Hot DQ White Dwarfs: Something Different
... dwarfs. It is based on a modified version of the code described at length in Bergeron et al. (1995), which is appropriate for pure hydrogen and pure helium atmospheric compositions, as well as mixed hydrogen and helium compositions, while energy transport by convection is treated within the mixing-l ...
... dwarfs. It is based on a modified version of the code described at length in Bergeron et al. (1995), which is appropriate for pure hydrogen and pure helium atmospheric compositions, as well as mixed hydrogen and helium compositions, while energy transport by convection is treated within the mixing-l ...
The coronal temperatures of low-mass main
... of the coronal properties of saturated stars. For example, if RX is the relevant parameter, then this would indicate that temperature scales somehow with how far a star is below the saturation threshold in rotation, given that saturation happens at a single mass-independent value of RX . It would fu ...
... of the coronal properties of saturated stars. For example, if RX is the relevant parameter, then this would indicate that temperature scales somehow with how far a star is below the saturation threshold in rotation, given that saturation happens at a single mass-independent value of RX . It would fu ...
SXVR-H814 handbook
... good focus and so you might want to try this to judge the high image quality that it is possible to achieve. Various other exposure options are available, as can be seen in the picture above. For example, you can ‘Bin’ the download 2x2, or more, to achieve greater sensitivity and faster download, or ...
... good focus and so you might want to try this to judge the high image quality that it is possible to achieve. Various other exposure options are available, as can be seen in the picture above. For example, you can ‘Bin’ the download 2x2, or more, to achieve greater sensitivity and faster download, or ...
Venus and Maya - Academic Program Pages at Evergreen
... months. It takes 2922 days for the Sun, Earth, Venus and Stars to all agree from a defined point. This number is very important in cyclic time, and the Mayans were fully aware of this alignment. These movements were recoded in the Venus tables of one of their 4 surviving books, the Dresden Codex; 5 ...
... months. It takes 2922 days for the Sun, Earth, Venus and Stars to all agree from a defined point. This number is very important in cyclic time, and the Mayans were fully aware of this alignment. These movements were recoded in the Venus tables of one of their 4 surviving books, the Dresden Codex; 5 ...
A non-LTE analysis of the hot subdwarf O star BD+28°4211
... (i.e., below 40 000 K). While known sdO stars in the field are outnumbered by sdBs (these stars show a number ratio ≈1:3; Heber 2009), the true reason for this relative lack of investigations must be found in the inherent challenge associated with the atmospheric modeling and spectroscopic analyses ...
... (i.e., below 40 000 K). While known sdO stars in the field are outnumbered by sdBs (these stars show a number ratio ≈1:3; Heber 2009), the true reason for this relative lack of investigations must be found in the inherent challenge associated with the atmospheric modeling and spectroscopic analyses ...
MEASURING ANGLES
... Have you ever thought how we determine the positions of stars, or the sizes of anything? If you want to know the size of Jupiter (or even just the moon), you can hardly fly to it with your ruler in your hand and measure it. However, the moon has a definite size in the sky. And what’s the size of the ...
... Have you ever thought how we determine the positions of stars, or the sizes of anything? If you want to know the size of Jupiter (or even just the moon), you can hardly fly to it with your ruler in your hand and measure it. However, the moon has a definite size in the sky. And what’s the size of the ...
Hubble`s Law
... If the universe is indeed infinite, then there should be at least one star at every visible point in the sky lighting it up in all directions. Imagine standing at the center of a very thick forest: there is always a tree in your line of sight, regardless of what direction you are facing. If the univ ...
... If the universe is indeed infinite, then there should be at least one star at every visible point in the sky lighting it up in all directions. Imagine standing at the center of a very thick forest: there is always a tree in your line of sight, regardless of what direction you are facing. If the univ ...
mg_colloq - University of Massachusetts Amherst
... Detection rate of individual sources is about 6% for both compact, 4% for non compact Consistent with the small incidence of AGN among LBG Absence of evidence is NOT evidence of absence, but presence of AGN does not seem obvious ...
... Detection rate of individual sources is about 6% for both compact, 4% for non compact Consistent with the small incidence of AGN among LBG Absence of evidence is NOT evidence of absence, but presence of AGN does not seem obvious ...
Word
... galaxies as described by Hubble's Law are all that is required to produce the basic Big Bang model of the Universe. In fact, Einstein in 1917, just two years after formulating General Relativity, applied the Cosmological Principle to GR and came within an ace of predicting the expansion of the Unive ...
... galaxies as described by Hubble's Law are all that is required to produce the basic Big Bang model of the Universe. In fact, Einstein in 1917, just two years after formulating General Relativity, applied the Cosmological Principle to GR and came within an ace of predicting the expansion of the Unive ...
Stellar Evolution
... B-star spectrum; Si II, Mn II, Cr II, Eu II, Sr II are strong. H lines strong, Ca II H & K strengthen toward later type. A-star spectrum; Si II, Mn II, Cr II, Eu II, Sr II are strong. A-star spectrum + Fe lines unusually strong. Metals, H lines weaken, Ca II strengthen — emission “bumps” appear in H ...
... B-star spectrum; Si II, Mn II, Cr II, Eu II, Sr II are strong. H lines strong, Ca II H & K strengthen toward later type. A-star spectrum; Si II, Mn II, Cr II, Eu II, Sr II are strong. A-star spectrum + Fe lines unusually strong. Metals, H lines weaken, Ca II strengthen — emission “bumps” appear in H ...
Parallax
... Of course astronomers are not ones to use simple methods. They have goobered up this measurement just like the ones with magnitude. So keep reading and the enumeration as to how astronomers use parallax to measure the distance to a star will be given. Except for our sun, the stars are pretty far aw ...
... Of course astronomers are not ones to use simple methods. They have goobered up this measurement just like the ones with magnitude. So keep reading and the enumeration as to how astronomers use parallax to measure the distance to a star will be given. Except for our sun, the stars are pretty far aw ...
sections 23-25 powerpoint
... disks surrounding supermassive black holes at their centres. Supermassive black hole. The term used to describe the central regions of most large galaxies, where millions of solar masses of matter occupy a very ...
... disks surrounding supermassive black holes at their centres. Supermassive black hole. The term used to describe the central regions of most large galaxies, where millions of solar masses of matter occupy a very ...
Lecture 15a - Sierra College Astronomy Home Page
... 0.5 million years (fast robot probes, fastest biological exploration) 5 million years (slow robot probes) 50 million years (slow biological exploration) 10 billion years Instead, it would be vastly more likely that if even one other civilization EVER occurred in our galaxy, it would have had billion ...
... 0.5 million years (fast robot probes, fastest biological exploration) 5 million years (slow robot probes) 50 million years (slow biological exploration) 10 billion years Instead, it would be vastly more likely that if even one other civilization EVER occurred in our galaxy, it would have had billion ...
Satellities - stoweschools.com
... Velocity of the Geostationary Satellite with respect to the sun ...
... Velocity of the Geostationary Satellite with respect to the sun ...
starwalk2 manual en
... The highlighted parameter will start changing accordingly. To make any parameter elapse automatically, tap one of them and drag the Time slider. The map sky will rotate. In order to stop that, tap the Time slider again. To return to the current time zone, tap ...
... The highlighted parameter will start changing accordingly. To make any parameter elapse automatically, tap one of them and drag the Time slider. The map sky will rotate. In order to stop that, tap the Time slider again. To return to the current time zone, tap ...
sections 16-18 instructor notes
... Jones, MNRAS, 190, 591, 1980; Heck & Lakaye, MNRAS, 184, 17, 1978; see Stothers, ApJ, 274, 20, 1983), which are too distant for direct measurement of their distances by standard techniques. Both classes of object are also relatively uncommon in terms of their local space densities, yet luminous enou ...
... Jones, MNRAS, 190, 591, 1980; Heck & Lakaye, MNRAS, 184, 17, 1978; see Stothers, ApJ, 274, 20, 1983), which are too distant for direct measurement of their distances by standard techniques. Both classes of object are also relatively uncommon in terms of their local space densities, yet luminous enou ...
Gamma Ray Bursts
... (~1000 km) – light must go through the source High luminosity and large distance imply high energy released. Compact source implies high energy density photons interact and produce e+e- pairs spectrum should not contain g with E>511keV Such photons are observed sources are close to us False tr ...
... (~1000 km) – light must go through the source High luminosity and large distance imply high energy released. Compact source implies high energy density photons interact and produce e+e- pairs spectrum should not contain g with E>511keV Such photons are observed sources are close to us False tr ...
Observational astronomy
Observational astronomy is a division of the astronomical science that is concerned with recording data, in contrast with theoretical astrophysics, which is mainly concerned with finding out the measurable implications of physical models. It is the practice of observing celestial objects by using telescopes and other astronomical apparatus.As a science, the study of astronomy is somewhat hindered in that direct experiments with the properties of the distant universe are not possible. However, this is partly compensated by the fact that astronomers have a vast number of visible examples of stellar phenomena that can be examined. This allows for observational data to be plotted on graphs, and general trends recorded. Nearby examples of specific phenomena, such as variable stars, can then be used to infer the behavior of more distant representatives. Those distant yardsticks can then be employed to measure other phenomena in that neighborhood, including the distance to a galaxy.Galileo Galilei turned a telescope to the heavens and recorded what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology.A traditional division of observational astronomy is given by the region of the electromagnetic spectrum observed: Optical astronomy is the part of astronomy that uses optical components (mirrors, lenses and solid-state detectors) to observe light from near infrared to near ultraviolet wavelengths. Visible-light astronomy (using wavelengths that can be detected with the eyes, about 400 - 700 nm) falls in the middle of this range. Infrared astronomy deals with the detection and analysis of infrared radiation (this typically refers to wavelengths longer than the detection limit of silicon solid-state detectors, about 1 μm wavelength). The most common tool is the reflecting telescope but with a detector sensitive to infrared wavelengths. Space telescopes are used at certain wavelengths where the atmosphere is opaque, or to eliminate noise (thermal radiation from the atmosphere). Radio astronomy detects radiation of millimetre to dekametre wavelength. The receivers are similar to those used in radio broadcast transmission but much more sensitive. See also Radio telescopes. High-energy astronomy includes X-ray astronomy, gamma-ray astronomy, and extreme UV astronomy, as well as studies of neutrinos and cosmic rays.Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is relatively transparent at the wavelengths being detected. Observatories are usually located at high altitudes so as to minimise the absorption and distortion caused by the Earth's atmosphere. Some wavelengths of infrared light are heavily absorbed by water vapor, so many infrared observatories are located in dry places at high altitude, or in space.The atmosphere is opaque at the wavelengths used by X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for a few wavelength ""windows"") far infrared astronomy, so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays is a rapidly expanding branch of astronomy.For much of the history of observational astronomy, almost all observation was performed in the visual spectrum with optical telescopes. While the Earth's atmosphere is relatively transparent in this portion of the electromagnetic spectrum, most telescope work is still dependent on seeing conditions and air transparency, and is generally restricted to the night time. The seeing conditions depend on the turbulence and thermal variations in the air. Locations that are frequently cloudy or suffer from atmospheric turbulence limit the resolution of observations. Likewise the presence of the full Moon can brighten up the sky with scattered light, hindering observation of faint objects.For observation purposes, the optimal location for an optical telescope is undoubtedly in outer space. There the telescope can make observations without being affected by the atmosphere. However, at present it remains costly to lift telescopes into orbit. Thus the next best locations are certain mountain peaks that have a high number of cloudless days and generally possess good atmospheric conditions (with good seeing conditions). The peaks of the islands of Mauna Kea, Hawaii and La Palma possess these properties, as to a lesser extent do inland sites such as Llano de Chajnantor, Paranal, Cerro Tololo and La Silla in Chile. These observatory locations have attracted an assemblage of powerful telescopes, totalling many billion US dollars of investment.The darkness of the night sky is an important factor in optical astronomy. With the size of cities and human populated areas ever expanding, the amount of artificial light at night has also increased. These artificial lights produce a diffuse background illumination that makes observation of faint astronomical features very difficult without special filters. In a few locations such as the state of Arizona and in the United Kingdom, this has led to campaigns for the reduction of light pollution. The use of hoods around street lights not only improves the amount of light directed toward the ground, but also helps reduce the light directed toward the sky.Atmospheric effects (astronomical seeing) can severely hinder the resolution of a telescope. Without some means of correcting for the blurring effect of the shifting atmosphere, telescopes larger than about 15–20 cm in aperture can not achieve their theoretical resolution at visible wavelengths. As a result, the primary benefit of using very large telescopes has been the improved light-gathering capability, allowing very faint magnitudes to be observed. However the resolution handicap has begun to be overcome by adaptive optics, speckle imaging and interferometric imaging, as well as the use of space telescopes.Astronomers have a number of observational tools that they can use to make measurements of the heavens. For objects that are relatively close to the Sun and Earth, direct and very precise position measurements can be made against a more distant (and thereby nearly stationary) background. Early observations of this nature were used to develop very precise orbital models of the various planets, and to determine their respective masses and gravitational perturbations. Such measurements led to the discovery of the planets Uranus, Neptune, and (indirectly) Pluto. They also resulted in an erroneous assumption of a fictional planet Vulcan within the orbit of Mercury (but the explanation of the precession of Mercury's orbit by Einstein is considered one of the triumphs of his general relativity theory).