All About Elements
... in the universe. Only Hydrogen is more abundant! These two elements were copiously formed during the creation of the universe. In the early stages of the universe, helium and hydrogen nuclei were actually formed. No atoms were formed until about 300,000 years after the Big Bang took place, when the ...
... in the universe. Only Hydrogen is more abundant! These two elements were copiously formed during the creation of the universe. In the early stages of the universe, helium and hydrogen nuclei were actually formed. No atoms were formed until about 300,000 years after the Big Bang took place, when the ...
Accretion of brown dwarfs
... primary tool to study stellar rotation and activity - positive correlation between rotation period and mass - rotational evolution determined by contraction + winds - change of dynamo in very low mass regime 2. Spectroscopic variability: close-up view on accretion behaviour - strong accretion rate v ...
... primary tool to study stellar rotation and activity - positive correlation between rotation period and mass - rotational evolution determined by contraction + winds - change of dynamo in very low mass regime 2. Spectroscopic variability: close-up view on accretion behaviour - strong accretion rate v ...
How To Find Newborn Black Holes Kazumi Kashiyama (UCB)
... Mass loss was included in the calculation, but due to the low metallicity, only 0.05 M⊙ and 0.15 M⊙ was lost in V24 and V36, respectively. Note that, if all the surface material accreted here, the black hole would rotate at nearly its maximum allowed value (i.e., the red line intersects the green on ...
... Mass loss was included in the calculation, but due to the low metallicity, only 0.05 M⊙ and 0.15 M⊙ was lost in V24 and V36, respectively. Note that, if all the surface material accreted here, the black hole would rotate at nearly its maximum allowed value (i.e., the red line intersects the green on ...
ppt
... feeding: binary companion star growth: accretor results from stellar evolution for AGN feeding: galaxy mergers? growth: accretion on to `seed’ black hole? Both problems better understood for binaries, so develop ideas and theory here first. ...
... feeding: binary companion star growth: accretor results from stellar evolution for AGN feeding: galaxy mergers? growth: accretion on to `seed’ black hole? Both problems better understood for binaries, so develop ideas and theory here first. ...
Magnetic fields in O-, B- and A-type stars on the main sequence
... fields are simple fields of globally dipole structure and they are extremely stable over time on long time scales. For these stars with radiative envelopes, it is proven that the fields are remnants of an early phase of the star-life and one speaks of fossil fields (see Sect. 3.1.3). Over the past decad ...
... fields are simple fields of globally dipole structure and they are extremely stable over time on long time scales. For these stars with radiative envelopes, it is proven that the fields are remnants of an early phase of the star-life and one speaks of fossil fields (see Sect. 3.1.3). Over the past decad ...
the challenge of wide-field transit surveys: the case of
... Nearly all of the more than 130 known extrasolar planets have been discovered by means of radial velocity observations. Such observations provide no information on the planet’s size, and, because of the unknown orbital inclination, only a lower limit on the mass of the planet can be established. One ...
... Nearly all of the more than 130 known extrasolar planets have been discovered by means of radial velocity observations. Such observations provide no information on the planet’s size, and, because of the unknown orbital inclination, only a lower limit on the mass of the planet can be established. One ...
in search of antimatter in the universe
... Nuclei (AGN) (See title, Figure 4,5) These colossal jets originate from the central super-massive black hole of the galaxy, flying through the galaxy around them at speeds close to the speed of light. It is possible that these jets contain electrons and positrons, meaning it is likely that Positroni ...
... Nuclei (AGN) (See title, Figure 4,5) These colossal jets originate from the central super-massive black hole of the galaxy, flying through the galaxy around them at speeds close to the speed of light. It is possible that these jets contain electrons and positrons, meaning it is likely that Positroni ...
Chemical abundances and winds of massive stars in M31: a B
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
... Numerous surveys have identified OB and WR stars beyond the Magellanic Clouds e.g. Massey et al. (1986); Moffat & Shara (1987), although little quantitative analysis has been carried out to date. The only detailed studies of WolfRayet stars beyond the Magellanic Clouds have been studies of late WN s ...
Article PDF - IOPscience
... consistent with a random distribution in terms of sky position. In Figure 2, we show the Kepler magnitude of the stars as a function of estimated distance; drawing upon Huber et al. 2014, a distance modulus is obtained from the spectral type implied from the effective temperature and known surface g ...
... consistent with a random distribution in terms of sky position. In Figure 2, we show the Kepler magnitude of the stars as a function of estimated distance; drawing upon Huber et al. 2014, a distance modulus is obtained from the spectral type implied from the effective temperature and known surface g ...
Final Stages of Stellar Evolution - supernovae and the synthesis of
... Final Stages of Stellar Evolution supernovae and the synthesis of heavy nuclei ...
... Final Stages of Stellar Evolution supernovae and the synthesis of heavy nuclei ...
A radio pulsing white dwarf binary star
... White dwarfs are compact stars, similar in size to Earth but ∼ 200,000 times more massive1 . Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the re ...
... White dwarfs are compact stars, similar in size to Earth but ∼ 200,000 times more massive1 . Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the re ...
Wolf-Rayet Stars
... early type (WNE) and classes 6 to 9 as late type (WNL). Similarly WC4-6 stars are designated as WCE, while WC7-9 stars are designated as WCL. Although there are important exceptions, WNE stars generally show no evidence for H emission while H emission is present in WNL stars. The distribution of Pop ...
... early type (WNE) and classes 6 to 9 as late type (WNL). Similarly WC4-6 stars are designated as WCE, while WC7-9 stars are designated as WCL. Although there are important exceptions, WNE stars generally show no evidence for H emission while H emission is present in WNL stars. The distribution of Pop ...
Rotation Periods and Relative Ages of Solar-Type Stars
... The metallicity of a star, a measure of the abundance of certain metals in a star’s photosphere, also serves as an indicator of age. For example, since the Sun is still burning hydrogen in its core, it is too “young” to produce heavy metals. Metals like calcium, iron, lithium, and magnesium, observe ...
... The metallicity of a star, a measure of the abundance of certain metals in a star’s photosphere, also serves as an indicator of age. For example, since the Sun is still burning hydrogen in its core, it is too “young” to produce heavy metals. Metals like calcium, iron, lithium, and magnesium, observe ...
sections 16-18 instructor notes
... in the direction of the Galactic centre. The results depend upon the assumption that all such stars are bound to the Galaxy and that their orbits are governed by the mass of the Galaxy concentrated inside the solar circle. The implied value of 0 is between 275 and 300 km/s with the last assumption, ...
... in the direction of the Galactic centre. The results depend upon the assumption that all such stars are bound to the Galaxy and that their orbits are governed by the mass of the Galaxy concentrated inside the solar circle. The implied value of 0 is between 275 and 300 km/s with the last assumption, ...
LIDAR Imaging Detector Could Build `Super Road Maps` of Planets
... fabricate, develop, and test a novel detector that will revolutionize future NASA planetary space missions in the area of radiation tolerance, low noise, low power, and low mass. These missions rely on low noise array detectors that must operate in the harsh radiation environment of space. Most curr ...
... fabricate, develop, and test a novel detector that will revolutionize future NASA planetary space missions in the area of radiation tolerance, low noise, low power, and low mass. These missions rely on low noise array detectors that must operate in the harsh radiation environment of space. Most curr ...
Abundances and possible diffusion of elements in M 67 stars⋆
... Methods. We have obtained VLT/FLAMES-UVES spectra and analysed these strictly differentially in order to explore chemicalabundance similarities and differences between the M 67 stars and the Sun and among the M 67 stars themselves. Results. Individual abundances of 19 different chemical elements are ob ...
... Methods. We have obtained VLT/FLAMES-UVES spectra and analysed these strictly differentially in order to explore chemicalabundance similarities and differences between the M 67 stars and the Sun and among the M 67 stars themselves. Results. Individual abundances of 19 different chemical elements are ob ...
Neutron star masses: dwarfs, giants and neighbors
... and Very Close Binaries We consider the possible existence of a common channel of evolution of binary systems, which results in a GRB during the formation of a BH or the birth of a magnetar during the formation of a NS. We assume that the rapid rotation of the core of a collapsing star can be explai ...
... and Very Close Binaries We consider the possible existence of a common channel of evolution of binary systems, which results in a GRB during the formation of a BH or the birth of a magnetar during the formation of a NS. We assume that the rapid rotation of the core of a collapsing star can be explai ...
Determining the Stellar Spin Axis Orientation
... the displacement caused by the instrumental profile from the one generated by the stellar rotation requires a special observing technique and additional instrument. We have developed a differential image rotator, a small instrument to be inserted between the telescope output and the slit, which spli ...
... the displacement caused by the instrumental profile from the one generated by the stellar rotation requires a special observing technique and additional instrument. We have developed a differential image rotator, a small instrument to be inserted between the telescope output and the slit, which spli ...
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.