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Stellar classification
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Light from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colours interspersed with absorption lines. Each line indicates an ion of a certain chemical element, with the line strength indicating the abundance of that ion. The relative abundance of the different ions varies with the temperature of the photosphere. The spectral class of a star is a short code summarising the ionization state, giving an objective measure of the photosphere's temperature and density.
Most stars are currently classified under the Morgan–Keenan (MKK) system using the letters O, B, A, F, G, K, and M, a sequence from hottest (O) to coolest (M). Useful mnemonics for remembering the spectral type letters are "Oh, Be A Fine Guy/Girl, Kiss Me" or "Oh Boy, An F Grade Kills Me". To also include the colder spectral classes L, T and Y, the first mnemonic can be extended to "Oh, Be A Fine Guy/Girl, Kiss Me Later Today, Yolo". Each letter class is then subdivided using a numeric digit with 0 being hottest and 9 being coolest (e.g. A8, A9, F0, F1 form a sequence from hotter to cooler).
In the MKK system a luminosity class is added to the spectral class using Roman numerals. This is based on the width of certain absorption lines in the star's spectrum which vary with the density of the atmosphere and so distinguish giant stars from dwarfs. Luminosity class I stars are supergiants, class III regular giants, and class V dwarfs or main-sequence stars, with II for bright giants, IV for sub-giants, and VI for sub-dwarfs. The full spectral class for the Sun is then G2V, indicating a main-sequence star with a temperature around 5,800K.
- 1 Secchi classes
- 2 Harvard spectral classification
- 3 Yerkes spectral classification
- 4 Spectral types
- 5 Extended spectral types
- 6 Stellar classification, habitability, and the search for life
- 7 Spectral peculiarities
- 8 Variable star classification
- 9 Photometric classification
- 10 See also
- 11 Notes
- 12 References
- 13 External links
Secchi classes[edit]
During the 1860s and 1870s, pioneering stellar spectroscopist Father Angelo Secchi created the Secchi classes in order to classify observed spectra. By 1866, he had developed three classes of stellar spectra:[1][2][3]
- Class I: white and blue stars with broad heavy hydrogen lines, such as Vega and Altair. This includes the modern class A and early class F.
- Class II: yellow stars—hydrogen less strong, but evident metallic lines, such as the Sun, Arcturus, and Capella. This includes the modern classes G and K as well as late class F.
- Class III: orange to red stars with complex band spectra, such as Betelgeuse and Antares. This corresponds to the modern class M.
In 1868, he discovered carbon stars, which he put into a distinct group:[4]
- Class IV: red stars with significant carbon bands and lines (carbon stars.)
In 1877, he added a fifth class:[5]
- Class V: emission-line stars, such as γ Cassiopeiae and Sheliak.
In the late 1890s, this classification began to be superseded by the Harvard classification, which is discussed in the remainder of this article.[6][7]
Harvard spectral classification[edit]
The Harvard classification system is a one-dimensional classification scheme. Stars vary in surface temperature from approximately 2,000 to 40,000 kelvin. Physically, the classes indicate the temperature of the star's atmosphere and are normally listed from hottest to coldest, as is done in the following table:
Note: The conventional color description takes into account only the peak of the stellar spectrum. However, in actuality stars radiate in all parts of the spectrum, and since all spectral colors combined appear white, the actual apparent colors the human eye would observe are lighter than the conventional color descriptions.
Class | Effective temperature[8][9] (kelvin) |
Conventional color description | Actual apparent color[10][11][12] | Mass[8][13] (solar masses) |
Radius[8][13] (solar radii) |
Luminosity[8][13] (bolometric) |
Hydrogen lines |
Fraction of all main-sequence stars[14] |
O | ≥ 33,000 K | blue | blue | ≥ 16 M☉ | ≥ 6.6 R☉ | ≥ 30,000 L☉ | Weak | ~0.00003% |
B | 10,000–33,000 K | blue white | deep blue white | 2.1–16 M☉ | 1.8–6.6 R☉ | 25–30,000 L☉ | Medium | 0.13% |
A | 7,500–10,000 K | white | blue white | 1.4–2.1 M☉ | 1.4–1.8 R☉ | 5–25 L☉ | Strong | 0.6% |
F | 6,000–7,500 K | yellow white | white | 1.04–1.4 M☉ | 1.15–1.4 R☉ | 1.5–5 L☉ | Medium | 3% |
G | 5,200–6,000 K | yellow | yellowish white | 0.8–1.04 M☉ | 0.96–1.15 R☉ | 0.6–1.5 L☉ | Weak | 7.6% |
K | 3,700–5,200 K | orange | pale yellow orange | 0.45–0.8 M☉ | 0.7–0.96 R☉ | 0.08–0.6 L☉ | Very weak | 12.1% |
M | 2,400–3,700 K | red | light orange red | 0.08–0.45 M☉ | ≤ 0.7 R☉ | ≤ 0.08 L☉ | Very weak | 76.45% |
L | 1,300–2,400 K | red brown[citation needed] | scarlet[citation needed] | 0.005–0.08 M☉ | 0.08–0.15 R☉ | 0.000,05–0.001 L☉ | Extremely weak | |
T | 500–1,300 K | brown[citation needed] | magenta[15][16][17] | 0.001–0.07 M☉ | 0.08–0.14 R☉ | 0.000,001–0.000,05 L☉ | Extremely weak | |
Y | ≤ 500 K | dark brown[citation needed] | black[citation needed] | 0.0005–0.02 M☉ | 0.08–0.14 R☉ | 0.000,000,1–0.000,001 L☉ | Extremely weak |
The mass, radius, and luminosity listed for each class are appropriate only for stars on the main-sequence portion of their lives and so are not appropriate for red giants. The spectral classes O through Y are subdivided by Arabic numerals (0–9), which can be further divided into half-subtypes. For example, A0 denotes the hottest stars in the A class and A9 denotes the coolest ones. The Sun is classified as G2. So far however, only Y dwarfs of subtypes 0–≈2 have been discovered.[18]
Secchi | Draper | Comment |
I | A, B, C, D | Hydrogen lines dominant. |
IV | N | Did not appear in the catalogue. |
O | Wolf–Rayet spectra with bright lines. | |
P | Planetary nebulae. | |
Q | Other spectra. |
The reason for the odd arrangement of letters is historical. The earlier classification of spectra by Angelo Secchi divided stars into those with prominent lines from the hydrogen Balmer series (group I, with a subtype representing many of the stars in the constellation of Orion); those with spectra which, like the Sun, showed calcium and sodium lines (group II); colored stars whose spectra showed wide bands (group III); and carbon stars (group IV).[21] In the 1880s, the astronomer Edward C. Pickering began to make a survey of stellar spectra at the Harvard College Observatory, using the objective-prism method. A first result of this work was the Draper Catalogue of Stellar Spectra, published in 1890. Williamina Fleming classified most of the spectra in this catalogue. It used a scheme in which the previously used Secchi classes (I to IV) were divided into more specific classes, given letters from A to N. Also, the letters O, P and Q were used, O for stars whose spectra consisted mainly of bright lines, P for planetary nebulae, and Q for stars not fitting into any other class.[19][20]
In 1897, another worker at Harvard, Antonia Maury, placed the Orion subtype of Secchi class I ahead of the remainder of Secchi class I, thus placing the modern type B ahead of the modern type A. She was the first to do so, although she did not use lettered spectral types, but rather a series of twenty-two types numbered from I to XXII.[22][23] In 1901, Annie Jump Cannon returned to the lettered types, but dropped all letters except O, B, A, F, G, K, and M, used in that order, as well as P for planetary nebulae and Q for some peculiar spectra. She also used types such as B5A for stars halfway between types B and A, F2G for stars one-fifth of the way from F to G, and so forth.[24][25] Finally, by 1912, Cannon had changed the types B, A, B5A, F2G, etc. to B0, A0, B5, F2, etc.[26][27] This is essentially the modern form of the Harvard classification system.
The fact that the Harvard classification of a star indicated its surface or photospheric temperature (or more precisely, its effective temperature) was not fully understood until after its development, though by the time the first Hertzsprung–Russell diagram was formulated (by 1914), this was generally suspected to be true.[28] In the 1920s, the Indian physicist Meghnad Saha derived a theory of ionization by extending well-known ideas in physical chemistry pertaining to the dissociation of molecules to the ionization of atoms. First applied to the solar chromosphere, he then applied it to stellar spectra.[29] The Harvard astronomer Cecilia Helena Payne (later to become Cecilia Payne-Gaposchkin) then demonstrated that the OBAFGKM spectral sequence is actually a sequence in temperature.[30] Because the classification sequence predates our understanding that it is a temperature sequence, the placement of a spectrum into a given subtype, such as B3 or A7, depends upon (largely subjective) estimates of the strengths of absorption features in stellar spectra. As a result, these subtypes are not evenly divided into any sort of mathematically representable intervals.
O, B, and A stars are sometimes called "early type″, while K and M stars are said to be "late type″. This stems from an early 20th-century model of stellar evolution in which stars were powered by gravitational contraction via the Kelvin–Helmholtz mechanism in which stars start their lives as very hot "early-type" stars, and then gradually cool down, thereby evolving into "late-type″ stars. This mechanism provided ages of the Sun that were much smaller than what is observed, and was rendered obsolete by the discovery that stars are powered by nuclear fusion — these span spectral classes down to late L. However, brown dwarfs, whose energy comes from gravitational attraction alone, 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; the faster the less massive they are — the highest-mass brown dwarfs can not have cooled to Y or even T dwarfs within the age of the universe . As this leads to a degeneracy between mass and age for given effective temperature and luminosity, no unique values can be assigned to a given spectral type.[13]
Spectrum images by Harvard spectral class[edit]
Conventional and apparent colors[edit]
The conventional color descriptions are traditional in astronomy, and represent colors relative to the mean color of an A-class star which is considered to be white. The apparent color[10] descriptions are what the observer would see if trying to describe the stars under a dark sky without aid to the eye, or with binoculars. The table colors used are D65 standard colors calculated for the midpoint of each spectral class (e.g. G5 or A5) and for main-sequence stars.[12] These are accurate representations of the actual color of the disk of a star. Most stars in the sky, except the brightest ones, appear white or bluish white to the unaided eye because they are too dim for color vision to work. Even the brightest stars do not have strong colors, and within color systems such CIE all blackbody colors fall within a central "white" area of unsaturated colors. Of course most people have never seen an M-class main-sequence star, certainly not bright enough to notice color. Red supergiants are cooler and redder than dwarfs of the same spectral type, and stars with particular spectral features such as carbon stars may be far redder than any black body, although they cannot be accurately reproduced on an RGB monitor. For example,
Cool red dwarf M5V |
Betelgeuze M2Ia |
Y CVn C5 |
The Sun itself is white and approximates a black body of 5780 K (see color temperature). It is sometimes called a yellow star, spectroscopically relative to Vega, may appear yellow or red when viewed through the atmosphere, or appear white if viewed when too bright for the eye to see any color. This is a natural consequence of the evolution of human optical senses: the response curve that maximizes the overall efficiency against solar illumination will by definition perceive the Sun as white although there is some subjective variation between observers. The D65 standard closely mimics the spectrum of the Sun although it is intended to represent a 6500K blackbody light source. The color of the Sun is subtly different from D65 and is a faint peachy shade relative to it.[31]
Yerkes spectral classification[edit]
The Yerkes spectral classification, also called the MKK system from the authors' initials, is a system of stellar spectral classification introduced in 1943 by William Wilson Morgan, Philip C. Keenan, and Edith Kellman from Yerkes Observatory.[32] This two-dimensional (temperature and luminosity) classification scheme is based on spectral lines sensitive to stellar temperature and surface gravity which is related to luminosity (whilst the Harvard classification is based on surface temperature only). Later, in 1953, after some revisions of list of standard stars and classification criteria, the scheme was named MK (by William Wilson Morgan and Phillip C. Keenan initials).[33]
Since the radius of a giant star is much greater than a dwarf star while their masses are roughly comparable, the gravity and thus the gas density and pressure on the surface of a giant star are much lower than for a dwarf. These differences manifest themselves in the form of luminosity effects which affect both the width and the intensity of spectral lines which can then be measured. Denser stars with higher surface gravity will exhibit greater pressure broadening of spectral lines.
A number of different luminosity classes are distinguished:
- 0 hypergiants
- I supergiants
- Ia-0 (hypergiants or extremely luminous supergiants (later addition)), Example: Eta Carinae (spectrum-peculiar)
- Ia (luminous supergiants), Example: Deneb (spectrum is A2Ia)
- Iab (intermediate luminous supergiants) Example: Betelgeuse (spectrum is M2Iab)
- Ib (less luminous supergiants)
- II bright giants
- IIa, Example: β Scuti (HD 173764) (spectrum is G4 IIa)
- IIab Example: HR 8752 (spectrum is G0Iab:)
- IIb, Example: HR 6902 (spectrum is G9 IIb)
- III normal giants
- IV subgiants
- IVa, Example: ε Reticuli (spectrum is K1–2 IVa-III)
- IVab
- IVb, Example: HR 672 A (spectrum is G0.5 IVb)
- V main-sequence stars (dwarfs)
- Va, Example: AD Leonis (spectrum M4Vae)
- Vab[34]
- Vb, Example: 85 Pegasi A (spectrum G5 Vb)
- "Vz", Example: LH10 : 3102 (spectrum O7 Vz), located in the Large Magellanic Cloud.[35]
- VI subdwarfs. Subdwarfs are generally represented with a prescript of sd or esd (extreme subdwarf) in front of the spectra.
- sd, Example: SSSPM J1930-4311 (spectrum sdM7)
- esd, Example: APMPM J0559-2903 (spectrum esdM7)
- VII (uncommon) white dwarfs. White dwarfs are represented with a prescript wD or WD.
Marginal cases are allowed; for instance a star classified as Ia-0 would be a very luminous supergiant, verging on hypergiant. Examples are below. The spectral type of the star is not a factor.
Marginal symbols | Example | Explanation |
- | G2 I-II | A star is between supergiant and bright giant. |
+ | O9.5 Ia+ | A star is a hypergiant star. |
/ | F2 IV/V | A star is either a subgiant or a dwarf star. |
Spectral types[edit]
The following illustration represents star classes with the colors very close to those actually perceived by the human eye. The relative sizes are for main-sequence (or "dwarf") stars.
Class O[edit]
Class O stars are very hot and extremely luminous, with most of their radiated output in the ultraviolet range. These are the rarest of all main-sequence stars. About 1 in 3,000,000 (0.00003%) of the main-sequence stars in the solar neighborhood are class O stars.[nb 1][14] Some of the most massive stars lie within this spectral class. Class O stars frequently have complicated surroundings which make measurement of their spectra difficult.
O stars have dominant lines of absorption and sometimes emission for He II lines, prominent ionized (Si IV, O III, N III, and C III) and neutral helium lines, strengthening from O5 to O9, and prominent hydrogen Balmer lines, although not as strong as in later types. Because they are so massive, class O stars have very hot cores and burn through their hydrogen fuel very quickly, so they are the first stars to leave the main sequence.
When the MKK classification scheme was first described in 1943, the only subtypes of class O used were O5 to O9.5.[36] The MKK scheme was extended to O9.7 in 1971[37] and O4 in 1978,[38] and new classification schemes have subsequently been introduced which add types O2, O3 and O3.5.[39]
- Examples:
- Alpha Camelopardalis
- Tau Canis Majoris
- Lambda Cephei
- Delta Circini A
- Plaskett's star
- Zeta Ophiuchi
- Delta Orionis
- Theta¹ Orionis C
- Sigma Orionis A
- Xi Persei
- Zeta Puppis
- Pismis 24-1
Class B[edit]
Class B stars are very luminous and blue. Their spectra have neutral helium, which are most prominent at the B2 subclass, and moderate hydrogen lines. Ionized metal lines include Mg II and Si II. As O and B stars are so powerful, they only live for a relatively short time, and thus they do not stray far from the area in which they were formed.
These stars tend to be found in their originating OB associations, which are associated with giant molecular clouds. The Orion OB1 association occupies a large portion of a spiral arm of our galaxy and contains many of the brighter stars of the constellation Orion. About 1 in 800 (0.125%) of the main-sequence stars in the solar neighborhood are class B stars.[nb 1][14]
- Examples:
Class A[edit]
Class A stars are among the more common naked eye stars, and are white or bluish-white. They have strong hydrogen lines, at a maximum by A0, and also lines of ionized metals (Fe II, Mg II, Si II) at a maximum at A5. The presence of Ca II lines is notably strengthening by this point. About 1 in 160 (0.625%) of the main-sequence stars in the solar neighborhood are class A stars.[nb 1][14]
Class F[edit]
Class F stars have strengthening H and K lines of Ca II. Neutral metals (Fe I, Cr I) beginning to gain on ionized metal lines by late F. Their spectra are characterized by the weaker hydrogen lines and ionized metals. Their color is white. About 1 in 33 (3.03%) of the main-sequence stars in the solar neighborhood are class F stars.[nb 1][14]
Class G[edit]
Class G stars are probably the best known, if only for the reason that the Sun is of this class. They make up about 7.5%, nearly one in thirteen, of the main-sequence stars in the solar neighborhood.[nb 1][14]
Most notable are the H and K lines of Ca II, which are most prominent at G2. They have even weaker hydrogen lines than F, but along with the ionized metals, they have neutral metals. There is a prominent spike in the G band of CH molecules. G is host to the "Yellow Evolutionary Void".[41] Supergiant stars often swing between O or B (blue) and K or M (red). While they do this, they do not stay for long in the yellow supergiant G classification as this is an extremely unstable place for a supergiant to be.
- Examples: The Sun, Alpha Centauri A, Capella, Tau Ceti, Kepler-22
Class K[edit]
- "K STAR" redirects here. For the Korean nuclear fusion project, see KSTAR.
Class K stars are orangish stars that are slightly cooler than the Sun. They make up about 12%, nearly one in eight, of the main-sequence stars in the solar neighborhood.[nb 1][14] Some K stars are giants and supergiants, such as Arcturus, while orange dwarfs, like Alpha Centauri B, are main-sequence stars.
They have extremely weak hydrogen lines, if they are present at all, and mostly neutral metals (Mn I, Fe I, Si I). By late K, molecular bands of titanium oxide become present. There is a suggestion that K Spectrum stars may potentially increase the chances of life developing on orbiting planets that are within the habitable zone.[42]
- Examples: Alpha Centauri B, Epsilon Eridani, Arcturus, Aldebaran, Algol B
Class M[edit]
Class M stars are by far the most common. About 76% of the main-sequence stars in the Solar neighborhood are class M stars.[nb 1][nb 2][14] However, because main-sequence stars of spectral class M have such low luminosities, none are bright enough to be visible to see with the unaided eye. The brightest known M-class main-sequence star is M0V Lacaille 8760 at magnitude 6.6 (the fractionally brighter Groombridge 1618 was once considered to be class M0 but is now considered to be as K5) and it is extremely unlikely that any brighter examples will be found.
Although most class M stars are red dwarfs, the class also hosts most giants and some supergiants such as VY Canis Majoris, Antares and Betelgeuse, as well as Mira variables. Furthermore, the late-M group holds hotter brown dwarfs that are above the L spectrum. This is usually in the range of M6.5 to M9.5. The spectrum of a class M star shows lines belonging to oxide molecules, TiO in particular, in the visible and all neutral metals, but absorption lines of hydrogen are usually absent. TiO bands can be strong in class M stars, usually dominating their visible spectrum by about M5. Vanadium monoxide bands become present by late M.
- Examples: NML Cygni, WOH G64, VY Canis Majoris (hypergiants)
- Examples: Betelgeuse, Antares (supergiants)
- Examples: Rasalgethi, Beta Pegasi (giants)
- Examples: Proxima Centauri, Barnard's star, Gliese 581, AD Leonis (red dwarfs)
- Examples: LEHPM 2-59,[43] SSSPM J1930-4311 (subdwarf)
- Example: APMPM J0559-2903 (extreme subdwarf)
- Examples: Teide 1 (field brown dwarf), GSC 08047-00232 B [44] (companion brown dwarf)
Extended spectral types[edit]
A number of new spectral types have been taken into use from newly discovered types of stars.[45]
Hot blue emission star classes[edit]
Spectra of some very hot and bluish stars exhibit marked emission lines from carbon or nitrogen, or sometimes oxygen.
Class W: Wolf–Rayet[edit]
Class W or WR represents the Wolf–Rayet stars, notable for spectra lacking hydrogen lines. Instead their spectra are dominated by broad emission lines of highly ionised helium, nitrogen, carbon and sometimes oxygen. They are thought to mostly be dying supergiants with their hydrogen layers blown away by stellar winds, thereby directly exposing their hot helium shells. Class W is further divided into subclasses according to the relative strength of nitrogen and carbon emission lines in their spectra (and outer layers).[46]
WR spectra range is listed below:
- WN,[46] spectrum dominated by NitrogenIII-V and HeliumI-II lines
- WNE (WN2 to WN5 with some WN6), hotter or "early"
- WNL (WN7 to WN9 with some WN6), cooler or "late"
- Extended WN classes WN10 and WN11 sometimes used for the Ofpe/WN9 stars[46]
- h tag used (e.g. WN9h) for WR with hydrogen emission and ha (e.g. WN6ha) for both hydrogen emission and absorption
- WN/C, WN stars plus strong CarbonIV lines, intermediate between WN and WC stars[46]
- WC,[46] spectrum with strong CarbonII-IV lines
- WCE (WC4 to WC6), hotter or "early"
- WCL (WC7 to WC9), cooler or "late"
- WO (WO1 to WO4), strong OxygenVI lines, extremely rare
Wolf–Rayet examples:
- Example: R136a1 (WN5h)
- Example: Gamma2 Velorum A (WC8)
- Example: WR93B (WO3)
The "Slash" stars[edit]
The slash stars are stars with O-type spectra and WN sequence in their spectra. The name slash comes from their spectra having a slash.
- Example spectra: Of/WNL[35]
There is a secondary group found with this spectra, a cooler, "intermediate" group with designation of Ofpe/WN9.[35] These stars have also been referred to as WN10 or WN11, but that has become less popular with the realisation of the evolutionary difference to other Wolf–Rayet stars. Recent discoveries of even rarer stars have extended the range of slash stars as far as O2-3.5If*/WN5-7, which are even hotter than the original slash stars.[47]
The magnetic O stars[edit]
They are O stars with strong magnetic fields. Designation is Of?p[35]
The "class" OB[edit]
In lists of spectra, the "spectrum OB" may occur. This is in fact not a spectrum, but a marker which means that "the spectrum of this star is unknown, but it belongs to an OB association, so probably either a class O or class B star, or perhaps a fairly hot class A star."
Cool red and brown dwarf classes[edit]
The new spectral types L, T and Y were created to classify infrared spectra of cool stars. This includes both red dwarfs and brown dwarfs that are very faint in the visual spectrum.[48]
Class L[edit]
Class L dwarfs get their designation because they are cooler than M stars and L is the remaining letter alphabetically closest to M. L does not mean lithium dwarf; a large fraction of these stars do not have lithium in their spectra. Some of these objects have masses large enough to support hydrogen fusion, but some are of substellar mass and do not, so collectively these objects should be referred to as L dwarfs, not L stars. They are a very dark red in color and brightest in infrared. Their atmosphere is cool enough to allow metal hydrides and alkali metals to be prominent in their spectra.[49][50] Due to low gravities in giant stars, TiO- and VO-bearing condensates never form. Thus, larger L-type stars can never form in an isolated environment. It may be possible for these L-type supergiants to form through stellar collisions, however, an example of which is V838 Monocerotis.
- L: 1,300–2,400 K, dwarfs (some stellar, some substellar) with metal hydrides and alkali metals prominent in their spectra.
- Example: VW Hyi
- Example: 2MASSW J0746425+2000321 binary[51]
- Component A is an L dwarf star
- Component B is an L brown dwarf
- Example: LSR 1610-0040 (subdwarf)[52]
- Example: V838 Monocerotis (supergiants)
Class T: methane dwarfs[edit]
Class T dwarfs are cool brown dwarfs with surface temperatures between approximately 700 and 1,300 K. Their emission peaks in the infrared. Methane is prominent in their spectra.[49][50]
- T: ~500–1,300 K, cooler brown dwarfs with methane in the spectrum
- Examples: SIMP 0136 (the brightest T dwarf discovered in northern hemisphere)[53]
- Examples: Epsilon Indi Ba & Epsilon Indi Bb
- Examples: CFBDS 1448 a T dwarf with an exoplanet orbiting it
Class T and L could be more common than all the other classes combined if recent research is accurate. Study of the number of proplyds (protoplanetary discs, clumps of gas in nebulae from which stars and planetary systems are formed) indicates that the number of stars in the galaxy should be several orders of magnitude higher than what we know about. It is theorized that these proplyds are in a race with each other. The first one to form will become a proto-star, which are very violent objects and will disrupt other proplyds in the vicinity, stripping them of their gas. The victim proplyds will then probably go on to become main-sequence stars or brown dwarfs of the L and T classes, which are quite invisible to us. Because brown dwarfs can live so long, these smaller bodies accumulate over time.
Class Y[edit]
The spectral class Y are brown dwarfs that are cooler than T dwarfs and have qualitatively different spectra from them. As of Aug 2013 17 objects have been placed in class Y.[54] Although such dwarfs have been modelled[55] and detected within forty light years by the Wide-field Infrared Survey Explorer (WISE)[45][56][57][58][59] there is no well-defined spectral sequence yet with prototypes. Nevertheless, several objects have been assigned spectral classes Y0, Y1, and Y2.[60] The spectra of these objects display absorption around 1.55 micrometers.[61] Delorme et al. has suggested that this feature is due to absorption from ammonia and that this should be taken as indicating the T–Y transition, making these objects of type Y0.[61][62] In fact, this ammonia-absorption feature is the main criterion that has been adopted to define this class.[60] However, this feature is difficult to distinguish from absorption by water and methane,[61] and other authors have stated that the assignment of class Y0 is premature.[63]
- Y: < 600 K, ultra-cool brown dwarfs
- Example: WISE 0410+1502, class Y0
- Example: WISE 0350-5658, class Y1
- Example: WISE 1405+5534, class Y1
The brown dwarf with the latest assigned spectral type, WISE 1828+2650, is a >Y2 dwarf with an effective temperature originally estimated around 300 K, the temperature of the human body.[56][57][64] Parallax measurements have however since shown, that its luminosity is inconsistent with it being colder than ~400 K; the likely coolest Y dwarf currently known is WD 0806−661B with approximately 350 K.[9]
The mass range for Y dwarfs is 9–25 Jupiter masses, but for young objects might reach below one Jupiter mass, which means that Y class objects straddle the 13-Jupiter mass deuterium-fusion limit that marks the division between brown dwarfs and planets.[60]
Carbon-related stars are stars whose spectra indicate production of carbon by helium triple-alpha fusion. With increased carbon abundance, and some parallel s-process heavy element production, the spectra of these stars become increasingly deviant from the usual late spectral classes G, K and M. The giants among those stars are presumed to produce this carbon themselves, but not too few of this class of stars are believed to be double stars whose odd atmosphere once was transferred from a former carbon star companion that is now a white dwarf.
Class C: carbon stars[edit]
Originally classified as R and N stars, these are also known as 'carbon stars'. These are red giants, near the end of their lives, in which there is an excess of carbon in the atmosphere. The old R and N classes ran parallel to the normal classification system from roughly mid G to late M. These have more recently been remapped into a unified carbon classifier C, with N0 starting at roughly C6. Another subset of cool carbon stars are the J-type stars, which are characterized by the strong presence of molecules of 13CN in addition to those of 12CN.[65] A few dwarf (that is, main-sequence) carbon stars are known, but the overwhelming majority of known carbon stars are giants or supergiants.
- C: Carbon stars, e.g. R CMi
- C-R: Formerly a class on its own representing the carbon star equivalent of late G to early K stars. Example: S Camelopardalis
- C-N: Formerly a class on its own representing the carbon star equivalent of late K to M stars. Example: R Leporis
- C-J: A subtype of cool C stars with a high content of 13C. Example: Y Canum Venaticorum
- C-H: Population II analogues of the C-R stars. Examples: V Ari, TT CVn[66]
- C-Hd: Hydrogen-Deficient Carbon Stars, similar to late G supergiants with CH and C2 bands added. Examples: HD 137613, R Coronae Borealis
Class S[edit]
Class S stars have zirconium monoxide lines in addition to (or, rarely, instead of) those of titanium monoxide, and are in between the class M stars and the carbon stars.[67] S stars have excess amounts of zirconium and other elements produced by the s-process, and have their carbon and oxygen abundances closer to equal than is the case for M stars. The latter condition results in both carbon and oxygen being locked up almost entirely in carbon monoxide molecules. For stars cool enough for carbon monoxide to form that molecule tends to "eat up" all of whichever element is less abundant, resulting in "leftover oxygen" (which becomes available to form titanium oxide) in stars of normal composition, "leftover carbon" (which becomes available to form the diatomic carbon molecules) in carbon stars, and "leftover nothing" in the S stars. The relation between these stars and the ordinary M stars indicates a continuum of carbon abundance. Like carbon stars, nearly all known S stars are giants or supergiants.
- Examples: S Ursae Majoris, BD Camelopardalis
In between the M class and the S class, border cases are named MS stars. In a similar way border cases between the S class and the C-N class are named SC or CS. The sequence M → MS → S → SC → C-N is believed to be a sequence of increased carbon abundance with age for carbon stars in the asymptotic giant branch.
- Examples: R Serpentis, ST Monocerotis (MS)
- Examples: CY Cygni, BH Crucis (SC)
White dwarf classifications[edit]
The class D (for Degenerate) is the modern classification used for white dwarfs – low-mass stars that are no longer undergoing nuclear fusion and have shrunk to planetary size, slowly cooling down. Class D is further divided into spectral types DA, DB, DC, DO, DQ, DX, and DZ. The letters are not related to the letters used in the classification of other stars, but instead indicate the composition of the white dwarf's visible outer layer or atmosphere.
- Examples: Sirius B (DA2), Procyon B (DA4), Van Maanen's star (DZ7)[68], Table 1
The white dwarf types are as follows:[69]
- DA: a hydrogen-rich atmosphere or outer layer, indicated by strong Balmer hydrogen spectral lines.
- DB: a helium-rich atmosphere, indicated by neutral helium, He I, spectral lines.
- DO: a helium-rich atmosphere, indicated by ionized helium, He II, spectral lines.
- DQ: a carbon-rich atmosphere, indicated by atomic or molecular carbon lines.
- DZ: a metal-rich atmosphere, indicated by metal spectral lines (a merger of the obsolete white dwarf spectral types, DG, DK and DM).
- DC: no strong spectral lines indicating one of the above categories.
- DX: spectral lines are insufficiently clear to classify into one of the above categories.
The type is followed by a number giving the white dwarf's surface temperature. This number is a rounded form of 50400/Teff, where Teff is the effective surface temperature, measured in kelvins. Originally, this number was rounded to one of the digits 1 through 9, but more recently fractional values have started to be used, as well as values below 1 and above 9.[69][70]
Two or more of the type letters may be used to indicate a white dwarf which displays more than one of the spectral features above. Also, the letter V is used to indicate a variable white dwarf.[69]
Extended white dwarf spectral types:[69]
- DAB: a hydrogen- and helium-rich white dwarf displaying neutral helium lines.
- DAO: a hydrogen- and helium-rich white dwarf displaying ionized helium lines.
- DAZ: a hydrogen-rich metallic white dwarf.
- DBZ: a helium-rich metallic white dwarf.
Variable star designations:
- DAV or ZZ Ceti: a hydrogen-rich pulsating white dwarf.[71], pp. 891, 895
- DBV or V777 Her: a helium-rich pulsating white dwarf.[72], p. 3525
- GW Vir, sometimes divided into DOV and PNNV: a hot helium-rich pulsating white dwarf (or pre-white dwarf.)[73], §1.1, 1.2;[74][75] These stars are generally PG 1159 stars, although some authors also include non-PG 1159 stars in this class.[73][76]
- DCV or Gliese 86 B: a cool helium-rich white dwarf.
Non-stellar spectral types: Classes P and Q[edit]
Finally, the classes P and Q are occasionally used for certain non-stellar objects. Type P objects are planetary nebulae and type Q objects are novae.
Degenerate and exotic stars[edit]
These objects are not stars but are stellar remnants. They are much dimmer and if placed on the HR diagram, would be placed further to the lower left-hand corner.[77]
Stellar classification, habitability, and the search for life[edit]
This section addresses the probability of life arising around other stars.
Stability, luminosity, and lifespan are all factors in stellar habitability. We only know of one star that hosts life, and that is our own; a G-class star with an abundance of heavy elements and low variability in brightness. It is also unlike many stellar systems in that it only has one star in it (see Planetary habitability, under the binary systems section).
Working from these constraints and the problems of having an empirical sample set of only one, the range of stars that are predicted to be able to support life as we know it is limited by a few factors. Of the main-sequence star types, stars more massive than 1.5 times that of the Sun (spectral types O, B, and A) age too quickly for advanced life to develop (using Earth as a guideline). On the other extreme, dwarfs of less than half the mass of the Sun (spectral type M) are likely to tidally lock planets within their habitable zone, along with other problems (see Habitability of red dwarf systems).[78] While there are many problems facing life on red dwarfs, due to their sheer numbers and longevity many astronomers continue to model these systems.
For these reasons NASA's Kepler Mission is searching for habitable planets at nearby main-sequence stars that are less massive than spectral type A but more massive than type M – making the most probable stars to host life dwarf stars of types F, G, and K.[78]
Spectral peculiarities[edit]
Additional nomenclature, in the form of lower-case letters, can follow the spectral type to indicate peculiar features of the spectrum.[79]
Code | Spectral peculiarities for stars |
: | Blending and/or uncertain spectral value |
... | Undescribed spectral peculiarities exist |
! | Special peculiarity |
comp | Composite spectrum |
e | Emission lines present |
[e] | "Forbidden" emission lines present |
er | "Reversed" center of emission lines weaker than edges |
ep | Emission lines with peculiarity |
eq | Emission lines with P Cygni profile |
ev | Spectral emission that exhibits variability |
f | N III and He II emission (for element name followed by roman numeral see spectral line) |
f* | NIV λ4058Å is stronger than the NIII λ4634Å, λ4640Å, & λ4642Å lines[80] |
f+ | SiIV λ4089Å & λ4116Å are emission in addition to the NIII line[80] |
(f) | N III emission, absence or weak absorption of He II |
(f+) | [81] |
((f)) | Displays strong HeII absorption accompanied by weak NIII emissions[82] |
((f*)) | [81] |
h | WR stars with emission lines due to hydrogen.[46] |
ha | WR stars with hydrogen emissions seen on both absorption and emission.[46] |
He wk | Weak He lines |
k | Spectra with interstellar absorption features |
m | Enhanced metal features |
n | Broad ("nebulous") absorption due to spinning |
nn | Very broad absorption features due to spinning very fast[83] |
neb | A nebula's spectrum mixed in |
p | Unspecified peculiarity, peculiar star. |
pq | Peculiar spectrum, similar to the spectra of novae |
q | Red & blue shifts line present |
s | Narrowly "sharp" absorption lines |
ss | Very narrow lines |
sh | Shell star features |
v | Variable spectral feature (also "var") |
w | Weak lines (also "wl" & "wk") |
Code | Abnormal CNO features[84] |
C | C absorption enhanced, N deficient |
N | N absorption enhanced, C and O deficient |
Code | If spectrum shows enhanced metal features |
Ba | Abnormally strong Barium |
Ca | Abnormally strong Calcium |
Cr | Abnormally strong Chromium |
Eu | Abnormally strong Europium |
He | Abnormally strong Helium |
Hg | Abnormally strong Mercury |
Mn | Abnormally strong Manganese |
Si | Abnormally strong Silicon |
Sr | Abnormally strong Strontium |
Tc | Technetium is present |
Code | Spectral peculiarities for white dwarfs |
P | Magnetic white dwarf with detectable polarization |
E | Emission lines present |
H | Magnetic white dwarf without detectable polarization |
V | Variable |
PEC | Spectral peculiarities exist |
For example, Epsilon Ursae Majoris is listed as spectral type A0pCr, indicating general classification A0 with strong emission lines of the element chromium. There are several common classes of chemically peculiar stars, where the spectral lines of a number of elements appear abnormally strong.
Variable star classification[edit]
Stars that exhibit change in luminosity are variable stars. There is a variable star classification scheme that encompasses existing stars that are classified in the spectra classification.
Photometric classification[edit]
Stars can also be classified using photometric data from any photometric system. For example, we can calibrate color index diagrams of U−B and B−V in the UBV system according to spectral and luminosity classes. Nevertheless, this calibration is not straightforward, because many effects are superimposed in such diagrams: interstellar reddening, color changes due to metallicity, and the blending of light from binary and multiple stars.
Photometric systems with more colors and narrower passbands allow a star's class, and hence physical parameters, to be determined more precisely. The most accurate determination comes of course from spectral measurements, but there is not always enough time to get qualitative spectra with high signal-to-noise ratio.
See also[edit]
- Astrograph
- Guest star (astronomy)
- Spectral signature
- Stellar evolution
- Star count, survey of stars
- UBV photometric system
- ^ a b c d e f g These proportions are fractions of stars brighter than absolute magnitude 16; lowering this limit will render earlier types even rarer while generally adding only to the M class.
- ^ This rises to 78.6% if we include all stars. (See the above note.)
- ^ Analyse spectrale de la lumière de quelques étoiles, et nouvelles observations sur les taches solaires, P. Secchi, Comptes Rendus des Séances de l'Académie des Sciences 63 (July–December 1866), pp. 364–368.
- ^ Nouvelles recherches sur l'analyse spectrale de la lumière des étoiles, P. Secchi, Comptes Rendus des Séances de l'Académie des Sciences 63 (July–December 1866), pp. 621–628.
- ^ pp. 60, 134, The Analysis of Starlight: One Hundred and Fifty Years of Astronomical Spectroscopy, J. B. Hearnshaw, Cambridge, UK: Cambridge University Press, 1986, ISBN 0-521-25548-1.
- ^ pp. 62–63, Hearnshaw 1986.
- ^ p. 60, Hearnshaw 1986.
- ^ Classification of Stellar Spectra: Some History
- ^ pp. 62–63, Stars and Their Spectra: An Introduction to the Spectral Sequence, James B. Kaler, Cambridge: Cambridge University Press, 1997, ISBN 0-521-58570-8.
- ^ a b c d Tables VII, VIII, Empirical bolometric corrections for the main-sequence, G. M. H. J. Habets and J. R. W. Heinze, Astronomy and Astrophysics Supplement Series 46 (November 1981), pp. 193–237, Bibcode: 1981A&AS...46..193H. Luminosities are derived from Mbol figures, using Mbol(☉)=4.75.
- ^ a b T. J. Dupuy & A. L. Kraus (2013). "Distances, Luminosities, and Temperatures of the Coldest Known Substellar Objects". Science. published online 5 September 2013: 1492–1495. arXiv:1309.1422. Bibcode:2013arXiv1309.1422D. doi:10.1126/science.1241917.
- ^ a b The Guinness book of astronomy facts & feats, Patrick Moore, 1992, 0-900424-76-1
- ^ "The Colour of Stars". Australia Telescope Outreach and Education. 2004-12-21. Retrieved 2007-09-26. — Explains the reason for the difference in color perception.
- ^ a b Charity, Mitchell. "What color are the stars?". Retrieved 2006-05-13.
- ^ a b c d Baraffe, Chabrier, Barman, Allard & Hauschildt (2003). "Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458". Astronomy and Astrophysics 402: 701. arXiv:astro-ph/0302293. Bibcode:2003A&A...402..701B. doi:10.1051/0004-6361:20030252.
- ^ a b c d e f g h LeDrew, G.; The Real Starry Sky, Journal of the Royal Astronomical Society of Canada, Vol. 95, No. 1 (whole No. 686, February 2001), pp. 32–33. Note: Table 2 has an error and so this article will use 824 as the assumed correct total of main-sequence stars
- ^ Brown Dwarfs (go halfway down the website to see a picture of a magenta |rowndwarf)
- ^ Burrows et al. The theory of brown |dwarfsandextrasolar giant planets. Reviews of Modern Physics 2001; 73: |719–65
- ^ http://spider.ipac.caltech.edu/staff/davy/2mass/science/comparison.html |> "An Artist's View of Brown Dwarf Types" Dr. Robert Hurt of the Infrared Processing and Analysis Center
- ^ J. D. Kirkpatrick et al. (2012). "Further Defining Spectral Type "Y″ and Exploring the Low-mass End of the Field Brown Dwarf Mass Function". The Astrophysical Journal 753: 156. arXiv:1205.2122. Bibcode:2012ApJ...753..156K. doi:10.1088/0004-637X/753/2/156.
- ^ a b The Draper Catalogue of stellar spectra photographed with the 8-inch Bache telescope as a part of the Henry Draper memorial, Edward C. Pickering, Annals of Harvard College Observatory 27 (1890), Bibcode: 1890AnHar..27....1P. See in particular pp. 1–4.
- ^ a b pp. 106–108, Hearnshaw 1986.
- ^ p. 60–63, Hearnshaw 1986; pp. 623–625, Secchi 1866.
- ^ pp. 111–112, Hearnshaw 1986.
- ^ Spectra of bright stars photographed with the 11-inch Draper Telescope as part of the Henry Draper Memorial, Antonia C. Maury and Edward C. Pickering, Annals of Harvard College Observatory 28, part 1 (1897), pp. 1–128, Bibcode: 1897AnHar..28....1M; see in particular Table I.
- ^ Spectra of bright southern stars photographed with the 13-inch Boyden telescope as part of the Henry Draper Memorial, Annie J. Cannon and Edward C. Pickering, Annals of Harvard College Observatory 28, part 2 (1901), pp. 129–263, Bibcode: 1901AnHar..28..129C; see in particular pp. 139–143.
- ^ pp. 117–119, Hearnshaw 1986.
- ^ Classification of 1,688 southern stars by means of their spectra, Annie Jump Cannon and Edward C. Pickering, Annals of Harvard College Observatory 56, #5 (1912), pp. 115–164, Bibcode: 1912AnHar..56..115C.
- ^ pp. 121–122, Hearnshaw 1986.
- ^ Relations Between the Spectra and Other Characteristics of the Stars, Henry Norris Russell, Popular Astronomy 22, no. 5, (May 1914), pp. 275–294, Bibcode: 1914PA.....22..275R, in particular p.277
- ^ Saha, M. N.; On a Physical Theory of Stellar Spectra, Proceedings of the Royal Society of London, Series A, Volume 99, Issue 697 (May 1921), pp. 135–153
- ^ Payne, C. H.; Stellar Atmospheres; A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars, Ph. D. Thesis, Radcliffe College, 1925
- ^ Andrew Hamilton. "What color is the sun?". Retrieved 2012-11-15.
- ^ Morgan, William Wilson; Keenan, Philip Childs; Kellman, Edith (1943), "An atlas of stellar spectra, with an outline of spectral classification", Chicago, Ill., The University of Chicago press
- ^ Phillip C. Keenan, William Wilson Morgan; Keenan, P C (1973). "Spectral Classification". Annual Reviews of Astronomy and Astrophysics (Annual Reviews) 11 (1): 29–50. Bibcode:1973ARA&A..11...29M. doi:10.1146/annurev.aa.11.090173.000333.
- ^ A Low-Dispersion Luminosity Indicator for Solar-Type Dwarfs, Barry, Don C. 1970
- ^ a b c d Multiwavelength Systematics of OB Spectra, Walborn, N. R., 2008
- ^ An atlas of stellar spectra, with an outline of spectral classification, W. W. Morgan, P. C. Keenan and E. Kellman, Chicago: The University of Chicago Press, 1943.
- ^ Walborn, N. R. (1971). "Some Spectroscopic Characteristics of the OB Stars: An Investigation of the Space Distribution of Certain OB Stars and the Reference Frame of the Classification". The Astrophysical Journal Supplement Series 23: 257. doi:10.1086/190239.
- ^ Revised MK Spectral Atlas for Stars Earlier than the Sun, W. W. Morgan, H. A. Abt, and J. W. Tapscott, Yerkes Observatory, University of Chicago and Kitt Peak National Observatory, 1978.
- ^ A New Spectral Classification System for the Earliest O Stars: Definition of Type O2, Nolan R. Walborn et al., The Astronomical Journal 123, #5 (May 2002), pp. 2754–2771, doi:10.1086/339831, Bibcode: 2002AJ....123.2754W.
- ^ "SIMBAD Object query : CCDM J02319+8915". Centre de Données astronomiques de Strasbourg. Retrieved 2010-06-10.
- ^ Checking the yellow evolutionary void. Three evolutionary critical Hypergiants: HD 33579, HR 8752 & IRC +10420
- ^ "On a cosmological timescale, The Earth's period of habitability is nearly over | International Space Fellowship". Spacefellowship.com. Retrieved 2012-05-22.
- ^ Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs, Adam J. Burgasser et al., 2006
- ^ Astrometric and Spectroscopic Confirmation of a Brown Dwarf Companion to GSC 08047-00232, G. Chauvin et al., 2004
- ^ a b Stars as Cool as the Human Body
- ^ a b c d e f g Physical Properties of Wolf–Rayet Stars, Crowther, Paul A., 2007
- ^ Crowther, P. A.; Walborn, N. R. (2011). "Spectral classification of O2-3.5 If*/WN5-7 stars". Monthly Notices of the Royal Astronomical Society 416 (2): 1311. arXiv:1105.4757. Bibcode:2011MNRAS.416.1311C. doi:10.1111/j.1365-2966.2011.19129.x.
- ^ Outstanding Issues in Our Understanding of L, T, and Y Dwarfs, J. D. Kirkpatrick, April 2007, arXiv:0704.1522. Accessed on line September 18, 2007.
- ^ a b Kirkpatrick et al., J. Davy; Reid, I. Neill; Liebert, James; Cutri, Roc M.; Nelson, Brant; Beichman, Charles A.; Dahn, Conard C.; Monet, David G. et al. (July 10, 1999). "Dwarfs Cooler than M: the Definition of Spectral Type L Using Discovery from the 2-µ ALL-SKY Survey (2MASS)". The Astrophysical Journal (The University of Chicago Press) 519 (2): 802–833. Bibcode:1999ApJ...519..802K. doi:10.1086/307414.
- ^ a b Kirkpatrick, J. Davy (2005). "New Spectral Types L and T". Annual Reviews of Astronomy and Astrophysics (Annual Reviews) 43 (1): 195–246. Bibcode:2005ARA&A..43..195K. doi:10.1146/annurev.astro.42.053102.134017.
- ^ Ultra-cool Diminutive Star Weighs In
- ^ LSR 1610-0040: The First Early-Type L Subdwarf, Lépine et al. 2003c
- ^ Discovery of the brightest T dwarf in the northern hemisphere, 2007
- ^ Discovery of the Y1 Dwarf WISE J064723.23-623235.5, J. Davy Kirkpatrick, Michael C. Cushing, Christopher R. Gelino, Charles A. Beichman, C. G. Tinney, Jacqueline K. Faherty, Adam Schneider, Gregory N. Mace, The Astrophysical Journal preprint (submitted 25 Aug 2013)
- ^ Y-Spectral class for Ultra-Cool Dwarfs, N.R.Deacon and N.C.Hambly, 2006
- ^ a b Wehner, Mike (2011-08-24). "NASA spots chilled-out stars cooler than the human body | Technology News Blog – Yahoo! News Canada". Ca.news.yahoo.com. Retrieved 2012-05-22.
- ^ a b NASA spots chilled-out stars cooler than the human body
- ^ NASA'S Wise Mission Discovers Coolest Class of Stars
- ^ The minimum Jeans mass, brown dwarf companion IMF, and predictions for detection of Y-type dwarfs, B. Zuckerman and I. Song, Astronomy and Astrophysics 493, #3 (January 2009), pp. 1149–1154, doi:10.1051/0004-6361:200810038, Bibcode: 2009A&A...493.1149Z.
- ^ a b c Distances, Luminosities, and Temperatures of the Coldest Known Substellar Objects, Trent J. Dupuy and Adam L. Kraus, Science Online (Sept 2013), doi:10.1126/science.1241917
- ^ a b c The Physical Properties of Four ~600 K T Dwarfs, S. K. Leggett et al., The Astrophysical Journal 695, #2 (April 2009), pp. 1517–1526, doi:10.1088/0004-637X/695/2/1517, Bibcode: 2009ApJ...695.1517L.
- ^ CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf transition?, P. Delorme et al., Astronomy and Astrophysics 482, #3 (May 2008), pp. 961–971, doi:10.1051/0004-6361:20079317, Bibcode: 2008A&A...482..961D.
- ^ Exploring the substellar temperature regime down to ~550K, Ben Burningham et al., Monthly Notices of the Royal Astronomical Society 391, #1 (November 2008), pp. 320–333, doi:10.1111/j.1365-2966.2008.13885.x, Bibcode: 2008MNRAS.391..320B; see the abstract.
- ^ European Southern Observatory. "A Very Cool Pair of Brown Dwarfs", 23 March 2011
- ^ Bouigue, R. 1954, Annales d'Astrophysique, Vol. 17, p.104
- ^ Spectral Atlas of Carbon Stars (Barnbaum+ 1996)
- ^ Keenan, P. C. 1954 Astrophysical Journal, vol. 120, p.484
- ^ A Determination of the Local Density of White Dwarf Stars, J. B. Holberg, Terry D. Oswalt and E. M. Sion, The Astrophysical Journal 571, #1 (May 2002), pp. 512–518.
- ^ a b c d A proposed new white dwarf spectral classification system, E. M. Sion, J. L. Greenstein, J. D. Landstreet, J. Liebert, H. L. Shipman, and G. A. Wegner, The Astrophysical Journal 269, #1 (June 1, 1983), pp. 253–257.
- ^ A Catalog of Spectroscopically Identified White Dwarfs, George P. McCook and Edward M. Sion, The Astrophysical Journal Supplement Series 121, #1 (March 1999), pp. 1–130.
- ^ Physics of white dwarf stars, D. Koester and G. Chanmugam, Reports on Progress in Physics 53 (1990), pp. 837–915.
- ^ White dwarfs, Gilles Fontaine and François Wesemael, in Encyclopedia of Astronomy and Astrophysics, ed. Paul Murdin, Bristol and Philadelphia: Institute of Physics Publishing and London, New York and Tokyo: Nature Publishing Group, 2001. ISBN 0-333-75088-8.
- ^ a b Mapping the Instability Domains of GW Vir Stars in the Effective Temperature-Surface Gravity Diagram, Quirion, P.-O., Fontaine, G., Brassard, P., Astrophysical Journal Supplement Series 171 (2007), pp. 219–248.
- ^ §1, Detection of non-radial g-mode pulsations in the newly discovered PG 1159 star HE 1429–1209, T. Nagel and K. Werner, Astronomy and Astrophysics 426 (2004), pp. L45–L48.
- ^ The Extent and Cause of the Pre-White Dwarf Instability Strip, M. S. O'Brien, Astrophysical Journal 532, #2 (April 2000), pp. 1078–1088.
- ^ UV spectroscopy of the hybrid PG 1159-type central stars of the planetary nebulae NGC 7094 and Abell 43, Ziegler, M. et al. 2009
- ^ Digital Demo Room Stellar Structure and Evolution Simulator(date unknown)
- ^ a b "Stars and Habitable Planets". Solstation.com. Retrieved 2012-05-22.
- ^ SkyTonight: The Spectral Types of Stars
- ^ a b Pismis 24-1: The Stellar Upper Mass Limit Preserved, J. Maíz Apellániz et al. 2006
- ^ a b Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud, Cecilia Fariña et al. 2009
- ^ Early-type stars in the core of the young open cluster Westerlund2, G.Rauw et al. 2006
- ^ Kaler, James B. (2011). Stars and Their Spectra: An Introduction to the Spectral Sequence (2nd ed.). Cambridge University Press. p. 88. ISBN 0-521-89954-0
- ^ Sota, A.; Maíz Apellániz, J.; Walborn, N. R.; Alfaro, E. J.; Barbá, R. H.; Morrell, N. I.; Gamen, R. C.; Arias, J. I. (2011). "The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-Violet at R ∼ 2500". The Astrophysical Journal Supplement Series 193 (2): 24. arXiv:1101.4002. Bibcode:2011ApJS..193...24S. doi:10.1088/0067-0049/193/2/24.
External links[edit]
- Libraries of stellar spectra, D. Montes, UCM
- The rate of period change in pulsating DB white dwarf stars, A. H. Corsico, L. G. Althaus, has the DAV, DBV, & DOV explanation.
- The Close DAO+dM Binary RE J0720-318: A Stratified White Dwarf with a Thin H Layer and a Possible Circumbinary Disk DAO type White Dwarf.
- The Spatial Distribution and Kinematics of Cool Metallic Line White Dwarfs, has DAZ and DBZ spectrums
- A K-Band Spectral Atlas of Wolf–Rayet Stars, has WC, WN, and WO spectrums
- Properties of the WO Wolf–Rayet stars, has WO spectrum ranging from WO1 to WO5
- Spectral Types for Hipparcos Catalogue Entries
- Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574, J. Davy Kirkpatrick et al.
- Stellar Spectral Classification, Richard O. Gray and Christopher J. Corbally
- Philippe Stee's homepage: Hot and Active Stars Research
- Merrifield, Michael; Bauer, Amanda; Häußler, Boris (2010). "Star Classification". Sixty Symbols. Brady Haran for the University of Nottingham.


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Nostalgia takes Hawaii's most renown songs and translates them all in to the native Hawaiian language. Amy & Willie showcase a fresh interpretation of these classic songs that the are recognized the world over, no matter what language the singer chooses.
Learn MoreMy Father's Granddaughter
My Father's Granddaughter came at a turning point in my life. During the process of recording this album my father passed into his next journey. Lloyd Gilliom, my father, grew up on the road with my Tutu Jennie. She would instill in him three of life's most important qualities that he later would pass on to me: Humility, Kindness and Love. As I tour the world sharing Hawaiian music, I am thankful that my daughter Madeline was able to spend time with my parents who became instrumental in helping me raise her in today's world. I would often witness my father teaching Madeline the same life lessons he taught me. Never a dull moment in the Gilliom `Ohana. Beautiful how the circle of life works.
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• Features many of Hawaii's top recording artists Learn More
Amy Hanaiali'i and Slack Key Masters of Hawai'i
A ground breaking collaboration between Hawaii's top selling female vocalist Amy Hanaialii and top performers/composers Jeff Peterson, Cyril Pahinui, Dennis Kamakahi, Sonny Lim and Chino Montero in the slack key guitar tradition.
One of the wonderful things about music is its ability to bring people together to share a connection that reaches beyond borders and boundaries. Music can immediately bond souls and create common ground. What happens when kindred spirits who share a deep respect for each other and Hawaiian culture come together to share their music in collaboration? We believe this recording is a great example of just this – creativity, camaraderie, spontaneity, passion, joy, laughter, gratitude, and above all aloha. We hope this recording is as much a joy to listen to, as it was to create.
Learn MoreIsland Love
Hawai`i is the most romantic place on earth… a place that surrounds us with such beauty that it inspires us to a love one another and this place. The spirit of love and aloha is what we hope to share with this music.
Here are a few of our favorite songs performed by some of the biggest artists in the industry.
Learn More
Friends and Family of Hawai'i
Four time GRAMMY nominee and Hawaii's top selling female vocalist of all time, Amy Hanaiali'i joins forces with some of the greatest male vocalists in Hawai'i on Amy Hanaiali'i Friends & Family of Hawai'i. Millions of CD's have sold collectively by this incomparable group of artists, including Willie Nelson, Keali'i Reichel, Robert Cazimero, Fiji
Learn MoreAumakua
Few Hawaiian musicians have risen to such national and international acclaim as Amy Hanaiali`i. Her 2008 album, `Aumakua, is a true embodiment of her consummate talent, featuring 14 fresh compositions that, combined, will comprise one of the most beautiful albums to come from a Hawaiian artist. Hanaiali`i offers her Hoku Award-winning falsetto-infused vocals to `Aumakua, a reverent assemblage of original songs and beloved, time-honored classics, set to the sweet, melodious style that is all her own. Replete with appearances by fellow award-winning artists, composers and arrangers, `Aumakua is an undeniable awards contender.
Learn MorePu`uhonua
A beautiful collection of traditional Hawaiian songs, multiple Hoku award winner Amy Hanaili`i offers this album for all to enjoy.
Learn MoreA Hawaiian Christmas
After an outstanding year of award-winning music, two-time GRAMMY® nominated Amy Hānaiali`i gracefully wraps it up in red and green with A Hawaiian Christmas. Featuring songs that were a part of Amy's childhood Christmas celebrations on the island of Maui, A Hawaiian Christmas is a special, personal collection of her musical memories. A Hawaiian Christmas is Amy's first Christmas album and it takes you back to the simple days in the islands, when holidays were all about family and friends. Invite Amy Hānaiali`i to share her holiday memories with your `ohana (family) this Christmas, and complete the season with A Hawaiian Christmas.
Learn More
SALE: Return to Romance
Regular Price: $15.98
Special Price: $2.00
"Return to Romance" combines lush orchestrations with the award-winning talents of some of Hawai`i's most recognizable artists to take you on a journey through all the exhilarations of love. Arranged by Honolulu Symphony Pops conductor Matt Catingub and produced by famed Allen Sviridoff, both Grammy Award winners, the album holds a prism up to romance, reflecting the many colors and hues of its beauty with a touch of aloha. Reminisce on romance, from young adoration with Raiatea Helm on "My Romance," to classics like "Let There Be Love," sung by the Brothers Cazimero, and one of the greatest love songs ever, "What Are You Doing for the Rest of Your Life?" interpreted beautifully by Amy Hanaiali`i.
Sold as is. All Sales Final. Learn More
Amy & Willie hit their stride with Hanaiali`i and it still is considered one of their finest works by the legion of fans that can't get enough of this wild combination of talent.
Learn MoreHawaiian Tradition
Hawaiian Tradition proved to be Amy & Willie's instant hit album and the public immediately embraced both their musical talent and incredible stage presence. As a new "group" they became an overnight success story.
Learn MorePick A Hit
The album's title, Pick A Hit, explains the CD perfectly. Pick A Hit is a compilation CD of all of Hawai'i's hottest Hawaiian music artists and their hits! A must have if you want hit songs, by Hawai'i's most respected artists.
Learn MoreHawaii, Music From The Islands Of Aloha
The Hawaiian Islands are brought to life in the form of this CD. From traditional to contemporary Hawaiian artists, they are all featured on this 15-track compilation CD. Once you put this CD into your stereo you'll never be able to take it out. The melodies are addicting and the chorus' are catchy! A definite must-have!
Learn MoreHawaii Songs of Aloha
Filmed in the historic Hawai`i Theatre, this national PBS special features Hawai`i's best musicians, singers and dancers on DVD. Performances by The Brothers Cazimero, Na Leo, HAPA, Makaha Sons, Amy & Willie, O'Brian Eselu, Jake Shimabukuro and many others.
Learn MorePride of Punahele II
Generation Hawaii
CONGRATULATIONS to Amy Hanaiali`i...2007 Na Hokuhanohano Award Winner for Album of the Year, Hawaiian Album of the Year, Female Vocalist of the Year and Best Engineered Album. "Generation Hawai`i" is Grammy nominated Amy Hanaiali`i at her best, in true form, representing her islands, her culture and her family legacy with the music she was born destined to share. It was produced by award winning producer, songwriter and musician Michael Ruff, who has worked with legends like Lionel Richie, Chaka Khan, Stevie Nicks and countless others.
Learn MoreSALE: Back To Romance
Regular Price: $15.98
Special Price: $2.00
On the heels of one of the best selling CD's of 2006 comes Back to Romance, a rare all-male recording of Hawai`i's leading men with the lush orchestrations of the Matt Catingub Orchestra of Hawai`i. Back to Romance represents a true expression of a man in love. From Robert Cazimero's dreamy rendition of "I Only Have Eyes For You" to Fiji's R&B touch on Paul & Linda McCartney's "My Love," each song was handpicked by the artists. What are men's most intimate thoughts of romance? With passion in their hearts and love on their minds, Hawai`i's premiere male recording artists and the Matt Catingub Orchestra of Hawai`i answer that question with Back to Romance.
Sold as is. All Sales Final. Learn More
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Nectar Monthly Honors February 2010
February, 2010 has come to a close. March brings spring which leads to BBQ's, running outdoors and most importantly, trips to God's country – Walla Walla, Lake Chelan and Woodinville. The short month of February saw nearly 1000 tweets, 27 posts and 21 wine reviews.
DrinkNectar is proud of the following in February:
- Participating in a local Social Media forum
- Top Ten listings at Post Rank for Wine Blogs
- Mention in Wine Enthusiast Online as most engaging wine blog
Below are some of my favorite tweets from February. With the closing of the 2010 Olympic Games in Vancouver – these are the gold medal winners of tweeters!
Wines of the Month
Best Value Under $15
While I didn't formally review this wine, I did have an impromptu visit with JJ Williams (aka 1EyeWineGuy) during a recent trip to Costco. A bottle of Lemberger was in my future.
- The Stuff: 100% Estate Lemberger from Red Mountain AVA Kiona Vineyards
- The Swirl: A dark strawberry color that was about 50% translucent. Muted jewel tones
- The Sniff: Bright strawberry and cherry with moderate earthiness and minerality
- The Sip: A sweet wash of cherry, vanilla and some cola flavors. The wine is sweet and soft with more substance on the back end with some spice and tannin
- The Score: At just $11 this is easily a 4 (out of 5). An incredible value for a wine that provides a variety of flavor
*Runner-up 2008 Chateau St. Michelle Riesling $6 – Reviewed Here
2004 Croze Cabernet Sauvignon – Reviewed Here
- The Stuff:100% Napa Valley Cabernet, 42 months in oak, 13%ABV, 637 cases made
- The Swirl: Nice dark rust colored plum with a little translucence (almost see to the bottom of the glass)
- The Sniff: I never wanted to stop smelling this wine. Floral perfume kissed me first, then gentle bright blueberry and strawberry aromas held hands and skipped through my nose. They were followed up by some mellow vanilla notes. This is the kind of wine scent you wish for in every bottle of Cabernet!
- The Sip: Definitely does not disappoint – The fruit is soft and supple like a long slow French kiss. The passion builds as some spicy pepper jumps in. The finish is super balanced and longs with enough tannin to keep the wine strong with food.
- The Score: At $35 this is a 5 (out of 5) wine for me. I love the complete package and would definitely buy this bottle again.
*Runner-up 2007 Arbor Crest Cabernet Franc
Random Favorite Highlights from February
The Post that Made Me Spit Wine Out of My Nose – Wine Bloggers Bite the Big One: This post from @DirtySouthWine (aka Hardy Wallace, aka NPAHardy) was in response to recent allegations that wine blobbers are a bunch of uninfluential, wine whores railing against traditional media and seeking free wine. This amazing post will have you laughing from poop to chainsaws.
Best Wine Event: #CaliCabs on February 11 brought over 50 California Wineries and hundreds of tweeters together with one common purpose. Promoting California Cabernet! The event was spearheaded by @RickBakas in the traditional grass roots method. If you liked #CaliCabs you'll love #SauvBlanc on March 4.
Best Wine Picture (tie) – This cute Valentine's Day tweet came from @SeattleWineGal depicting love in the form of two wine bottle openers.
@SuppleWine makes the list for the second month in a row, this time for his Wine in the Wild series featuring Super Model Julie Ordon and a glass of Sauvignon Blanc.
Best wine quote: "A wine so delicious my tongue wanted to make love to my tonsils." – From @goodgrape from a February 11 post.
Best Social Media Post: This is such a difficult category because so much good stuff comes out each month. I went with a presentation by @lunabeanmedia to a group of Walla Walla wine makers! Social Media for Wineries
Best Blog Feature: Sean Sullivan from @WaWineReport contributes a weekly labor of love for Washington wine enthusiasts. Only one stop is needed to stay "in the know" for everything pertaining to Washington Wine. Washington Wine Round-Up
DrinkNectar Most Viewed Post: Wine Ripped off and Ticked Off (60+ comments) – A look at the horrible wine practices of restaurants and their 400% mark-up, uninspired wine lists and crappy wine glasses.
9 Comments:
By uberVU - social comments 01 Mar 2010
Social comments and analytics for this post…
This post was mentioned on Twitter by bestwine: Nectar Monthly Honors February 2010 | Drink Nectar: Best Wine Event: #CaliCabs on February 11 brought over 50 Cal… http://bit.ly/cP54y3…
By Sip with Me! 01 Mar 2010
Great post, I totally agree, @dirtysouthwine's blog was righteous! And Ripped Off & Ticked Off brought light to that dark area – ugly restaurant mark-up. I hope to someday make your list of favorites… cheers!
By Ed Thralls 02 Mar 2010
Nice recap for the month, which was very busy and successful for you. Well Done! You make the rest of us hacks feel good and look good. Of course, it's better to look good than to feel good (5 points if you guess this quote).
Keep it up and here's to a better March, which includes your #WAMerlot tasting!
By Sip with Me! 02 Mar 2010
Wow, I'm honored you even considered me – and called me creative and funny! Coming from you, I don't take that lightly. It wasn't an easy story to tell, but one that's kinda been itching to get out. Cheers and I look forward to what March has in store!!
By Most Tweeted Articles by wine Experts: MrTweet 03 Mar 2010
Your article was most tweeted by wine experts in the Twitterverse…
Come see other top popular articles surfaced by wine experts!…


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Wikipedia's most-viewed articles in 2012 were...
English speakers seem to be interested in action movies, boy bands, and Facebook.
New stats compiled by Swedish software engineer Johan Gunnarsson detail the top 100 most-viewed articles on Wikipedia over the past year. The online encyclopedia doesn't create its own year-end list but does let people read its log files, according to AllThingsD. This top 100 list compiled by Gunnarsson, which comes in several languages, is the first time users can see Wikipedia's most popular articles over the course of a year.
For the English language Wikipedia, which is the most popular version of the site, "… Read more


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A meeting on Wednesday, Feb. 6, in Montrose will give irrigation companies and districts and ag producers a chance to tell what they think about various programs offered to reduce salinity off-farm and on-farm in the Colorado River and its tributaries like the Gunnison.
Programs such as the Bureau of Reclamation's Basinwide and Basin States Programs and USDA-NRCS's EQIP have been underway for several years.
An independent consultant has been hired by the Bureau to find out what agricultural producers and water managers think about these programs.
The meeting is designed to get answers to questions like these:
• If you have participated in these programs, what did you like? What did you not like?
• If you haven't participated in these programs, why not? What has kept you from participating?
• Do you have ideas for how program promoters could increase participation in these programs?
The meeting will be held at the Holiday Inn Express, 1391 S. Townsend Avenue, Montrose, from 11:30 a.m. to 2 p.m. A complimentary lunch will be served. For more information, contact MaryLou Smith at Colorado Water Institute, Colorado State University, MaryLou.Smith@
Colostate.edu or call (970) 491-5899.


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Science upd8
These resources have been produced by the Association for Science Education (ASE) and the Centre for Science Education at Sheffield Hallam University. Based on contemporary issues, they help to make science accessible, relevant and engaging to secondary school students.
The range of resources utilises a variety of teaching and learning strategies. They cover all areas of the science curriculum and provide materials such as activity sheets, simulations, video clips and teacher guidance.
HEALTH and SAFETY
Any use of a resource that includes a practical activity must include a risk assessment.
Please note that collections may contain ARCHIVE resources, which were developed at a much earlier date.
Since that time there have been significant changes in the rules and guidance affecting laboratory practical work.
Further information is provided in our Health and Safety guidance.
Collection author
Resource by: upd8


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Summer in Santa Clarita is filled with so many fun things to do. Here's to the poolside barbecues with friends and family, trips to the beach, warm summer nights, staying up late, sleeping in and enjoying one of the many exciting events going on this month in our Valley. There's plenty to do, so we hope you are enjoying your summer while staying close to home, shopping locally and keeping cool!
We are very pleased to feature Captain Becker and the Santa Clarita Valley Sheriff's Foundation on the cover of this issue. Join us and show your support for the SCV Sherriff's Foundation as they raise funds for a much-needed mobile command post at the SCV Sheriff's Station. Our city is one of the safest communities in the state, and we have our local law enforcement to thank for that. Let's continue to support their efforts to raise funds that will not only benefit the department, but also the safety of our community. See our cover story on the facing page, and how you can enter to win a cruise for two! Tickets for the Opportunity Drawing are only $5 each and there is no limit on how many you can purchase.
It's summer, and you know what that means, Santa Clarita? It's time for the City's popular and free Concerts in the Park series, every Saturday, beginning July 7 with The Shoemaker Brothers. The Series will continue every Saturday through August 25. It's a perfect way to spend your summer evenings rockin' out to great music with your neighbors, friends and family. Learn more about the Series on page 23.
Poker enthusiasts, it's time to ante up for the Michael Hoefflin Foundation. On Saturday, July 14, there will be a Texas Hold'Em Poker Tournament at Diamond Jim's Casino in Rosamond. Bring your poker face and support a great cause. See details on page 8.
Get those stilettos out and join the Soroptimist International of Greater Santa Clarita Valley as they will host their High Heel a Thon to stomp out domestic and dating violence, also on Saturday, July 14. Gather on Main Street in Old Town Newhall and show your support! Turn to page 19 for more information on the event.
Despite the challenges of today's economic realities, many businesses have demonstrated entrepreneurial success in the Santa Clarita Valley. Let's recognize and celebrate our local businesses and their achievements by voting for individuals, businesses or non-profit organizations for the first SCV Leadership Awards. There's still time to vote, and winners will be determined based on the number of votes received. See page 3 for details about how to nominate, as well as the SCV Leadership Awards dinner.
It's also time to vote for your favorites for the 2nd Annual élite Ultimate Home & Garden Awards. Enter your name, tell us who you believe to be the best of the best and see if your favorites take top prize, as winners will be announced in the October/November issue of élite Magazine. Turn to page 6 for more information.
Are you new to The Magazine of Santa Clarita or haven't advertised in awhile? Be a part of our Meet the New Merchants feature, and allow our readers to get to know a little more about you and your business. Turn to page 27 to see this month's new merchants.
Finally, Fourth of July marks Independence Day. Celebrate America's birthday and take a moment to honor the soldiers who have served and are continuing to serve our country so we can enjoy the many freedoms we have today.
Until Next Time,
Linda, Moe and Alex Hafizi
SCV Unscripted
Constant Contact
Digital Edition
Articles - This Issue
- Celebrate Entrepreneurial Achievements Vote Now for the SCV Leadership Awards
- Take a Cruise, Support Your Local Sheriffs!
- A Note from the Publishers - July 2012
- Vote for Your Favorites! Ultimate Home & Garden Awards
- Don't Miss Out on the Star Studded Event Dancing With Our Stars Tickets Now Available
- Bring Your Poker Face Come Support the Michael Hoefflin Foundation
- Local Alumnus Enters Boys & Girls Club Hall of Fame
- SISCV receives a $6,000 Grant from SI of the Americas
- Valencia Country Club Site of 22nd Annual COC Foundation Golf Tourney
- Zonta Installs New Officers and Names Zontian of the Year


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Judy Moody and the NOT Bummer Summer comes out on June 10. Treat your kids to a pre-movie tasting of must-try Judy Moody favorites inspired by the movie.
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Vacuum Filters
Who does not love a clean house free from grime and dust? Vacuum cleaner filters are the essential parts of the vacuum cleaner that keep the dirt sucked up by the cleaner in the machine. It helps kill the germs and contaminants that are trapped within. They are positioned such that they can trap the dust mites and pollutants before it reaches the motor and the exhaust. There are various kinds of filters available including the ultra fine air filter and some vacuum cleaning systems even use water as a filter. Water filtration helps trap wet dust that is not airborne. Having a fully functional vacuum filter is critical to maintain the suction and dirt handling ability of the vacuum cleaner. You are not just saving yourself from the harmful effects of these dust particles but also saving the critical parts of the vacuum cleaning system from failure. We recommend you change vacuum filters regularly, once in six months atleast.
Want to find a filter for your vacuum cleaning system? At GoVacuum, we have a full range of filters including motor filters and HEPA filters. The vacuum cleaner is a formidable cleaning tool today and the combination of its cleaning capacity and ease of use are major factors that influence the buying decision. We seek to provide all the information about vacuum cleaning systems and various replacement parts including vacuum filters which you can use to extend the life of your vacuum cleaner for several years.
Riccar 1700, 1800 HEPA Exhaust Filter and Charcaol Filter Set Riccar Part # RF17
This is the replacement HEPA filter, and charcoal pre-motor filter set for the Riccar full size canister vacuum cleaners. Included in this package is 1 HEPA Filter, and 1 Charcoal pre-motor filter. These filters should be replaced at least once a year, Learn More -
Riccar HEPA Filter & Motor Filter Kit Set for Riccar Radiance RAD Vacuum Cleaners; Replaces Riccar
Vacuum HEPA Filter and Motor Filter Fits Riccar Radiance RAD & RADP Upright Vacuum Cleaner models. Replaces Riccar Part # RF9-1 (RF91). This set includes 3 Filters - a HEPA Filter, Charcoal filter and Motor Filter.Includes 3 Filters - Here's the details of each filter:- 1 Foam Charcoal filter, located right next to the vacuum bag in a bracket- 1 Exhaust HEPA Filter, located on the side of the vacuum cleaner inside a filter bracket. - 1 Motor filter, the smallest of the filters (a small squarel white filter), located on the bottom of the upright where the body of the vacuum meets the bottom red color base. Fits the following Riccar Series Vacuum Cleaner Canister Models:Riccar Radiance RAD VacuumRiccar RADP VacuumRiccar Radiance VacuumRiccar Radiance Premium VacuumReplacing Your Riccar Vacuum Cleaner FilterYour Riccar is equipped with a 3 filters to capture fine dust particles and purify air before it exits the vacuum cleaner. It is important to change the motor filter regularly - app Learn More -
Riccar RF-18 HEPA Filter For Models Pristine, Charisma, and Starbright
Riccar HEPA filter designed to fit the following Riccar canister vacuum cleaner models: Charisma, Starbright, and the Pristine. Riccar Item # RF-18. Riccar RFI8 canister vacuum HEPA filter will also fit Simplicity models; Verve, and Jessie. Learn More -
Riccar RF-17 HEPA Filter Fit Riccar 1700, 1800
Fits Riccar canister vacuum models 1800 & 1700 canister vacuum cleaners using Riccar HEPA & Charcoal filter part RF17. Riccar RF-17 HEPA & Charcoal Canister vacuum cleaner Will Also fit Simplicity full size canister models. Package contains 1 high effici Learn More -
Electrostatic Post Filter Pleated w/Rubber Frame 8900 Series
Upgraded HEPA Electrostatic exhaust filter. Will fit all Riccar 8900 series upright vacuum cleaners including models, 8900, 8905, 8920, 8925, and 8955. Riccar part # RF8900P-1. Also will fit Simplicity series 7 models. Learn More -
Riccar 1500 Canister HEPA & Secondary Filter Set RF-15
This is a single pack of the genuine Riccar HEPA and Secondary filters, part# RF15, for the Riccar 1500 Series Canister Vacuum Cleaners. Learn More -
Genuine Riccar 8000 Post Filter # RF8-2
Genuine Riccar 8000 Post Filter # RF8-2 fits Riccar models 8600, 8625, 8650 and 8850. Riccar Part Number: RF8-2. It is recommended to change filter after every 3 to 6 months. Learn More -
Riccar 8900 Series Pleated Hepa Media Filter, Riccar part # RF89-2 (1 Pack)
Riccar 8900 Series Pleated Hepa Media Filter, Riccar part # RF89-2 (1 Pack) Learn More -
Generic Riccar RCF89-2 8000 Series Vacuum Cleaner Charcoal Filters
Generic Riccar RCF89-2 8000 Series Vacuum Cleaner Charcoal Filters fits Riccar models 8000.Riccar Part Number: RCF89-2. Pack of 3. Learn More -
Riccar 8900 Series Pre-Motor Filter With Charcoal RCFT89
This is a 2 pack of genuine replacement Riccar Pre-motor with charcoal filters, part RCFT89, for the Riccar 8900 Series Upright Vacuums. Learn More


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Strathmore Writing Soft Gray Paper - 8 1/2 x 11 in 88 lb Bristol Laid 30% Recycled 125 per Package
Quick Overview
Strathmore Writing comes in text, cover and cover bristol weights and offers a range of subtle colors in wove and laid surfaces.Reviews
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Product Description
Strathmore Writing comes in text, cover and cover bristol weights and offers a range of subtle colors in wove and laid surfaces. Strathmore Writing specialty paper and envelopes are the paper and envelopes of choice for companies and individuals who want to express their environmental values while exuding elegance and quality. You will admire the premium quality of Strathmore papers when you hold them in your hand. The colors are elegant, the surface structures and fiber formations are as close to perfection as you can achieve in paper making. The entire line of Strathmore Script specialty paper and envelopes are manufactured using non-polluting, renewable wind-generated electricity and is offered in 30% recycled shades.
End Uses
- Business Cards
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- Greeting Cards
- Menus
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- Place Setting Cards
- Pocket Folders
- Report Covers
- Table Tents
- Wedding Place Cards
Eco Features
- Elemental Chlorine Free
- Green Seal Certified
- Green-e Certification
- Lignin Free
- Made Using Wind Power
- 30+% Recycled
- Carbon Neutral
- Printing Tips
Printing Applications
- Offset Lithography
- Sheet-Fed Offset
- Specs
Paper Specifications
Basis Weight G/M2 Caliper PPI Sheffield Opacity Brightness 88 lb Bristol 238 13.8 144 310 99 G/M2 = Grams per square meter
Caliper = Thickness i.e. 1.0 = .001"
PPI = Pages Per Inch
Sheffield = Smoothness measure
Opacity = Level of opacity
Brightness = Whiteness value
Paperator™ Color Value System
We have measured these papers with a Spectrometer to establish the closest CMYK and RGB colors to this paper. The measurements we took are as follows.
Color Name CMYK sRGB Soft Gray C = 2
You can enter these color values into your graphics programs to reproduce these paper colors on screen or by printing them with your inkjet or color laser printer. Remember these color values are not exact and should not be used for proofing and only provide an indication of the paper's color for mock-ups and presentations. Best used in conjunction with paper samples and may require some color adjustment and calibration to your equipment.
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Perforated Paper
Please see our selection of Perforated Papers options for your ticket, return receipt, business card and standard perforating requirements.
We can perforate any paper from 20 lb bond, all text weight papers and up to 80 lb cover paper. We are currently working to automate this function. Until then please contact us with your perforated paper request for pricing, email@example.com
Paper Cutting
Paper Cutting Charges
- 1st Cut: $14.97
- Additional Cuts: $5.97
When you want to cut three reams of 8 1/2 x 11 down to 5 1/2 x 8 1/2 you pay:- 1st Cut: $14.97
- 2 additional cuts at $5.97 per cut is $11.94
- Your total cutting charge is $26.91
Paper Scoring
We can help you with your paper scoring needs by providing professional scoring services for all text weights and up to 90 lb cover paper.
Paper Scoring Charges
1st Ream / Package: $20 per score - max 2 parallel scores per page
Additional Reams / Packages: $15
Maximum sheet size: 4" x 4" min. & 19" x 20" max


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TROUBLE FOR SURE AT COMEX. tAKE DELIVERY FOLKS
that why the first blast up!
having delivery problems
I agree it is a goo deal around 25K I cant afforf t20k, but will buy 4k shares.
I had mentioned a few days ago that the Senate approved the tax. It is now solely up to the President. There are no legal proceedings as this is Mexico. I dumped at 12 and also sold exk with a one dollar gain. If it gets signed by the Prez this crashes to five bucks.
I knew these guys were going to approve this law and only the President of Mexico can stop it now. It is a big fricking problem. I'm Out of all Mexican stocks
Told you guys last night! If you all have a brain you will start slowly pulling dough out of banks and put it into coins like silver, gold and platinum.
Ahhh, now you get it!
Well frigging think again. Go to Drudge, etc as it is starting to spread. No more wire transfers out of the country for small businesses! I kid you not and for the first time in a while I will sleep well knowing I have a million bucks in pm stocks and coins and bars (50/50). I am worried about the few hundred grand I have on deposit in U.S. banks.. This just might be it folks, I KID YOU NOT.
It is moved to the right hand column at the top. Get this, Jim SInclair just sent be an email and he said it is REAL!
cash withdrawals. People, this means capital controls. It could also mean a currency devaluation on Nov. 17 or thereabouts. That is the date the the letters say the full force of the new rules. Unless these are two fake letters , this is serious stuff. Prepare for banks runs as I think the US dollar is collapsing overseas.
Its true!
it is an error on kitco duh.
Are You Serious? Why don't you let me know the difference of the manipulation with the CFTC and old BartILOCKS as opposed to no CFTC. It is a rigged game and it won't change.
2 plus 2 together! Wake up as it is not a coincidence. However, i hope that the ebt cards shut down for good. Let obama's morons fend for themselves.
I am very troubled by what appears to be a conspiracy to drive the prices of metals into the ground. It seems to be as crooked as the libor rigging.
How about the trillion or so when we all sue over the rigging of the silver market! bill is a bargain for JPM, and I vote NO WAY.
your own butts because when this derivative bubble pops and JPM crashes gold will be at $7000 plus per ounce. Of the aforementioned, I am totally sure.


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More information about Women's Volleyball Championship |
The Elder Scrolls Online MMO Launches April 4th, 2014, Later For PS4 And Xbox One
The Elder Scrolls Online MMO release date has been announced for various platforms. (2:04) The Elder Scrolls Online
War in Cyrodiil Trailer (2:04) Legends Of Persia
Legends Of Persia trailer. (2:04) Fish vs. Crabs
Fish vs. Crabs trailer. (1:26) Rock'N Racing Off Road
Rock\'N Racing Off Road teaser trailer. (1:57)
More On GameRevolution |


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NEW MOVIES The Christmas Spirit Starring Nicollette Sheridan & Olympia Dukakis Santa Switch Starring Ethan Erickson & Sean Astin Hats Off to Christmas! Starring Haylie Duff & Antonio Cupo ALL MOVIES >>
ORIGINAL SERIES When Calls the Heart Starring Lori Loughlin, Erin Krakow & Daniel Lissing Home & Family Hosted by Mark Steines and Cristina Ferrare Debbie Macomber's Cedar Cove Starring Andie MacDowell ALL SERIES >>
The Doctor is Out! But don't worry, Frasier will return to its regular time period in January.
Are You Listening? Check out our video quiz and guess which celebrities are calling Frasier!
Episode Guide Frasier ran for eleven seasons--get the details on the early years with our guide.
Frasier Quotes Check out some of the hilarious lines from this Emmy-winning sitcom.
The Cast So you love the characters, but how much do you know about the cast? Get the details now.
Photo Gallery Enjoy images from the early seasons to the final one in our photo gallery.