass function at low masses. (ii) Towards the Mag ...
THE DYNAMICAL STRUCTURE AND EVOLUTION OF GIANT
... range of physical conditions, from hot X-ray emitting plasma to cold molecular gas. The molecular gas is of particular importance because it is believed to be the site of all the star formation that occurs in galaxies. In the Milky Way, molecular gas constitutes about half the total mass of gas with ...
... range of physical conditions, from hot X-ray emitting plasma to cold molecular gas. The molecular gas is of particular importance because it is believed to be the site of all the star formation that occurs in galaxies. In the Milky Way, molecular gas constitutes about half the total mass of gas with ...
PP Chapter 28 Text
... Life cycle of stars: • Begins as a nebula • Advances to a protostar • Becomes a star when fusion in its core occurs Depending on its mass, the star may become a red giant and then burn out to become a white dwarf. ...
... Life cycle of stars: • Begins as a nebula • Advances to a protostar • Becomes a star when fusion in its core occurs Depending on its mass, the star may become a red giant and then burn out to become a white dwarf. ...
Anisotropy of the Hectometer Cosmic Radio Background
... a 0.1 degree and the spacecraft rotation period. By way of illustration, Fig. 1 shows oscillograms of the signals from the S-antenna output in the December 27, 1997 session. When RAD1 is switched from the standard mode (the beginning and end of the records correspond to this mode) to the mode of sca ...
... a 0.1 degree and the spacecraft rotation period. By way of illustration, Fig. 1 shows oscillograms of the signals from the S-antenna output in the December 27, 1997 session. When RAD1 is switched from the standard mode (the beginning and end of the records correspond to this mode) to the mode of sca ...
A physical interpretation of the `red Sirius` anomaly
... The predicted time-scale for the temperature, luminosity and radius of a newly exposed, degenerate , 1-M( core to reach the currently determined values for Sirius B is , 107 ±108 yr, enormously large compared with the time-scale of the red Sirius anomaly. If standard single-star models are applicabl ...
... The predicted time-scale for the temperature, luminosity and radius of a newly exposed, degenerate , 1-M( core to reach the currently determined values for Sirius B is , 107 ±108 yr, enormously large compared with the time-scale of the red Sirius anomaly. If standard single-star models are applicabl ...
disks surviving the radiation pressure of radio pulsars
... The radiation pressure of a radio pulsar does not necessarily disrupt a surrounding disk. The position of the inner radius of a thin disk around a neutron star, determined by the balance of stresses, can be estimated by comparing the electromagnetic energy density generated by the neutron star as a ...
... The radiation pressure of a radio pulsar does not necessarily disrupt a surrounding disk. The position of the inner radius of a thin disk around a neutron star, determined by the balance of stresses, can be estimated by comparing the electromagnetic energy density generated by the neutron star as a ...
Chemical evolution models for the dwarf spheroidal galaxies Leo 1
... The initial total mass is the main driver of the system in their simulation, contrary to LM03 and LM04 in which the SF and wind efficiencies play the major role. Since the final gas mass predicted in their simulations is much higher than the values inferred by observations, they claim the necessity of ...
... The initial total mass is the main driver of the system in their simulation, contrary to LM03 and LM04 in which the SF and wind efficiencies play the major role. Since the final gas mass predicted in their simulations is much higher than the values inferred by observations, they claim the necessity of ...
Star Captures by Quasar Accretion Disks: A Possible Explanation of
... t0 is the total time during which stars can be captured by the black hole. This is valid if one makes the approximation of a full loss-cylinder 1 , i.e., one assumes that when stars are captured their orbits are immediately replenished by relaxation processes. The slope of this relation is in good a ...
... t0 is the total time during which stars can be captured by the black hole. This is valid if one makes the approximation of a full loss-cylinder 1 , i.e., one assumes that when stars are captured their orbits are immediately replenished by relaxation processes. The slope of this relation is in good a ...
Grosdidier et al. 1998
... • Wolf-Rayet stars are believed to be evolved, very massive (M > 30 M) and metal-rich (> 1/3 Z). • Extreme mass loss (dM/dt up to 10-4 M /yr) at high velocities (up to 2000 km/s). Total mass loss can be a significant fraction of the ZAMS mass. • Occurs during He-core burning, so later burning sta ...
... • Wolf-Rayet stars are believed to be evolved, very massive (M > 30 M) and metal-rich (> 1/3 Z). • Extreme mass loss (dM/dt up to 10-4 M /yr) at high velocities (up to 2000 km/s). Total mass loss can be a significant fraction of the ZAMS mass. • Occurs during He-core burning, so later burning sta ...
Which Phase of the Interstellar Medium Corelates with the Star
... et al. 2010), while the prevalence of galactic-scale instabilities is very insensitive to metallicity. Moreover, any successful model must also be able to relate the SFR to observable quantities, which include H i and CO, but not (generally) the total mass of H2 . At present observations possess lim ...
... et al. 2010), while the prevalence of galactic-scale instabilities is very insensitive to metallicity. Moreover, any successful model must also be able to relate the SFR to observable quantities, which include H i and CO, but not (generally) the total mass of H2 . At present observations possess lim ...
Five Planets and an Independent Confirmation of
... are used to model the wavelength scale and the instrumental profile of the telescope and spectrometer optics for each observation (Marcy & Butler 1992; Butler et al. 1996) The iodine cell at Lick Observatory has not been changed over the entire duration of the planet search project, helping to prese ...
... are used to model the wavelength scale and the instrumental profile of the telescope and spectrometer optics for each observation (Marcy & Butler 1992; Butler et al. 1996) The iodine cell at Lick Observatory has not been changed over the entire duration of the planet search project, helping to prese ...
white dwarf
... magnetic field of the primary being dragged through the secondary • As relative spin rate of primary decreases, locking can occur due to the dipole-dipole magnetostatic interaction between primary and (weaker) secondary magnetic field ...
... magnetic field of the primary being dragged through the secondary • As relative spin rate of primary decreases, locking can occur due to the dipole-dipole magnetostatic interaction between primary and (weaker) secondary magnetic field ...
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.