Lecture 14
... Alternative unit of distance “1 Light Year is the distance traveled by light in one year.” Relation to other units: 1 light year (ly) is equivalent to 0.31 pc 63,270 AU ...
... Alternative unit of distance “1 Light Year is the distance traveled by light in one year.” Relation to other units: 1 light year (ly) is equivalent to 0.31 pc 63,270 AU ...
Proficiency Step #5--
... and well-established set of “different” constellations. Many of the stars have Arabic names—a testament to the advanced astronomical “science” practiced by middle-eastern “astronomers” of centuries past. This proficiency step will deal primarily with constellations of the northern hemisphere since i ...
... and well-established set of “different” constellations. Many of the stars have Arabic names—a testament to the advanced astronomical “science” practiced by middle-eastern “astronomers” of centuries past. This proficiency step will deal primarily with constellations of the northern hemisphere since i ...
Searching for RR Lyrae Stars in M15
... constantly switching between ionization levels in helium. The abundance of helium is also believed to be important in determining the course of evolution and pulsation properties of an RR Lyrae star. Since a RR Lyrae star is a relatively low-mass star, nucleosynthesis of several amounts of elements ...
... constantly switching between ionization levels in helium. The abundance of helium is also believed to be important in determining the course of evolution and pulsation properties of an RR Lyrae star. Since a RR Lyrae star is a relatively low-mass star, nucleosynthesis of several amounts of elements ...
Hidden57_rf
... Nonetheless, until the mid-20th century our knowledge of the Universe was limited almost entirely to the narrow band of light that could penetrate the Earth’s atmosphere and was visible to our eyes or to sensitive photographic plates loaded at the focus of increasingly large telescopes. With these r ...
... Nonetheless, until the mid-20th century our knowledge of the Universe was limited almost entirely to the narrow band of light that could penetrate the Earth’s atmosphere and was visible to our eyes or to sensitive photographic plates loaded at the focus of increasingly large telescopes. With these r ...
The Current Status of Galaxy Formation
... where α = e2 /(h̄c) and αg = Gm2p /e2 are the electromagnetic and gravitational fine structure constants. For a cooling function Λ(T ) ∝ T β , over the relevant temperature range (105 − 107 K), one can take β ≈ −1/2 for a low metallicity plasma (Gnat & Sternberg, 2007). The result is that one finds ...
... where α = e2 /(h̄c) and αg = Gm2p /e2 are the electromagnetic and gravitational fine structure constants. For a cooling function Λ(T ) ∝ T β , over the relevant temperature range (105 − 107 K), one can take β ≈ −1/2 for a low metallicity plasma (Gnat & Sternberg, 2007). The result is that one finds ...
Main-Sequence Stars and the Sun
... Lines from other ions and neutral atoms. In atoms with three or more electrons, each electron experiences attraction by the positive nucleus, and repulsion from the other electrons. When the atom becomes ionized, the remaining electrons are held more tightly, and the energy required for the excitati ...
... Lines from other ions and neutral atoms. In atoms with three or more electrons, each electron experiences attraction by the positive nucleus, and repulsion from the other electrons. When the atom becomes ionized, the remaining electrons are held more tightly, and the energy required for the excitati ...
Rotation Periods and Relative Ages of Solar-Type Stars
... Isochrones are theoretical plots of various-aged stars on axes of log Teff (effective temperature) and δMbol (bolometric luminosity). Also, Ca II H (396.8 nm) and K (383.4 nm) chromospheric emissions are empirically linked to ages (Soderblom et al. 1991). By fitting Strömgren uvby-Hβ photometry data ...
... Isochrones are theoretical plots of various-aged stars on axes of log Teff (effective temperature) and δMbol (bolometric luminosity). Also, Ca II H (396.8 nm) and K (383.4 nm) chromospheric emissions are empirically linked to ages (Soderblom et al. 1991). By fitting Strömgren uvby-Hβ photometry data ...
Physical structure of the local interstellar medium
... medium, observed by the Hubble Space Telescope, provide important information about the chemical abundance, ionization, temperature, kinematics, density, morphology, and turbulent structures of the local interstellar medium. Fortunately, nearly all observations of nearby stars contain useful local i ...
... medium, observed by the Hubble Space Telescope, provide important information about the chemical abundance, ionization, temperature, kinematics, density, morphology, and turbulent structures of the local interstellar medium. Fortunately, nearly all observations of nearby stars contain useful local i ...
Gamma-Ray Bursts: The Brightest Explosions in the Universe Arne
... (Introduction to the The ultra-luminous Universe: Gamma-Ray Bursts and Active Galactic Nuclei Session) ...
... (Introduction to the The ultra-luminous Universe: Gamma-Ray Bursts and Active Galactic Nuclei Session) ...
PHY104 - Introduction to Astrophysics
... experiment described earlier, but perform an experiment in which we reduce the intensity of the light so much that only one photon illuminates the plate with the slits at any one time. Now, let us put a special camera in place of the screen, that can detect each photon as it arrives at the screen. W ...
... experiment described earlier, but perform an experiment in which we reduce the intensity of the light so much that only one photon illuminates the plate with the slits at any one time. Now, let us put a special camera in place of the screen, that can detect each photon as it arrives at the screen. W ...
Stellar contents and star formation in the young open cluster Stock 8
... dynamical evolution, their mass function (MF) can be considered as the IMF. However, a recent study by Kroupa (2007) argues that even in the youngest clusters, it is difficult to trace the IMF, as clusters evolve rapidly and therefore eject a fraction of their members even at a very young age. There ...
... dynamical evolution, their mass function (MF) can be considered as the IMF. However, a recent study by Kroupa (2007) argues that even in the youngest clusters, it is difficult to trace the IMF, as clusters evolve rapidly and therefore eject a fraction of their members even at a very young age. There ...
A very massive runaway star from Cygnus OB2⋆
... Although the identication of BD+43 3654 as a likely runaway star dates back to van Buren & McCray (1988), no spectral classication is available in that work. Subsequent papers by van Buren et al. (1995) and Noriega-Crespo et al. (1997) refer to the star as a unspecied B-type but do not report ded ...
... Although the identication of BD+43 3654 as a likely runaway star dates back to van Buren & McCray (1988), no spectral classication is available in that work. Subsequent papers by van Buren et al. (1995) and Noriega-Crespo et al. (1997) refer to the star as a unspecied B-type but do not report ded ...
S282_2 Introduction to active galaxies
... Why would the atoms be in motion? An obvious reason is that they are ‘hot’. Atoms in a hot gas, for example, will be moving randomly with a range of speeds related to the temperature of the gas. For a gas of atoms of mass m at a temperature T, the velocity dispersion is given by ...
... Why would the atoms be in motion? An obvious reason is that they are ‘hot’. Atoms in a hot gas, for example, will be moving randomly with a range of speeds related to the temperature of the gas. For a gas of atoms of mass m at a temperature T, the velocity dispersion is given by ...
The Spectra ot Novae
... higher excitation at light minima and lowest at the maxima. The few available measures of energy distribution in the continuum yield highest colour temperatures at the minima (BEILEKE and HACHENBERG, 1935). These correlations become understandable if we regard the maxima as secondary outbursts, in w ...
... higher excitation at light minima and lowest at the maxima. The few available measures of energy distribution in the continuum yield highest colour temperatures at the minima (BEILEKE and HACHENBERG, 1935). These correlations become understandable if we regard the maxima as secondary outbursts, in w ...
Large-eddy simulations of isolated disc galaxies with thermal and
... Miura et al. 2012) before they are destroyed by supernova explosions (SNe) and stellar winds. Actively star-forming molecular clouds are known to be strongly supersonically turbulent with typical velocity dispersions around 10 km s−1 (e.g. Leroy et al. 2008; Stilp et al. 2013), or larger in interact ...
... Miura et al. 2012) before they are destroyed by supernova explosions (SNe) and stellar winds. Actively star-forming molecular clouds are known to be strongly supersonically turbulent with typical velocity dispersions around 10 km s−1 (e.g. Leroy et al. 2008; Stilp et al. 2013), or larger in interact ...
The extreme ultraviolet and X-ray Sun in Time: High
... on the MS, giving observational constraints on the percentiles at these ages (with 230, 134, and 36 stars, respectively at the considered ages). We use additional constraints for pre-mainsequence (PMS) rotation from the ≈2 Myr cluster NGC 6530 (28 stars; Henderson & Stassun 2012) and the ≈12 Myr clu ...
... on the MS, giving observational constraints on the percentiles at these ages (with 230, 134, and 36 stars, respectively at the considered ages). We use additional constraints for pre-mainsequence (PMS) rotation from the ≈2 Myr cluster NGC 6530 (28 stars; Henderson & Stassun 2012) and the ≈12 Myr clu ...
Galaxies
... Astronomers therefore prefer to quote redshifts rather than distances The look-back time is the time when light was emitted from a distant object For very distant objects it is less than the redshift would indicate, as the object has receded in the meantime Astronomy 1-2 ...
... Astronomers therefore prefer to quote redshifts rather than distances The look-back time is the time when light was emitted from a distant object For very distant objects it is less than the redshift would indicate, as the object has receded in the meantime Astronomy 1-2 ...
The Life of a Star
... other half is used to raise Ei (star is heated). Another interpretation is that since the star must radiate (because it is hotter than the universe at large), at the same time it heats up and shrinks (although parts { the envelope { might well and does expand, nevertheless). 2 ...
... other half is used to raise Ei (star is heated). Another interpretation is that since the star must radiate (because it is hotter than the universe at large), at the same time it heats up and shrinks (although parts { the envelope { might well and does expand, nevertheless). 2 ...
Test 4 Review Clicker Questions
... b) small irregular galaxies that orbit the Milky Way. c) large molecular clouds in the disk of our Galaxy. d) the brightest ionized hydrogen regions in our Galaxy. e) spiral nebulae originally discovered ...
... b) small irregular galaxies that orbit the Milky Way. c) large molecular clouds in the disk of our Galaxy. d) the brightest ionized hydrogen regions in our Galaxy. e) spiral nebulae originally discovered ...
Article PDF - IOPscience
... _ to primordial helium. Variations in helium and metal due content result in deviations from this value of less than 10%. This is a very small e†ect compared to that of other gas phases. Ionized gas in H II regions and hotter plasma is of negligible mass in spiral galaxies, but not so molecular gas. ...
... _ to primordial helium. Variations in helium and metal due content result in deviations from this value of less than 10%. This is a very small e†ect compared to that of other gas phases. Ionized gas in H II regions and hotter plasma is of negligible mass in spiral galaxies, but not so molecular gas. ...
AGN surveys to study galaxy evolution along cosmic times
... from the far-IR for the photodissociation and HII region lines, through the mid-IR for the AGN lines, to the near-IR for the coronal lines, ensure that we can observe these different tracers by minimising the effect of dust extinction. The rich rest-frame mid-IR spectra, that have been recently observ ...
... from the far-IR for the photodissociation and HII region lines, through the mid-IR for the AGN lines, to the near-IR for the coronal lines, ensure that we can observe these different tracers by minimising the effect of dust extinction. The rich rest-frame mid-IR spectra, that have been recently observ ...
WISE General Presentation - Georgia Southern University
... Infrared Light • In 1800 William Herschel discovered “invisible light” • It’s energy with all the same characteristics as visible light, but is not sensed by the human eye • The light Herschel discovered was just beyond the red part of the spectrum. So it was named “infrared” ...
... Infrared Light • In 1800 William Herschel discovered “invisible light” • It’s energy with all the same characteristics as visible light, but is not sensed by the human eye • The light Herschel discovered was just beyond the red part of the spectrum. So it was named “infrared” ...
JHK standard stars for large telescopes: the UKIRT Fundamental
... from Landolt’s (1983) equatorial UBVRI standards and the compilation of potential Hubble Space Telescope (HST ) reference sources by Turnshek et al. (1990), supplemented by additional main-sequence objects with solar-like colours from the old open cluster M67 (Eggen & Sandage 1964) and subgiants fro ...
... from Landolt’s (1983) equatorial UBVRI standards and the compilation of potential Hubble Space Telescope (HST ) reference sources by Turnshek et al. (1990), supplemented by additional main-sequence objects with solar-like colours from the old open cluster M67 (Eggen & Sandage 1964) and subgiants fro ...
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived blue stars forged in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. The first known H II region was the Orion Nebula, which was discovered in 1610 by Nicolas-Claude Fabri de Peiresc.H II regions are named for the large amount of ionised atomic hydrogen they contain, referred to as H II, pronounced H-two by astronomers (an H I region being neutral atomic hydrogen, and H2 being molecular hydrogen). Such regions have extremely diverse shapes, because the distribution of the stars and gas inside them is irregular. They often appear clumpy and filamentary, sometimes showing bizarre shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster of birthed stars such as the Pleiades.H II regions can be seen to considerable distances in the universe, and the study of extragalactic H II regions is important in determining the distance and chemical composition of other galaxies. Spiral and irregular galaxies contain many H II regions, while elliptical galaxies are almost devoid of them. In the spiral galaxies, including the Milky Way, H II regions are concentrated in the spiral arms, while in the irregular galaxies they are distributed chaotically. Some galaxies contain huge H II regions, which may contain tens of thousands of stars. Examples include the 30 Doradus region in the Large Magellanic Cloud and NGC 604 in the Triangulum Galaxy.