Closed Loop Performance
... At 1000 Hz closed loop we can achieve 65 nm rms error in tower ~95nm “on-sky”. NOTE that this is a linear stretch. This is much better than the 190 nm rms ...
... At 1000 Hz closed loop we can achieve 65 nm rms error in tower ~95nm “on-sky”. NOTE that this is a linear stretch. This is much better than the 190 nm rms ...
the UKIRT Fundamental and Extended lists
... We present high-precision JHK photometry with the 3.8-m UK Infrared Telescope (UKIRT) of 82 standard stars, 28 from the widely used preliminary list known as the ‘UKIRT Faint Standards’, referred to here as the Fundamental List, and 54 additional stars referred to as the Extended List. The stars hav ...
... We present high-precision JHK photometry with the 3.8-m UK Infrared Telescope (UKIRT) of 82 standard stars, 28 from the widely used preliminary list known as the ‘UKIRT Faint Standards’, referred to here as the Fundamental List, and 54 additional stars referred to as the Extended List. The stars hav ...
Spectral line mapping of the Milky Way
... outflows. However, even more important will be the availability of a coherent picture of all phases of the interstellar medium, to study their interrelationship. This includes answering questions on how the atomic gas evolves into molecular gas, creating the molecular clouds from which new stars wil ...
... outflows. However, even more important will be the availability of a coherent picture of all phases of the interstellar medium, to study their interrelationship. This includes answering questions on how the atomic gas evolves into molecular gas, creating the molecular clouds from which new stars wil ...
NAS biographical memoir of Martin Schwarzschild
... to burn its nuclear fuel through a sequence of phases: main sequence (like the sun) to red giant (like our neighbor Arcturus) to degenerate dwarf (like another neighbor, Sirius B). By now there have been innumerable quantitative tests of the theory. And it works! A normal star of mass similar to tha ...
... to burn its nuclear fuel through a sequence of phases: main sequence (like the sun) to red giant (like our neighbor Arcturus) to degenerate dwarf (like another neighbor, Sirius B). By now there have been innumerable quantitative tests of the theory. And it works! A normal star of mass similar to tha ...
March 2016 BRAS Addendum Newsletter
... times? Testimony of Aratus, Cicero, Horace, Seneca, and Ptolemy – all of these ancient writers described Sirius with terms that can only be described as “ruddy”, “reddish”, “blazing as fire”, etc. Al Sufi, in the tenth century does not mention Sirius among stars which he classified as red. There are ...
... times? Testimony of Aratus, Cicero, Horace, Seneca, and Ptolemy – all of these ancient writers described Sirius with terms that can only be described as “ruddy”, “reddish”, “blazing as fire”, etc. Al Sufi, in the tenth century does not mention Sirius among stars which he classified as red. There are ...
Asymptotic Giant Branch stars viewed up-close and far-off
... and 14 N and 13 C to the surface. The change in the surface abundance ratio of 12 C/13 C is from ≈ 90 to ≈ 20 (Charbonnel 1994). The helium core continues to contract. Eventually, helium ignites through the triple-alpha process. Pressure and temperature are independent of each other in the degenerat ...
... and 14 N and 13 C to the surface. The change in the surface abundance ratio of 12 C/13 C is from ≈ 90 to ≈ 20 (Charbonnel 1994). The helium core continues to contract. Eventually, helium ignites through the triple-alpha process. Pressure and temperature are independent of each other in the degenerat ...
Annual report 2004 - Département d`Astrophysique, Géophysique et
... We have gathered and analysed a timeseries of 1493 high-quality multicilour Geneva photometric data of the B3V Cep star HD 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies ...
... We have gathered and analysed a timeseries of 1493 high-quality multicilour Geneva photometric data of the B3V Cep star HD 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies ...
Accreting neutron stars: strong gravity and type I bursts - UvA-DARE
... Another technique under investigation is asteroseismology. This is a fairly new approach in NSs and is still at its very early stages. However, in principle, analyzing different frequencies found during the bursts of magnetars (NSs with magnetic fields above ∼ 1014 G, Watts, 2011), or the signals en ...
... Another technique under investigation is asteroseismology. This is a fairly new approach in NSs and is still at its very early stages. However, in principle, analyzing different frequencies found during the bursts of magnetars (NSs with magnetic fields above ∼ 1014 G, Watts, 2011), or the signals en ...
Five New Giant Exoplanets from the California
... its cool temperature resides outside the lowest temperature for which our continuous and molecular opacities are accurate. The luminosity of each star is determined from the apparent V-band magnitude, the bolometric correction, and the parallax from Hipparcos. From Teff and the luminosity, we determ ...
... its cool temperature resides outside the lowest temperature for which our continuous and molecular opacities are accurate. The luminosity of each star is determined from the apparent V-band magnitude, the bolometric correction, and the parallax from Hipparcos. From Teff and the luminosity, we determ ...
HS0702+ 6043: A star showing both short-period p
... Subdwarf B stars populate the extreme horizontal branch (EHB) in the effective temperature range of 22 000 to 40 000 K and have surface gravity values from log g=5.0 to 6.2 in cgs units. The masses of these hot, evolved objects should cluster around 0.5 M⊙ as suggested by evolution theory (Han et al ...
... Subdwarf B stars populate the extreme horizontal branch (EHB) in the effective temperature range of 22 000 to 40 000 K and have surface gravity values from log g=5.0 to 6.2 in cgs units. The masses of these hot, evolved objects should cluster around 0.5 M⊙ as suggested by evolution theory (Han et al ...
ASTRO-114--Lecture 37-
... beginning our discussion on stars, by talking about our star the Sun. We are now going to shift to all the other stars and so we’re now moving out of the solar system to the rest of the universe. Keep in mind, if you’re trying to visualize an average star, the Sun will do fine. So we have already be ...
... beginning our discussion on stars, by talking about our star the Sun. We are now going to shift to all the other stars and so we’re now moving out of the solar system to the rest of the universe. Keep in mind, if you’re trying to visualize an average star, the Sun will do fine. So we have already be ...
Presentation - Copernicus.org
... Solar System properties that depend on birth environment: - evidence of short-lived radionuclides in meteorites - dynamical properties of outer planets and Kuiper Belt ...
... Solar System properties that depend on birth environment: - evidence of short-lived radionuclides in meteorites - dynamical properties of outer planets and Kuiper Belt ...
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.