The Birth and Evolution of Brown Dwarfs
... • Two new spectral classes have been defined for ultracool dwarfs. • The L class is characterized by weak or absent TiO, strong FeH, and huge alkali lines. Teff~2200K-1400K. • The T class is characterized by CH4. Teff<1400K. • A 35MJupiter evolves from M-type at 10 Myr to T type at 1 Gyr. ...
... • Two new spectral classes have been defined for ultracool dwarfs. • The L class is characterized by weak or absent TiO, strong FeH, and huge alkali lines. Teff~2200K-1400K. • The T class is characterized by CH4. Teff<1400K. • A 35MJupiter evolves from M-type at 10 Myr to T type at 1 Gyr. ...
A search for a new class of pulsating DA white dwarf stars in the DB
... down to the low temperature limit set by the age of the Galaxy, it is a remarkable and intriguing fact that few helium atmosphere white dwarfs occur in the effective temperature range between 45 000 ≥ T eff ≥ 30, 000 K. The DOs and DBs are found on either side of this temperature range, but only a v ...
... down to the low temperature limit set by the age of the Galaxy, it is a remarkable and intriguing fact that few helium atmosphere white dwarfs occur in the effective temperature range between 45 000 ≥ T eff ≥ 30, 000 K. The DOs and DBs are found on either side of this temperature range, but only a v ...
Chemical abundances and winds of massive stars in M31: a Btype
... 2.2 Keck I HIRES and HST STIS spectroscopy of OB 10-64 OB 10-64 was observed with the 10-m Keck I telescope, using HIRES on 1997 September 27 and again on the 1999 October 6–7, giving a total of 4 3600 s exposures. A 1.1-arcsec slit was used giving a resolution of approximately 35 000, yielding a ...
... 2.2 Keck I HIRES and HST STIS spectroscopy of OB 10-64 OB 10-64 was observed with the 10-m Keck I telescope, using HIRES on 1997 September 27 and again on the 1999 October 6–7, giving a total of 4 3600 s exposures. A 1.1-arcsec slit was used giving a resolution of approximately 35 000, yielding a ...
Compa ring between Spectroscopic and Photometric Method for
... This is the most popular and accessible method in astronomy. Photometry is the measurement of the intensity of electromagnetic radiation usually expressed in apparent magnitude. Apparent magnitude is a numerical scale to describe how bright each star appears in the sky. The lower the magnitude, the ...
... This is the most popular and accessible method in astronomy. Photometry is the measurement of the intensity of electromagnetic radiation usually expressed in apparent magnitude. Apparent magnitude is a numerical scale to describe how bright each star appears in the sky. The lower the magnitude, the ...
PDF file - Memorie della SAIt
... a fossil record of the nucleosynthesis that occurred several Gyr ago in halo AGB stars. They are dwarfs or giants, whose surface composition was polluted by the wind of an AGB companion. Then, the C and s-element enhancements are ashes of the nucleosynthesis occurred in the He-rich inter-shell of a ...
... a fossil record of the nucleosynthesis that occurred several Gyr ago in halo AGB stars. They are dwarfs or giants, whose surface composition was polluted by the wind of an AGB companion. Then, the C and s-element enhancements are ashes of the nucleosynthesis occurred in the He-rich inter-shell of a ...
Stars: Their Life and Afterlife
... White dwarfs have a mass of ~1.2 MŸ or less. This limit is imposed by two conditions. First, if the mass were much greater than this, the gravitational force would be able to overcome the electron degeneracy pressure, and the star would contract and heat to the point where further fusion – and evol ...
... White dwarfs have a mass of ~1.2 MŸ or less. This limit is imposed by two conditions. First, if the mass were much greater than this, the gravitational force would be able to overcome the electron degeneracy pressure, and the star would contract and heat to the point where further fusion – and evol ...
The formation of the galaxy is believed to be similar
... can be divided into 2 phases: a spherical gas cloud (halo) collapsed to form the stars in the Milky Way's spheroid, then rapidly rotating gas collapsed into a disk-shaped configuration of stars. Since disk stars have higher metallicity, which is most likely? Gas ejected from the a) spheroid stars en ...
... can be divided into 2 phases: a spherical gas cloud (halo) collapsed to form the stars in the Milky Way's spheroid, then rapidly rotating gas collapsed into a disk-shaped configuration of stars. Since disk stars have higher metallicity, which is most likely? Gas ejected from the a) spheroid stars en ...
Spectral classification of O–M stars on the basis of UBV photometry
... analyzed stars have been assigned to a single or two rather close estimates of spectra. In the last case an average value was adopted. Another 40% of stars have obtained two substantially different estimates of spectra. Double results of the classifying process based on U BV data originates as a rul ...
... analyzed stars have been assigned to a single or two rather close estimates of spectra. In the last case an average value was adopted. Another 40% of stars have obtained two substantially different estimates of spectra. Double results of the classifying process based on U BV data originates as a rul ...
26.4 Groups of Stars
... When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other. ...
... When Giovanni Riccioli used a telescope like this one to observe a star in the handle of the Big Dipper, he discovered two stars that orbit each other. ...
How Many Stars in the Sky?
... age. Stars vary in brightness, color, mass, temperature, and age. Stars are classified by colors as related to their surface temperature. The coolest stars are orange, then red, yellow, green, blue and finally blue-white. The size of a star on a photograph tells us about its brightness. Large star ...
... age. Stars vary in brightness, color, mass, temperature, and age. Stars are classified by colors as related to their surface temperature. The coolest stars are orange, then red, yellow, green, blue and finally blue-white. The size of a star on a photograph tells us about its brightness. Large star ...
sections 7-8 instructor notes
... Line blanketing affects the observed colours of late-type stars, low Z stars exhibiting an ultraviolet excess relative to high Z stars. The relationship is calibrated relative to the Hyades relation at BV ...
... Line blanketing affects the observed colours of late-type stars, low Z stars exhibiting an ultraviolet excess relative to high Z stars. The relationship is calibrated relative to the Hyades relation at BV ...
MAIN SEQUENCE STARS, Red Giants and White Dwarfs
... enters the SUPERGIANT phase. • The ESCAPE VELOCITY from such big stars gets low: Vesc = (2 G M / R)1/2 as R increases while M stays the same. • They lose a lot of mass via winds. • Also, RGs and SGs are subject to opacity driven instabilities which cause the outer layers to expand and cool and contr ...
... enters the SUPERGIANT phase. • The ESCAPE VELOCITY from such big stars gets low: Vesc = (2 G M / R)1/2 as R increases while M stays the same. • They lose a lot of mass via winds. • Also, RGs and SGs are subject to opacity driven instabilities which cause the outer layers to expand and cool and contr ...
Carbon Stars - The OzSky Star Safari
... A Few Strange Definitions and Concepts when Describing Stellar Evolution • Burn. Hydrogen does not burn with a chemical reaction with oxygen, but is consumed through a fusion process to form helium which then “burns” to form carbon. • Ash. Again, no chemical combustion occurs. Ash refers to the ...
... A Few Strange Definitions and Concepts when Describing Stellar Evolution • Burn. Hydrogen does not burn with a chemical reaction with oxygen, but is consumed through a fusion process to form helium which then “burns” to form carbon. • Ash. Again, no chemical combustion occurs. Ash refers to the ...
The Galactic evolution of phosphorus
... therein). This is not the case for phosphorus, that, before this work, had never been analysed systematically in cool stars. The reason why was already given by Struve (1930): no P i line is available in the “ordinary” range of the observed spectra of stars of spectral type F, G, or K. Some P ii and ...
... therein). This is not the case for phosphorus, that, before this work, had never been analysed systematically in cool stars. The reason why was already given by Struve (1930): no P i line is available in the “ordinary” range of the observed spectra of stars of spectral type F, G, or K. Some P ii and ...
... is quite violent and rapid, occurring within about 1000 years. Therefore, we must ask whether or not it is plausible to find four runaway stars among 44 trapezia. Trapezia may also evolve dynamically in a less violent way, if they start out from a virialized state (Allen et al. 1974b). In this case, ...
Multiple Choice, continued Stars, Galaxies, and the Universe
... Today, we know that Copernicus was right: the stars are very far from Earth. In fact, stars are so distant that a new unit of length—the light-year—was created to measure their distance. A light-year is a unit of length equal to the distance that light travels through space in 1 year. Because the sp ...
... Today, we know that Copernicus was right: the stars are very far from Earth. In fact, stars are so distant that a new unit of length—the light-year—was created to measure their distance. A light-year is a unit of length equal to the distance that light travels through space in 1 year. Because the sp ...
IND 6 - 1 Stars and Stellar Evolution In order to better understand
... You will fill out a short flow chart / concept map to help you with basic stellar evolution and the different evolutionary paths. There are words you will need in the description following: As we learned in the “Star Clusters” lab, MASS is the Great Determinator. Therefore, when a star runs out of h ...
... You will fill out a short flow chart / concept map to help you with basic stellar evolution and the different evolutionary paths. There are words you will need in the description following: As we learned in the “Star Clusters” lab, MASS is the Great Determinator. Therefore, when a star runs out of h ...
takes its time doing so. The coolest white dwarfs
... mostly hydrogen atmosphere white dwarfs, though the statistics have taken into account the contribution from white dwarfs without hydrogen. The cooler white dwarfs were identified from the Lutyen Half Second proper motion catalogusing a method developed by Schmidt 1975. There were over 80 stars know ...
... mostly hydrogen atmosphere white dwarfs, though the statistics have taken into account the contribution from white dwarfs without hydrogen. The cooler white dwarfs were identified from the Lutyen Half Second proper motion catalogusing a method developed by Schmidt 1975. There were over 80 stars know ...
PHYS3380_102815_bw - The University of Texas at Dallas
... significant break around 1M; R /Mξ, with ξ≈0.57 for M > 1M, and ξ≈0.8 for M < 1M. This division marks the onset of a convective envelope. Convection tends to increase the flow of energy out of the star, which causes the star to contract slightly. As a result, stars with convective envelopes lie b ...
... significant break around 1M; R /Mξ, with ξ≈0.57 for M > 1M, and ξ≈0.8 for M < 1M. This division marks the onset of a convective envelope. Convection tends to increase the flow of energy out of the star, which causes the star to contract slightly. As a result, stars with convective envelopes lie b ...
hwd_ewd_v3 - X-ray and Observational Astronomy Group
... White dwarfs are thus divided into two main groups according to whether or not their spectra are dominated by one or other of these elements. The hydrogen-rich stars are given the classification DA, while the helium-rich white dwarfs are designated DO if He II features are present (hotter than about ...
... White dwarfs are thus divided into two main groups according to whether or not their spectra are dominated by one or other of these elements. The hydrogen-rich stars are given the classification DA, while the helium-rich white dwarfs are designated DO if He II features are present (hotter than about ...
Stellar Properties
... • a star could be very bright because is was very close to us; not because it was truly bright • two stars in the same constellation might not be close to each other; one could be much farther away ...
... • a star could be very bright because is was very close to us; not because it was truly bright • two stars in the same constellation might not be close to each other; one could be much farther away ...
Geol. 655 Isotope Geochemistry
... known. We also have what appears to be a reasonably successful theory of nucleosynthesis. Physicists, like all scientists, are attracted to simple theories. Not surprisingly then, the first ideas about nucleosynthesis attempted to explain the origin of the elements by single processes. Generally, th ...
... known. We also have what appears to be a reasonably successful theory of nucleosynthesis. Physicists, like all scientists, are attracted to simple theories. Not surprisingly then, the first ideas about nucleosynthesis attempted to explain the origin of the elements by single processes. Generally, th ...
Distant Stars - How far away is it
... the dual nature of light as both a particle and a wave. Viewing light as a wave, we cover the full electromagnetic spectrum, followed by blackbody radiation. Then using known luminosity from nearby stars, we map star color to temperature and star temperature to luminosity – the basic H-R Diagram. To ...
... the dual nature of light as both a particle and a wave. Viewing light as a wave, we cover the full electromagnetic spectrum, followed by blackbody radiation. Then using known luminosity from nearby stars, we map star color to temperature and star temperature to luminosity – the basic H-R Diagram. To ...
theh – rdiagramsofyoungclust ersandtheformati on ofp
... the interstellar medium, one can estimate the absorption in the early solar nebula. Let us assume its radius was comparable to the present radius of pluto's orbit, and its mass ten times the present mass of the planetary system, hence the density of the solar nebula at that stage was 2.5 X 10-14 gm/ ...
... the interstellar medium, one can estimate the absorption in the early solar nebula. Let us assume its radius was comparable to the present radius of pluto's orbit, and its mass ten times the present mass of the planetary system, hence the density of the solar nebula at that stage was 2.5 X 10-14 gm/ ...
Chapter14(4-7-11)
... must have formed early in the galaxy’s history, before the gas settled into a disk. ...
... must have formed early in the galaxy’s history, before the gas settled into a disk. ...
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.