Searching for the oldest, most metal-poor stars in the SkyMapper Survey
... 1. Normalize the spectra. The processed and reduced echelle spectra from the MagellanClay telescope for each star are high-resolution (0.7” slit R = λ/∆λ ∼ 30, 000 and 1.0” slit R ∼ 35, 000) line spectra. Each spectrum possess ∼ 30 orders, which are small pieces of the spectrum. The wavelength rang ...
... 1. Normalize the spectra. The processed and reduced echelle spectra from the MagellanClay telescope for each star are high-resolution (0.7” slit R = λ/∆λ ∼ 30, 000 and 1.0” slit R ∼ 35, 000) line spectra. Each spectrum possess ∼ 30 orders, which are small pieces of the spectrum. The wavelength rang ...
arXiv:hep-ph/9910471 25 Oct 1999
... stars are being destroyed by strangelets is Rdestr ∼ N? P? /T0 = V R, with P? as in Eq. (5). It would not be possible to have a 50% addition of a completely new type of (strangelet) supernova without unacceptably upsetting our understanding of this field. The condition Rdestr < RSN/2 yields p < 10− ...
... stars are being destroyed by strangelets is Rdestr ∼ N? P? /T0 = V R, with P? as in Eq. (5). It would not be possible to have a 50% addition of a completely new type of (strangelet) supernova without unacceptably upsetting our understanding of this field. The condition Rdestr < RSN/2 yields p < 10− ...
PSC100 Summary Chapters 10 to Chapter 20
... temperatures and densities in the core that push the outer layers of the star outward. These outer layers cool so that the star not only appears much larger but also takes on a reddish coloration. This period of a star's life is called the RED GIANT phase. Meanwhile the core is really much hotter du ...
... temperatures and densities in the core that push the outer layers of the star outward. These outer layers cool so that the star not only appears much larger but also takes on a reddish coloration. This period of a star's life is called the RED GIANT phase. Meanwhile the core is really much hotter du ...
Brown et al. 2008 Studying Resolved Stellar
... Figure 6 shows a synthetic CMD of a 3 ×108 solar masses stellar population obtained with a constant SF over a 12 Gyr lifetime. The color encoding reflects the stellar ages. Superimposed are diagnostic boxes, designed to sample well defined age ranges. The number of stars counted within each box is p ...
... Figure 6 shows a synthetic CMD of a 3 ×108 solar masses stellar population obtained with a constant SF over a 12 Gyr lifetime. The color encoding reflects the stellar ages. Superimposed are diagnostic boxes, designed to sample well defined age ranges. The number of stars counted within each box is p ...
A SEARCH FOR JUPITER-MASS COMPANIONS TO NEAR
... correlated periodogram evaluated at a period of 100 yr ranges from 5.2 for Cep (see Figure 3) to 7.4 for Boo A. None of the corresponding periodogram false alarm probabilities is less than 0.01 (i.e., the low-frequency periodogram values do not exceed the 99 per cent signi cance level). The latt ...
... correlated periodogram evaluated at a period of 100 yr ranges from 5.2 for Cep (see Figure 3) to 7.4 for Boo A. None of the corresponding periodogram false alarm probabilities is less than 0.01 (i.e., the low-frequency periodogram values do not exceed the 99 per cent signi cance level). The latt ...
Estimating the Age of Supernova Remnants - Chandra X
... most of the gas in the remnant is not from the star. As the ejected material expands outwards, it encounters and intermingles with the interstellar medium and propels it outward, building up the outer shock wave. The volume through which the remnant has expanded and the density of the interstellar m ...
... most of the gas in the remnant is not from the star. As the ejected material expands outwards, it encounters and intermingles with the interstellar medium and propels it outward, building up the outer shock wave. The volume through which the remnant has expanded and the density of the interstellar m ...
Bamberg_VanGrootel - ORBi
... Former close-in giant planets/BDs were deeply engulfed in the red giant envelope The planets’ volatile layers were removed and only the dense cores survived and ...
... Former close-in giant planets/BDs were deeply engulfed in the red giant envelope The planets’ volatile layers were removed and only the dense cores survived and ...
The Naked Eye Stars as Data Supporting Galileo`s
... in proportions found in Bright Star Catalog (i.e. real sky). Top right -numbers calculated via equation 3. Bottom left, equal numbers of each magnitude. Bottom right -- numbers of each magnitude selected at random. If stars are not suns scattered through space then there is no reason for the real sk ...
... in proportions found in Bright Star Catalog (i.e. real sky). Top right -numbers calculated via equation 3. Bottom left, equal numbers of each magnitude. Bottom right -- numbers of each magnitude selected at random. If stars are not suns scattered through space then there is no reason for the real sk ...
Precision age indicators that exploit chemically peculiar stars
... Finally, coolest of all, C stars arise late in the lives of 1.5−4 M stars on the asymptotic giant branch where a third dredge-up convects sufficient C to the surface to tip the number ratio C/O > 1 (Marigo et al. 2008). The mass range translates to population ages between 0.5 and 5 Gyr for heavy elem ...
... Finally, coolest of all, C stars arise late in the lives of 1.5−4 M stars on the asymptotic giant branch where a third dredge-up convects sufficient C to the surface to tip the number ratio C/O > 1 (Marigo et al. 2008). The mass range translates to population ages between 0.5 and 5 Gyr for heavy elem ...
Neutron stars as probes of extreme energy density matter
... stars await further developments in the treatment of atmospheres, and additional data. The magnificence of the seven is yet to be realized! 3.2.2 Quiescent neutron stars. Between episodes of intermittent accretion from a companion star, many neutron stars are known to go through long periods of quie ...
... stars await further developments in the treatment of atmospheres, and additional data. The magnificence of the seven is yet to be realized! 3.2.2 Quiescent neutron stars. Between episodes of intermittent accretion from a companion star, many neutron stars are known to go through long periods of quie ...
Space astrometry 2: Scientific results from Hipparcos
... • coldest excursion of little ice-age, and correlated with disappearance of sun spots • probe of solar activity, solar dynamo, sun spot cycle, and climate • monitoring Sun-like stars within 60 pc probes activity versus age (Wright 2004, 2006) (3) Various other studies of Sun’s orbit, spiral arm + Ga ...
... • coldest excursion of little ice-age, and correlated with disappearance of sun spots • probe of solar activity, solar dynamo, sun spot cycle, and climate • monitoring Sun-like stars within 60 pc probes activity versus age (Wright 2004, 2006) (3) Various other studies of Sun’s orbit, spiral arm + Ga ...
400 Years of Stellar Rotation
... into the early chemical evolution of gal axies. Rotation has an impact on the nature of progenitors of core-collapse events and of long soft gamma ray bursts. The range of initial masses that give birth to white dwarfs, neutron stars and black holes will probably also depend to some extent on rotat ...
... into the early chemical evolution of gal axies. Rotation has an impact on the nature of progenitors of core-collapse events and of long soft gamma ray bursts. The range of initial masses that give birth to white dwarfs, neutron stars and black holes will probably also depend to some extent on rotat ...
3. Measuring Distances and Magnitudes
... some units such as in feet, km, light years, parsecs etc. It has been excruciatingly difficult to measure astronomical distances until this century. Astronomical Unit: 1AU is the distance from the centre of the Sun at which a particle of negligible mass, in an unperturbed circular orbit, would have ...
... some units such as in feet, km, light years, parsecs etc. It has been excruciatingly difficult to measure astronomical distances until this century. Astronomical Unit: 1AU is the distance from the centre of the Sun at which a particle of negligible mass, in an unperturbed circular orbit, would have ...
Penentuan Jarak dalam Astronomi II
... (a) Single stars that are typically below ~8 MSun becomes red giant just after their life on the Main Sequence Red giants lose mass and evolve (often through a Planetary Nebulae stage) into White Dwarfs (b) More massive stars become supergiants Supergiants undergo Type II (and extremely massive – Ty ...
... (a) Single stars that are typically below ~8 MSun becomes red giant just after their life on the Main Sequence Red giants lose mass and evolve (often through a Planetary Nebulae stage) into White Dwarfs (b) More massive stars become supergiants Supergiants undergo Type II (and extremely massive – Ty ...
Fundamentals of Atmospheric Chemistry and Astrochemistry
... electromagnetic spectrum (UV‐vis, infrared, microwave etc) for different regions of space (stars, interstellar regions, and so on), and can be interpreted in order to establish the atomic and molecular composition of these regions. Ground‐based telescopes are limited to studying regions of the el ...
... electromagnetic spectrum (UV‐vis, infrared, microwave etc) for different regions of space (stars, interstellar regions, and so on), and can be interpreted in order to establish the atomic and molecular composition of these regions. Ground‐based telescopes are limited to studying regions of the el ...
Space astrometry 3: Gaia: scientific rationale, principles, and data analysis
... torque models, etc), as well as instrument calibration terms (evolve only slowly with time), and slit ambiguities • also corrected for aberration and GR light-bending • the efficient solution of the large system of equations was not trivial (Cholesky sparse matrix factorisation) 2. an arbitrary orig ...
... torque models, etc), as well as instrument calibration terms (evolve only slowly with time), and slit ambiguities • also corrected for aberration and GR light-bending • the efficient solution of the large system of equations was not trivial (Cholesky sparse matrix factorisation) 2. an arbitrary orig ...
Star Formation in Disks: Spiral Arms, Turbulence, and Triggering
... can compress the gas a lot. Thermal instabilities compress the gas too, but usually in small regions where self-gravity is not important. Magnetic fields cause slight compression when the gas rearranges itself on the field lines following a Parker instability, but this rearrangement alone is not enoug ...
... can compress the gas a lot. Thermal instabilities compress the gas too, but usually in small regions where self-gravity is not important. Magnetic fields cause slight compression when the gas rearranges itself on the field lines following a Parker instability, but this rearrangement alone is not enoug ...
Supermassive black holes - University of Texas Astronomy Home
... We don’t know which massive stars do which! Tendency to think that more massive stars are more prone to making black holes, but the rotation of the star, the presence of a binary companion, and other factors may influence the outcome. ...
... We don’t know which massive stars do which! Tendency to think that more massive stars are more prone to making black holes, but the rotation of the star, the presence of a binary companion, and other factors may influence the outcome. ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.