Stars
... Pressure and gravity in balance Stars attempt to maintain equilibrium by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. W ...
... Pressure and gravity in balance Stars attempt to maintain equilibrium by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. W ...
The spectroscopic Hertzsprung-Russell diagram
... the absolute brightnesses, i.e. the distances, are required to properly order the stars in the HR diagram. Also for stars in star clusters, where the distance may still be unknown, but the distances of all stars are roughly equal, order can be achieved in what we now call color-magnitude diagrams, s ...
... the absolute brightnesses, i.e. the distances, are required to properly order the stars in the HR diagram. Also for stars in star clusters, where the distance may still be unknown, but the distances of all stars are roughly equal, order can be achieved in what we now call color-magnitude diagrams, s ...
A Spitzer mid-infrared spectral survey of mass
... The (M K , J − K ) diagram in Fig. 1(a) shows most of the AGB stars which are known to be mid-IR point sources in the LMC. Also shown is a representative sample of the much more numerous field stars without thick dust shells. The most numerous stars in any stellar population are low-mass stars. In F ...
... The (M K , J − K ) diagram in Fig. 1(a) shows most of the AGB stars which are known to be mid-IR point sources in the LMC. Also shown is a representative sample of the much more numerous field stars without thick dust shells. The most numerous stars in any stellar population are low-mass stars. In F ...
Celebrating Astronomy: The Life of a Star
... of interstellar gas and dust… clouds rotate as they collapse … conserving angular momentum … forming the smaller clumps that will become stars ...
... of interstellar gas and dust… clouds rotate as they collapse … conserving angular momentum … forming the smaller clumps that will become stars ...
NSDL/NSTA Web Seminar: Celebrating Astronomy: A Star`s Story
... of interstellar gas and dust… clouds rotate as they collapse … conserving angular momentum … forming the smaller clumps that will become stars ...
... of interstellar gas and dust… clouds rotate as they collapse … conserving angular momentum … forming the smaller clumps that will become stars ...
Distance determination for RAVE stars using stellar models
... by F0 (Z, τ, m). Throughout this paper we assume solar-scaled metallicities, which means that [α/Fe] = 0 and [M/H] = [Fe/H], where [M/H] is defined as log(Z/Z ). For our study we use the Y 2 (Yonsei-Yale) models (Demarque et al. 2004). These models can be downloaded from the Y 2 website1 , where al ...
... by F0 (Z, τ, m). Throughout this paper we assume solar-scaled metallicities, which means that [α/Fe] = 0 and [M/H] = [Fe/H], where [M/H] is defined as log(Z/Z ). For our study we use the Y 2 (Yonsei-Yale) models (Demarque et al. 2004). These models can be downloaded from the Y 2 website1 , where al ...
A non-LTE analysis of the hot subdwarf O star BD+28°4211
... larger region in the HR diagram, and this distribution is not as homogeneous as in the case of the sdBs. While most of the latter are helium poor, the majority of sdO stars has an atmosphere enriched in helium, and they are thought to be the results of various peculiar evolutionary paths2 . One stri ...
... larger region in the HR diagram, and this distribution is not as homogeneous as in the case of the sdBs. While most of the latter are helium poor, the majority of sdO stars has an atmosphere enriched in helium, and they are thought to be the results of various peculiar evolutionary paths2 . One stri ...
HWWS 2010 - Monash University
... • Latter two are both likely classes of magnetars, (possibly young) systems with extremely high magnetic fields 1014– 1015 G • Compact central objects (CCOs) about which very little is known, associated with supernova remnants Galloway, “Accreting Neutron Stars – tiny Galactic Powerhouses” ...
... • Latter two are both likely classes of magnetars, (possibly young) systems with extremely high magnetic fields 1014– 1015 G • Compact central objects (CCOs) about which very little is known, associated with supernova remnants Galloway, “Accreting Neutron Stars – tiny Galactic Powerhouses” ...
A very massive runaway star from Cygnus OB2⋆
... 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 dedicated observations, and no other spectroscopic classication ...
... 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 dedicated observations, and no other spectroscopic classication ...
Barium and europium abundances in cool dwarf stars and
... barium the Ba ii λ4554 line is significantly strengthened compared with the case of solar even-to-odd isotopic ratio 82: 18. In Paper I we showed this difference can be easily detected if it exists: for example, for the star BD 66◦ 268 with [Fe/H] = −2.2 it consists of 0.2 dex in terms of abundances ...
... barium the Ba ii λ4554 line is significantly strengthened compared with the case of solar even-to-odd isotopic ratio 82: 18. In Paper I we showed this difference can be easily detected if it exists: for example, for the star BD 66◦ 268 with [Fe/H] = −2.2 it consists of 0.2 dex in terms of abundances ...
ASTRONOMY AND ASTROPHYSICS Barium and europium
... halo stars are of the r-process origin. Much observational efforts were invested in testing this idea. For extremely metalpoor stars with metallicities [Fe/H] ≤ −2.4 McWilliam (1998) has derived an average [Eu/Ba] = 0.69, consistent with pure rprocess nucleosynthesis provided that the data of Arland ...
... halo stars are of the r-process origin. Much observational efforts were invested in testing this idea. For extremely metalpoor stars with metallicities [Fe/H] ≤ −2.4 McWilliam (1998) has derived an average [Eu/Ba] = 0.69, consistent with pure rprocess nucleosynthesis provided that the data of Arland ...
A re-appraisal of the habitability of planets around M dwarf
... power source. These same named luminosity classes are also numbered for abbreviation; I, II, III, IV, and V runs from supergiant to dwarf. Our own Sun is spectral type G2 and luminosity class V (or dwarf). Less massive dwarf stars are cool, such as M dwarfs. The length of time a particular star rema ...
... power source. These same named luminosity classes are also numbered for abbreviation; I, II, III, IV, and V runs from supergiant to dwarf. Our own Sun is spectral type G2 and luminosity class V (or dwarf). Less massive dwarf stars are cool, such as M dwarfs. The length of time a particular star rema ...
A Reappraisal of The Habitability of Planets around M Dwarf Stars
... power source. These same named luminosity classes are also numbered for abbreviation; I, II, III, IV, and V runs from supergiant to dwarf. Our own Sun is spectral type G2 and luminosity class V (or dwarf). Less massive dwarf stars are cool, such as M dwarfs. The length of time a particular star rema ...
... power source. These same named luminosity classes are also numbered for abbreviation; I, II, III, IV, and V runs from supergiant to dwarf. Our own Sun is spectral type G2 and luminosity class V (or dwarf). Less massive dwarf stars are cool, such as M dwarfs. The length of time a particular star rema ...
Evolved, single, slowly rotating... but magnetically active
... We see three possible scenarios to get out of this puzzle. First, the photometric period may not be the rotation period but a spotcycle period and the star is seen nearly pole on. Second, as put forward by Stȩpień (1993), the star is an evolved Ap star and its magnetic field is therefore thought t ...
... We see three possible scenarios to get out of this puzzle. First, the photometric period may not be the rotation period but a spotcycle period and the star is seen nearly pole on. Second, as put forward by Stȩpień (1993), the star is an evolved Ap star and its magnetic field is therefore thought t ...
12C13C1414N21312C/13C3he43He/4He Sub-surface
... While the envelope convection zones may, at first glance, be negligible for the internal evolution of hot massive stars, they may cause observable phenomena at the stellar surface. The reason is that the zones are located very close to the photosphere for some mass interval (see below). Here, we wil ...
... While the envelope convection zones may, at first glance, be negligible for the internal evolution of hot massive stars, they may cause observable phenomena at the stellar surface. The reason is that the zones are located very close to the photosphere for some mass interval (see below). Here, we wil ...
Part IV: Stars
... interior, photons can only travel a fraction of a millimeter before “colliding” with an electron and deflecting into a new direction. So photons bounce around at random and only slowly make their way out of the Sun. Mathematical models use the observed composition and mass of the Sun, along with the ...
... interior, photons can only travel a fraction of a millimeter before “colliding” with an electron and deflecting into a new direction. So photons bounce around at random and only slowly make their way out of the Sun. Mathematical models use the observed composition and mass of the Sun, along with the ...
Lecture18
... diagram”): find a “main sequence” where stars spend most of their lives burning hydrogen. Mass is the controlling factor along main sequence: High mass=High Luminosity=Hot Temperature=Blue Color=Large Radius=Short Lifetime. Smallest stars live for trillions of years! Thursday, November 4, 2010 ...
... diagram”): find a “main sequence” where stars spend most of their lives burning hydrogen. Mass is the controlling factor along main sequence: High mass=High Luminosity=Hot Temperature=Blue Color=Large Radius=Short Lifetime. Smallest stars live for trillions of years! Thursday, November 4, 2010 ...
Spiral Arms - Harry Kroto
... of the Galaxy is initially straight (Bulge rotates like a solid body), then Keplerian for a short distance, then it flattens off at large radius. The fact that the rotation curve is approximately flat out to very large radii implies that the mass of the Galaxy grows linearly with distance beyond the ...
... of the Galaxy is initially straight (Bulge rotates like a solid body), then Keplerian for a short distance, then it flattens off at large radius. The fact that the rotation curve is approximately flat out to very large radii implies that the mass of the Galaxy grows linearly with distance beyond the ...
Star formation in a galactic outflow
... million years (Myr). Determining the kinematics of such a stellar population is difficult, since most stellar features (especially the ones associated with young stars) are heavily contaminated by the strong nebular emission lines. However, we have recovered the kinematics of the young stellar popul ...
... million years (Myr). Determining the kinematics of such a stellar population is difficult, since most stellar features (especially the ones associated with young stars) are heavily contaminated by the strong nebular emission lines. However, we have recovered the kinematics of the young stellar popul ...
T
... monitored the star α Centauri B, which is a K-type star substantially smaller than our Sun. During 7 hours we collected a total of 420 spectra with typical SNR of 500 each at λ=550 nm. The radial-velocity measurement sequence plotted in Figure 4a indicates a dispersion of 51 cm/s but the zoom shown ...
... monitored the star α Centauri B, which is a K-type star substantially smaller than our Sun. During 7 hours we collected a total of 420 spectra with typical SNR of 500 each at λ=550 nm. The radial-velocity measurement sequence plotted in Figure 4a indicates a dispersion of 51 cm/s but the zoom shown ...
A spectroscopic investigation of the O
... which no evidence of binarity is found can never be definitely considered as single. Even if no RV shift is detected, the system could be seen under a particular orientation, have a very long period or perhaps a high eccentricity, thereby making the RV variations not significant over a long timescal ...
... which no evidence of binarity is found can never be definitely considered as single. Even if no RV shift is detected, the system could be seen under a particular orientation, have a very long period or perhaps a high eccentricity, thereby making the RV variations not significant over a long timescal ...
PoS(EVN 2014)058 - Proceeding of science
... The greatest barrier to understanding massive stars is the nature and magnitude of their massloss, which has profound implications for many areas of astrophysics including stellar evolution. Recent results have strongly challenged the current models and it is now recognised that there is significant ...
... The greatest barrier to understanding massive stars is the nature and magnitude of their massloss, which has profound implications for many areas of astrophysics including stellar evolution. Recent results have strongly challenged the current models and it is now recognised that there is significant ...
Extrasolar Cosmochemistry
... atmosphere. These stars are typically the radius of Earth and slowly cool from an initial outer temperature above 100,000 K. Once the effective temperature of the atmosphere falls below 20,000 K, radiative levitation—the process of supporting an element in the atmosphere by the upward flow of radiati ...
... atmosphere. These stars are typically the radius of Earth and slowly cool from an initial outer temperature above 100,000 K. Once the effective temperature of the atmosphere falls below 20,000 K, radiative levitation—the process of supporting an element in the atmosphere by the upward flow of radiati ...
Searching for RR Lyrae Stars in M15
... RR Lyrae stars are not variable stars their whole lives. Instead, they are formed as a result of stellar evolution. RR Lyrae stars evolve the way lowmass stars are expected to. A RR Lyrae star is believed to have started off as a main sequence star with a mass around 0.8 M . The progenitor of a RR ...
... RR Lyrae stars are not variable stars their whole lives. Instead, they are formed as a result of stellar evolution. RR Lyrae stars evolve the way lowmass stars are expected to. A RR Lyrae star is believed to have started off as a main sequence star with a mass around 0.8 M . The progenitor of a RR ...
Seeds of a Tychonic Revolution: Telescopic Observations of the
... disks are spurious. They have nothing to do with the actual sizes of the stars. They are manifestations of the Airy disk formed by the telescope through diffraction. All stars have the same Airy disk diameter (roughly 10 arcseconds for a telescope like Mareo’s), which is a function only of wavelengt ...
... disks are spurious. They have nothing to do with the actual sizes of the stars. They are manifestations of the Airy disk formed by the telescope through diffraction. All stars have the same Airy disk diameter (roughly 10 arcseconds for a telescope like Mareo’s), which is a function only of wavelengt ...
Stellar classification
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Light from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with absorption lines. Each line indicates an ion of a certain chemical element, with the line strength indicating the abundance of that ion. The relative abundance of the different ions varies with the temperature of the photosphere. The spectral class of a star is a short code summarizing the ionization state, giving an objective measure of the photosphere's temperature and density.Most stars are currently classified under the Morgan–Keenan (MK) system using the letters O, B, A, F, G, K, and M, a sequence from the hottest (O type) to the coolest (M type). Each letter class is then subdivided using a numeric digit with 0 being hottest and 9 being coolest (e.g. A8, A9, F0, F1 form a sequence from hotter to cooler). The sequence has been expanded with classes for other stars and star-like objects that do not fit in the classical system, such class D for white dwarfs and class C for carbon stars.In the MK system a luminosity class is added to the spectral class using Roman numerals. This is based on the width of certain absorption lines in the star's spectrum which vary with the density of the atmosphere and so distinguish giant stars from dwarfs. Luminosity class 0 or Ia+ stars for hypergiants, class I stars for supergiants, class II for bright giants, class III for regular giants, class IV for sub-giants, class V for main-sequence stars, class sd for sub-dwarfs, and class D for white dwarfs. The full spectral class for the Sun is then G2V, indicating a main-sequence star with a temperature around 5,800K.