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HD 177765
HD 177765 is a white-hued star in the southern constellation of Sagittarius. With an apparent magnitude of 9.15, it is too faint to be seen by the naked eye from Earth, but is dimly visible using binoculars. It is located at a distance of according to Gaia EDR3 parallax measurements. Description The star is classified as a rapidly oscillating Ap star (roAp star). It shows super-solar abundances of chromium and strontium as well as many rare-earth elements such as europium and cerium, but is depleted of carbon and nickel. In 2012, the star was found to pulsate with a low radial velocity amplitude of 7–150 m/s and a period of 23.6 minutes, the latter being the longest out of any known roAp star at the time. Two additional pulsation frequencies were detected in 2016. The precise stellar parameters vary from publication to publication, but the star is considered to be part of a group of evolved roAp stars with long pulsation periods, alongside β CrB A and HD 11611 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagittarius (constellation)
Sagittarius is one of the constellations of the zodiac and is located in the Southern celestial hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its old astronomical symbol is (♐︎). Its name is Latin for "archery, archer". Sagittarius is commonly represented as a centaur drawing a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus and Microscopium to the east. The center of the Milky Way lies in the westernmost part of Sagittarius (see Sagittarius A). Visualizations As seen from the northern hemisphere, the constellation's brighter stars form an easily recognizable asterism (astronomy), asterism known as "the Teapot". The stars Delta Sagittarii, δ Sgr (Kaus Media), Epsilon Sagittarii, ε Sgr (Kaus Australis), Zeta Sagittarii, ζ Sgr (Ascella), and Phi Sagittarii, φ Sgr form the body of the pot; Lambda Sagittarii, λ Sgr (Kaus Borealis) is the point of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slow to react with air under standard conditions because a passivation layer of nickel oxide forms on the surface that prevents further corrosion. Even so, pure native nickel is found in Earth's crust only in tiny amounts, usually in ultramafic rocks, and in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere. Meteoric nickel is found in combination with iron, a reflection of the origin of those elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earth's outer and inner cores. Use of nickel (as natural meteoric nickel–iron alloy) has been traced as far back as 3500 BCE. Nickel was first isolated and classifie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Draper Catalogue Objects
Henry may refer to: People and fictional characters * Henry (given name), including lists of people and fictional characters * Henry (surname) * Henry, a stage name of François-Louis Henry (1786–1855), French baritone Arts and entertainment * Henry (2011 film), ''Henry'' (2011 film), a Canadian short film * Henry (2015 film), ''Henry'' (2015 film), a virtual reality film * ''Henry: Portrait of a Serial Killer'', a 1986 American crime film * Henry (comics), ''Henry'' (comics), an American comic strip created in 1932 by Carl Anderson * "Henry", a song by New Riders of the Purple Sage Places Antarctica * Henry Bay, Wilkes Land Australia *Henry River (New South Wales) *Henry River (Western Australia) Canada * Henry Lake (Vancouver Island), British Columbia * Henry Lake (Halifax County), Nova Scotia * Henry Lake (District of Chester), Nova Scotia New Zealand * Lake Henry (New Zealand) * Henry River (New Zealand) United States * Henry, Illinois * Henry, Indiana * Henry, Nebras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A-type Stars
A type or type A may refer to: Science * A-type asteroid, a type of relatively uncommon inner-belt asteroids * A type blood, a type in the ABO blood group system * A-type inclusion, a type of cell inclusion * A-type potassium channel, a type of voltage-gated potassium channel * A type proanthocyanidin, a specific type of flavonoids * A-type star, a class of stars * Type A climate, a type in the Köppen climate classification * Type A flu, a type of influenza virus * Type A evaluation of uncertainty, an uncertainty in measurement that can be inferred, for example, from repeated measurement * Type A personality, a personality type in the Type A and Type B personality theory * Hemophilia type A, a type of haemophilia * A-type granite a type of granite rock * Adenosine receptor Technology * Type A Dolby Noise Reduction, a type of Dolby noise-reduction system * Type A plug (see also NEMA connector) * Type A submarine, a class of submarines in the Imperial Japanese Navy which served ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapidly Oscillating Ap Stars
Rapidly oscillating Ap stars (roAp stars) are a subtype of the Ap star, Ap star class that exhibit short-timescale rapid Photometry (astronomy), photometric or radial velocity variations. The known periods range between 5 and 23 minutes. They lie in the Delta Scuti variable, δ Scuti instability strip on the main sequence. Discovery The first roAp star to be discovered was HD 101065 (Przybylski's Star) in 1961. The oscillations were discovered by Donald Kurtz using the telescope at the South African Astronomical Observatory, who saw 10–20-millimagnitude variations in the light curve of the star with a period of 12.15 minutes. Classification The roAp stars are sometimes referred to as rapidly oscillating α2 Canum Venaticorum variables. Both the roAp stars and some Alpha2 Canum Venaticorum variable, α2 CVn variables lie on the δ Scuti instability strip and are magnetic chemically peculiar stars, but the roAp stars have very short periods less than an hour. Oscillations The roA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VizieR
A vizier (; ; ) is a high-ranking political advisor or Minister (government), minister in the Near East. The Abbasids, Abbasid caliphs gave the title ''wazir'' to a minister formerly called ''katib'' (secretary), who was at first merely a helper but afterwards became the representative and successor of the ''dapir'' (official scribe or secretary) of the Sasanian Empire, Sassanian kings. In modern usage, the term has been used for government Minister (government), ministers in much of the Middle East and beyond. Several alternative spellings are used in English, such as ''vizir'', ''wazir'', and ''vezir''. Etymology Vizier may be derived from the Arabic ''wazara'' (), from the Semitic root ''W-Z-R''. The word is mentioned in the Quran, where Aaron is described as the ''wazir'' (helper) of Moses, as well as the word ''wizr'' (burden) which is also derived from the same root. It was later adopted as a title, in the form of ''wazīr āl Muḥammad'' () by the proto-Shi'a leaders ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emission Line
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected ones of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible. Types of line spectra Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nuclei) and a single photon. When a photon has about the right amount of energy (which is connected to its frequency) to allow a change in the energy state of the system (in the case of an atom this is usually an electron changing orbitals), the photon is absorbed. Then the energy will be spontaneously re-emitted, either as one photon at the same f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 116114
Rapidly oscillating Ap stars (roAp stars) are a subtype of the Ap star class that exhibit short-timescale rapid photometric or radial velocity variations. The known periods range between 5 and 23 minutes. They lie in the δ Scuti instability strip on the main sequence. Discovery The first roAp star to be discovered was HD 101065 ( Przybylski's Star) in 1961. The oscillations were discovered by Donald Kurtz using the telescope at the South African Astronomical Observatory, who saw 10–20-millimagnitude variations in the light curve of the star with a period of 12.15 minutes. Classification The roAp stars are sometimes referred to as rapidly oscillating α2 Canum Venaticorum variables. Both the roAp stars and some α2 CVn variables lie on the δ Scuti instability strip and are magnetic chemically peculiar stars, but the roAp stars have very short periods less than an hour. Oscillations The roAp stars oscillate in high-overtone, low-degree, non-radial pressure modes. The usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Coronae Borealis
Beta Coronae Borealis (β Coronae Borealis, abbreviated Beta CrB, β CrB) is a binary star in the constellation of Corona Borealis. It appears to the naked eye to be a single star and is the second-brightest star in its constellation with an apparent visual magnitude varying between 3.65 and 3.72. Based on parallax measurements taken during the Hipparcos mission, it is approximately 112 light-years from the Sun. The two components are designated Beta Coronae Borealis A (officially named Nusakan , the traditional name of the system) and B. Nomenclature ''β Coronae Borealis'' ( Latinised to ''Beta Coronae Borealis'') is the system's Bayer designation. The designations of the two components as ''Beta Coronae Borealis A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). It bore the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from Gravitational collapse, 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 existence. Initially the energy is generated by the fusion of hydrogen atoms at the stellar core, 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 st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude
The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the variable's extreme values. In older texts, the phase of a periodic function is sometimes called the amplitude. Definitions Peak amplitude and semi-amplitude For symmetric periodic waves, like sine waves or triangle waves, ''peak amplitude'' and ''semi amplitude'' are the same. Peak amplitude In audio system measurements, telecommunications and others where the measurand is a signal that swings above and below a reference value but is not sinusoidal, peak amplitude is often used. If the reference is zero, this is the maximum absolute value of the signal; if the reference is a mean value ( DC component), the peak amplitude is the maximum ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radial Velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity onto the relative direction or line-of-sight (LOS) connecting the two points. The radial speed or range rate is the temporal rate of the distance or range between the two points. It is a signed scalar quantity, formulated as the scalar projection of the relative velocity vector onto the LOS direction. Equivalently, radial speed equals the norm of the radial velocity, modulo the sign. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from the Earth (or approaches it, for a negative radial velocity). Formulation Given a differentiable vector \mathbf r \in \mathbb^3 defining the instantaneous relative position of a target with respe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
