– 1 – 1. Emission Lines in Nearby Galaxies 1.1.
... To determine the ionization levels of the various elements, one needs to know the electron temperature. The strength of forbidden lines is easy to calculate since they are almost always optically thin in HII regions and the density is low, so collisional de-excitation can be ignored. This results in ...
... To determine the ionization levels of the various elements, one needs to know the electron temperature. The strength of forbidden lines is easy to calculate since they are almost always optically thin in HII regions and the density is low, so collisional de-excitation can be ignored. This results in ...
talk
... Baryonic fraction for NGC 3741 (within the extent of the gas disk) ~ 0.18 ► comparable to other galaxies with less extended HI disk No evidence for baryon loss (measured within the extent of gas disk) in faint dwarf galaxies (contradiction to simulations of galaxy formation !) To reconcile rot ...
... Baryonic fraction for NGC 3741 (within the extent of the gas disk) ~ 0.18 ► comparable to other galaxies with less extended HI disk No evidence for baryon loss (measured within the extent of gas disk) in faint dwarf galaxies (contradiction to simulations of galaxy formation !) To reconcile rot ...
celestial navigation heaven`s guide for mere
... the galaxy, one of several events might occur to cause its gravitational collapse. GMCs may either collide with each other or pass through dense regions of spiral arms. Spiral arms are regions of stars which extend from the centre of spiral and barred spiral galaxies. Sometimes, nearby supernova exp ...
... the galaxy, one of several events might occur to cause its gravitational collapse. GMCs may either collide with each other or pass through dense regions of spiral arms. Spiral arms are regions of stars which extend from the centre of spiral and barred spiral galaxies. Sometimes, nearby supernova exp ...
ancient cultures 114 - Stellenbosch University
... mundane and inappropriate as domestic lighting when viewed from a distance). In true astronomical terms, however, a star is a giant ball of gas, constantly undergoing nuclear processes, and as such constantly emitting electromagnetic waves. The light waves produced from these reactions are particula ...
... mundane and inappropriate as domestic lighting when viewed from a distance). In true astronomical terms, however, a star is a giant ball of gas, constantly undergoing nuclear processes, and as such constantly emitting electromagnetic waves. The light waves produced from these reactions are particula ...
Distance determination for RAVE stars using stellar models
... errors of <35%, while 50% (8073) and 75% (12 110) have relative (statistical) errors smaller than 45% and 50%, respectively. Our various tests show that we can reliably estimate distances for main-sequence stars, but there is an indication of potential systematic problems with giant stars owing to u ...
... errors of <35%, while 50% (8073) and 75% (12 110) have relative (statistical) errors smaller than 45% and 50%, respectively. Our various tests show that we can reliably estimate distances for main-sequence stars, but there is an indication of potential systematic problems with giant stars owing to u ...
- StealthSkater
... planets. Apparently the formation of a planetary system robs the star of much of its rotational momentum. For two reasons, then, we eliminate stars of class 'F4' and above: (1) most of them rotate rapidly and thus seem to be planet-less; and (2) their stable lifespans are too brief for advanced life ...
... planets. Apparently the formation of a planetary system robs the star of much of its rotational momentum. For two reasons, then, we eliminate stars of class 'F4' and above: (1) most of them rotate rapidly and thus seem to be planet-less; and (2) their stable lifespans are too brief for advanced life ...
Rocky planetesimals as the origin of metals in DZ stars
... where hydrogen is detected or inferred (Dufour et al. 2007) versus height above the Galactic mid-plane and tangential speed. No obvious pattern is seen, although there may be a higher density of DZA stars near the Galactic disc and perhaps also towards more modest speeds, but the former may be an ob ...
... where hydrogen is detected or inferred (Dufour et al. 2007) versus height above the Galactic mid-plane and tangential speed. No obvious pattern is seen, although there may be a higher density of DZA stars near the Galactic disc and perhaps also towards more modest speeds, but the former may be an ob ...
Stellar evolution – Part III of III - Inside Mines
... • The Iron core is likely more massive than the Chandrasekhar limit (1.4 M☉). • Therefore the electron pressure cannot balance the gravitational collapse, which occurs extremely quickly. Within 1/10th of a second, the collapse causes temperature to soar to 5x109 K! • In the core, the trapped g-rays ...
... • The Iron core is likely more massive than the Chandrasekhar limit (1.4 M☉). • Therefore the electron pressure cannot balance the gravitational collapse, which occurs extremely quickly. Within 1/10th of a second, the collapse causes temperature to soar to 5x109 K! • In the core, the trapped g-rays ...
The white dwarf population within 40 pc of the Sun
... decades now that the evolution of white dwarfs is determined by a simple gravothermal process. However, although the basic picture of white dwarf evolution has remained unchanged for some time, we now have very reliable and accurate evolutionary tracks, which take into account all the relevant physi ...
... decades now that the evolution of white dwarfs is determined by a simple gravothermal process. However, although the basic picture of white dwarf evolution has remained unchanged for some time, we now have very reliable and accurate evolutionary tracks, which take into account all the relevant physi ...
The Milky Way - The Independent School
... As you begin studying galaxies, you will discover they are classified into different types, and that will lead you to insights into how galaxies form and evolve. In the next chapter, you will discover that some galaxies are violently active, and that will give you more clues to the evolution of gala ...
... As you begin studying galaxies, you will discover they are classified into different types, and that will lead you to insights into how galaxies form and evolve. In the next chapter, you will discover that some galaxies are violently active, and that will give you more clues to the evolution of gala ...
File - Mr. Catt`s Class
... relatively slow speed, which can be detected only by its gravitational interactions; it appears to be quite abundant throughout the universe. ...
... relatively slow speed, which can be detected only by its gravitational interactions; it appears to be quite abundant throughout the universe. ...
Understanding the Astrophysics of Galaxy Evolution: the role of
... correlated with dark matter halo mass and so the best link to the underlying cosmological model. A survey must be large (∼ few ×105 galaxies) in order to disentangle covariances in the physical properties of galaxies. One reason it is so difficult to understand how galaxies form is because almost al ...
... correlated with dark matter halo mass and so the best link to the underlying cosmological model. A survey must be large (∼ few ×105 galaxies) in order to disentangle covariances in the physical properties of galaxies. One reason it is so difficult to understand how galaxies form is because almost al ...
Joint formation of QSOs and spheroids: QSOs as clocks of star
... Direct and indirect observational evidence leads to the conclusion that high-redshift QSOs did shine in the core of early-type protogalaxies during their main episode of star formation. Exploiting this fact, we derive the rate of formation of this kind of stellar system at high redshift by using the ...
... Direct and indirect observational evidence leads to the conclusion that high-redshift QSOs did shine in the core of early-type protogalaxies during their main episode of star formation. Exploiting this fact, we derive the rate of formation of this kind of stellar system at high redshift by using the ...
THE N/O RATIO IN EARLY B-TYPE MAIN SEQUENCE STARS AS
... logC , logN , and logO for MS B-stars found in Ref. 14, together with recent estimates of the abundances of C, N, and O for the sun [15,16]. The latter were obtained using nonstationary hydrodynamic 3D models of the solar atmosphere. We note that the elemental abundances here and in the ...
... logC , logN , and logO for MS B-stars found in Ref. 14, together with recent estimates of the abundances of C, N, and O for the sun [15,16]. The latter were obtained using nonstationary hydrodynamic 3D models of the solar atmosphere. We note that the elemental abundances here and in the ...
Astronomy Astrophysics
... disk field is subsequently divided into 152 tiles, while the bulge field contains 196 tiles (Fig. 1). The data reduction was carried out in the canonical manner associated with infrared imaging, and details of the procedure are described by Irwin et al. (2004). In Borissova et al. (2011) we searched ...
... disk field is subsequently divided into 152 tiles, while the bulge field contains 196 tiles (Fig. 1). The data reduction was carried out in the canonical manner associated with infrared imaging, and details of the procedure are described by Irwin et al. (2004). In Borissova et al. (2011) we searched ...
The evolution of the Sun`s birth cluster and the search for the solar
... The Sun’s birth cluster will undergo all the disruptive processes described above and thus dissolve, leading to the spreading out of its stars over the Galactic disk. The subsequent distribution of the solar siblings was studied by Portegies Zwart (2009), who evolved the Sun’s birth cluster in an ax ...
... The Sun’s birth cluster will undergo all the disruptive processes described above and thus dissolve, leading to the spreading out of its stars over the Galactic disk. The subsequent distribution of the solar siblings was studied by Portegies Zwart (2009), who evolved the Sun’s birth cluster in an ax ...
Meteor Shower Observations
... Just as sporadic meteors tend to be more numerous in the predawn hours, so do shower meteors. A few meteoroid swarms, however, catch Earth from behind. Most notably the Arietid Meteor shower catches Earth from behind in June of each year. This results in evening meteors rather day predawn meteors. T ...
... Just as sporadic meteors tend to be more numerous in the predawn hours, so do shower meteors. A few meteoroid swarms, however, catch Earth from behind. Most notably the Arietid Meteor shower catches Earth from behind in June of each year. This results in evening meteors rather day predawn meteors. T ...
Unlocking the secrets of stellar haloes using combined star counts
... haloes can also be studied through surface photometry, i.e. observations of the integrated light from large numbers of unresolved stars within each system. Both techniques have their strong sides as well as shortcomings. Star counts can trace structures much further out into the halo, but this metho ...
... haloes can also be studied through surface photometry, i.e. observations of the integrated light from large numbers of unresolved stars within each system. Both techniques have their strong sides as well as shortcomings. Star counts can trace structures much further out into the halo, but this metho ...
High precision effective temperatures for 181 F-
... between A0 and K3 by using IRFM and achieved an accuracy of 0.9%. DB98 derived Teff for 537 dwarfs and giants by the empirical method of surface brightness and Johnson broadband (V − K) color, the accuracy claimed is ±1%. Whenever 2 or 3 estimates were available for a given star, we averaged them wi ...
... between A0 and K3 by using IRFM and achieved an accuracy of 0.9%. DB98 derived Teff for 537 dwarfs and giants by the empirical method of surface brightness and Johnson broadband (V − K) color, the accuracy claimed is ±1%. Whenever 2 or 3 estimates were available for a given star, we averaged them wi ...
Ptolemy: on trial for fraud
... be disputed (Graßhoff 1990), but it still stood in HipparPtolemy’s star catalogue led Arab astronomers page of unchallenged in the 1970s. Then a geophysichus’ lost catas early as the 10th century to suspect that Ptolemy’s cist, Robert R Newton, charged that Ptolemy, alogue came to Ptolemy had taken ...
... be disputed (Graßhoff 1990), but it still stood in HipparPtolemy’s star catalogue led Arab astronomers page of unchallenged in the 1970s. Then a geophysichus’ lost catas early as the 10th century to suspect that Ptolemy’s cist, Robert R Newton, charged that Ptolemy, alogue came to Ptolemy had taken ...
On the Spiral Structure of the Milky Way Galaxy
... instability due to regular magnetic field directed along the arm. Observational indications for this assumption were recently found in the north-western fragment of the S4 spiral arm in the Andromeda galaxy, just the arm with regular wave-shaped magnetic field along it detected long ago [see 7, 8]. ...
... instability due to regular magnetic field directed along the arm. Observational indications for this assumption were recently found in the north-western fragment of the S4 spiral arm in the Andromeda galaxy, just the arm with regular wave-shaped magnetic field along it detected long ago [see 7, 8]. ...
Galaxy Evolution
... times brighter than stars like the Sun, their total luminosity will approximately equal that of 2 × 1010 of these. Thus, during the star formation activity the galaxy increases its luminosity by ∼ 20%. Its colors also become bluer, because the radiation emitted by massive stars is very rich of light ...
... times brighter than stars like the Sun, their total luminosity will approximately equal that of 2 × 1010 of these. Thus, during the star formation activity the galaxy increases its luminosity by ∼ 20%. Its colors also become bluer, because the radiation emitted by massive stars is very rich of light ...
Brightest Stars : Discovering the Universe Through the Sky`s Most
... under skies significantly degraded by human-made light pollution. In such a world, it is the brightest stars that everybody can see, even people who have only their unaided eyes to use. Are all the major kinds of stars represented by the twenty-one brightest, the stars of the so-called 1st magnitude ...
... under skies significantly degraded by human-made light pollution. In such a world, it is the brightest stars that everybody can see, even people who have only their unaided eyes to use. Are all the major kinds of stars represented by the twenty-one brightest, the stars of the so-called 1st magnitude ...
Published in Contemp. Phys. 51, 464-465 (2010).
... over the next ∼60,000 years when it reaches its closest distance of ∼8 light years. Then ...
... over the next ∼60,000 years when it reaches its closest distance of ∼8 light years. Then ...
Perseus (constellation)
Perseus, named after the Greek mythological hero Perseus, is a constellation in the northern sky. It was one of 48 listed by the 2nd-century astronomer Ptolemy and among the 88 modern constellations defined by the International Astronomical Union (IAU). It is located in the northern celestial hemisphere near several other constellations named after legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west.The galactic plane of the Milky Way passes through Perseus but is mostly obscured by molecular clouds. The constellation's brightest star is the yellow-white supergiant Alpha Persei (also called Mirfak), which shines at magnitude 1.79. It and many of the surrounding stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol (Beta Persei), linked with ominous legends because of its variability, which is noticeable to the naked eye. Rather than being an intrinsically variable star, it is an eclipsing binary. Other notable star systems in Perseus include X Persei, a binary system containing a neutron star, and GK Persei, a nova that peaked at magnitude 0.2 in 1901. The Double Cluster, comprising two open clusters quite near each other in the sky, was known to the ancient Chinese. The constellation gives its name to the Perseus Cluster (Abell 426), a massive galaxy cluster located 250 million light-years from Earth. It hosts the radiant of the annual Perseids meteor shower—one of the most prominent meteor showers in the sky.