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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 ...
Ch17_lecture
... • Beyond the Milky Way are billions of other galaxies • Some galaxies are spiral like the Milky Way while others are egg-shaped or completely irregular in appearance • Besides shape, galaxies vary greatly in the star, gas, and dust content and some are more “active” than others • Galaxies tend to cl ...
... • Beyond the Milky Way are billions of other galaxies • Some galaxies are spiral like the Milky Way while others are egg-shaped or completely irregular in appearance • Besides shape, galaxies vary greatly in the star, gas, and dust content and some are more “active” than others • Galaxies tend to cl ...
A Second Shell in the Fornax dSph Galaxy
... 1998) and proper motion measurements indicate it is on a polar orbit with a small eccentricity (e = 0.27) and is currently at perigalacticon (Dinescu et al. 2004). Moreover, Fornax contains a mass larger than all the other Galactic dSphs combined (excluding Sagittarius), which further precludes the ...
... 1998) and proper motion measurements indicate it is on a polar orbit with a small eccentricity (e = 0.27) and is currently at perigalacticon (Dinescu et al. 2004). Moreover, Fornax contains a mass larger than all the other Galactic dSphs combined (excluding Sagittarius), which further precludes the ...
chemical compositions of rv tauri stars and related objects
... & Lambert (1990) noted the resemblance of the observed abundance pattern with that of the interstellar gas in which the metals are depleted through fractionation in the interstellar grains. Bond (1991) suggested that the extreme metal deficiency of HR 4049 like objects could be caused by the selecti ...
... & Lambert (1990) noted the resemblance of the observed abundance pattern with that of the interstellar gas in which the metals are depleted through fractionation in the interstellar grains. Bond (1991) suggested that the extreme metal deficiency of HR 4049 like objects could be caused by the selecti ...
banff04
... higher accretion rates and mass outflow rates (e.g. Pudritz 1985). • Disk photo-evaporation could create a low-velocity disk outflow (e.g. Hollenbach et al. 1994; Yorke & Welz 1996). • Radiation pressure higher for dusty gas (e.g. Wolfire & Cassinelli 1987), may contribute to flow acceleration and a ...
... higher accretion rates and mass outflow rates (e.g. Pudritz 1985). • Disk photo-evaporation could create a low-velocity disk outflow (e.g. Hollenbach et al. 1994; Yorke & Welz 1996). • Radiation pressure higher for dusty gas (e.g. Wolfire & Cassinelli 1987), may contribute to flow acceleration and a ...
Astronomy 101-lecture 8 Astrochemistry
... –What is Astrochemistry? –Chemical Reactions in Space –How to Observe Molecules ...
... –What is Astrochemistry? –Chemical Reactions in Space –How to Observe Molecules ...
THREE Li-RICH K GIANTS - Indian Institute of Astrophysics
... Here we report results from the first high-resolution spectroscopic analyses of three Li-rich candidates taken from de la Reza et al. (1997), who proposed the stars to be probably Li-rich from the observation that the strength of the Li i k6707 doublet was equal to or greater than the strength of th ...
... Here we report results from the first high-resolution spectroscopic analyses of three Li-rich candidates taken from de la Reza et al. (1997), who proposed the stars to be probably Li-rich from the observation that the strength of the Li i k6707 doublet was equal to or greater than the strength of th ...
The rebirth of Supernova 1987A a study of the ejecta-ring collision
... & Zwicky. They searched for SNe by comparing images of galaxies taken at two different occasions. By comparing the older image with the newer, any bright spot, that was present in the newer but not in the older image, was considered to be a SN candidate. Spectra showed two distinct types of SNe. The ...
... & Zwicky. They searched for SNe by comparing images of galaxies taken at two different occasions. By comparing the older image with the newer, any bright spot, that was present in the newer but not in the older image, was considered to be a SN candidate. Spectra showed two distinct types of SNe. The ...
Hypervelocity Stars and the Galactic Center
... A massive black hole (MBH) will inevitably unbind stars from the Galaxy. Hills (1988) coined the term “hypervelocity star” (hereafter HVS) to describe a star ejected at ∼1000 km s−1 from a three-body interaction with a MBH. HVSs are a general consequence of MBHs in any galaxy (e.g. Sherwin et al. 20 ...
... A massive black hole (MBH) will inevitably unbind stars from the Galaxy. Hills (1988) coined the term “hypervelocity star” (hereafter HVS) to describe a star ejected at ∼1000 km s−1 from a three-body interaction with a MBH. HVSs are a general consequence of MBHs in any galaxy (e.g. Sherwin et al. 20 ...
The role of tidal interactions in star formation
... 2001). Even in the context of standard accretion disc models, a binary companion may play an important role by limiting the growth in radius of the disc and thus preventing the accretion time from becoming too long (Calvet et al. 2000); in this case most of the angular momentum of the system must go ...
... 2001). Even in the context of standard accretion disc models, a binary companion may play an important role by limiting the growth in radius of the disc and thus preventing the accretion time from becoming too long (Calvet et al. 2000); in this case most of the angular momentum of the system must go ...
Observed Properties of Exoplanets: Masses, Orbits, and Metallicities
... of stars harboring giant planets with M < 13MJup within 5 AU is at least 88/1330 = 6.6%. This is no doubt a lower limit as planets between 3–5 AU are not efficiently detected due to the limited duration, 6–8 years, of our Doppler survey. The 12 stars with two or more planets imply an occurrence rate ...
... of stars harboring giant planets with M < 13MJup within 5 AU is at least 88/1330 = 6.6%. This is no doubt a lower limit as planets between 3–5 AU are not efficiently detected due to the limited duration, 6–8 years, of our Doppler survey. The 12 stars with two or more planets imply an occurrence rate ...
INFRARED DUST BUBBLES: PROBING THE DETAILED
... bubble morphological properties such as angular diameter, shell thickness, and eccentricity. Bubbles and/or H ii regions identified by MIR emission present a new and powerful tool to study the interaction of young, hot stars with their environment. Young stars impact the ambient interstellar medium ...
... bubble morphological properties such as angular diameter, shell thickness, and eccentricity. Bubbles and/or H ii regions identified by MIR emission present a new and powerful tool to study the interaction of young, hot stars with their environment. Young stars impact the ambient interstellar medium ...
SOME CONSTRAINTS ON GALAXY EVOLUTION IMPOSED BY
... removal) S (ellipticals) • 3 S (spirals), one would expect the population of metalrich globulars in ellipticals to be (on average) twice as large as that of the metalpoor primordial ones. What little information is presently available suggests that metal-rich and metal-poor clusters actually occur w ...
... removal) S (ellipticals) • 3 S (spirals), one would expect the population of metalrich globulars in ellipticals to be (on average) twice as large as that of the metalpoor primordial ones. What little information is presently available suggests that metal-rich and metal-poor clusters actually occur w ...
Star Formation and Dynamics in the Galactic Centre
... of stars, obtained by means of near-infrared (NIR) spectra of the stellar population in the central parsecs (e.g. McGinn et al. 1989; Sellgren et al. 1990; Haller et al. 1996). These early measurements indicated the presence of ∼ 3 × 106 M⊙ confined in ∼ 0.1 pc, corresponding to a minimum density of ...
... of stars, obtained by means of near-infrared (NIR) spectra of the stellar population in the central parsecs (e.g. McGinn et al. 1989; Sellgren et al. 1990; Haller et al. 1996). These early measurements indicated the presence of ∼ 3 × 106 M⊙ confined in ∼ 0.1 pc, corresponding to a minimum density of ...
Chemical abundances of metal-poor RR Lyrae stars in the Magellanic Clouds
... In galaxies that experienced star formation throughout cosmic history, the identification of purely old populations is difficult. For instance, the abundant red giants can cover an age range of more than ten Gyr. Thus one can either turn to globular clusters as easily identifiable and reliably age-d ...
... In galaxies that experienced star formation throughout cosmic history, the identification of purely old populations is difficult. For instance, the abundant red giants can cover an age range of more than ten Gyr. Thus one can either turn to globular clusters as easily identifiable and reliably age-d ...
THE DISRUPTION OF STELLAR CLUSTERS CONTAINING
... for a cluster to reach within the central parsec, it must either be very massive (>106 M ) or have formed near the GC (at <5 pc). They found that, in both cases, a very high central density (108 M pc3) is required and concluded that this scenario is implausible. Hansen & Milosavljević (2003) su ...
... for a cluster to reach within the central parsec, it must either be very massive (>106 M ) or have formed near the GC (at <5 pc). They found that, in both cases, a very high central density (108 M pc3) is required and concluded that this scenario is implausible. Hansen & Milosavljević (2003) su ...
LARGE-SCALE EXTENDED EMISSION AROUND THE HELIX
... This image showed some faint loops extending to r = 200 from the Helix’s center, superposed on a faint, azimuthally symmetric halo. This latter halo was removed by five iterations of a Lucy-Richardson deconvolution, which allowed a better look at the point-symmetric structures extending out from the ...
... This image showed some faint loops extending to r = 200 from the Helix’s center, superposed on a faint, azimuthally symmetric halo. This latter halo was removed by five iterations of a Lucy-Richardson deconvolution, which allowed a better look at the point-symmetric structures extending out from the ...
GOMOS data characterisation and error estimation
... Compared to the Sun, stars are point-like sources, and thus provide an excellent pointing information. The disadvantage compared to the solar occultation is the low signal-to-noise ratio. GOMOS is following about 180 different stars while they are descending behind the Earth limb. Since the stars di ...
... Compared to the Sun, stars are point-like sources, and thus provide an excellent pointing information. The disadvantage compared to the solar occultation is the low signal-to-noise ratio. GOMOS is following about 180 different stars while they are descending behind the Earth limb. Since the stars di ...
Giant planet and brown dwarf formation
... age of 3 Gyr (resp. 1 Gyr) BD’s with effective temperatures below 400 K (resp. ∼550-600 K) must be less massive than 0.012 M , i.e. below the D-burning limit for solar composition (Chabrier et al., 2000a). So far, the WISE survey has even discovered 1 field BD with Tef f . 350 K, reaching the tempe ...
... age of 3 Gyr (resp. 1 Gyr) BD’s with effective temperatures below 400 K (resp. ∼550-600 K) must be less massive than 0.012 M , i.e. below the D-burning limit for solar composition (Chabrier et al., 2000a). So far, the WISE survey has even discovered 1 field BD with Tef f . 350 K, reaching the tempe ...
Towards a deterministic model of planetary formation. III. Mass
... we do not include interaction from other major planets, formation of these Neptune-mass planets is beyond scope of the present paper. On the other hand, no gas giant planets has been found around GJ436. GJ436b is dynamically-isolated, so that its formation must be considered without help of other gi ...
... we do not include interaction from other major planets, formation of these Neptune-mass planets is beyond scope of the present paper. On the other hand, no gas giant planets has been found around GJ436. GJ436b is dynamically-isolated, so that its formation must be considered without help of other gi ...
Microlensing Events by Proxima Centauri in 2014 and 2016
... To refine the impact parameters and times of closest approach, we obtained Hubble Space Telescope (HST ) images of the field on 2012 October 1. Observations were taken with the UVIS channel of the Wide Field Camera 3 (WFC3) in the F475W, F555W, F606W, and F814W filters. Since the background stars ar ...
... To refine the impact parameters and times of closest approach, we obtained Hubble Space Telescope (HST ) images of the field on 2012 October 1. Observations were taken with the UVIS channel of the Wide Field Camera 3 (WFC3) in the F475W, F555W, F606W, and F814W filters. Since the background stars ar ...
Classical Oe Stars in the Field of the Small Magellanic Cloud
... shape the evolution of their host galaxies through strong stellar winds and radiative feedback, which shock heat and ionize the surrounding gas, injecting energy into the interstellar medium (ISM). Moreover, when massive stars end their lives as core-collapse supernovae, the shockwaves can trigger o ...
... shape the evolution of their host galaxies through strong stellar winds and radiative feedback, which shock heat and ionize the surrounding gas, injecting energy into the interstellar medium (ISM). Moreover, when massive stars end their lives as core-collapse supernovae, the shockwaves can trigger o ...
Title The molecular envelope around the red supergiant VY CMa
... diffuse and extended envelope, and (3) a high-velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (120 ) viewed close to the line of sight (i ¼ 15 ). Our model can explain the main features ...
... diffuse and extended envelope, and (3) a high-velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (120 ) viewed close to the line of sight (i ¼ 15 ). Our model can explain the main features ...
New Evidence for Mass-Loss from δ Cephei from H i 21
... pattern in the VLA images caused by large-scale Galactic emission diminishes near VLSR = 13.8 km s−1 . Furthermore, that same channel exhibits an extended H i emission region centered near the position of δ Cephei. Looking toward higher velocities, we find a series of 15 contiguous channels where spa ...
... pattern in the VLA images caused by large-scale Galactic emission diminishes near VLSR = 13.8 km s−1 . Furthermore, that same channel exhibits an extended H i emission region centered near the position of δ Cephei. Looking toward higher velocities, we find a series of 15 contiguous channels where spa ...
on the absolute age of the metal-rich globular m71
... system. Once we obtained the global catalog (master list of stars) of the entire data set we ran ALLFRAME (Stetson 1994) simultaneously over the entire set of images. We obtained a list of 370,000 stars with at least one measurement in four different photometric bands. To calibrate the instrumental ...
... system. Once we obtained the global catalog (master list of stars) of the entire data set we ran ALLFRAME (Stetson 1994) simultaneously over the entire set of images. We obtained a list of 370,000 stars with at least one measurement in four different photometric bands. To calibrate the instrumental ...
Planetary nebula
![](https://commons.wikimedia.org/wiki/Special:FilePath/NGC6543.jpg?width=300)
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.