Hydrogen Greenhouse Planets Beyond the Habitable Zone
... 3). Significant atmospheric loss usually ceases by ∼2 Gyr. Planets around M dwarfs, with their lower X-ray luminosities, can retain their H2 -He atmospheres close to the star. However, these stars, especially those of mid- to late-M spectral type, may vary greatly in their EUV flux (Reiners & Basri ...
... 3). Significant atmospheric loss usually ceases by ∼2 Gyr. Planets around M dwarfs, with their lower X-ray luminosities, can retain their H2 -He atmospheres close to the star. However, these stars, especially those of mid- to late-M spectral type, may vary greatly in their EUV flux (Reiners & Basri ...
The Milky Way Galaxy
... Shapley determined the distances to a number of globular clusters using the period-luminosity law for Cepheids. He noted that most globular clusters had linear diameters of about 25 pc. He could then use their angular diameters to get approximate distance for clusters whose stars were too faint to ...
... Shapley determined the distances to a number of globular clusters using the period-luminosity law for Cepheids. He noted that most globular clusters had linear diameters of about 25 pc. He could then use their angular diameters to get approximate distance for clusters whose stars were too faint to ...
Monday, April 28
... – Assumed all stars have the same absolute brightness – Counts stars as a function of apparent magnitude – Brighter stars closer to us; fainter stars further away – Cut off in brightness corresponds to a cut off at a certain distance. ...
... – Assumed all stars have the same absolute brightness – Counts stars as a function of apparent magnitude – Brighter stars closer to us; fainter stars further away – Cut off in brightness corresponds to a cut off at a certain distance. ...
Math Notes - UNC Physics and Astronomy
... cancel out and consequently do not affect the speed at which the object orbits. Only mass interior to the object’s orbit matters. Solving for M
... cancel out and consequently do not affect the speed at which the object orbits. Only mass interior to the object’s orbit matters. Solving for M
Summary: Modes of Star Formation
... form by stellar coalescence. Neither of these hypotheses can yet be excluded, and a further intermediate possibility suggested here is that interactions between dense star-forming cores are involved. In fact, such a picture seems almost unavoidable, because if one imagines that accretion is the domi ...
... form by stellar coalescence. Neither of these hypotheses can yet be excluded, and a further intermediate possibility suggested here is that interactions between dense star-forming cores are involved. In fact, such a picture seems almost unavoidable, because if one imagines that accretion is the domi ...
- EPJ Web of Conferences
... The transiting hot Saturns HAT-P-12b (Hartman et al. 2009) and HAT-P-18b (Hartman et al. 2010a) are two cases where the BS appeared to correlate with the measured RVs suggesting that these might in fact be blends. We used blendanal to analyze both systems and concluded that neither could be modeled ...
... The transiting hot Saturns HAT-P-12b (Hartman et al. 2009) and HAT-P-18b (Hartman et al. 2010a) are two cases where the BS appeared to correlate with the measured RVs suggesting that these might in fact be blends. We used blendanal to analyze both systems and concluded that neither could be modeled ...
November - LVAstronomy.com
... monthly summary. We also accept digital imaging. Visual astronomy depends on what’s seen through the eyepiece. Not only does it satisfy an innate curiosity, but it allows the visual observer to discover the beauty and the wonderment of the night sky. Before photography, all observations depended on ...
... monthly summary. We also accept digital imaging. Visual astronomy depends on what’s seen through the eyepiece. Not only does it satisfy an innate curiosity, but it allows the visual observer to discover the beauty and the wonderment of the night sky. Before photography, all observations depended on ...
ASTR 31: Descriptive Astronomy
... Helium capture The triple-alpha reaction and the major carbon and oxygen burning reactions are helium capture reactions. The capture of helium nuclei continues until silicon is created, at which point the supply of helium nuclei in the star’s core is depleted: 20Ne + 4He → 24Mg + 24Mg + 4He ...
... Helium capture The triple-alpha reaction and the major carbon and oxygen burning reactions are helium capture reactions. The capture of helium nuclei continues until silicon is created, at which point the supply of helium nuclei in the star’s core is depleted: 20Ne + 4He → 24Mg + 24Mg + 4He ...
Document
... • The mission will yield a variety of data to calibrate dynamo models, sampling many different sets of physical conditions and evolutionary phases. ...
... • The mission will yield a variety of data to calibrate dynamo models, sampling many different sets of physical conditions and evolutionary phases. ...
Class notes 2 - University of Texas Astronomy
... ~ 1 pc ~ 4 × 107 their radius (⇒ don't collide within lifetime of Galaxy, ~ 1010 years); ⎯ majority are fainter, cooler, and of lower mass than the Sun; ⎯ about half are double or multiple systems. Space between stars: contains gas and dust. Gas may be cold or hot, dense or tenuous. ...
... ~ 1 pc ~ 4 × 107 their radius (⇒ don't collide within lifetime of Galaxy, ~ 1010 years); ⎯ majority are fainter, cooler, and of lower mass than the Sun; ⎯ about half are double or multiple systems. Space between stars: contains gas and dust. Gas may be cold or hot, dense or tenuous. ...
ppt
... WGACAT “stars” (type unknown) re-classified; most are indeed stars, most in direction of LMC/SMC 53 new XRB candidates; 50% increase in number known in WGACAT. These are mostly high-mass XRB candidates with bright optical counterparts. IAU JD08, 2003-07-18 ...
... WGACAT “stars” (type unknown) re-classified; most are indeed stars, most in direction of LMC/SMC 53 new XRB candidates; 50% increase in number known in WGACAT. These are mostly high-mass XRB candidates with bright optical counterparts. IAU JD08, 2003-07-18 ...
News from high-mass twin stars
... The pomerons (wavy lines) couple to different quarks (solid lines) in quark matter (as in the hNJL Lagrangian) or to quarks in different baryons in nuclear matter (giving rise to repulsive 3- and 4- body interactions). ...
... The pomerons (wavy lines) couple to different quarks (solid lines) in quark matter (as in the hNJL Lagrangian) or to quarks in different baryons in nuclear matter (giving rise to repulsive 3- and 4- body interactions). ...
Life Cycle of the Stars
... This H–R diagram shows the evolution of stars somewhat more and somewhat less massive than the Sun. The shape of the paths is similar, but they wind up in different places on the main sequence. ...
... This H–R diagram shows the evolution of stars somewhat more and somewhat less massive than the Sun. The shape of the paths is similar, but they wind up in different places on the main sequence. ...
GG_CERN_0707
... Cored mass profiles, with similar mean mass densities ~0.1M/pc3, ~5GeV/cc An apparent characteristic (minimum) mass dark ...
... Cored mass profiles, with similar mean mass densities ~0.1M/pc3, ~5GeV/cc An apparent characteristic (minimum) mass dark ...
The Milky Way Galaxy
... Plotting stars on HR diagrams showed that the populations differed in age and metallicity (enrichment of elements heavier than Helium): Pop I young and metal rich Pop II old and metal poor ...
... Plotting stars on HR diagrams showed that the populations differed in age and metallicity (enrichment of elements heavier than Helium): Pop I young and metal rich Pop II old and metal poor ...
MilkyWay
... Plotting stars on HR diagrams showed that the populations differed in age and metallicity (enrichment of elements heavier than Helium): Pop I young and metal rich Pop II old and metal poor ...
... Plotting stars on HR diagrams showed that the populations differed in age and metallicity (enrichment of elements heavier than Helium): Pop I young and metal rich Pop II old and metal poor ...
two dozen compact sources and a massive disk
... 0. Pre-protocluster massive cloud core without collapse mm 1. Early protocluster massive stars have begun to form mm 2. Protocluster HII region begins to evolve FIR, mm, cm 3. Evolved protoclusters cluster begins to emerge MIR - mm 4. Young cluster cluster has emerged from cloud NIR - mm 5. Cluster ...
... 0. Pre-protocluster massive cloud core without collapse mm 1. Early protocluster massive stars have begun to form mm 2. Protocluster HII region begins to evolve FIR, mm, cm 3. Evolved protoclusters cluster begins to emerge MIR - mm 4. Young cluster cluster has emerged from cloud NIR - mm 5. Cluster ...
Astronomical Distance Determination • etc.
... corresponds to 53 AU/yr. Most of the nearby stars are moving along with us, but not precisely. Barnards star moves 10.25 arc sec per year and hundreds of other stars move over 1 arc sec per year. The suns average drift over a number of years compared with the local average, gives a longer baseline ...
... corresponds to 53 AU/yr. Most of the nearby stars are moving along with us, but not precisely. Barnards star moves 10.25 arc sec per year and hundreds of other stars move over 1 arc sec per year. The suns average drift over a number of years compared with the local average, gives a longer baseline ...
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.