December - Weasner
... send that boat to the celestial breaker’s yard, on the grounds that it was too unwieldy. Despite being thought of as a far-southern group, I was able to hunt out a variety of targets from Northern England ! M47 was a large grouping of some 25 brighter stars which showed up well despite the Full Moon ...
... send that boat to the celestial breaker’s yard, on the grounds that it was too unwieldy. Despite being thought of as a far-southern group, I was able to hunt out a variety of targets from Northern England ! M47 was a large grouping of some 25 brighter stars which showed up well despite the Full Moon ...
Dust and molecular gas in the most distant quasars
... Msun already exist. • Require measurements of the bulge dynamical mass. • Resolve the stellar bulge at near-IR wavelengths. – Not yet; • Require gas supply from outside; • Rapid supper-massive black hole accretion occurs prior to the formation of the stellar bulge. ...
... Msun already exist. • Require measurements of the bulge dynamical mass. • Resolve the stellar bulge at near-IR wavelengths. – Not yet; • Require gas supply from outside; • Rapid supper-massive black hole accretion occurs prior to the formation of the stellar bulge. ...
ASTRO-114--Lecture 38-
... importance because it was assumed that the brightest stars were the most important ones. And so they were labeled as first magnitude. And, as I said, there are about 20 of them all around the sky. Then astronomers labeled a second group of stars as second magnitude. So you might think of those as se ...
... importance because it was assumed that the brightest stars were the most important ones. And so they were labeled as first magnitude. And, as I said, there are about 20 of them all around the sky. Then astronomers labeled a second group of stars as second magnitude. So you might think of those as se ...
Galaxy Structure
... In the last few years, independent evidence points to the existence of a bar in the inner Galaxy. This evidence results from NIR photometry (Blitz and Spergel 1991; Weiland et al 1994; Dwek et al 1995), from IRAS source counts (Nakada et al 1991; Whitelock and Catchpole 1992; Nikolaev and Weinberg 1 ...
... In the last few years, independent evidence points to the existence of a bar in the inner Galaxy. This evidence results from NIR photometry (Blitz and Spergel 1991; Weiland et al 1994; Dwek et al 1995), from IRAS source counts (Nakada et al 1991; Whitelock and Catchpole 1992; Nikolaev and Weinberg 1 ...
The local density of matter mapped by Hipparcos
... As samples taken further away from the plane are more dominated by kinematically hotter stars, this effect widens the velocity distribution. Another effect stems from measurement errors in the parallaxes ± these scatter more distant stars into the sample. These stars must, in order to meet the appar ...
... As samples taken further away from the plane are more dominated by kinematically hotter stars, this effect widens the velocity distribution. Another effect stems from measurement errors in the parallaxes ± these scatter more distant stars into the sample. These stars must, in order to meet the appar ...
Astronomy 112: The Physics of Stars Class 1 Notes
... extended mnemonic Oh Be A Fine Girl/guy, Kiss Me Like That, which proves one thing – astronomers have way too much time on their hands. There has been a theoretical proposal that a new type of spectral class should appear for objects even dimmer than T dwarfs, although no examples of such an object ...
... extended mnemonic Oh Be A Fine Girl/guy, Kiss Me Like That, which proves one thing – astronomers have way too much time on their hands. There has been a theoretical proposal that a new type of spectral class should appear for objects even dimmer than T dwarfs, although no examples of such an object ...
Orbital Orientations of Exoplanets: Hat-p-4b is Prograde and Hat
... that the formation and migration processes are similar, but that the subsequent tidal evolution is different (Winn et al. 2010a). In this hypothesis, cool stars are observed to have low obliquities because tidal evolution drove them into alignment, while hot stars retain their “primordial” obliquiti ...
... that the formation and migration processes are similar, but that the subsequent tidal evolution is different (Winn et al. 2010a). In this hypothesis, cool stars are observed to have low obliquities because tidal evolution drove them into alignment, while hot stars retain their “primordial” obliquiti ...
Effect of the stellar spin history on the tidal evolution of close
... Results. For Sun-like stars, the different tidal evolution between initially rapidly and slowly rotating stars is only evident for extremely close-in gas giants orbiting highly dissipative stars. However, for very low-mass stars the effect of the initial rotation of the star on the planet’s evolution ...
... Results. For Sun-like stars, the different tidal evolution between initially rapidly and slowly rotating stars is only evident for extremely close-in gas giants orbiting highly dissipative stars. However, for very low-mass stars the effect of the initial rotation of the star on the planet’s evolution ...
Direct Imaging Searches Around White Dwarfs - X
... Disks identified as near-IR and mid-IR excesses, 500oK < T < 1200oK Disks within a few solar radii of the WDs Material within the disks is being accreted onto the WD atmosphere – Finally explains WDs with metal-polluted atmospheres ...
... Disks identified as near-IR and mid-IR excesses, 500oK < T < 1200oK Disks within a few solar radii of the WDs Material within the disks is being accreted onto the WD atmosphere – Finally explains WDs with metal-polluted atmospheres ...
All About MACHO
... high speeds, this “dark matter” must be distributed in large roundish halos surrounding the stellar component of spiral galaxies. This is true of basically every spiral galaxy measured, including our own Milky Way. On scales larger than galaxies, even more dark matter is required to explain the spee ...
... high speeds, this “dark matter” must be distributed in large roundish halos surrounding the stellar component of spiral galaxies. This is true of basically every spiral galaxy measured, including our own Milky Way. On scales larger than galaxies, even more dark matter is required to explain the spee ...
Chapter 2 Stellar Dynamics in Galaxies
... the galaxy might evolve with time, as a result only of the internal encounters between stars. The truth, however, is rather different. Close star-star encounters are extremely rare and even the effects of distant encounters are so slight that it takes an extremely long time for the dynamics of galax ...
... the galaxy might evolve with time, as a result only of the internal encounters between stars. The truth, however, is rather different. Close star-star encounters are extremely rare and even the effects of distant encounters are so slight that it takes an extremely long time for the dynamics of galax ...
Classification of Variable Stars
... V1668 Cyg. These are stars in constellations for which all of the letter combinations have been exhausted. (i.e. V746 Oph is the 746th variable to be discovered in Ophiuchus.) Variable star names are determined by a committee appointed by the International Astronomical Union (I.A.U.). The assignment ...
... V1668 Cyg. These are stars in constellations for which all of the letter combinations have been exhausted. (i.e. V746 Oph is the 746th variable to be discovered in Ophiuchus.) Variable star names are determined by a committee appointed by the International Astronomical Union (I.A.U.). The assignment ...
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.