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PV Telescopii
PV Telescopii, also known as HD 168476, is a variable star in the southern constellation of Telescopium. It is too dim to be visible to the naked eye, having an apparent visual magnitude that has been measured varying from 9.24 down to 9.40. The star is the prototype of a class of objects called PV Telescopii variables. It is located at an estimated distance of approximately from the Sun, but is drifting closer with a radial velocity of −169 km/s. This is an extreme helium star that shows a highly-processed atmosphere. It is a blue-white hued B-type supergiant star with a peculiar spectrum that has "weak hydrogen lines and enhanced lines of He and C". This object may be a late thermal pulse post- AGB star or the result of a merger of two white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Line
The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , which is equivalent to the vacuum wavelength of in free space. This frequency falls below the microwave region of the electromagnetic spectrum, which begins at 3.0 GHz (10 cm wavelength), and it is observed frequently in radio astronomy because those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light. This line is also the theoretical basis of the hydrogen maser. The microwaves of the hydrogen line come from the atomic transition of an electron between the two hyperfine levels of the hydrogen 1 s ground state that have an energy difference of []. It is called the ''spin-flip transition''. The frequency, , of the quantum, quanta that are emitted by this transition between tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Draper Catalogue Objects
Henry may refer to: People *Henry (given name) *Henry (surname) * Henry Lau, Canadian singer and musician who performs under the mononym Henry Royalty * Portuguese royalty ** King-Cardinal Henry, King of Portugal ** Henry, Count of Portugal, Henry of Burgundy, Count of Portugal (father of Portugal's first king) ** Prince Henry the Navigator, Infante of Portugal ** Infante Henrique, Duke of Coimbra (born 1949), the sixth in line to Portuguese throne * King of Germany ** Henry the Fowler (876–936), first king of Germany * King of Scots (in name, at least) ** Henry Stuart, Lord Darnley (1545/6–1567), consort of Mary, queen of Scots ** Henry Benedict Stuart, the 'Cardinal Duke of York', brother of Bonnie Prince Charlie, who was hailed by Jacobites as Henry IX * Four kings of Castile: **Henry I of Castile **Henry II of Castile **Henry III of Castile **Henry IV of Castile * Five kings of France, spelt ''Henri'' in Modern French since the Renaissance to italianize the name and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Durchmusterung Objects
In astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, compiled by the Bonn Observatory in Germany from 1859 to 1903. The name comes from ('run-through examination'), a German word used for a systematic survey of objects or data. The term has sometimes been used for other astronomical surveys, including not only stars, but also the search for other celestial objects. Special tasks include celestial scanning in electromagnetic wavelengths shorter or longer than visible light waves. Original catalog The 44 years of work on the Bonner Durchmusterung (abbreviated BD), initiated by Friedrich Argelander and largely carried out by his assistants, resulted in a catalogue of the positions and apparent magnitudes of approximately 325,000 stars to apparent magnitude 9–10. The catalogue was accompanied by charts plotting the positions of the stars, and was the basis for the ''Astronomische Gesellschaft Katalog'' (AGK) and ''Smithsonia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PV Telescopii Variables
PV may refer to: Places * Paceville, Malta * Puerto Vallarta, Mexico * Postal village, a settlement that has a post office United States * Palos Verdes Peninsula, California * Prescott Valley, Arizona * Prairie Village, Kansas Politics * Partido Verde (other), several political parties * Peoples Voice, a political party in Singapore * Preferential voting (other), a category of electoral systems Science and technology * Photovoltaics, a technology for converting sunlight into electricity * Potential vorticity, in fluid dynamics * Presta valve, one of the two common tire valves * Process variable, in control systems * Programmed visibility, of traffic signals Biology and medicine * Parvalbumin, a calcium-binding albumin protein * Pathovar, a bacterial strain or set of strains with the same or similar characteristics * Pemphigus vulgaris, a chronic blistering skin disease * ''Per vaginam'', through/via the vagina * Periventricular nucleus, of the hypothalamus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-type Supergiants
B type or Type B may refer to: Astronomy * B-type asteroid, a type of relatively uncommon type of carbonaceous asteroid * B-type giant, a type of blue giant star * B-type star, a type of star Biology * B type blood, a type in the ABO blood group system * B type inclusion, a type of inclusions in cells infected with poxvirus * B-type natriuretic peptide, a type of brain natriuretic peptides * B type proanthocyanidin, a specific type of flavanoids * Type B evaluation of uncertainty, an uncertainty in measurement inferred from scientific judgement or other information concerning the possible values of the quantity * Type B personality, a type in the Type A and Type B personality theory Others * B-type warbird, a type of Romulan starship * Type B videotape, an open-reel videotape format * Curtiss-built B-type, a type of B class blimp * LGOC B-type, a model of double-decker bus that was introduced in London on 1910 * Mann Egerton Type B, a 1910s British maritime patrol aircraft * To ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radial Pulsations
The unqualified term instability strip usually refers to a region of the Hertzsprung–Russell diagram largely occupied by several related classes of pulsating variable stars: Delta Scuti variables, SX Phoenicis variables, and rapidly oscillating Ap stars (roAps) near the main sequence; RR Lyrae variables where it intersects the horizontal branch; and the Cepheid variables where it crosses the supergiants. RV Tauri variables are also often considered to lie on the instability strip, occupying the area to the right of the brighter Cepheids (at lower temperatures), since their stellar pulsations are attributed to the same mechanism. Position on the HR diagram The Hertzsprung–Russell diagram plots the real luminosity of stars against their effective temperature (their color, given by the temperature of their photosphere). The instability strip intersects the main sequence, (the prominent diagonal band that runs from the upper left to the lower right) in the region of A and F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymptotic Giant Branch
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives. Observationally, an asymptotic-giant-branch star will appear as a bright red giant with a luminosity ranging up to thousands of times greater than the Sun. Its interior structure is characterized by a central and largely inert core of carbon and oxygen, a shell where helium is undergoing fusion to form carbon (known as helium burning), another shell where hydrogen is undergoing fusion forming helium (known as hydrogen burning), and a very large envelope of material of composition similar to main-sequence stars (except in the case of carbon stars). Stellar evolution When a star exhausts the supply of hydrogen by nuclear fusion processes in its core, the core contracts and its temperature increases, causing the outer l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Thermal Pulse
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives. Observationally, an asymptotic-giant-branch star will appear as a bright red giant with a luminosity ranging up to thousands of times greater than the Sun. Its interior structure is characterized by a central and largely inert core of carbon and oxygen, a shell where helium is undergoing fusion to form carbon (known as helium burning), another shell where hydrogen is undergoing fusion forming helium (known as hydrogen burning), and a very large envelope of material of composition similar to main-sequence stars (except in the case of carbon stars). Stellar evolution When a star exhausts the supply of hydrogen by nuclear fusion processes in its core, the core contracts and its temperature increases, causing the outer lay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supergiant
Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K. Definition The title supergiant, as applied to a star, does not have a single concrete definition. The term ''giant star'' was first coined by Hertzsprung when it became apparent that the majority of stars fell into two distinct regions of the Hertzsprung–Russell diagram. One region contained larger and more luminous stars of spectral types A to M and received the name ''giant''. Subsequently, as they lacked any measurable parallax, it became apparent that some of these stars were significantly larger and more luminous than the bulk, and the term ''super-giant'' arose, quickly adopted as ''supergiant''. Spectral luminosity class Supergiant stars can be identified on the basis of thei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequency interval or band. Light curves can be periodic, as in the case of eclipsing binaries, Cepheid variables, other periodic variables, and transiting extrasolar planets, or aperiodic, like the light curve of a nova, a cataclysmic variable star, a supernova or a microlensing event or binary as observed during occultation events. The study of the light curve, together with other observations, can yield considerable information about the physical process that produces it or constrain the physical theories about it. Variable stars Graphs of the apparent magnitude of a variable star over time are commonly used to visualise and analyse their behaviour. Although the categorisation of variable star types is increasingly done from their s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
