Observation of Circumstellar Disks: Dust and Gas Components
... Observations show that the mass accretion rate (and the mass ejection rate) decreases from the protostars to the Class III phases by several orders of magnitude (Hartmann et al., 1998; Boss, 2004). Despite the uncertainties resulting from the various observational methods and tracers used for measur ...
... Observations show that the mass accretion rate (and the mass ejection rate) decreases from the protostars to the Class III phases by several orders of magnitude (Hartmann et al., 1998; Boss, 2004). Despite the uncertainties resulting from the various observational methods and tracers used for measur ...
The Formation and Early Evolution of Young Massive Clusters
... Comparing the demographics of young massive cluster (YMC) progenitor clouds and YMCs across the Galaxy shows that gas in the Galactic Center can accumulate to a high enough density that molecular clouds already satisfy the criteria used to define YMCs, without forming stars. In this case formation c ...
... Comparing the demographics of young massive cluster (YMC) progenitor clouds and YMCs across the Galaxy shows that gas in the Galactic Center can accumulate to a high enough density that molecular clouds already satisfy the criteria used to define YMCs, without forming stars. In this case formation c ...
Galaxies and Active Galaxies
... • In elliptical galaxies, the gravity of the visible matter is not strong enough to accelerate the stars as much as they are. • Something else must be adding to the gravity of the galaxies without shining. March 7, 2006 ...
... • In elliptical galaxies, the gravity of the visible matter is not strong enough to accelerate the stars as much as they are. • Something else must be adding to the gravity of the galaxies without shining. March 7, 2006 ...
150 Million ly - Northern Michigan University
... • Quasar Luminosities range from 1038 to 1042 W • Milky Way’s Luminosity is 1037 W • Radiation from Galaxies is mostly a mixture of normal star light, hence blackbody radiation usually from star temps of 2500 to 50,000 K • Quasars have radiation stronger in the x-rays and gamma rays implying temps o ...
... • Quasar Luminosities range from 1038 to 1042 W • Milky Way’s Luminosity is 1037 W • Radiation from Galaxies is mostly a mixture of normal star light, hence blackbody radiation usually from star temps of 2500 to 50,000 K • Quasars have radiation stronger in the x-rays and gamma rays implying temps o ...
University of Groningen Photo-ionization studies of nebulae
... Abstract — A parameter study of the spectral evolution of a typical post-AGB star, with particular emphasis on the evolution of the infrared colors, is presented. The models are based on the latest evolutionary tracks for hydrogen burning post-AGB stars. For such tracks the evolutionary rate is very ...
... Abstract — A parameter study of the spectral evolution of a typical post-AGB star, with particular emphasis on the evolution of the infrared colors, is presented. The models are based on the latest evolutionary tracks for hydrogen burning post-AGB stars. For such tracks the evolutionary rate is very ...
STEREO observations of long period variables
... In order to extract the sample, the first step was to select those stars showing the largest difference in the weighted mean magnitude observed by the two satellites. We anticipated that the majority of these would be due to systematic effects, mostly relating to flat-fielding near the edges of the ...
... In order to extract the sample, the first step was to select those stars showing the largest difference in the weighted mean magnitude observed by the two satellites. We anticipated that the majority of these would be due to systematic effects, mostly relating to flat-fielding near the edges of the ...
The VLT LEGA-C Spectroscopic Survey: The Physics of Galaxies at
... typically well over 5 Gyr and it is difficult to resolve star formation histories from integrated spectra. Now LEGA-C is obtaining spectra of similar quality for ∼3200 K-band selected galaxies in the redshift range 0.6 < z < 1.0, at a look-back time of 6 − 8 Gyr. LEGA-C is a 4-year, 128-night Public ...
... typically well over 5 Gyr and it is difficult to resolve star formation histories from integrated spectra. Now LEGA-C is obtaining spectra of similar quality for ∼3200 K-band selected galaxies in the redshift range 0.6 < z < 1.0, at a look-back time of 6 − 8 Gyr. LEGA-C is a 4-year, 128-night Public ...
The effect of starspots on the radii of low-mass
... of (1 − β)−N compared to unspotted stars of the same luminosity, where β is the equivalent covering fraction of dark starspots and N 0.45 ± 0.05. This is a much stronger inflation than predicted by Spruit & Weiss for main-sequence stars with the same β, where N ∼ 0.2–0.3. These models have been co ...
... of (1 − β)−N compared to unspotted stars of the same luminosity, where β is the equivalent covering fraction of dark starspots and N 0.45 ± 0.05. This is a much stronger inflation than predicted by Spruit & Weiss for main-sequence stars with the same β, where N ∼ 0.2–0.3. These models have been co ...
High Resolution Chandra Spectroscopy of Gamma Cassiopeia (B0
... thermal spectrum of the X-rays. However, while the star is now established as part of a binary system (see Harmanec et al. 2000; Miroshnichenko, Bjorkman, & Krugov 2002), the wide separation (P ≈ 204 days, with low to moderate eccentricity) makes it difficult to understand the high Lx if the compani ...
... thermal spectrum of the X-rays. However, while the star is now established as part of a binary system (see Harmanec et al. 2000; Miroshnichenko, Bjorkman, & Krugov 2002), the wide separation (P ≈ 204 days, with low to moderate eccentricity) makes it difficult to understand the high Lx if the compani ...
Revised physical elements of the astrophysically important O9.5+O9
... respect since the internal structure of the stars can also be tested. Aims. Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornerstones of critical tests of stellar evolutionary theory for massive stars. Neverthele ...
... respect since the internal structure of the stars can also be tested. Aims. Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornerstones of critical tests of stellar evolutionary theory for massive stars. Neverthele ...
The Massive Star Population of Cygnus OB2
... light from a binary companion, which in involved systems is cooler than the primary, will make the primary appear cooler and more luminous, which could potentially lead to the star being diagnosed as more evolved and higher-mass. The binary population of massive stars in Cyg OB2 has recently been we ...
... light from a binary companion, which in involved systems is cooler than the primary, will make the primary appear cooler and more luminous, which could potentially lead to the star being diagnosed as more evolved and higher-mass. The binary population of massive stars in Cyg OB2 has recently been we ...
SN 2011dh and the progenitors of Type IIb supernovae Mattias Ergon
... Core-collapse supernovae (SNe) are the observed events following the collapse of the core of evolved massive stars. The gravitational energy released creates a powerful shock that disrupts the star and ejects the heated material into the surrounding circumstellar medium. The observed properties depe ...
... Core-collapse supernovae (SNe) are the observed events following the collapse of the core of evolved massive stars. The gravitational energy released creates a powerful shock that disrupts the star and ejects the heated material into the surrounding circumstellar medium. The observed properties depe ...
Chapter 16
... • Disk systems with no evidence of arms • Thought by Hubble to be intermediate between S and E galaxies, several theories now vie to explain their appearance (e.g., an S0 lacks gas to produce O and B stars to light up any spiral arms that may exist) ...
... • Disk systems with no evidence of arms • Thought by Hubble to be intermediate between S and E galaxies, several theories now vie to explain their appearance (e.g., an S0 lacks gas to produce O and B stars to light up any spiral arms that may exist) ...
Neutron stars: the densest state of condensed matter
... Search for a neutron star in the Crab nebula The Crab nebula was observed during a lunar occultation on 7 July 1964. The size of the x-ray source was estimated as 1 light-year∼ 1013 km (size of the nebula 11 ly). This was much larger than the typical size of a neutron star (10-20 km). In 1965 Antho ...
... Search for a neutron star in the Crab nebula The Crab nebula was observed during a lunar occultation on 7 July 1964. The size of the x-ray source was estimated as 1 light-year∼ 1013 km (size of the nebula 11 ly). This was much larger than the typical size of a neutron star (10-20 km). In 1965 Antho ...
Microlensing Events by Proxima Centauri in 2014 and 2016
... rapidly to the right (west-northwest). A second green circle marks the pair of background stars. Although it might appear from a cursory inspection of the ground-based images in Figure 1 that close passages must occur frequently, passages as close as ∼1′′. 5 are actually rare. Moreover, Proxima is e ...
... rapidly to the right (west-northwest). A second green circle marks the pair of background stars. Although it might appear from a cursory inspection of the ground-based images in Figure 1 that close passages must occur frequently, passages as close as ∼1′′. 5 are actually rare. Moreover, Proxima is e ...
Sources of Stellar Energy and the Theory of the Internal Constitution
... inconsistency in the stellar energy problem arises for the reason that the main principles of interaction between matter and radiant energy need to be developed further. Much of the phenomena and empirical correlations discovered by observational astrophysics are linked to the problem of the origin ...
... inconsistency in the stellar energy problem arises for the reason that the main principles of interaction between matter and radiant energy need to be developed further. Much of the phenomena and empirical correlations discovered by observational astrophysics are linked to the problem of the origin ...
Probing the Impact of Stellar Duplicity on Planet Occurrence with
... the formation mechanism, whereas Boss (2006) claims that giant planets are able to form in binaries with periastrons as small as 25 AU. Other studies on the subject concluded that planetesimal accretion is perturbed but remains possible in various binary systems closer than 50 AU (Thébault et al. 2 ...
... the formation mechanism, whereas Boss (2006) claims that giant planets are able to form in binaries with periastrons as small as 25 AU. Other studies on the subject concluded that planetesimal accretion is perturbed but remains possible in various binary systems closer than 50 AU (Thébault et al. 2 ...
Probing the Impact of Stellar Duplicity on Planet Occurrence with
... the formation mechanism, whereas Boss (2006) claims that giant planets are able to form in binaries with periastrons as small as 25 AU. Other studies on the subject concluded that planetesimal accretion is perturbed but remains possible in various binary systems closer than 50 AU (Thébault et al. 2 ...
... the formation mechanism, whereas Boss (2006) claims that giant planets are able to form in binaries with periastrons as small as 25 AU. Other studies on the subject concluded that planetesimal accretion is perturbed but remains possible in various binary systems closer than 50 AU (Thébault et al. 2 ...
FY1995 Q1 Oct-Dec NO.. - National Optical Astronomy Observatory
... elements compared to hydrogen is constant from star to star. This suggests that the cluster formation was rapid, occurring in less than the characteristic time for heavy metal enrichment by Type II supernovae. (In fact, the energetics of these supernovae may have been responsible for clearing the ga ...
... elements compared to hydrogen is constant from star to star. This suggests that the cluster formation was rapid, occurring in less than the characteristic time for heavy metal enrichment by Type II supernovae. (In fact, the energetics of these supernovae may have been responsible for clearing the ga ...
Gaia - STScI
... Bright stars will give rigid tie between LSST and Gaia. Faint stars (down to 26th and beyond) will deliver the new science. Gaia has 2 fields of regard in same focal plane. At some star density, confusion will degrade accuracy. LSST has bigger images but a single field of regard. LSST can do differe ...
... Bright stars will give rigid tie between LSST and Gaia. Faint stars (down to 26th and beyond) will deliver the new science. Gaia has 2 fields of regard in same focal plane. At some star density, confusion will degrade accuracy. LSST has bigger images but a single field of regard. LSST can do differe ...
ON THE ORIGIN OF THE SALPETER SLOPE FOR THE INITIAL
... we are interested only in the upper IMF, however, scale-free cloud fragmentation plausibly dominates in this regime. But we note that our model contrasts with those in which the IMF slope results from physics that causes fragmentation into a steeper core mass distribution (e.g., Padoan & Nordlund 20 ...
... we are interested only in the upper IMF, however, scale-free cloud fragmentation plausibly dominates in this regime. But we note that our model contrasts with those in which the IMF slope results from physics that causes fragmentation into a steeper core mass distribution (e.g., Padoan & Nordlund 20 ...
Near-uniform internal rotation of the main sequence γ Doradus
... 2013; Cantiello et al. 2014). All of this indicates that some physics is missing in models of angular momentum transport in stellar interiors. Kepler observations show that the problem already exists on the main sequence. Two asteroseismic studies of rotation in main-sequence A stars have yielded un ...
... 2013; Cantiello et al. 2014). All of this indicates that some physics is missing in models of angular momentum transport in stellar interiors. Kepler observations show that the problem already exists on the main sequence. Two asteroseismic studies of rotation in main-sequence A stars have yielded un ...
A comparison of the s- and r-process element evolution in local
... Results. We predict that the [s-r/Fe] ratios in dSphs are generally different than the corresponding ratios in the Milky Way, at the same [Fe/H] values. This is interpreted as a consequence of the time-delay model coupled with different star formation histories. In particular, the star-formation is le ...
... Results. We predict that the [s-r/Fe] ratios in dSphs are generally different than the corresponding ratios in the Milky Way, at the same [Fe/H] values. This is interpreted as a consequence of the time-delay model coupled with different star formation histories. In particular, the star-formation is le ...
Challenges in Planet Formation
... the contrast in gas surface density Σdead /ΣMRI is proportional to αMRI /αdead (e.g. Martin et al., 2012). In 2D models (r, z), however, there is no simple proportionality, because the gas can flow near the surface of the disk (Bitsch et al., 2014b). Recent studies have shown that the MRI is likely ...
... the contrast in gas surface density Σdead /ΣMRI is proportional to αMRI /αdead (e.g. Martin et al., 2012). In 2D models (r, z), however, there is no simple proportionality, because the gas can flow near the surface of the disk (Bitsch et al., 2014b). Recent studies have shown that the MRI is likely ...
Finding high-redshift dark stars with the James Webb Space
... the dark matter halo (density and velocity structure). In particular, these dependencies are rather degenerate; the impact of a short equilibrium timescale can for example be mimicked by a denser dark matter halo. This picture is further complicated by the fact that accretion may also continue to so ...
... the dark matter halo (density and velocity structure). In particular, these dependencies are rather degenerate; the impact of a short equilibrium timescale can for example be mimicked by a denser dark matter halo. This picture is further complicated by the fact that accretion may also continue to so ...
Planetary nebula
A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word ""nebula"" is Latin for mist or cloud and the term ""planetary nebula"" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, appearing as a bright coloured planetary nebula at several discrete visible wavelengths.Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances.In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.