query: the differences between the different spectral types of stars are primarily due to

pos: Stellar classification the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan-Keenan (MK) system using the letters "O", "B", "A", "F", "G", "K", and "M", a sequence from the hottest ("O" type) to the coolest ("M" type). Each letter class is then subdivided using a numeric digit with "0" being hottest and "9" being coolest (e.g. A8, A9, F0, and F1 form a sequence from hotter to cooler). The sequence has been expanded with classes for other stars and star-like objects that do not fit in the classical system, such as class "D"

neg: Stellar classification Stellar classification In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The "spectral class" of a star is a short code primarily summarizing

neg: Hypergiant or is just an artifact of our observations. Model details vary but there are many areas of agreement. Some of these distinctions are not necessarily helpful in establishing relationships between different types of stars or the differences between them since they have been developed based on differing criteria and for different purposes. Although most supergiant stars are less luminous than hypergiants of the same temperature, a few fall in the same luminosity range. Ordinary supergiants lack the strong H emission and broadened spectral lines that indicate rapid mass loss in the hypergiants. Lower mass supergiants do not return from the

neg: Supergiant star partly to different methods for assigning luminosity classes at different spectral types, and partly to actual physical differences in the stars. The bolometric luminosity of a star reflects its total output of electromagnetic radiation at all wavelengths. For very hot and very cool stars, the bolometric luminosity is dramatically higher than the visual luminosity, sometimes several magnitudes or a factor of five or more. This bolometric correction is approximately one magnitude for mid B, late K, and early M stars, increasing to three magnitudes (a factor of 15) for O and mid M stars. All supergiants are larger and more

neg: Supergiant star before reaching the asymptotic giant branch. A distinct grouping is made up of high-luminosity supergiants at early B (B0-2) and very late O (O9.5), more common even than main sequence stars of those spectral types. The relative numbers of blue, yellow, and red supergiants is an indicator of the speed of stellar evolution and is used as a powerful test of models of the evolution of massive stars. The supergiants lie more or less on a horizontal band occupying the entire upper portion of the HR diagram, but there are some variations at different spectral types. These variations are due

neg: Stellar classification cool as they age and so progress to later spectral types. Brown dwarfs start their lives with M-type spectra and will cool through the L, T, and Y spectral classes, faster the less massive they are; the highest-mass brown dwarfs cannot have cooled to Y or even T dwarfs within the age of the universe. Because this leads to an unresolvable overlap between spectral types effective temperature and luminosity for some masses and ages of different L-T-Y types, no distinct temperature or luminosity values can be given. Class L dwarfs get their designation because they are cooler than M stars

neg: Chi Cygni around M6e at maximum brightness. After the S class was introduced, χ Cygni was considered intermediate between class M and class S, for example either S5e or M6-M8e. Later more sensitive spectra near minimum gave spectral types as late as M10 or S10,1e. Under the revised classification system for S stars, designed to better reflect the gradation between M stars and carbon stars, χ Cygni at normal maximum was classified as S6 Zr2 Ti6 or S6+/1e, considered equivalent to MS6+. Spectral types at different phases of variation ranged from S6/1e to S9/1-e although no measurements were taken at minimum brightness.

neg: Stellar classification been subsumed into the new C class as C-R and C-N. Stellar classification In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The

neg: Capella been given various spectral types of late (cooler) F or early (warmer) G. The MK spectral types of the two stars have been measured a number of times, and they are both consistently assigned a luminosity class of III indicating a giant star. The composite spectrum appears to be dominated by the primary star due to its sharper absorption lines; the lines from the secondary are broadened and blurred by its rapid rotation. The composite spectral class is given as approximately G3III, but with a specific mention of features due to a cooler component. The most recent specific published types

neg: Variable star single giant stars with spectral types G and K and show strong chromospheric emission lines. Examples are FK Com, HD 199178 and UZ Lib. A possible explanation for the rapid rotation of FK Comae stars is that they are the result of the merger of a (contact) binary. BY Draconis stars are of spectral class K or M and vary by less than 0.5 magnitudes (70% change in luminosity). Alpha-2 Canum Venaticorum (α CVn) variables are main-sequence stars of spectral class B8–A7 that show fluctuations of 0.01 to 0.1 magnitudes (1% to 10%) due to changes in their magnetic fields.

neg: Mercury-manganese star The following table includes the brightest stars in this group. Mercury-manganese star A mercury-manganese star is a type of chemically peculiar star with a prominent spectral line at 398.4 nm, due to absorption from ionized mercury. These stars are of spectral type B8, B9, or A0, corresponding to surface temperatures between about 10,000 and 15,000 K, with two distinctive characteristics: Their rotation is relatively slow, and as a consequence their atmosphere is relatively calm. It is thought, but has not been proven, that some types of atoms sink under the force of gravity, while others are lifted towards the exterior

neg: Asteroseismology light. The oscillations are low-order pressure modes, excited by the kappa mechanism acting on the iron opacity bump. White dwarfs are characterized by spectral type, much like ordinary stars, except that the relationship between spectral type and effective temperature does not correspond in the same way. Thus, white dwarfs are known by types DO, DA and DB. Cooler types are physically possible but the Universe is too young for them to have cooled enough. White dwarfs of all three types are found to pulsate. The pulsators are known as GW Virginis stars (DO variables, sometimes also known as PG 1159

neg: Molecules in stars of elements, and so indicate elemental composition of the star. Different molecules are characteristic of different kinds of stars, and are used to classify them. Because there can be numerous spectral lines of different strength, conditions at different depths in the star can be determined. These conditions include temperature and speed towards or away from the observer. The spectrum of molecules has advantages over atomic spectral lines, as atomic lines are often very strong, and therefore only come from high in the atmosphere. Also the profile of the atomic spectral line can be distorted due to isotopes or overlaying of

neg: 88 Tauri an A-type star. The "m" in its spectral type means that it is an Am star, also known as a metallic-line star. These types of stars have spectra indicating varying amounts of metals, like iron. The rest of the stars in 88 Tauri A have spectral types ranging from F5 to G2-3, meaning that they are regular F-type or G-type main-sequence stars. The spectral types for 88 Tauri Ab1 and Ab2 are less certain, because their spectral lines are weaker, hence the colon after G2. Aa1 does not appears to be rotating synchronously with its companion (nor does it have

neg: Main sequence for stars of non-uniform composition.) A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan. The MK classification assigned each star a spectral type—based on the Harvard classification—and a luminosity class. The Harvard classification had been developed by assigning a different letter to each star based on the strength of the hydrogen spectral line, before the relationship between spectra and temperature was known. When ordered by temperature and when duplicate classes were removed, the spectral types of stars followed, in order of decreasing temperature with colors ranging from blue to red, the

neg: Doppler imaging Doppler imaging Inhomogeneous structures on stellar surfaces, i.e. temperature differences, chemical composition or magnetic fields, create characteristic distortions in the spectral lines due to the Doppler effect. These distortions will move across spectral line profiles due to the stellar rotation. The technique to reconstruct these structures on the stellar surface is called Doppler-imaging, often based on the Maximum Entropy image reconstruction to find the stellar image. This technique gives the smoothest and simplest image that is consistent with observations. To understand the magnetic field and activity of stars, studies of the Sun are not sufficient. Therefore, studies of other stars

neg: Red supergiant star planetary nebula. AGB stars may develop spectra with a supergiant luminosity class as they expand to extreme dimensions relative to their small mass, and they may reach luminosities tens of thousands times the sun's. Intermediate "super-AGB" stars, around , can undergo carbon fusion and may produce an electron capture supernova through the collapse of an oxygen-neon core. Main-sequence stars, burning hydrogen in their cores, with masses between will have temperatures between about 25,000K and 32,000K and spectral types of early B, possibly very late O. They are already very luminous stars of due to rapid CNO cycle fusion of hydrogen

neg: R99 only as a candidate. R99 R99 (HD 269445) is a star in the Large Magellanic Cloud in the constellation Dorado. It is classified as a luminous blue variable and is one of the most luminous stars known. R99 has a peculiar spectrum that has been described as OBf:pe, "unclassifiable", peculiar WN10, "similar to the unusual LBV HD 5980", "unique", and Ofpe/WN9. The Ofpe/WN9 type remains even though other stars of this type have been reclassified to types between WN9 and WN11. R99 has significant differences to those other stars which preclude it being given a simple WN spectral type: the

neg: R99 R99 R99 (HD 269445) is a star in the Large Magellanic Cloud in the constellation Dorado. It is classified as a luminous blue variable and is one of the most luminous stars known. R99 has a peculiar spectrum that has been described as OBf:pe, "unclassifiable", peculiar WN10, "similar to the unusual LBV HD 5980", "unique", and Ofpe/WN9. The Ofpe/WN9 type remains even though other stars of this type have been reclassified to types between WN9 and WN11. R99 has significant differences to those other stars which preclude it being given a simple WN spectral type: the ultraviolet spectrum is strongly

neg: Alpha Cygni variable Alpha Cygni variable Alpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time others parts expand. They are supergiant stars of spectral types B or A. Variations in brightness on the order of 0.1 magnitudes are associated with the pulsations, which often seem irregular, due to beating of multiple pulsation periods. The pulsations typically have periods of several days to several weeks. The prototype of these stars, Deneb (α Cygni), exhibits fluctuations in brightness between magnitudes +1.21 and +1.29. Small amplitude rapid variations have been known

neg: Zeta Ursae Majoris resolution using the Navy Prototype Optical Interferometer. The two components of ζ Ursae Majoris (Mizar Aa and Ab) are observed to be identical, with the exception of slightly different radial velocity variations which indicate very slightly different masses. The spectral lines of the two stars can be observed separately and both are given a spectral type of A2Vp. They are Ap stars, chemically peculiar due to stratification of some heavy elements in the photosphere of slowly-rotating hot stars. In this case, they show elevated abundances of strontium and silicon. With the assumption of identical physical properties for the two stars,

neg: RV Tauri variable confused with the spectroscopic sub-types which use capital letters, often appended to RV: RVA; RVB; and RVC. The General Catalogue of Variable Stars uses acronyms consisting of capital letters to identify variability types, and so uses RVA and RVB to refer to the two photometric sub-types. RV Tau variables exhibit changes in luminosity which are tied to radial pulsations of their surfaces. Their changes in brightness are also correlated with changes in their spectral type. While at their brightest, the stars have spectral types F or G. At their dimmest, their spectral types change to K or M. The difference

neg: S-type star half the smaller intensity. Y is the "abundance class". It is also a digit between 1 and 9, assigned by multiplying the ratio of ZrO and TiO bands by the temperature class. This calculation generally yields a number which can be rounded down to give the abundance class digit, but this is modified for higher values: In practice, spectral types for new stars would be assigned by referencing to the standard stars, since the intensity values are subjective and would be impossible to reproduce from spectra taken under different conditions. A number of drawbacks came to light as S stars

neg: Mercury-manganese star Mercury-manganese star A mercury-manganese star is a type of chemically peculiar star with a prominent spectral line at 398.4 nm, due to absorption from ionized mercury. These stars are of spectral type B8, B9, or A0, corresponding to surface temperatures between about 10,000 and 15,000 K, with two distinctive characteristics: Their rotation is relatively slow, and as a consequence their atmosphere is relatively calm. It is thought, but has not been proven, that some types of atoms sink under the force of gravity, while others are lifted towards the exterior of the star by radiation pressure, making a heterogeneous atmosphere.

neg: Color–color diagram effective temperature of the star can still be determined, as magnitude differences between each color will be unique for that temperature. As such, color-color diagrams can be used as a means of representing the stellar population, much like a Hertzsprung–Russell diagram, and stars of different spectral classes will inhabit different parts of the diagram. This feature leads to applications within various wavelength bands. In the stellar locus, stars tend to align in a more or less straight feature. If stars were perfect black bodies, the stellar locus would be a pure straight line indeed. The divergences with the straight line

neg: White dwarf the other pulsating variable white dwarfs known, arises from non-radial gravity wave pulsations. Known types of pulsating white dwarf include the "DAV", or "ZZ Ceti", stars, including HL Tau 76, with hydrogen-dominated atmospheres and the spectral type DA; "DBV", or "V777 Her", stars, with helium-dominated atmospheres and the spectral type DB; and "GW Vir stars", sometimes subdivided into "DOV" and "PNNV" stars, with atmospheres dominated by helium, carbon, and oxygen. GW Vir stars are not, strictly speaking, white dwarfs, but are stars which are in a position on the Hertzsprung-Russell diagram between the asymptotic giant branch and the white dwarf

neg: Exciton from for the electron and the hole leading to different types of excitons in the same material. Even high-lying bands can be effective as femtosecond two-photon experiments have shown. At cryogenic temperatures, many higher excitonic levels can be observed approaching the edge of the band, forming a series of spectral absorption lines that are in principle similar to hydrogen spectral series. An intermediate case between Frenkel and Wannier excitons, "charge-transfer excitons" (sometimes called simply "CT excitons") occur when the electron and the hole occupy adjacent molecules. They occur primarily in ionic crystals. Unlike Frenkel and Wannier excitons they display a

neg: Pulsating white dwarf Pulsating white dwarf A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. Known types of pulsating white dwarfs include DAV, or ZZ Ceti, stars, with hydrogen-dominated atmospheres and the spectral type DA; DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB; and GW Vir stars, with atmospheres dominated by helium, carbon, and oxygen, and the spectral type PG 1159. (Some authors also include non-PG 1159 stars in the class of GW Vir stars.) GW Vir stars may be subdivided into DOV and PNNV stars; they

neg: Yellow supergiant star Yellow supergiant star A yellow supergiant star is a star, generally of spectral type F or G, having a supergiant luminosity class (e.g. Ia or Ib). They are stars that have evolved away from the main sequence, expanding and becoming more luminous. Yellow supergiants are smaller than red supergiants; naked eye examples include Canopus and Polaris. Many of them are variable stars, mostly pulsating Cepheids such as δ Cephei itself. Yellow supergiants generally have spectral types of F and G, although sometimes late A or early K stars are included. These spectral types are characterised by hydrogen lines that are

neg: Horizontal branch usually more metal-rich population I counterparts to HB stars (which belong to population II). Both HB stars and clump giants are fusing helium to carbon in their cores, but differences in the structure of their outer layers result in the different types of stars having different radii, effective temperatures, and color. Since color index is the horizontal coordinate in a Hertzsprung–Russell diagram, the different types of star appear in different parts of the CMD despite their common energy source. In effect, the red clump represents one extreme of horizontal-branch morphology: all the stars are at the red end of the

neg: Red clump have undergone a helium flash and are now fusing helium in their cores. Red clump stellar properties vary depending on their origin, most notably on the metallicity of the stars, but typically they have early K spectral types and effective temperatures around 5,000 K. The absolute visual magnitude of red clump giants near the sun has been measured at an average of +0.81 with metallicities between −0.6 and +0.4 dex. There is a considerable spread in the properties of red clump stars even within a single population of similar stars such as an open cluster. This is partly due to

neg: Musca star of spectral type B5V that varies between magnitudes 3.84 and 3.86 over a period of 2.7 days. It is a variable of a different type, classed as a slowly pulsating B star, a type of variable. It is around five times as massive as our Sun. Beta Muscae is a binary star system around 341 light-years distant that is composed of two blue-white main-sequence stars of spectral types B2V and B3V that orbit each other every 194 years. They are eight and six times as massive as the Sun, respectively, and have about 3.5 times its diameter. Zeta Muscae

neg: Spica orbit was found to be only slightly larger at . The MK spectral classification of Spica is typically considered to be an early B-type main sequence star. Individual spectral types for the two components are difficult to assign accurately, especially for the secondary due to the Struve–Sahade effect. The Bright Star Catalogue derived a spectral class of B1 III-IV for the primary and B2V for the secondary, but later studies have given various different values. The primary star has a stellar classification of B1 III–IV. The luminosity class matches the spectrum of a star that is midway between a subgiant

neg: Neural facilitation synapse changes in response to stimuli. These changes in filtration affect information transmission and encoding in response to repeated stimuli. In humans, sound localization is primarily accomplished using information about how the intensity and timing of a sound vary between each ear. Neuronal computations involving these interaurual intensity differences (IIDs) and interaural time differences (ITDs) are typically carried out in different pathways in the brain. Short-term plasticity likely assists in differentiating between these two pathways: short-term facilitation dominates in intensity pathways, while short-term depression dominates in temporal pathways. These different types of short-term plasticity allow for different kinds of information

neg: Asteroid Asteroid Spectroscopic Survey resulted in a modified version of the Tholen taxonomy with 24 different types. Both systems have three broad categories of C, S, and X asteroids, where X consists of mostly metallic asteroids, such as the M-type. There are also several smaller classes. The proportion of known asteroids falling into the various spectral types does not necessarily reflect the proportion of all asteroids that are of that type; some types are easier to detect than others, biasing the totals. Originally, spectral designations were based on inferences of an asteroid's composition. However, the correspondence between spectral class and composition

neg: H II region It contains around 200 hot OB and Wolf-Rayet stars, which heat the gas inside it to millions of degrees, producing bright X-ray emissions. The total mass of the hot gas in NGC 604 is about 6,000 Solar masses. As with planetary nebulae, estimates of the abundance of elements in H II regions are subject to some uncertainty. There are two different ways of determining the abundance of metals (metals in this case are elements other than hydrogen and helium) in nebulae, which rely on different types of spectral lines, and large discrepancies are sometimes seen between the results derived from

neg: B-type main-sequence star often have strong magnetic fields in their photosphere. In contrast, there are also helium-weak B-type stars with understrength helium lines and strong hydrogen spectra. Other chemically peculiar B-types stars are mercury–manganese stars with spectral types B7-B9. Finally, the aforementioned Be stars show a prominent emission spectrum of hydrogen. B-type stars known to have planets include the main-sequence B-types HIP 78530 b, the subgiants Kappa Andromedae b and a few (19 are now known) B-type subdwarfs. B-type main-sequence star A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have

neg: O-type star luminosity and this is the primary means of assigning luminosity classes to the late O-type stars. Stars of types O3 to O8 are classified as luminosity class sub-type Vz if they have a particularly strong 468.6 nm ionised helium line. The line's presence is thought to indicate extreme youth; the "z" stands for zero-age. To help with the classification of O-type stars, standard examples are listed for most of the defined types. The following table gives one of the standard stars for each spectral type. In some cases, a standard star has not been defined. For spectral types O2 to

neg: Circumstellar habitable zone circumstellar habitable zone is actually limited to stars in certain types of systems or of certain spectral types. Binary systems, for example, have circumstellar habitable zones that differ from those of single-star planetary systems, in addition to the orbital stability concerns inherent with a three-body configuration. If the Solar System were such a binary system, the outer limits of the resulting circumstellar habitable zone could extend as far as 2.4 AU. With regard to spectral types, Zoltán Balog proposes that O-type stars cannot form planets due to the photoevaporation caused by their strong ultraviolet emissions. Studying ultraviolet emissions, Andrea Buccino

neg: OPN1LW genes in the array. The slight difference in OPN1LW and OPN1MW absorption spectra is due to a handful of amino acid differences between the two highly similar genes. OPN1LW and OPN1MW both have six exons. Amino acid dimorphisms on exon 5 at positions 277 and 285 are the most influential on the spectral differences observed between LWS and MWS pigments. There are 3 amino acid changes on exon 5 for OPN1LW and OPN1MW that contribute to the spectral shift seen between their respective opsin: OPN1MW has phenylalanine at positions 277 and 309, and alanine at 285; OPN1LW have tyrosine at

neg: Pulsating white dwarf However, it is also possible that it is a white dwarf binary system with a carbon-oxygen accretion disk. Pulsating white dwarf A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. Known types of pulsating white dwarfs include DAV, or ZZ Ceti, stars, with hydrogen-dominated atmospheres and the spectral type DA; DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB; and GW Vir stars, with atmospheres dominated by helium, carbon, and oxygen, and the spectral type PG 1159. (Some authors also include non-PG 1159 stars in

neg: Spectral atlas spectral classification, a spectral atlas is a collection of standard spectra of stars with known spectral types, against which a spectrum of an unknown star is compared. It is analogous to an identification key in biology. Originally, such atlases included reproductions of the monochrome spectra as recorded on photographic plates, as in the original Morgan-Keenan-Kellman atlas and other atlases. These atlases include identifications and notations for use of those spectral features to be used as discriminators between close spectral types. With very large surveys of the sky which include automated assignment of spectral classification from the digital spectra data, graphical

neg: Nebula that the emission spectrum nebulae are nearly always associated with stars having spectral classifications of B or hotter (including all O-type main sequence stars), while nebulae with continuous spectra appear with cooler stars. Both Hubble and Henry Norris Russell concluded that the nebulae surrounding the hotter stars are transfomed in some manner. There are a variety of formation mechanisms for the different types of nebulae. Some nebulae form from gas that is already in the interstellar medium while others are produced by stars. Examples of the former case are giant molecular clouds, the coldest, densest phase of interstellar gas, which

neg: Plaskett's Star for their spectral types. It has been suggested that the star may be twice as far away as assumed, not a member of the Monoceros OB2 association, and each component would be about four times as luminous as currently calculated. The masses derived from the binary orbit are also somewhat higher than expected from the spectral types, but with considerable uncertainty due to assumptions about the inclination. Plaskett's Star Plaskett's Star, also known as HR 2422 and V640 Monocerotis, is a spectroscopic binary at a distance of around 6600 light-years. It is one of the most massive binary stars known,

neg: Wolf–Rayet star confusing spectral features. For example, high luminosity O stars can develop helium and nitrogen in their spectra with some emission lines, while some WR stars have hydrogen lines, weak emission, and even absorption components. These stars have been given spectral types such as O3 If/WN6 and are referred to as slash stars. Class O supergiants can develop emission lines of helium and nitrogen, or emission components to some absorption lines. These are indicated by spectral peculiarity suffix codes specific to this type of star: These codes may also be combined with more general spectral type qualifiers such as p or

neg: Stellar classification a luminosity class can be assigned purely from examination of the spectrum. A number of different "luminosity classes" are distinguished, as listed in the table below. Marginal cases are allowed; for example, a star may be either a supergiant or a bright giant, or may be in between the subgiant and main-sequence classifications. In these cases, two special symbols are used: For example, a star classified as A3-4III/IV would be in between spectral types A3 and A4, while being either a giant star or a subgiant. Sub-dwarf classes have also been used: VI for sub-dwarfs (stars slightly less luminous than

neg: Main sequence dwarfs such as red dwarfs, orange dwarfs, and yellow dwarfs are indeed much smaller and dimmer than other stars of those colors. However, for hotter blue and white stars, the size and brightness difference between so-called "dwarf" stars that are on the main sequence and the so-called "giant" stars that are not becomes smaller; for the hottest stars it is not directly observable. For those stars the terms "dwarf" and "giant" refer to differences in spectral lines which indicate if a star is on the main sequence or off it. Nevertheless, very hot main-sequence stars are still sometimes called dwarfs,

neg: W Serpentis systems can develop an optically thick disc and are segregated as a separate class of W Serpentis stars. The classes may also represent different types of system altogether, with the W Serpentis type being younger and more massive. The spectral types of the component stars are not known; the hotter brighter star has been classed as an F-type giant. However, it appears to be completely obscured by material, and another theory holds that it is a hot main sequence star with the surrounding material responsible for the spectrum as it appears to be too luminous to be an F-class star.

neg: 1 Ceti 1 Ceti 1 Ceti is a star in the constellation of Cetus. With an apparent magnitude of about 6.2, the star is barely visible to the naked eye (see Bortle scale). Parallax estimates made by the Hipparcos spacecraft put it at a distance of about 620 light years (190 parsecs) away from the Earth. 1 Ceti has a spectral type of K1III, implying a K-type giant. These types of stars are generally reddish-colored stars with spectral types from K to M, with radii that are 10 to 100 times larger than the Sun. The "CNII" in its spectral type indicates

neg: Metamerism (color) (fluorescent or halide lights). Similar problems can occur in apparel manufactured from different types of dye or using different types of fabric, or in quality color printing using different types of inks. Papers manufactured with optical brighteners are especially susceptible to color changes when lights differ in their short wavelength radiation, which can cause some papers to fluoresce. Color matches made in the paint industry are often aimed at achieving a spectral color match rather than just a tristimulus (metameric) color match under a given spectrum of light. A spectral color match attempts to give two colors the same spectral

neg: Hyades (star cluster) giants. Their present spectral type is K0 III, but all are actually "retired A stars" of around . An additional "white giant" of type A7 III is the primary of θ² Tauri, a binary system that includes a less massive companion of spectral type A; this pair is visually associated with θ¹ Tauri, one of the four red giants, which also has an A-type binary companion. The remaining population of confirmed cluster members includes numerous bright stars of spectral types A (at least 21), F (about 60), and G (about 50). All these star types are concentrated much more densely

neg: Subdwarf Hot subdwarfs, of spectral types O and B, also termed "extreme horizontal-branch stars" are an entirely different class of objects to cool subdwarfs. These stars represent a late stage in the evolution of some stars, caused when a red giant star loses its outer hydrogen layers before the core begins to fuse helium. The reasons why this premature mass loss occurs are unclear, but the interaction of stars in a binary star system is thought to be one of the main mechanisms. Single subdwarfs may be the result of a merger of two white dwarfs or gravitational influence from substellar

neg: Hyades (star cluster) within the tidal radius of the Hyades than within an equivalent 10-parsec radius of the Earth. By comparison, our local 10-parsec sphere contains only 4 A stars, 6 F stars, and 21 G stars. The Hyades' cohort of lower-mass stars – spectral types K and M – remains poorly understood, despite proximity and long observation. At least 48 K dwarfs are confirmed members, along with about a dozen M dwarfs of spectral types M0-M2. Additional M dwarfs have been proposed, but few are later than M3, and only about 12 brown dwarfs are currently reported. This deficiency at the bottom

neg: Blue giant develop from more massive and less common stars, and because they have short lives in the blue giant stage. The name blue giant is sometimes misapplied to other high-mass luminous stars, such as main-sequence stars, simply because they are large and hot. Blue giant is not a strictly defined term and it is applied to a wide variety of different types of stars. What they have in common is: a moderate increase in size and luminosity compared to main-sequence stars of the same mass or temperature, and are hot enough to be called blue, meaning spectral class O, B, and

neg: Spectral color spectral color has the maximal saturation. In color spaces which include all, or most spectral colors, they form a part of boundary of the set of all real colors. If luminance is counted, then spectral colors form a surface, otherwise their locus is a curve in a two-dimensional chromaticity space. Theoretically, only RGB-implemented colors which might be really spectral are its primaries: red, green, and blue, whereas any other (mixed) color is inherently non-spectral. But due to different chromaticity properties of different spectral segments, and also due to practical limitations of light sources, the actual distance between RGB pure color

neg: Hipparcos not included in the published "Hipparcos Catalogue". Constraints on total observing time, and on the uniformity of stars across the celestial sphere for satellite operations and data analysis, led to an Input Catalogue of some 118,000 stars. It merged two components: first, a survey of around 58,000 objects as complete as possible to the following limiting magnitudes: V<7.9 + 1.1sin|b| for spectral types earlier than G5, and V<7.3 + 1.1sin|b| for spectral types later than G5 (b is the Galactic latitude). Stars constituting this survey are flagged in the "Hipparcos Catalogue". The second component comprised additional stars selected according to

neg: Blue giant temperatures over 30,000 K, and more than 100,000 times the luminosity of the Sun (). Astronomers still differ over whether to classify at least one of the stars as a supergiant, based on subtle differences in the spectral lines. Stars found in the blue giant region of the HR diagram can be in very different stages of their lives, but all are evolved stars that have largely exhausted their core hydrogen supplies. In the simplest case, a hot luminous star begins to expand as its core hydrogen is exhausted, and first becomes a blue subgiant then a blue giant, becoming

neg: BY Draconis variable are similar to RS CVn stars, which are another class of variable stars that have active chromospheres. BY Draconis variable BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with starspots, and other chromospheric activity. Resultant brightness fluctuations are generally less than 0.5 magnitudes. Light curves of BY Draconis variables are quasiperiodic. The period is close to the star's mean

neg: Auriga (constellation) of 40 minutes. There are many other variable stars of different types in Auriga. ψ Aurigae (Dolones) is an orange-hued supergiant, which ranges between magnitudes 4.8 and 5.7, though not with a regular period. It has a spectral class of K5Iab, an average magnitude of 4.91, and an absolute magnitude of −5.7. Dolones is 3,976 light-years from Earth. RT Aurigae is a Cepheid variable which ranges between magnitudes 5.0 and 5.8 over a period of 3.7 days. A yellow-white supergiant, it lies at a distance of 1,600 light-years. It was discovered to be variable by English amateur T.H. Astbury in

neg: Wolf–Rayet star an absorption line in O supergiants and an emission line in WN stars. Criteria for the following slash star spectral types are given, using the nitrogen emission lines at 463.4-464.1 nm, 405.8 nm, and 460.3-462.0 nm, together with a standard star for each type: Another set of slash star spectral types is in use for Ofpe/WN stars. These stars have O supergiant spectra plus nitrogen and helium emission, and P Cygni profiles. Alternatively they can be considered to be WN stars with unusually low ionisation levels and hydrogen. The slash notation for these stars was controversial and an alternative was

neg: Musca days. It is a yellow-white supergiant ranging between spectral types F7Ib and G2Ib, located around 2037 light-years away. S Muscae is likewise a classical Cepheid, a yellow-white supergiant ranging between spectral types F6Ib and G0Ib and magnitudes 5.89 to 6.49 over a period of 9.66 days. A luminous star around 5.9 times as massive as the Sun, it is a binary star with a blue-white main-sequence star companion likely to be of spectral type B3V to B5V with a mass of just over 5 solar masses, one of the hottest and brightest companions of a cepheid known. The two stars

neg: Stellar classification set of spectral peculiarity symbols are used for white dwarfs than for other types of stars: Stellar remnants are objects associated with the death of stars. Included in the category are white dwarfs, and as can be seen from the radically different classification scheme for class D, non-stellar objects are difficult to fit into the MK system. The Hertzsprung-Russell diagram, which the MK system is based on, is observational in nature so these remnants cannot easily be plotted on the diagram, or cannot be placed at all. Old neutron stars are relatively small and cold, and would fall on the

neg: Hertzsprung–Russell diagram thereby obtain absolute magnitudes for those stars. There are several forms of the Hertzsprung–Russell diagram, and the nomenclature is not very well defined. All forms share the same general layout: stars of greater luminosity are toward the top of the diagram, and stars with higher surface temperature are toward the left side of the diagram. The original diagram displayed the spectral type of stars on the horizontal axis and the absolute visual magnitude on the vertical axis. The spectral type is not a numerical quantity, but the sequence of spectral types is a monotonic series that reflects the stellar surface

neg: Northern fur seal hind limbs are in a plantigrade stance and are able to rotate under the body for quadrupedal locomotion and support. When swimming, there are two different types of movement: locomotion and diving. These seals swim primarily with forelimb propulsion due to their physiology. They have flexible joints between vertebrae for better maneuverability in the water as well as “greater muscular leverage” for pectoral strokes. Stroke patterns are different for different dive types and locomotion, and stroke rates vary for individuals since there’s a relationship between maximum stroke rate and body size. The northern fur seal is found in the north

neg: William Henry Stanley Monck of yellow stars, one dull and near and the other bright and remote; this idea was later taken up by J. Gore of Sligo. He drew a lot of attention to the relationship between the proper motions of stars and their spectral types, and later dealt with it again in "Astronomy and Astrophysics, vols xi. and xii." He returned once more to the subject, and from discussion of the Dunsink catalogue of 717 stars made a demonstration that the earlier types of stars are endowed with a smaller proper motion than later. Monck was elected a corresponding member of the

neg: Red supergiant star supergiants are still rotating and the differential rotation rate can be very large. Supergiant luminosity classes are easy to determine and apply to large numbers of stars, but they group a number of very different types of star into a single category. An evolutionary definition restricts the term supergiant to those massive stars which start core helium fusion without developing a degenerate helium core and without undergoing a helium flash. They will universally go on to burn heavier elements and undergo core collapse resulting in a supernova. Less massive stars may develop a supergiant spectral luminosity class at relatively low

neg: Stellar classification 1912, Cannon had changed the types B, A, B5A, F2G, etc. to B0, A0, B5, F2, etc. This is essentially the modern form of the Harvard classification system. A common mnemonic for remembering the order of the spectral type letters, from hottest to coolest, is "Oh, Be A Fine Guy/Girl, Kiss Me". A luminosity classification known as the Mount Wilson system was used to distinguish between stars of different luminosities. This notation system is still sometimes seen on modern spectra. The stellar classification system is taxonomic, based on type specimens, similar to classification of species in biology: The categories are

neg: Red dwarf was also used, but sometimes it also included stars of spectral type K. In modern usage, the definition of a "red dwarf" still varies. When explicitly defined, it typically includes late K- and early to mid-M-class stars, but in many cases it is restricted just to M-class stars. In some cases all K stars are included as red dwarfs, and occasionally even earlier stars. The coolest true main-sequence stars are thought to have spectral types around L2 or L3, but many objects cooler than about M6 or M7 are brown dwarfs, insufficiently massive to sustain hydrogen-1 fusion. Red dwarfs are

neg: Asteroid spectral types a simple taxonomic system for asteroids based on color, albedo, and spectral shape. The three categories were labelled "C" for dark carbonaceous objects, "S" for stony (silicaceous) objects, and "U" for those that did not fit into either C or S. This basic division of asteroid spectra has since been expanded and clarified. A number of classification schemes are currently in existence, and while they strive to retain some mutual consistency, quite a few asteroids are sorted into different classes depending on the particular scheme. This is due to the use of different criteria for each approach. The two most

neg: X-type asteroid X-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions. In the Tholen classification the X-group consists of the following types: Since in this scheme the albedo is crucial in discriminating between the above types, some objects for which albedo information was not available were assigned an X-type. An example of this is 50 Virginia. The SMASS classification does not use albedo, but several spectral types are distinguished on the basis of spectral features which were too subtle to be visible in the broad-band ECAS survey used for the Tholen scheme. The

neg: Westerlund 2 K and more luminous than . There are around 20 further O class stars in the cluster, all main sequence objects implying a very young age for the cluster. Several Wolf–Rayet stars are found in the vicinity of Westerlund 2, although not in the central core. WR20a, a binary consisting of two WR stars, and the single stars WR20aa, WR20b, and WR20c are all thought to be members of the cluster, although possibly now runaway members. All five Wolf Rayets are extremely young massive objects with OIf/WN spectral types, amongst the most luminous stars in the galaxy. This composite spectral

neg: Main sequence Sequence. At Princeton University, Henry Norris Russell was following a similar course of research. He was studying the relationship between the spectral classification of stars and their actual brightness as corrected for distance—their absolute magnitude. For this purpose he used a set of stars that had reliable parallaxes and many of which had been categorized at Harvard. When he plotted the spectral types of these stars against their absolute magnitude, he found that dwarf stars followed a distinct relationship. This allowed the real brightness of a dwarf star to be predicted with reasonable accuracy. Of the red stars observed by

neg: W Ursae Majoris variable two stars both hotter than the Sun, having spectral types A or F, and periods of 0.4 to 0.8 day. The W-types have cooler spectral types of G or K and shorter periods of 0.22 to 0.4 day. The difference between the surface temperatures of the components is less than several hundred kelvins. A new subclass was introduced in 1978: B-type. The B-types have larger surface temperature difference. In 2004 the H (high mass ratio) systems were discovered by Sz. Csizmadia and P. Klagyivik. The H-types have a higher mass ratio than formula_1 (formula_2 = (secondary's mass)/(primary's mass)) and they

neg: Personality type tend to be somewhat more neurotic than thinking types. The worrier's tendency to experience a fearful affect, could be manifested in Jung's feeling type. General overview: Three modern theories closely associated with Jung's personality types: Other theories: Personality type Personality type refers to the psychological classification of different types of individuals. Personality types are sometimes distinguished from personality traits, with the latter embodying a smaller grouping of behavioral tendencies. Types are sometimes said to involve "qualitative" differences between people, whereas traits might be construed as "quantitative" differences. According to type theories, for example, introverts and extraverts are two fundamentally different

neg: Petroleum coke energy content, petcoke emits between 30 and 80 percent more CO than coal per unit of weight. The difference between coal and coke in CO production per unit of energy produced depends upon the moisture in the coal, which increases the CO per unit of energy – heat of combustion) and on the volatile hydrocarbons in coal and coke, which decrease the CO per unit of energy. There are at least four basic types of petroleum coke, namely, needle coke, honeycomb coke, sponge coke and shot coke. Different types of petroleum coke have different microstructures due to differences in operating

neg: Subdwarf Subdwarf A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. On an Hertzsprung–Russell diagram subdwarfs appear to lie below the main sequence. The term "subdwarf" was coined by Gerard Kuiper in 1939, to refer to a series of stars with anomalous spectra that were previously labeled as "intermediate white dwarfs". Like ordinary main-sequence stars, cool subdwarfs (of spectral types G to M) produce their energy from hydrogen fusion.

neg: Metallicity types of stars, based on the spectral peculiarities that were later attributed to metallicity, led astronomer Walter Baade in 1944 to propose the existence of two different populations of stars. These became commonly known as Population I (metal-rich) and Population II (metal-poor) stars. A third stellar population was introduced in 1978, known as Population III stars. These extremely metal-poor stars were theorised to have been the "first-born" stars created in the Universe. Astronomers use several different methods to describe and approximate metal abundances, depending on the available tools and the object of interest. Some methods include determining the fraction of

neg: WR 30a out and the line widths suggest a giant class is most likely. WR 30a is a close spectroscopic binary containing a WO4 star and a non-supergiant O5 star. They orbit each other every 4.916 days. Although spectral lines from both stars can be detected and orbital radial velocity variations measured, the orbit is still poorly known. The primary has highly broadened emission lines which are difficult to measure accurately, and the secondary has a relatively low orbital speed due to its high mass. Measurements of different spectral lines and different portions of line profiles lead to different results. Some components

neg: Chemical imaging imaging spectrometer, based on a Focal Plane Array. Some words common in spectroscopy, optical microscopy and photography have been adapted or their scope modified for their use in chemical imaging. They include: resolution, field of view and magnification. There are two types of resolution in chemical imaging. The spectral resolution refers to the ability to resolve small energy differences; it applies to the spectral axis. The spatial resolution is the minimum distance between two objects that is required for them to be detected as distinct objects. The spatial resolution is influenced by the field of view, a physical measure of

neg: S-type star on ZrO strength. This table shows the spectral types of a number of well-known S stars as they were classified at various times. Most of the stars are variable, usually of the Mira type. Where possible the table shows the type at maximum brightness, but several of the Ake types in particular are not at maximum brightness and so have a later type. ZrO and TiO band intensities are also shown if they are published (an x indicates that no bands were found). If the abundances are part of the formal spectral type then the abundance index is shown. There

neg: Delta Velorum arcseconds apart. The two stars, with approximate spectral types of G8V and K0V, are expected to be more distant than δ Velorum and not physically associated. HD 76653 is a probable (96% chance) co-moving companion; the two have an estimated physical separation of with similar proper motions. Both are likely members of the Ursa Major Moving Group. The brightnesses of the three stars have been measured at visual and infrared wavelengths using adaptive optics. The physical properties implied by their surface brightnesses and colour indices suggests spectral types of A2IV, A4V, and F8V respectively. More precise physical properties for the

neg: Doppler imaging can be used for finding both dark (cool) and bright (hot) spots. Doppler imaging Inhomogeneous structures on stellar surfaces, i.e. temperature differences, chemical composition or magnetic fields, create characteristic distortions in the spectral lines due to the Doppler effect. These distortions will move across spectral line profiles due to the stellar rotation. The technique to reconstruct these structures on the stellar surface is called Doppler-imaging, often based on the Maximum Entropy image reconstruction to find the stellar image. This technique gives the smoothest and simplest image that is consistent with observations. To understand the magnetic field and activity of stars,

neg: Yellow supergiant star practice luminosity classes are still usually assigned by comparison against standard stars. Some yellow supergiant spectral standard stars: Yellow supergiants have a relatively narrow range of temperatures corresponding to their spectral types, from about 4,000 K to 7,000 K. Their luminosities range from about upwards, with the most luminous stars exceeding . The high luminosities indicate that they are much larger than the sun, from about to . The masses of yellow supergiants vary greatly, from less than the sun for stars such as W Virginis to or more (e.g. V810 Centauri). Corresponding surface gravities (log(g) cgs) are around 1–2

neg: Astronomical spectroscopy scrutiny due to the very large peculiar velocities of the galaxies in the cluster. Just as planets can be gravitationally bound to stars, pairs of stars can orbit each other. Some binary stars are visual binaries, meaning they can be observed orbiting each other through a telescope. Some binary stars, however, are too close together to be resolved. These two stars, when viewed through a spectrometer, will show a composite spectrum: the spectrum of each star will be added together. This composite spectrum becomes easier to detect when the stars are of similar luminosity and of different spectral class. Spectroscopic

neg: Beta Cephei variable Beta Cephei variable Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200,000 K in their interiors. These stars are usually hot blue-white stars of spectral class B and should not be confused with Cepheid variables, which are named after Delta Cephei and are luminous supergiant stars. Beta Cephei variables are main-sequence stars of masses between about 7 and 20 M (that is, 7–20 times as massive as the sun).

neg: Lipopolysaccharide instead of TLR4), and completely cylindrical lipid A like that of "Rhodobacter sphaeroides" is antagonistic to TLRs. LPS gene clusters are highly variable between different strains, subspecies, species of bacterial pathogens of plants and animals. Normal human blood serum contains anti-LOS antibodies that are bactericidal and patients that have infections caused by serotypically distinct strains possess anti-LOS antibodies that differ in their specificity compared with normal serum. These differences in humoral immune response to different LOS types can be attributed to the structure of the LOS molecule, primarily within the structure of the oligosaccharide portion of the LOS molecule. In

neg: 1 Ceti a cyanide in its spectrum. 1 Ceti 1 Ceti is a star in the constellation of Cetus. With an apparent magnitude of about 6.2, the star is barely visible to the naked eye (see Bortle scale). Parallax estimates made by the Hipparcos spacecraft put it at a distance of about 620 light years (190 parsecs) away from the Earth. 1 Ceti has a spectral type of K1III, implying a K-type giant. These types of stars are generally reddish-colored stars with spectral types from K to M, with radii that are 10 to 100 times larger than the Sun. The "CNII"

neg: 63 Ceti 63 Ceti 63 Ceti is a star in the constellation of Cetus. With an apparent magnitude of about 5.9, the star is barely visible to the naked eye (see Bortle scale). Parallax estimates made by the Hipparcos spacecraft put it at a distance of about 390 light years (129 parsecs) away from the Earth. 63 Ceti has a spectral type of K0III, implying a K-type giant. These types of stars are generally reddish-colored stars with spectral types from K to M, with radii that are 10 to 100 times larger than the Sun. 63 Ceti fits this description, with a

neg: Catalog of Stellar Identifications Catalog of Stellar Identifications The Catalog of Stellar Identifications (CSI) is a star catalog which was constructed to facilitate cross-referencing between different star catalogs. It contains designations and basic data for, as of 1983, approximately 440,000 stars, and was created by merging the Smithsonian Astrophysical Observatory Star Catalog, the Henry Draper Catalogue, the AGK2/3, the Cape Photographic Catalogue, the Cape Zone Catalogue, the Yale Zone Catalogue, the Cape Catalogue of Faint Stars, and the Boss General Catalogue. It contains stellar coordinates, magnitudes, spectral types, proper motions, and cross-references to designations in the previously mentioned catalogs. It also gives cross-references to

neg: B-type main-sequence star 200 km/s. Spectral objects known as "Be stars" are massive yet non-supergiant entities that notably have, or had at some time, one or more Balmer lines in emission, with the hydrogen-related electromagnetic radiation series projected out by the stars being of particular scientific interest. Be stars are generally thought to feature unusually strong stellar winds, high surface temperatures, and significant attrition of stellar mass as the objects rotate at a curiously rapid rate, all of this in contrast to many other main-sequence star types. Though the related terminologies are confusingly ambiguous, spectral objects known as "B(e)" or "B[e] stars" are

neg: Lyra is RR Lyrae, the prototype of the large class of variables known as RR Lyrae variables, which are pulsating variables similar to Cepheids, but are evolved population II stars of spectral types A and F. Such stars are usually not found in a galaxy's thin disk, but rather in the galactic halo. Such stars serve as standard candles, and thus are a reliable way to calculate distances to the globular clusters in which they reside. RR Lyrae itself varies between magnitudes 7 and 8 while exhibiting the Blazhko effect. The easternmost star designated by Flamsteed, 19 Lyrae, is also a

neg: Antares . Comparison of the effective temperature and luminosity of Antares to theoretical evolutionary tracks for massive stars suggest a progenitor mass of and an age of 12 million years (MYr), or an initial mass of and an age of 11 to 15 MYr. Massive stars like Antares are expected to become supernovae. Like most cool supergiants, Antares size has much uncertainty due to the tenuous and translucent nature of the extended outer regions of the star. Defining an effective temperature is difficult due to spectral lines being generated at different depths within the atmosphere, and linear measurements produce different results

neg: Stellar classification all main-sequence stars. About 1 in 3,000,000 (0.00003%) of the main-sequence stars in the solar neighborhood are O-type stars. Some of the most massive stars lie within this spectral class. O-type stars frequently have complicated surroundings that make measurement of their spectra difficult. O-type spectra formerly were defined by the ratio of the strength of the He II λ4541 relative to that of He I λ4471, where λ is the wavelength, measured in ångströms. Spectral type O7 was defined to be the point at which the two intensities are equal, with the He I line weakening towards earlier types. Type

neg: Herbig Ae/Be star blue color of our sky). Analogs of Herbig Ae/Be stars in the smaller mass range (<2 ) – F, G, K, M spectral type pre-main-sequence stars – are called T Tauri stars. More massive (>8 ) stars in pre-main-sequence stage are not observed, because they evolve very quickly: when they become visible (i.e. disperses surrounding circumstellar gas and dust cloud), the hydrogen in the center is already burning and they are main-sequence objects. Planets around Herbig Ae/Be stars include: Herbig Ae/Be star A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young (<10Myr) star of spectral types A

neg: Supergiant star HR diagram as the hottest blue supergiants and main-sequence stars. The most massive and luminous main-sequence stars are almost indistinguishable from the supergiants they quickly evolve into. They have almost identical temperatures and very similar luminosities, and only the most detailed analyses can distinguish the spectral features that show they have evolved away from the narrow early O-type main-sequence to the nearby area of early O-type supergiants. Such early O-type supergiants share many features with WNLh Wolf–Rayet stars and are sometimes designated as slash stars, intermediates between the two types. Luminous blue variables (LBVs) stars occur in the same region

neg: Maya society forms of the skulls, osteologists are able to differentiate between little difference in deformation styles to help understand minute differences between styles, and what these differences may mean. Interpretation of these different cranium types has been debated, but it is clear the shapes are different dependent based on time and region. As stated previously, Spanish and other European records provided detailed descriptions of cranium modification within their historical records. Some of the information the Spaniards recorded included the different types of methods, and the popular materials used for cranium modification. Lastly, other archaeological remains including art depictions, or figurines exhibiting

neg: Hot band of real systems due to anharmonic couplings of normal modes. Combination bands typically have weak spectral intensities, but can become quite intense in cases where the anharmonicity of the vibrational potential is large. Broadly speaking, there are two types of combination bands. A difference transition, or difference band, occurs between excited states of two different vibrations. Using the 3 mode example from above, formula_9 ← formula_10, is a difference transition. For difference bands involving transfer of a single quantum of excitation, as in the example, the frequency is approximately equal to the difference between the fundamental frequencies. The difference is

neg: NGC 6811 contained some 6000 stars at birth, but gravitational interactions and stellar evolution have since reduced the number to 1000. The spectral types of most of its stars range from mid-F to early-K, with surface temperatures relatively similar to the Sun's; the rest include A2-types, several O-types, and more than 100 B-types. Sixteen stars have been observed to vary in brightness, twelve of which are Delta Scuti variables. Its Trumpler classification is III 1r—it is "a rich cluster with equally bright stars with no noticeable central concentration". The stars do, however, have an unusual (if not concentrated) distribution, with an apparent

neg: Tucana sequence stars of spectral types K2V and K3V, which can be seen individually as stars one arcsecond apart with a telescope such as a Dobsonian with high power. Lambda Tucanae is an optical double—that is, the name is given to two stars (Lambda and Lambda) which appear close together from our viewpoint, but are in fact far apart in space. Lambda is itself a binary star, with two components—a yellow-white star of spectral type F7IV-V and an apparent magnitude of 6.22, and a yellow main sequence star of spectral type G1V and an apparent magnitude of 7.28. The system is

neg: Balmer series and this value, for an infinitely heavy nucleus, is = . The Balmer series is particularly useful in astronomy because the Balmer lines appear in numerous stellar objects due to the abundance of hydrogen in the universe, and therefore are commonly seen and relatively strong compared to lines from other elements. The spectral classification of stars, which is primarily a determination of surface temperature, is based on the relative strength of spectral lines, and the Balmer series in particular is very important. Other characteristics of a star that can be determined by close analysis of its spectrum include surface gravity

neg: South African type ET tender was more due to the additional stoking equipment. These appear to have been the only differences between the Types JT and ET tenders. Only the last batch of 100 Class 15F locomotives, built by NBL, were delivered new with Type ET tenders, which were numbered in the range from 3057 to 3156 for their engines. An oval number plate, bearing the engine number and often also the locomotive class and tender type, was attached to the rear end of the tenders. Since many tender types are interchangeable between different locomotive classes and types, a tender classification system was adopted by