Radiation astronomy/Yellows

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This is a true-color image of Io taken by the Galileo probe. Credit: NASA.

Yellow astronomy is astronomy applied to the various extraterrestrial yellow sources of radiation, especially at night. It is also conducted above the Earth's atmosphere and at locations away from the Earth as a part of explorational (or exploratory) yellow astronomy.

Seeing the yellow Sun and feeling the warmth of its rays is probably a student's first encounter with an astronomical yellow radiation source.

There are yellow objects and emission lines in the yellow portion of the visible spectrum from 570 to 590 nm in wavelength.

Astronomy[edit]

Main source: Astronomy

"When they [the Anasazi] built the kiva, they first put up beams of four different trees. These were the trees that were planted in the underworld for the people to climb up on. In the north, under the foundation they placed yellow turquoise; in the west, blue turquoise, in the south, red, and in the east, white turquoise."[1]

"The rising of the moon [on the morning of August 8, 1988. The moon's declination was 28.5°.] between the chimneys [of the kiva] is visible from the Chimney Rock Pueblo only at the times of major northern standstill occurring every 18.61 years."[1]

Radiation[edit]

Main source: Radiation
sRGB rendering of the spectrum of visible light
Color Frequency Wavelength
violet 668–789 THz 380–450 nm
blue 631–668 THz 450–475 nm
cyan 606–630 THz 476–495 nm
green 526–606 THz 495–570 nm
yellow 508–526 THz 570–590 nm
orange 484–508 THz 590–620 nm
red 400–484 THz 620–750 nm

"To see day objects with most distinctness, I require a less concave lens by one degree than for seeing the stars best by night, the cause of which seems to be, that the bottom of the eye being illuminated by the day objects, and thereby rendered a light ground, obscures the fainter colours blue indigo and violet in the circle of dissipation, and therefore the best image of the object will be found in the focus of the bright yellow rays, and not in that of the mean refrangible ones, or the dark green, agreeable to Newton's remark, and consequently nearer the retina of a short-sighted person; but the parts of the retina surrounding the circle of dissipation of a star being in the dark, the fainter colours, blue, indigo, and violet, will have some share in forming the image, and consequently the focus will be shorter."[2] Bold added.

"The error due to color loses its disturbing effect because the photographic plate is not sensitive for the red and yellow rays, while the photographically active rays of shorter wave-length are well united by the objective."[3]

"The star brightness increase in 1964 was considerably different in yellow and blue rays. ... Extensive tables and graphs represent the mean photographic and photovisual curve of V1329 Cyg observed in Moscow and Odessa, brightness curves in blue and yellow rays, brightness increases, and brightness minima before and after an outburst."[4]

"The GE Reveal bulb is marketed as the bulb that is made to “specially filter out yellow rays that hide life's true colors.” This is accomplished by the use of neodymium in the glass."[5]

Planetary sciences[edit]

"U-Pb ages of zircon from the Firehole and Analcite ash beds in the Eocene Green River Formation (Wyoming, United States) are indistinguishable from 40Ar/39Ar ages of sanidine after adjusting the latter to the astronomically calibrated age of 28.201 Ma for the Fish Canyon sanidine standard."[6]

"Calibrating Green River Formation 40Ar/39Ar ages to the 28.201 Ma age for Fish Canyon sanidine permits the first direct comparison of specific Green River Formation strata to the astronomical solution for Early Eocene insolation. This comparison supports the hypothesis that periods of fluvial deposition coincided with minima in long and short eccentricity, and that periods of lake expansion and evaporite deposition correspond to eccentricity maxima."[6]

"Euhedral, pale yellow zircons were isolated from the Analcite and Firehole ash beds by hand-crushing and heavy liquid concentration."[6]

Color astronomy[edit]

These are examples of the various colors of yellow. Credit: Badseed.
Complements of yellow have a dominant wavelength in the range 380 to 480 nm. The green lines show several possible pairs of complementary colors. Credit: Dicklyon.
The image is of a horse colored with yellow ochre. from Lascaux cave. Credit: Cro-Magnon peoples.
This shows a field of yellow rapeseed. Credit: Petr Kratochvil.

Def. "[t]he colour of gold or butter; the colour obtained by mixing green and red light, or by subtracting blue from white light"[7] is called yellow.

Def.

a "bright yellow colour, resembling the metal gold"[8]

is called

gold.

"Yellow, in the form of yellow ochre pigment made from clay, was one of the first colors used in prehistoric cave art. The cave of Lascaux has an image of a horse colored with yellow estimated to be 17,300 years old."[9]

Shades of yellow contains a more diverse set of yellow or yellow-like colors.

Minerals[edit]

Main source: Minerals

Tarapacaite is a natural mineral pigment composed of potassium chromate which is a likely source of yellow.

Precious metal minerals[edit]

This is an image of a naturally occurring gold nugget. Credit: USGS.

At right is an image of a piece of native gold discovered as part of a placer deposit, a gold nugget.

Chalcogen minerals[edit]

The image shows native sulfur, yellow, and calcite crystals, clear or white. Credit: Didier Descouens.
This shows sulfur crystals from the Smithsonian Institution. Credit: Deglr6328.

"Sulfur occurs naturally as the pure element (native sulfur) and as sulfide and sulfate minerals. ... Being abundant in native form, sulfur was known in ancient times, mentioned for its uses in ancient India, ancient Greece, China and Egypt. ... Octasulfur is a soft, bright-yellow solid with only a faint odor, similar to that of matches."[10]

Cubanite[edit]

These are bronze to brass-yellow, striated, cyclically-twinned cubanite crystals from the Chibougamau mines of Quebec. Credit: Rob Lavinsky.

"Cubanite is a yellow mineral of copper, iron, and sulfur, CuFe2S3.[11] ... Cubanite occurs in high temperature hydrothermal deposits with pyrrhotite and pentlandite as intergrowths with chalcopyrite. It results from exsolution from chalcopyrite at temperatures below 200 to 210 °C.[12] It has also been reported from carbonaceous chondrite meteorites.[12]"[13]

Microlite[edit]

The image shows pale-yellow microlite on lepidolite. Credit: Rob Lavinsky.

"Microlite is composed of sodium calcium tantalum oxide with a small amount of fluorine (Na,Ca)2Ta2O6(O,OH,F). Microlite is a mineral in the pyrochlore group that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals with a refractive index of 2.0 to 2.2. Microlite is also called djalmaite. Microlite occurs as a primary mineral in lithium-bearing granite pegmatites, and in miarolitic cavities in granites."[14]

Orpiment[edit]

Orpiment is a yellow to orange mineral on Earth. Credit: USGS.

"Orpiment, [Arsenic trisulfide] As2S3, is a common monoclinic arsenic sulfide mineral. ... Orpiment is an orange to yellow mineral that is found worldwide [on Earth], and occurs as a sublimation product in volcanic fumaroles, low temperature hydrothermal veins, hot springs and as a byproduct of the decay of another arsenic mineral, realgar."[15]

Pyrite[edit]

Pyrite cubic crystals are on marl from Navajún, Rioja, Spain. Credit: CarlesMillan.

"The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale brass-yellow hue have earned it the nickname fool's gold because of its superficial resemblance to gold. ... Pyrite is the most common of the sulfide minerals [on Earth]. ... Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds, and as a replacement mineral in fossils. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37 wt% gold.[16]"[17]

Satterlyite[edit]

This Satterlyite sample is from the Rapid Creek area of northern Yukon, Canada. Credit: Chris857.

"Satterlyite is a hydroxyl bearing iron phosphate mineral. The mineral can be found in phosphetic shales ... Satterlyite is part of the phosphate mineral group. Satterlyite is a transparent, light brown to light yellow mineral ... Satterlyite has a formula of (Fe2+,Mg,Fe3+)2(PO4)(OH). ... satterlyite [occurs] in nodules in shale in the Big Fish River (Mandarino, 1978). These nodules were about 10 cm in diameter, some would consist of satterlyite only and others would show satterlyite with quartz, pyrite, wolfeite or maricite."[18]

"Holtedahlite, a mineral that was found in Tingelstadtjern quarry in Norway, with the formula (Mg12PO4)5(PO3OH,CO3)(OH,O)6 is isostructural with satterlyite (Raade, 1979). Infrared absorption powder spectra show that satterlyite is different than natural haltedahlite in that there is no carbonate for phosphate substitution (Kolitsch, 2002). Satterlyite is also structurally related to phosphoellenbergerite, a mineral that was discovered in Modum, Norway; near San Giocomo Vallone Di Gilba, in Western Alps of Italy (Palache, 1951); the minerals formula is Mg14(PO4)5(PO3OH)2(OH)6 (Kolitsch, 2002)."[18]

Actinide minerals[edit]

The Carnotite is from the Happy Jack Mine, Utah. Credit: USGS.

"Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K2(UO2)2(VO4)2·3H2O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present. ... Carnotite is a bright to greenish yellow mineral that occurs typically as crusts and flakes in sandstones. Amounts as low as one percent will color the sandstone a bright yellow. The high uranium content makes carnotite an important uranium ore and also radioactive. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates. It is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone and concentrations around petrified logs."[19]

Silicate minerals[edit]

This image shows yellow-brown spurrite from New Mexico, USA. Credit: Dave Dyet.

Spurrite is a nesosilicate that can occur naturally as a yellow mineral. "Its chemical formula is Ca5(SiO4)2CO3.[20] Spurrite is generally formed in contact metamorphism zones as mafic magmas are intruded into carbonate rocks.[21]"[22]

Mineraloids[edit]

Limonite is an amorphous mineraloid of a range of hydrated iron oxides. Credit: USGS.

"Limonite is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the two principle iron ores, the other being hematite, and has been mined for the production of iron since at least 2500 BCE.[23][24] ... Although originally defined as a single mineral, limonite is now recognized as a mixture of related hydrated iron oxide minerals, among them goethite, akaganeite, lepidocrocite, and jarosite. Individual minerals in limonite may form crystals, but limonite does not, although specimens may show a fibrous or microcrystalline structure,[25] and limonite often occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, botryoidal, reniform or stalactitic. Because of its amorphous nature, and occurrence in hydrated areas limonite often presents as a clay or mudstone. However there are limonite pseudomorphs after other minerals such as pyrite.[26] This means that chemical weathering transforms the crystals of pyrite into limonite by hydrating the molecules, but the external shape of the pyrite crystal remains. Limonite pseudomorphs have also been formed from other iron oxides, hematite and magnetite; from the carbonate siderite and from iron rich silicates such as almandine garnets. ... Limonite usually forms from the hydration of hematite and magnetite, from the oxidation and hydration of iron rich sulfide minerals, and chemical weathering of other iron rich minerals such as olivine, pyroxene, amphibole, and biotite. It is often the major iron component in lateritic soils. ... One of the first uses was as a pigment. The yellow form produced yellow ochre for which Cyprus was famous,[27]."[28]

Theoretical yellow astronomy[edit]

Here's a theoretical definition:

Def. astronomy applied to the various terrestrial or extraterrestrial yellow sources of radiation, especially at night is called yellow astronomy.

It is also conducted above the Earth's atmosphere and at locations away from the Earth as a part of explorational (or exploratory) yellow astronomy.

"The lack of long period Cepheids of Population I with P > 45 d in the Galaxy as opposed to the Magellanic Clouds, has fascinated observers and theoreticians for many years."[29]

Entities[edit]

A Statue of Krishna in the Sri Mariamman Temple, Singapore has Krishna shown with a flute. Credit: AngMoKio.
This image shows the blue skinned Krishna with yellow silk dhoti. Credit: Nasir khan Saikat.
The image shows the classical planet Krishna leaning against a white cow. Credit: Parvati and Ossopunk.

"Krishna ... is the [Daśāvatāra] eighth [avatar] incarnation of Lord Vishnu in Hinduism. ... Worship of the deity Krishna, either in the form of Vasudeva, Bala Krishna or Gopala can be traced to as early as 4th century BC.[30][31] ... He is often shown wearing a yellow silk dhoti and a peacock feather crown. ... The Harivamsa describes intricate relationships between Krishna Vasudeva, Sankarsana, Pradyumna and Aniruddha that would later form a Vaishnava concept of primary quadrupled expansion, or avatar.[32]"[33]

"The Hindu Atharva Veda speaks of the "four heavenly directions, having the wind as lord, upon which the sun looks out."63 This, of course, can only be the central sun, who is Brahma, a god of four faces. The myths also attribute four faces to Shiva.64 The central sun Prajapati takes the form of the four-eyed, four-faced, and four-armed Vivvakarman, the "all maker".65 Agni, too, faces "in all directions,"66 as does Krishna.67 ... There can no longer be any doubt that the four-eyed or four-faced god is Saturn, for the sun-planet appears in Babylonian myth as Ea (Sumerian Enki)-a god of four eyes that "behold all things."73"[34]

"The bansuri is one of the most important instruments in Hindu mythology. It was the instrument played by Krishna, who Hindus believe is the eighth reincarnation of the god Vishnu, when he was in child form. Its use in Buddhist paintings can be identified as early as CE 100."[35]

Radiation astronomy sources[edit]

Notation: let the symbol EMSS represent the Einstein Medium Sensitivity Survey.

The "presence of an excess of X-ray luminous "yellow" stars, already found with the analysis of the stellar content of the Einstein Medium Sensitivity Survey (MSS), is confirmed by the EMSS, whose substantially larger size sample allows to draw conclusions with a higher statistical significance than the MSS"[36].

An "excess of X-ray luminous "yellow" stars in the X-ray selected samples, [have been] tentatively identified with a population of active RS CVn-like binaries, or a population of active young late-type stars."[36]

"The comparison between ... model predictions and the observed stellar source counts for yellow stars in the reference EMSS subsample shows a clear excess that peaks in the F-G spectral type range where the 70 observed sources have to be compared with the ~24 predicted ones. This excess is statistically significant at more than 99.8% level. ... this excess is concentrated for B - V ranging from 0.5 to 1.0 (corresponding to mv ranging from 8 to 12) which corresponds, in the EMSS, to normal main sequence stars with spectral type comprised between F and early K."[36]

This "excess is real, and most likely doe to some high X-ray luminosity population with optical characteristics similar to normal main sequence yellow stars."[36]

There is also "an excess for the A/F star groups mainly due to the occurrence of stars with fx/fv ratio higher than the mean values for each group and suggest that this could be explained by the occurrence of a large number of X-ray unresolved binary systems with an active M star companion than the predicted ones."[36]

"For yellow stars, the current state-of-art knowledge in terms of X-ray luminosity functions is not able to account for all of the observed yellow stellar sources in the EMSS, so that, to explain the observed source counts, a new population of stellar-like X-ray emitting sources with optical characteristics similar to normal main sequence yellow stars must be hypothesized. ... based on current knowledge, this population is likely to be (at least partly) composed of very young (and therefore highly X-ray luminous) yellow stars, perhaps of the kind variously indicated by previous authors as WTTS or NTTS, or simply by near ZAMS objects."[36]

Objects[edit]

"An abundance analysis of the yellow symbiotic system AG Draconis reveals it to be a metal-poor K-giant ([Fe/H]=-1.3) which is enriched in the heavy s-process elements. ... the other yellow symbiotic stars are probably low-metallicity objects as well."[37]

Continua[edit]

In Fig. 4, "A density tracing of the spectrum of θ Lyr, K0 II. Straight chords through the yellow continuum toward the blue and from λ 4750 along the green depression to the Mg I "b" triplet lines define the break-angle α (α here is about 12°)."[38]

Emissions[edit]

Emission lines are usually unique to the chemical elements. As the emissions are produced by the release of specific wavelength photons when electrons drop to a lower energy level, absorption lines may be produced as electrons rise to this higher energy level.

Bands[edit]

"Data in two spectral bands (green: λ 5253-5353, and yellow: λ 5824-5844) were taken on several sunspot groups during February 1974. ... the general level of circular polarization is weaker [in the yellow band]. The peak magnitudes of the linear polarization [PL ≡ (Q2 + U2)½/I] (Figs. 1C and 2C) are comparable in both colors; the spatial distribution is, however, markedly different. Whereas in the green PL is fairly uniform over both type 1 [penumbra] and 2 ["speckled" possibly umbra] regions, in the yellow PL appears strong only in region 2; the linear polarization associated with region 1 has nearly vanished."[39]

"The behavior of the azimuth of the linear polarization at various points in the sunspot is markedly different in the two colors. In the green, one can clearly see a generally radial pattern over the entire spot; no such general pattern is apparent in the yellow, but a less pronounced radial pattern in the core of the spot does remain. It should be noted that the more complex area in the green corresponds to the "speckled" type 2 region."[39]

Backgrounds[edit]

"The left panel shows the Northern Lights or Aurora Borealis in the form of an arch in all the delicate colors, in which may be dimly seen the figures of the White Men of the North dancing around their camp-fires. The central panel shows the sun-god on a brilliant yellow background, the moon-goddess on a paler background, while in the upper right may be seen the Pleiades as conceived by the Indians, and in the upper left the Big Dipper and the North Star, these corner representations with the Milky Way or sky-trail between them are shown in silver on a background of deep blue."[40]

"When the corresponding diagonals of Fig. 1. Fig. 2. J the Nicols are parallel, or nearly so, the bands arc white upon a deep reddish-purple ground, as shown in fig. 1; with the Nicols crossed, the hands are dark upon a light greenish-yellow background, as represented in fig."[41]

Meteors[edit]

"The train spectrum consisted of a red continuum, yellow continuum, and about 50 atomic lines between 3700–9000 Å. The yellow continuum, possibly due to NO2, was also detected in the persistent train."[42]

"On November 18, 1999 at 04h00m29s UT, about two hours after the maximum of the 1999 Leonid meteor storm, a very bright Leonid meteor appeared over the island of Corse, France, and produced an afterglow evolving into a persistent train that was visible to the naked eye for several minutes."[42]

Cosmic rays[edit]

"The yellow supergiant content of nearby galaxies can provide a critical test of stellar evolution theory, bridging the gap between the hot, massive stars and the cool red supergiants. But, this region of the color-magnitude diagram is dominated by foreground contamination, requiring membership to somehow be determined."[43]

"The program exposures were extracted, using the dome flat field exposures as reference, and wavelength corrected. As the He-Ne-Ar exposures were obtained in the afternoon, and the grating might even be removed and reinserted before the program exposures, a zero-point shift in wavelength was determined for each of the M31 spectra using the O I λ5577 night sky line. ... Consecutive exposures of each M31 configuration were then summed, after cosmic rays were first identified and removed by comparing a median of the exposures to the individual exposures."[43] Bold added.

Neutrons[edit]

"A comparison of the heavy-element abundance distribution in [AG Draconis] with theoretical nucleosynthesis calculations shows that the s-process is defined by a relatively large neutron exposure (τ=1.3 mb-1), while an analysis of the rubidium abundance suggests that the s-process occurred at a neutron density of about 2 [x] 108 cm-3."[37]

The "K giant in AG Dra [has a] Teff ~ 4100 - 4400 K. ... [With a best fit to spectroscopic data of Teff = 4300 K.]"[37]

Observed heavy-element abundances may be used "to probe two aspects of the s-process:

  1. ... the relative abundance distribution of elements analysed ... [determines] the neutron exposure τ characterizing the s-process efficiency, and
  2. ... the abundance of Rb ... is sensitive to neutron density [providing] constraints on the s-process neutron density Nn."[37]

The "s-process branch point [is] at the β-unstable nucleus 85Kr ...

  1. dominated by 85Rb (at 'low' neutron densities) or
  2. 87Rb (at 'high' neutron densities)."[37]

Due to the difference "in neutron-capture cross sections" (σ), σ(85Rb)/σ(87Rb) ~ 25, "the s-process abundance of Rb increases dramatically with increasing neutron density. The Rb abundances have been used to infer neutron densities in both

  1. a small number of barium stars ... and in
  2. three metal-poor giants of the globular cluster ω Cen."[37]

Comparison shows "a clear and striking increase in the [Rb/Zr] ratio with decreasing [Fe/H] ratio ... is evidence of an increasing s-process neutron density with decreasing metallicity."[37]

Numbers "from Malaney & Lambert (1988) and Malaney (1987a) [can be used] to determine the s-process abundance ratio Rb/Zr as a function of the neutron density Nn. ... [First the observed abundances are corrected for previous in flow.] ... ignoring the one extremely Rb-rich ω Cen giant ... The other 8 stars are characterized extremely well by a linear increase of log Nn with decreasing [Fe/H]".[37]

Protons[edit]

"As a result of ion irradiation a modification (evolution) of the original target can be generated and new materials can be produced. Bonds in the target material may in fact be broken by energy deposition around the "hot" track of incoming ions. The recombination of fragments produces new and also complex molecules. If carbon is present in the target, even long chain polymer-like substances that are stable above room temperature can be produced ... The presence of organic material in the [solar system], possibly produced by bombarding ions ... seems now well supported by recent findings from space missions as from Voyager at the Uranian system".[44]

The "colour of the organic layers [synthesized organic samples of frozen CH4 (T ~ 10 K) ice] depends on the amount of energy deposited by the bombarding beam [~ 1016 protons (1.5 MeV) cm-2 and ~ 1017 protons cm-2]. When first extracted after a (relatively) low ion fluence the materials appear yellow, becoming darker and darker if again bombarded at higher doses."[44]

"The evolution of organics to carbonaceous material induced by ion irradiation is ... a well established phenomenon independent of the type of original carbon containing material."[44]

Electrons[edit]

"The temperature of yellow coronal regions is ... about 2.5 [x] 106 [K]. ... although some ions Ca XV will exist at lower, as well as higher temperatures."[45]

"The AS prominences [AS in Menzel-Evans' classification [4];] move with velocities exceeding by far the velocities of other types of prominences [7], [8]. As short-living phenomena, they are condensed quickly and the temperature of the coronal gases should rise in the early stages of their condensation. Indeed, the AS prominences use to be allied with yello line emission (λ 5694)."[45]

"The yellow line is namely due to the ion Ca XV, according to Edlen's and Waldmeier's identification. ... the line λ 5694 is emitted by 3P1 - 3P0 transition of Ca XV."[45]

"The solar corona is not in thermodynamical equilibrium. In particular, the photo-recombination is compensated with electron impact ionization, while the reverse processes viz. the photoionization and recombination by impact with two electrons are there negligible."[45]

Positrons[edit]

Calculations of "the changes in the surface chemical composition of intermediate-mass stars in the first phase of convection dredge-up ... has been used to determine the changes in the surface chemical composition of stars with masses 2.5, 5, 10, 20 Mʘ due to nuclear reactions of the pp chains, the triple CNO cycle, and the NeNa and MgAl cycles."[46]

"We followed the changes that take place in 30 reactions in the abundances of the electrons, positrons, and 24 nuclides, a complete list of which, together with their initial abundances (in the proportions of Cameron [i0]), is given in [17]."[46]

Rocky objects[edit]

"Euhedral crystals [from the Lodran meteorite AMNH 314] of olivine and clear pale yellow fragments of orthopyroxene (Opx) and two green grains were examined by precession camera."[47]

Heliums[edit]

Main sources: Chemicals/Heliums and Heliums
The spectrum shows the lines in the visible due to emission from elemental helium. Credit:Teravolt.
This is a spectrum of Ring Nebula (M57) in range 450.0 — 672.0 nm. Credit: Minami Himemiya.

"The helium emission lines behave in a qualitatively similar way to the calcium triplet. The 5876 Å line (Fig. 1e) is the dominant line in all the spectra, although two other transitions (6678 and 7065) are also in emission in most of the stars and have nearly identical profiles."[48] He I is 587.6 nm, a yellow emission line. The He I photospheric emission line "narrow component is present in emission ... with [chromospheric] veilings larger than 0.4, being conspicuous even in those heavily veiled stars".[49] The chromospheric veiling apparently results in the emission broadening of the He I emission from the chromosphere which is partially added to the He I narrow emission from the photosphere.[49]

"The radiative loss for both broad and narrow emission--i.e., the excess of emission over the external continuum expressed in percentages of the photospheric fluxes--is Fph(1 + ν)EWobs, where Fph is the nearby photospheric flux and EWobs is the equivalent width of the observed emission component."[49] "[B]y assumption, [the dynamo] controls the narrow component fluxes."[49]

In the spectrum at right the yellow He I emission line is detected and recorded at normalized intensities (to the oxygen III line) from the Ring Nebula.

Carbons[edit]

Main sources: Chemicals/Carbons and Carbons
The spectrum shows the lines in the visible due to emission from elemental carbon. Credit:Teravolt.

Carbon has one line in the yellow.

Nitrogens[edit]

Main sources: Chemicals/Nitrogens and Nitrogens
The spectrum shows the lines in the visible due to emission from elemental nitrogen. Credit:Kurgus.

Nitrogen has a yellow forbidden line, specifically N II at 575.5 nm, that may be used to indicate nitrogen abundances and contribute to nitrogen/oxygen (N/O) abundance gradients. Surveys of H II regions in spiral galaxies have suggested that N/O abundance ratios increase from outer-arm nebulae to inner-arm nebulae.[50] "Electron temperatures are generally derived from the ratio of auroral to nebular lines in [O III] or [N II]."[51] "[B]ecause of the proximity of strong night-sky lines at λ4358 and λλ5770, 5791, the auroral lines of [O III] λ4363 and [N II] λ5755 are often contaminated."[51]

"The nitrogen abundance appears to increase with decreasing galactocentric distance. ... A least-squares solution weighting the points equally gives a magnitude for the gradient d(log N/H)/dr = -0.10 ± 0.03 kpc-1."[51] "The ratio N/O clearly increases with decreasing R. A least-squares fit to the data ... gives d(log N/O)/dr = -0.06 ± 0.02 kpc-1."[51]

Oxygens[edit]

Main sources: Chemicals/Oxygens and Oxygens
The spectrum shows the lines in the visible due to emission from elemental oxygen. Credit: Teravolt.

Oxygen has two yellow lines.

Fluorines[edit]

Main sources: Chemicals/Fluorines and Fluorines
This diagram contains the emission and absorption lines for the element fluorine. Credit: Alex Petty.

Fluorine has several lines in the yellow as shown in the above spectrum.

Neons[edit]

Main sources: Chemicals/Neons and Neons
This is a visual spectrum of neon showing its many emission lines. Credit: McZusatz.

There is a "bright yellow line of neon X [at] 5852.488 [Å, 585.2488 nm.]"[52]

Sodiums[edit]

Main sources: Chemicals/Sodiums and Sodiums

"Fraunhofer's original (1817) designations of absorption lines in the solar spectrum"[53]

Letter Wavelength (nm) Chemical origin Colour range
A
759.37
atmospheric O2
dark red
B
686.72
atmospheric O2
red
C
656.28
hydrogen alpha
red
D1
589.59
neutral sodium
red orange
D2
589.00
neutral sodium
yellow
E
526.96
neutral iron
green
F
486.13
hydrogen beta
cyan
G
431.42
CH molecule
blue
H
396.85
ionised calcium
dark violet
K
393.37
ionised calcium
dark violet"

Sodium produces two spectral lines known as D1 and D2, or the "sodium doublet". Their average wavelength, 589.3 nm, is often just called "D".

Def. "[a] street lamp in which electricity is passed through sodium vapour to emit a yellow light", from Wiktionary sodium vapor lamp, is called a sodium vapor lamp.

Calciums[edit]

Main sources: Chemicals/Calciums and Calciums

During the limb flares of December 18, 1956, a coronal line at 569.4 nm, a yellow line, occurred at 1822 UTC, 1900 UTC, undiminished up to 20,000 km above the solar limb, and at 2226 UTC, is identified as Ca XV.[54] "The coronal temperature was 4000000°."[54] "The December 18, 1956, flare appears to have been a violent condensation of material from a dense coronal cloud above an active region."[54]

Alloys[edit]

Main sources: Chemicals/Alloys and Alloys

"The earliest brasses may have been natural alloys made by smelting zinc-rich copper ores.[55]"[56]

Sun[edit]

Main sources: Stars/Sun and Sun (star)
This is a visual image of the Sun with some sunspots visible. The two small spots in the middle have about the same diameter as our planet Earth. Credit: NASA.
This graph shows the temperature and density of the Sun's atmosphere from Skylab observations. Credit: John A. Eddy, NASA.

A natural division of astronomical bodies, or objects, between rocky bodies, astronomical objects with solid surfaces, or solids and liquids predominately on the surface, and gas bodies, astronomical objects with gases predominately detected and apparently constituting a surface, may be an informative approach toward stellar science.

Depending primarily upon gas temperature, the presence of gas may be used to determine the composition of the gas body observed, at least the outer layer. Early spectroscopy[57] of the Sun using estimates of "the line intensities of several lines by eye [to derive] the abundances of ... elements ... [concluded] that the Sun [is] largely made of hydrogen."[58]

The second image at right describes graphically the temperature and density of the Sun's atmosphere from the photosphere upwards. "The Sun's photosphere has a temperature between 4500 and 6000 K[59] (with an effective temperature of 5777 K) and a density of about [2 x 10-4kg/m3;[60] other stars may have hotter or cooler photospheres. The Sun's photosphere is composed of convection cells called granules—cells of gas each approximately 1000 km in diameter[61] with hot rising gas in the center and cooler gas falling in the narrow spaces between them. Each granule has a lifespan of only about eight minutes, resulting in a continually shifting "boiling" pattern. Grouping the typical granules are super granules up to 30,000 kilometers in diameter with lifespans of up to 24 hours. These details are too fine to see on other stars."[62]

Mercury[edit]

Main source: Mercury

"[H]igh-resolution spectral measurements of Mercury show emission in sodium D lines (Potter and Morgan 1985a). This suggests a substantial sodium population in Mercury's atmosphere ... possibly due to photo-sputtering of the planetary surface"[63].

Venus[edit]

Main source: Venus

"Selected images of Venus [show] cloud configurations in yellow light".[64] These images are photographs taken between October 3, 1943, and March 14, 1945.[64]

Earth[edit]

Main source: Earth
The image shows the Sahara desert from space. Credit: NASA.

"Spectral properties of certain palagonitic soils found on Mauna Kea, Hawaii are similar to the spectral properties measured by earth-based telescopes for Martian soils [1,2,3]. ... Three layers with distinctly different colors (upper red, middle black, lower yellow) were sampled from hydrothermally altered basaltic tephra just below the summit of Mauna Kea."[65]

"The clay fractions (< 2 µm) of three palagonite samples-MK11 (red), MK12 (black), and MK13 (yellow) collected at an elevation of 4145 meters near the summit of Mauna Kea volcano in Hawaii ... The fine fractions of the black (MK12) and yellow (MK13) samples were similar to those of martian bright regions in terms of their overall shape."[66]

At right is a composite image of the Sahara. Most of the images are from the MODIS imager onboard the Terra satellite.

Moon[edit]

"There is ... a dearth of basalt compositions corresponding to differentiates of the yellow glasses. ... After olivine and chromite, differentiates of the Apollo 14 and 17 yellow glass magmas should differ only slightly in crystallization sequence. ... For green and yellow glasses, liquids are saturated only with olivine and chromite; for red and black glasses, negative slope represents liquids saturated with olivine and chromite, positive slope indicates olivine, chromite, and armalcolite."[67]

"An unusual yellowish glass is found in the interstices, in fracture fillings, and as encrustations of a few uncommon, mildly fragmented KREEP basalt particles in Apollo 15 soils."[68]

Ferrobasalts in the Apollo 11 specimens have yellow materials present. "Irregular fragments of vesicular glass, pale yellow to golden brown are abundant. Some are up to half a millimeter across."[69]

Mars[edit]

Main source: Mars

"The most striking change in the nontronite was color. The original nontronite was olive-yellow, corresponding to 25.Y 6/6 in the Munsell color chart (3). The material shocked to 180 kbar turned yellow-brown, 1.0Y 5/6, and the nontronite brought to 300 kbar was strong brown, 7.5Y 4/6."[70]

"[L]ittle Fe+2 (... is the case for most yellow nontronites)."[70]

Io[edit]

Main sources: Volcanoes/Io and Io
Io, the most volcanic body in the solar system, is seen in the highest resolution obtained to date by NASA's Galileo spacecraft. Credit: NASA.
This global view of Io, is obtained from the tenth orbit of Jupiter by NASA's Galileo spacecraft. Credit: NASA.
This image of Io continues to the left around the rocky object. Credit: NASA.
This composite of images from Galileo and Voyager 1 shows Io's north pole. Credit: U.S. Geological Survey and NASA.
This composite is of Io's south pole. Credit: U.S. Geological Survey and NASA.
In the same way that the Moon always has the same side facing Earth, Io always has the same side facing Jupiter. Credit: U.S. Geological Survey and NASA.

Io "is the innermost of the four Galilean moons of the planet Jupiter and, with a diameter of 3,642 kilometres (2,263 mi), the fourth-largest moon in the Solar System. ... With over 400 active volcanoes, Io is the most geologically active object in the Solar System.[71][72] ... Most of Io's surface is characterized by extensive plains coated with sulfur and sulfur dioxide frost. ... Io's volcanism is responsible for many of the satellite's unique features. Its volcanic plumes and lava flows produce large surface changes and paint the surface in various shades of yellow, red, white, black, and green, largely due to allotropes and compounds of sulfur."[73]

In the image at right, "[t]he smallest features that can be discerned are 2.5 kilometers in size. There are rugged mountains several kilometers high, layered materials forming plateaus, and many irregular depressions called volcanic calderas. Several of the dark, flow-like features correspond to hot spots, and may be active lava flows. There are no landforms resembling impact craters, as the volcanism covers the surface with new deposits much more rapidly than the flux of comets and asteroids can create large impact craters. The picture is centered on the side of Io that always faces away from Jupiter; north is to the top."[74]

"Color images acquired on September 7, 1996 have been merged with higher resolution images acquired on November 6, 1996 by the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. The color is composed of data taken, at a range of 487,000 kilometers, in the near-infrared, green, and violet filters and has been enhanced to emphasize the extraordinary variations in color and brightness that characterize Io's face. The high resolution images were obtained at ranges which varied from 245,719 kilometers to 403,100 kilometers."[74]

The second image at right is a "global view of Jupiter's moon, Io, ... obtained during the tenth orbit of Jupiter by NASA's Galileo spacecraft. Io, which is slightly larger than Earth's moon, is the most volcanically active body in the solar system. In this enhanced color composite, deposits of sulfur dioxide frost appear in white and grey hues while yellowish and brownish hues are probably due to other sulfurous materials. Bright red materials, such as the prominent ring surrounding Pele, and "black" spots with low brightness mark areas of recent volcanic activity and are usually associated with high temperatures and surface changes. One of the most dramatic changes is the appearance of a new dark spot (upper right edge of Pele), 400 kilometers (250 miles)in diameter which surrounds a volcanic center named Pillan Patera. The dark spot did not exist in images obtained 5 months earlier, but Galileo imaged a 120 kilometer (75 mile) high plume erupting from this location during its ninth orbit. North is to the top of the picture which was taken on September 19, 1997 at a range of more than 500,000 kilometers (310,000 miles) by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft."[75]

The third image at right continues around Io to the left.

The fourth image is of Io's north pole. "[The] new basemap [and the polar images] of Jupiter's moon Io was produced by combining the best images from both the Voyager 1 and Galileo Missions. Although the subjovian hemisphere of Io was poorly seen by Galileo, superbly detailed Voyager 1 images cover longitudes from 240 W to 40 W and the nearby southern latitudes. A monochrome mosaic of the highest resolution images from both Galileo and Voyager 1 was assembled that includes 51 Voyager 1 images with spatial resolutions sometimes exceeding the 1 km/pixel scale of the final mosaic. Because this mosaic is made up of images taken at various local times of day, care must be taken to note the solar illumination direction when deciding whether topographic features display positive or negative relief. In general, the illumination is from the west over longitudes 40 to 270 W, and from the east over longitudes 270 W to 40 W. Color information was later superimposed from Galileo low phase angle violet, green, and near-infrared (756 nanometer wavelength) images. The Galileo SSI camera's silicon CCD was sensitive to longer wavelengths than the vidicon cameras of Voyager, so that distinctions between red and yellow hues can be more easily discerned. The "true" colors that would be visible to the eye are similar but much more muted than shown here. Image resolutions range from 1 to 10 km/pixel along the equator, with the poorest coverage centered on longitude 50 W."[76]

The fifth image is of Io's south pole.

The last image is an animated image showing a 1 Io day of rotation. "In the same way that the Moon always has the same side facing Earth, Io always has the same side facing Jupiter. The movie shows two speeded-up rotations of Io (a single rotation really takes 1.77 days), and begins with a view of the Jupiter-facing hemisphere. With rotation in an easterly direction, after two seconds the volcano Prometheus (on the equator) comes into view. The massive red deposit around Pele (seconds 5-10) is the most distinctive expression of volcanic activity on Io, and just to the north-west is the horse shoe-shaped Loki Patera, the most powerful volcano on Io. The animation was made using a computer program that wrapped the Io mosaic around a sphere to produce a globe. In all, 360 images were used, each differing by one degree in longitude from the previous image."[77]

Stars[edit]

Main source: Stars

The Secchi Class II consists of yellow stars with evident metallic lines.[78]

"The Harvard classification system is a one-dimensional classification scheme. Stars vary in surface temperature from about 2,000 to 40,000 kelvins. 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:"[78]

Class Temperature[79]
K
Conventional color Apparent color[80][81][82] Mass[79]
(solar masses, Mʘ)
Radius[79]
(solar radii, Rʘ)
Luminosity[79]
(bolometric, Lʘ)
Hydrogen
lines
Fraction of all
main sequence stars[83]
O ≥ 33,000 K blue blue ≥ 16 ≥ 6.6 ≥ 30,000 Weak ~0.00003%
B 10,000–33,000 K blue to blue white blue white 2.1–16 1.8–6.6 25–30,000 Medium 0.13%
A 7,500–10,000 K white white to blue white 1.4–2.1 1.4–1.8 5–25 Strong 0.6%
F 6,000–7,500 K yellowish white white 1.04–1.4 1.15–1.4 1.5–5 Medium 3%
G 5,200–6,000 K yellow yellowish white 0.8–1.04 0.96–1.15 0.6–1.5 Weak 7.6%
K 3,700–5,200 K orange yellow orange 0.45–0.8 0.7–0.96 0.08–0.6 Very weak 12.1%
M ≤ 3,700 K red orange red ≤ 0.45 ≤ 0.7 ≤ 0.08 Very weak 76.45%

"Stars of spectral classes F and G, such as our sun Sol, have color temperatures that make them look "yellowish".[84] The first astronomer to classify stars according to their color was F. G. W. Struve in 1827. One of his classifications was flavae, or yellow, and this roughly corresponded to stars in the modern spectral range F5 to K0.[85] The Strömgren photometric system for stellar classification includes a 'y' or yellow filter that is centered at a wavelength of 550 nm and has a bandwidth of 20–30 nm.[86][87]"[9]

Yellow degenerates[edit]

The image is an optical negative centered on the SIMBAD coordinates J2000.0 for Van Maanen's star. Image is from the Palomar 48-inch Schmidt reflecting telescope. Van Maanen's star is the largest black dot center top right. Credit: NASA/IPAC Extragalactic Database.
This is an Hertzsprung-Russell diagram. Note that luminosity class VII has color class G stars within. Credit: Spacepotato.
GJ 3223 is also designated LHS 1547. It is a white dwarf that is also color class G, a yellow degenerate. Credit: Aladin at SIMBAD.

EG 5 is a yellow degenerate.[88] EG 5 is another designation for Van Maanen's star.[89]

"Van Maanen's star (van Maanen 2) is a white dwarf star. Out of the white dwarfs known, it is the third closest to the Sun, after Sirius B and Procyon B, in that order, and the closest known solitary white dwarf.[90][91]"[92]

The optical negative at right was taken earlier than the current coordinates for Van Maanen's star, which are at the center of the negative.

Van Maanen's star has a radius of 9,000 ± 1,400 km.[93] It's effective surface temperature is 6,220 ± 240 K.[94]

Degenerate stars are white dwarfs of spectral luminosity class VII.

Some yellow degenerate stars are of white dwarf spectral type DC (which show no detectable lines) mostly below Teff < 10,000 K.[88]

At left is an Hertzsprung-Russell diagram which shows that luminosity class VII has color class G stars within.

At lower right is a close to true color visual image of GJ 3223, a yellow degenerate white dwarf.[88] It is similar to other luminosity class VII yellow degenerates LHS 3369 and LHS 3399. Each is color class G, often written "g"[88] when referring to white dwarfs.

Yellow subdwarfs[edit]

Yellow subdwarfs are in luminosity class VI. "[Y]ellow high-velocity subdwarfs are easily confused with white dwarfs in a proper-motion selection."[88]

HD 64090 is a color class G0 subdwarf.

Yellow main sequence stars[edit]

HD 86226 is a spectral type G2V yellow main sequence star. Credit: Aladin at SIMBAD.

The closest G2V yellow main sequence star is the Sun described above.

At right is a visual image in close to true color of the main sequence single star HD 86226. It has a parallax of 22.20 mas, but is not an X-ray source. A substellar companion HD 86226b has been detected.

Yellow subgiants[edit]

V972 Scorpii is a variable star of the delta Scuti type. Spectral type is G2IV. Credit: Aladin at SIMBAD.

"A subgiant star is a star that is slightly brighter than a normal main-sequence (dwarf) star of the same spectral class, but not as bright as true giant stars. Although certain subgiants appear to be simply unusually bright metal-rich hydrogen-fusing stars (in the same way subdwarfs are unusually dim metal-poor hydrogen-fusing stars), they are generally believed to be stars that are ceasing or have already ceased fusing hydrogen in their cores."[95]

"Many subgiants are rich in metals, and commonly host orbiting planets."[95]

At right is a visual image in close to true color of V972 Scorpii, which is a variable star of the delta Sct type. It has spectral type G2IV and is a star in a cluster. The system includes components CCDM J16234-2622 A and CCDM J16234-2622 B. Component A is a dwarf star in a double star system with component B. Component A is apparently V972 Scuti.

Yellow giants[edit]

Alpha Microscopii is a spectral type G7III yellow giant star in a double system. Credit: Aladin at SIMBAD.

Alpha Microscopii is a spectral type G7III yellow giant star in a double system.

"This star has an optical visual companion, CCDM J20500-3347B, of apparent visual magnitude 10.0 approximately 20.4 arcseconds away at a position angle of 166°. It has no physical connection to the star described above.[96]"[97]

Barium stars[edit]

Main sources: Stars/Bariums and Barium stars

"Barium stars are spectral class G to K giants, whose spectra indicate an overabundance of s-process elements by the presence of singly ionized barium, Ba II, at λ 455.4 nm. Barium stars also show enhanced spectral features of carbon, the bands of the molecules CH, CN and C2."[98]

"Observational studies of their radial velocity suggested that all barium stars are binary stars[99][100][101] Observations in the ultraviolet using [the] International Ultraviolet Explorer detected white dwarfs in some barium star systems."[98]

"Barium stars are believed to be the result of mass transfer in a binary star system. The mass transfer occurred when the presently-observed giant star was on the main sequence. Its companion, the donor star, was a carbon star on the asymptotic giant branch (AGB), and had produced carbon and s-process elements in its interior. These nuclear fusion products were mixed by convection to its surface. Some of that matter "polluted" the surface layers of the main sequence star as the donor star lost mass at the end of its AGB evolution, and it subsequently evolved to become a white dwarf. We are observing these systems an indeterminate amount of time after the mass transfer event, when the donor star has long been a white dwarf, and the "polluted" recipient star has evolved to become a red giant.[102][103]"[98]

Barium stars exhibit carbon and s-process elements at their surfaces suggesting surface fusion possible during mass transfer or without it.

"The mass transfer hypothesis predicts that there should be main sequence stars with barium star spectral peculiarities. At least one such star, HR 107, is known.[104]"[98]

"Prototypical barium stars include zeta Capricorni, HR 774, and HR 4474."[98]

Yellow supergiants[edit]

"A yellow supergiant (YSG) is a supergiant star of spectral type F or G.[105] These stars usually have masses between 15 and 20 solar masses. These stars, like any other supergiant, are older and swing between blue and red phases depending on the chemical elements they consume in their cores. Until now it had been thought that few supergiants spend a long time in the transitional yellow phase. These systems may be the progenitors of rare supernovae linked to yellow supergiants. Only [a] few such supernovae have been detected - most supergiants go supernova when at the blue (or hot) phase or red (or cool) phase."[106]

DY Persei variable[edit]

"DY Persei variables are a subclass of R Coronae Borealis variables. They are carbon-rich asymptotic giant branch stars that exhibit pulsational variability of AGB stars and irregular variability of RCB stars."[107]

"The star DY Persei is the prototype of this tiny class of variable stars."[107]

"DY Persei ... in the Perseus constellation ... [pulsates] like red variables, ... [and fades] from sight like R Coronae Borealis variables."[108]

R Coronae Borealis variable[edit]

The graph is of an AAVSO light curve of fadings by R Coronae Borealis, the prototype star. Credit: Jimstars.

"[An] R Coronae Borealis variable (abbreviated RCB) is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation (a few tenths of a magnitude), and one irregular unpredictably sudden fading by 1 to 9 magnitudes."[109]

"The prototype star [is] R Coronae Borealis ... [O]nly about 100 RCB variables have been identified,[110] making this class a very rare kind of star."[109]

"The fading is caused by condensation of carbon to soot, making the star fade in visible light while measurements in infrared light exhibit no real luminosity decrease. R Coronae Borealis variables are typically supergiant stars in the spectral classes F and G (by convention called "yellow"), with typical C2 and CN molecular bands, characteristic of yellow supergiants. RCB star atmospheres do however lack hydrogen by an abundance of 1 part per 1,000 down to 1 part per 1,000,000 relative to helium and other chemical elements, while the universal abundance of hydrogen is about 3 to 1 relative to helium."[109]

"There is a considerable variation in spectrum between various RCB specimens. Most of the stars with known spectrum are either F to G class ("yellow") supergiants, or a comparatively cooler C-R type carbon star supergiant. Three of the stars are however of the "blue" B type, for example VZ Sagittarii, and one is a "red" giant star, V482 Cygni of type M5III. Four stars are unusually and inexplicably poor in iron absorption lines in the spectrum.[111] The constant features are prominent Carbon lines, strong atmospheric Hydrogen deficiencies, and obviously the intermittent fadings."[109]

Yellow hypergiants[edit]

Rho Cassiopeiae is a semi-regular pulsating star of spectral class G2Ia0e. Credit: Aladin at SIMBAD.

"ρ Cas, HR 8752 and IRC+10420, three well-studied yellow hypergiants, are situated at or close to the red border of the [yellow evolutionary] void."[112]

"Generally speaking, a yellow hypergiant is a massive star with an extended atmosphere, which can be classified as spectral class from late A to K, with a mass of as much as 20-50 solar masses. Yellow hypergiants, such as Rho Cassiopeiae in the constellation Cassiopeia, have been observed to experience periodic eruptions, resulting in periodic or continuous dimming of the star, respectively. Yellow hypergiants appear to be extremely rare in the universe. Due to their extremely rapid rate of consumption of nuclear fuel, yellow hypergiants generally only remain on the main sequence for a few million years before destroying themselves in a massive supernova or hypernova. Yellow hypergiants are post-red supergiants, rapidly evolving toward the blue supergiant phase."[113]

"According to the current physical models of stars, a yellow hypergiant should possess a convective core surrounded by a radiative zone, as opposed to a sun-sized star, which consists of a radiative core surrounded by a convective zone (Seeds, 2005). Due to the extremely high pressures which exist at the core of a yellow hypergiant, portions of the core or perhaps the entire core may be composed of degenerate matter."[113]

These stars have "powerful magnetic fields"[113].

Yellow evolutionary void[edit]

"G is host to the "Yellow Evolutionary Void".[112] 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 G classification as this is an extremely unstable place for a supergiant to be."[78]

"[T]he yellow evolutionary void ... is an area in the Hertzspung-Russell diagram where atmospheres of blueward evolving super- and hypergiants are moderately unstable ... For [such stars] (in hydrostatic equilibrium)

  1. a negative density gradient occurs,
  2. the sum of all accelerations, including wind, turbulence and pulsations, is zero or negative,
  3. the sonic point of the stellar wind is reached in or below photospheric levels, and
  4. Γ1 ≤ 4/3 indicating some level of dynamic instability in part of the atmosphere."[112]

Yellow galaxies[edit]

This image shows a cluster of yellow galaxies near the middle of the photograph. Credit: STScl/NASA.

The image at right "shows several blue, loop-shaped objects that are multiple images of the same galaxy, duplicated by the gravitational lens effect of the cluster of yellow galaxies near the middle of the photograph. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object."[114]

Hypotheses[edit]

Main source: Hypotheses
  1. Each of the planets revolving around Sol can be seen in the yellow.

See also[edit]

References[edit]

  1. 1.0 1.1 J. McKim Malville and Claudia Putnam (1993). Prehistoric Astronomy in the Southwest. 3005 Center Green Drive, Suite 220, Boulder, CO USA: Big Earth Publishing. pp. 108. ISBN 1555661165. http://books.google.com/books?id=7qRpuKG6xVQC&source=gbs_navlinks_s. Retrieved 2013-09-12. 
  2. Nevil Maskelyne (June 18 1789). "An Attempt to Explain a Difficulty in the Theory of Vision, Depending on the Different Refrangibility of Light". Philosophical Transactions of the Royal Society of London 79: 256-64. http://www.jstor.org/stable/106696. Retrieved 2013-09-13. 
  3. J. Hartmann (May 1908). "An Improvement of the Foucault Knife-Edge Test in the Investigation of Telescope Objectives". The Astrophysical Journal 27: 254-9. doi:10.1086/141552. http://adsabs.harvard.edu/abs/1908ApJ....27..254H. Retrieved 2013-09-13. 
  4. V. P. Arkhipova; O. E. Mandel (April 1991). "Photographic observations of V1329 CYG". Pis'ma v Astronomicheskii Zhurnal 17 (04): 359-67. http://adsabs.harvard.edu/abs/1991PAZh...17..359A. Retrieved 2013-09-13. 
  5. Jennifer J. Birriel (September 2008). "Demonstrating Absorption Spectra Using Commercially Available Incandescent Light Bulbs". Astronomy Education Review 7 (2): 147-57. doi:10.3847/AER2008035. http://link.aip.org/link/?AERSCZ/7/147/1. Retrieved 2013-09-13. 
  6. 6.0 6.1 6.2 M. Elliot Smith, K.R. Chamberlain, B.S. Singer and A.R. Carroll (2010). "Eocene clocks agree: Coeval 40Ar/39Ar, U-Pb, and astronomical ages from the Green River Formation". Geology 38 (6): 527-30. doi:10.1130/G30630.1. http://geology.gsapubs.org/content/38/6/527.short. Retrieved 2013-09-14. 
  7. "yellow". Wiktionary (San Francisco, California: Wikimedia Foundation, Inc). September 1, 2013. https://en.wiktionary.org/wiki/yellow. Retrieved 2013-09-02. 
  8. "gold, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. August 28, 2013. Retrieved 2013-09-02. 
  9. 9.0 9.1 "Yellow, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 12, 2013. Retrieved 2013-09-16. 
  10. "Sulfur, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 3, 2013. Retrieved 2013-09-16. 
  11. Webmineral
  12. 12.0 12.1 Handbook of Mineralogy
  13. "Cubanite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. February 26, 2013. Retrieved 2013-09-16. 
  14. "Microlite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. February 27, 2013. Retrieved 2013-09-15. 
  15. "Orpiment, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. May 17, 2013. Retrieved 2013-09-16. 
  16. M. E. Fleet and A. Hamid Mumin, Gold-bearing arsenian pyrite and marcasite and arsenopyrite from Carlin Trend gold deposits and laboratory synthesis, American Mineralogist 82 (1997) pp. 182–193
  17. "Pyrite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 11, 2013. Retrieved 2013-09-16. 
  18. 18.0 18.1 "Satterlyite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. January 31, 2013. Retrieved 2013-09-16. 
  19. "Carnotite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 20, 2013. Retrieved 2013-09-16. 
  20. Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, and Abraham Rosenzweig: Dana's new mineralogy, p. 1106. John Wiley & Sons, 1997
  21. Smith, J.V. (1960) "The Crystal structure of Spurrite, Ca5(SiO4)2CO3". Acta. Cryst. 13, 454
  22. "Spurrite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 15, 2013. Retrieved 2013-09-16. 
  23. MacEachern, Scott (1996) "Iron Age beginnings north of the Mandara Mountains, Cameroon and Nigeria" pp. 489–496 In Pwiti, Gilbert and Soper, Robert (editors) (1996) Aspects of African Archaeology: Proceedings of the Tenth Pan-African Congress University of Zimbabwe Press, Harare, Zimbabwe, ISBN 978-0-908307-55-5; archived here by Internet Archive on 11 March 2012
  24. Diop-Maes, Louise Marie (1996) "La question de l'Âge du fer en Afrique" ("The question of the Iron Age in Africa") Ankh 4/5: pp. 278–303, in French; archived here by Internet Archive on 25 January 2008
  25. Boswell, P. F. and Blanchard, Roland (1929) "Cellular structure in limonite" Economic Geology 24(8): pp. 791–796
  26. Northrop, Stuart A. (1959) "Limonite" Minerals of New Mexico (revised edition) University of New Mexico Press, Albuquerque, New Mexico, pp. 329–333 }}
  27. Constantinou, G. and Govett, G. J. S. (1972) "Genesis of sulphide deposits, ochre and umber of Cyprus" Transactions of the Institution of Mining and Metallurgy" 81: pp. 34–46
  28. "Limonite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. 16 September 2013. Retrieved 2013-09-16. 
  29. A. M. van Genderen (August 1980). "A Discussion on Three Yellow Variable Supergiants in and Near the Cepheid Instability Strip: V 810 Cen (=HD 101947), Tr. 27-102 (=HD 159378) and BL Tel (F), Based on VBLUW Photometry and the Long-period Cepheids Absence in the Galaxy". Astronomy & Astrophysics 88 (1-2): 77-83. http://adsabs.harvard.edu/abs/1980A%26A....88...77V. Retrieved 2013-09-16. 
  30. Hein, Norvin. "A Revolution in Kṛṣṇaism: The Cult of Gopāla: History of Religions, Vol. 25, No. 4 (May, 1986 ), pp. 296-317". www.jstor.org. JSTOR 1062622. 
  31. James Rodney Hastings and John A Selbie (2nd edition 1925-1940, reprint 1955, 2003) [1908-26]. Encyclopedia of Religion and Ethics (Volume 4 of 24 ( Behistun (continued) to Bunyan.) ed.). Edinburgh: Kessinger Publishing, LLC. p. 476. ISBN 0-7661-3673-6. http://books.google.com/?id=Kaz58z--NtUC&pg=PA540&vq=Krishna. Retrieved 2008-05-03. pp.540-42
  32. Couture, André (2006). "The emergence of a group of four characters (Vasudeva, Samkarsana, Pradyumna, and Aniruddha) in the Harivamsa: points for consideration". Journal of Indian Philosophy 34 (6): 571–585. doi:10.1007/s10781-006-9009-x. http://www.springerlink.com/index/141N2426N4806068.pdf. 
  33. "Krishna, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 15, 2013. Retrieved 2013-09-16. 
  34. David N. Talbott (1980). The Saturn Myth. Garden City, New York, USA: Knopf Doubleday & Company, Inc.. pp. 419. ISBN 0-385-11376-5. http://books.google.com/books?id=tNVlQgAACAAJ&hl=en. Retrieved 2013-01-03. 
  35. that bloke on the underground (8 October 2013). "Bansuri". Indian Music Project. Retrieved 2015-12-02. 
  36. 36.0 36.1 36.2 36.3 36.4 36.5 S. Sciortino, F. Favata, and G. Micela (April 1995). "The stellar coronal component of the Galaxy. II. an analysis of the stellar content of the Einstein Extended Medium Sensitivity Survey". Astronomy and Astrophysics 296 (04): 370-9. http://adsabs.harvard.edu/full/1995A%26A...296..370S. Retrieved 2013-09-16. 
  37. 37.0 37.1 37.2 37.3 37.4 37.5 37.6 37.7 V.V. Smith, K. Cunha, A. Jorissen, and H.M.J. Boffin (November 1996). "Abundances in the symbiotic star AG Draconis: the barium-symbiotic connection". Astronomy and Astrophysics 315 (11): 179-93. http://adsabs.harvard.edu/abs/1996A%26A...315..179S. Retrieved 2013-09-21. 
  38. Hyron Spinrad and David B. Wood (January 1965). "Magnesium Hydride in Cool Stars and Galaxies". The Astrophysical Journal 141 (01): 109-14. doi:10.1086/148092. http://adsabs.harvard.edu/abs/1965ApJ...141..109S. Retrieved 2013-09-18. 
  39. 39.0 39.1 R. M. E. Illing, D. A. Landman, & D. L. Mickey (June 1975). "Broad-band circular polarization of sunspots - Spectral dependence and theory". Astronomy and Astrophysics 41 (2): 183-5. http://adsabs.harvard.edu/full/1975A%26A....41..183I. Retrieved 2013-09-16. 
  40. Clyde Fisher (May 1934). "The Hayden Planetarium of the American Museum of Natural History". Popular Astronomy 42 (415): 233-43. http://articles.adsabs.harvard.edu//full/1934PA.....42..233F. Retrieved 2013-09-18. 
  41. Arthur W. Wright (1874). "III. On the polarization of the zodiacal light". Philosophical Magazine Series 4 48 (315): 13-21. doi:10.1080/14786447408641068. http://www.tandfonline.com/doi/pdf/10.1080/14786447408641068. Retrieved 2013-09-18. 
  42. 42.0 42.1 Jiří Borovička, Peter Jenniskens (2000). "Time resolved spectroscopy of a Leonid fireball afterglow". Earth, Moon, and Planets 82-83: 399-428. http://link.springer.com/article/10.1023/A:1017071524899. Retrieved 2013-09-18. 
  43. 43.0 43.1 Maria R. Drout, Philip Massey, Georges Meynet, Susan Tokarz and Nelson Caldwell (September 2009). "Yellow Supergiants in the Andromeda Galaxy (M31)". The Astrophysical Journal 703 (1): 441-60. doi:10.1088/0004-637X/703/1/441. http://iopscience.iop.org/0004-637X/703/1/441/fulltext/. Retrieved 2013-09-21. 
  44. 44.0 44.1 44.2 G. Andronico, G. A. Baratta, F. Spinella, and G. Strazzulla (October 1987). "Optical evolution of laboratory-produced organics - applications to Phoebe, Iapetus, outer belt asteroids and cometary nuclei". Astronomy and Astrophysics 184 (1-2): 333-6. http://adsabs.harvard.edu/full/1987A%26A...184..333A. Retrieved 2013-09-25. 
  45. 45.0 45.1 45.2 45.3 J. Kleczek (1957). "Temperature of Yellow Coronal Regions". Bulletin of the Astronomical Institutes of Czechoslovakia 8: 68-70. http://adsabs.harvard.edu/full/1957BAICz...8...68K. Retrieved 2013-09-26. 
  46. 46.0 46.1 P. A. Denisenkov (September-October 1989). "Origin of anomalous sodium abundances in yellow supergiants". Astrophysics 31 (2): 588-97. http://www.springerlink.com/index/UR5K48T7538H0762.pdf. Retrieved 2013-09-26. 
  47. H. Mori, Hiroshi Takeda, M. Prinz and G. E. Harlow (March 1984). "Mineralogical and Crystallographic Studies of Lodranite and Primitive Achondrite Groups Bearing on Their Genetic Link". Lunar and Planetary Science XV: 567-8. http://adsabs.harvard.edu/full/1984LPI....15..567M. Retrieved 2013-09-15. 
  48. James Muzerolle, Lee Hartmann, and Nuria Calvet (July 1998). "Emission-Line Diagnostics of T Tauri Magnetospheric Accretion. I. Line Profile Observations". The Astronomical Journal 116 (1): 455-68. http://iopscience.iop.org/1538-3881/116/1/455. Retrieved 2012-01-23. 
  49. 49.0 49.1 49.2 49.3 C. C. Batalha, N. M. Stout-Batalha, G. Basri, and M. A. O. Terra (March 1996). "The Narrow Emission Lines of T Tauri Stars". The Astrophysical Journal Supplement 103 (3): 211. doi:10.1086/192275. 
  50. Leonard Searle (1971). The Astrophysical Journal 168: 327. 
  51. 51.0 51.1 51.2 51.3 S. A. Hawley (September 1, 1978). "The chemical composition of galactic and extragalactic H II regions". The Astrophysical Journal 224 (9): 417-36. doi:10.1086/156389. 
  52. Harold D. Babcock (May 1923). "A study of the green auroral line by the interference method". The Astrophysical Journal 57 (05): 209-21. doi:10.1086/142747. http://adsabs.harvard.edu/full/1923ApJ....57..209B. Retrieved 2013-01-18. 
  53. "Astronomical spectroscopy, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. February 19, 2013. Retrieved 2013-03-27. 
  54. 54.0 54.1 54.2 Harold Zirin (March 1959). "Physical Conditions in Limb Flares and Active Prominences. II. a Remarkable Limb Flare, December 18, 1956". Astrophysical Journal 129 (3): 414-23. doi:10.1086/146633. 
  55. Craddock, P.T. and Eckstein, K (2003) "Production of Brass in Antiquity by Direct Reduction" in Craddock, P.T. and Lang, J. (eds) Mining and Metal Production Through the Ages London: British Museum pp. 226–7
  56. "Brass, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. August 13, 2013. Retrieved 2013-09-16. 
  57. H. N. Russell (1929). The Astrophysical Journal 70: 11-82. 
  58. Sarbani Basu and H. M. Antia (March 2008). "HelioseismologyandSolarAbundances". Physics Reports 457 (5-6): 217-83. doi:10.1016/j.physrep.2007.12.002. 
  59. The Sun - Introduction
  60. "SP-402 A New Sun: The Solar Results From Skylab". 
  61. "NASA/Marshall Solar Physics". NASA. 
  62. "Photosphere, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. July 3, 2012. Retrieved 2012-07-17. 
  63. C. T. Russell, D. N. Baker and J. A. Slavin (January 1, 1988). Faith Vilas, Clark R. Chapman, Mildred Shapley Matthews. ed. The Magnetosphere of Mercury, In: Mercury. Tucson, Arizona, United States of America: University of Arizona Press. pp. 514-61. ISBN 0816510857. Bibcode: 1988merc.book..514R. http://www-ssc.igpp.ucla.edu/personnel/russell/papers/magMercury.pdf. Retrieved 2012-08-23. 
  64. 64.0 64.1 A Dollfus (August 1, 1998). "History of planetary science. The Pic du Midi planetary observation Project: 1941–1971". Planetary and Space Science 46 (8): 1037-73. http://www.sciencedirect.com/science/article/pii/S0032063398000348. Retrieved 2013-09-14. 
  65. D. C. Golden, R. V. Morris, D. W. Ming, R. K. Vempati, and H. V. Lauer (March 1991). "Mineralogy of Palagonitic Soils from Hawaii". Abstracts of the Lunar and Planetary Science Conference 22 (03): 449-50. http://adsabs.harvard.edu/abs/1991LPI....22..449G. Retrieved 2013-09-14. 
  66. D. C. Golden, D. W. Ming, R. V. Morris and H. V. Lauer Jr. (December 1992). Mars surface weathering products and spectral analogs: Palagonites and synthetic iron minerals, In: Workshop on the Martian Surface and Atmosphere Through Time". Lunar and Planetary Institute. pp. 59-60. http://adsabs.harvard.edu/full/1992msat.work...59G. Retrieved 2013-09-15. 
  67. J. Longhi (1990). John W. Delano and Grant H. Heiken. ed. Differentiates of the Picritic Glass Magmas: The Missing Mare Basalts, In: Workshop on Lunar Volcanic Glasses: Scientific and Resource Potential. 3303 NASA Road 1, Houston, TX 77058 USA: Lunar and Planetary Institute. pp. 46-7. http://adsabs.harvard.edu/full/1990lgvp.work...46L. Retrieved 2013-09-15. 
  68. Abhijit Basu (1992). "Origin of Yellow Glasses Associated with Apollo 15 KREEP Basalt Fragments". Proceedings of Lunar and Planetary Science 22: 365-72. http://adsabs.harvard.edu/full/1992LPSC...22..365B. Retrieved 2013-09-15. 
  69. J. V. Smith, A. T. Anderson, R. C. Newton, E. J. Olsen, A. V. Isaacson (1970). "Petrologic history of the moon inferred from petrography, mineralogy and petrogenesis of Apollo 11 rocks". Geochimica et Cosmochimica Acta Supplement 1: 897-925. http://adsabs.harvard.edu/full/1970GeCAS...1..897S. Retrieved 2013-09-16. 
  70. 70.0 70.1 Ray J. Weldon, Mark B. Boslough, and T. J. Ahrens (March 1980). "Shock-Induced Color Changes in Nontronite: A Possible Martian Surface Process". Lunar and Planetary 6 (03): 1234-5. http://adsabs.harvard.edu/full/1980LPI....11.1234W. Retrieved 2013-09-14. 
  71. Rosaly MC Lopes (2006). "Io: The Volcanic Moon". In Lucy-Ann McFadden, Paul R. Weissman, Torrence V. Johnson. Encyclopedia of the Solar System. Academic Press. pp. 419–431. ISBN 978-0-12-088589-3. https://books.google.com/books?isbn=0080474985. 
  72. Lopes, R. M. C.; et al. (2004). "Lava lakes on Io: Observations of Io’s volcanic activity from Galileo NIMS during the 2001 fly-bys". Icarus 169 (1): 140–174. doi:10.1016/j.icarus.2003.11.013. 
  73. "Io (moon), In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. June 7, 2012. Retrieved 2012-06-08. 
  74. 74.0 74.1 File:Iosurface gal.jpg, In: Wikimedia Commons. San Francisco, California: Wikimedia Foundation, Inc. September 15, 2011. http://commons.wikimedia.org/wiki/File:Iosurface_gal.jpg. Retrieved 2012-07-17. 
  75. "File:PIA01667-Io's Pele Hemisphere After Pillan Changes.jpg, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. September 15, 2010. Retrieved 2012-07-17. 
  76. "File:Io (north pole) from Galileo and Voyager missions.jpg, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. September 19, 2011. Retrieved 2012-07-18. 
  77. "File:Iorotateing1day.ogg, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. August 3, 2011. Retrieved 2012-07-18. 
  78. 78.0 78.1 78.2 "Stellar classification, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 19, 2013. Retrieved 2013-03-27. 
  79. 79.0 79.1 79.2 79.3 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(ʘ)=4.75.
  80. The Guinness book of astronomy facts & feats, Patrick Moore, 1992, 0-900424-76-1
  81. "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.
  82. What color are the stars?, Mitchell Charity. Accessed online March 19, 2008.
  83. Glenn LeDrew (February 2001). "The Real Starry Sky". Journal of the Royal Astronomical Society of Canada 95 (1 (whole No. 686, February 2001)): 32–33. Note: Table 2 has an error and so this article will use 824 as the assumed correct total of main-sequence stars. 
  84. Ron Miller (2005). Stars and Galaxies. Twenty-First Century Books. p. 22. ISBN 9780761334668. http://books.google.com/?id=QL9uAfad1ggC&pg=PA22. 
  85. Paul Murdin (1984). Colours of the stars. CUP Archive. p. 18. ISBN 052125714X. https://books.google.com/books?isbn=052125714X. 
  86. Bengt Strömgren. "Main Sequence Stars, Problems of Internal Constitution and Kinematics (George Darwin Lecture)". Quarterly Journal of the Royal Astronomical Society 8: 8–37. 
  87. Andrew Norton, W. Alan Cooper (2004). Observing the universe: a guide to observational astronomy and planetary science. Cambridge University Press. p. 63. ISBN 0521603935. https://books.google.com/books?isbn=0521603935. 
  88. 88.0 88.1 88.2 88.3 88.4 Jesse L. Greenstein (September 1974). "Photometry of a Pleiades candidate and composite white dwarfs". The Astronomical Journal 79 (9): 964-6. doi:10.1086/111638. 
  89. Strasbourg astronomical Data Center (July 19, 2012). "NAME VAN MAANEN STAR -- White Dwarf". Strasbourg, France: Centre de Données astronomiques de Strasbourg. Retrieved 2012-07-18. 
  90. "The One Hundred Nearest Star Systems". RECONS. 2008-01-01. Retrieved 2008-12-08. 
  91. Holberg, J. B.; Oswalt, Terry D.; Sion, E. M. (May 2002). "A Determination of the Local Density of White Dwarf Stars". The Astrophysical Journal 571 (1): 512–518. doi:10.1086/339842. 
  92. "Van Maanen's star, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. July 2, 2012. Retrieved 2012-07-08. 
  93. Gatewood, G.; Russell, J. (July 1974). "Astrometric determination of the gravitational redshift of van Maanen 2 (EG 5)". Astronomical Journal 79: 815–818. doi:10.1086/111613. 
  94. Edward M. Sion; Holberg, J. B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (December 2009). "The White Dwarfs Within 20 Parsecs of the Sun: Kinematics and Statistics". The Astronomical Journal 138 (6): 1681–1689. doi:10.1088/0004-6256/138/6/1681. 
  95. 95.0 95.1 "Subgiant, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. June 7, 2012. Retrieved 2012-07-18. 
  96. Alpha Mic, Jim Kaler, Stars. Accessed on line September 4, 2008.
  97. "Alpha Microscopii, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 24, 2012. Retrieved 2012-07-17. 
  98. 98.0 98.1 98.2 98.3 98.4 "Barium star, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. February 25, 2013. Retrieved 2013-09-22. 
  99. McClure et al., Astrophysical Journal Letters, vol. 238, L35-L38, May 1980
  100. McClure, R.D. & Woodsworth, A.W. Astrophysical Journal, vol. 352, pp. 709–723, April 1990.
  101. Jorissen, A. & Mayor, M. Astronomy & Astrophysics, vol. 198, pp. 187–199, June 1988
  102. McClure, R. Journal of the Royals Astronomical Society of Canada, vol 79, pp. 277–293, Dec. 1985
  103. Boffin, H. M. J. & Jorissen, A., Astronomy & Astrophysics, vol. 205, pp. 155–163, October 1988
  104. Tomkin, J., Lambert, D.L., Edvardsson, B., Gustafsson, B., & Nissen, P.E., Astronomy & Astrophysics, vol 219, pp. L15-L18, July 1989
  105. Cesare Chiosi and Andre Maeder (1986). "The evolution of massive stars with mass loss". Annual review of astronomy and astrophysics 24: 329–75.. doi:10.1146/annurev.aa.24.090186.001553. .
  106. "Yellow supergiant, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. December 25, 2011. Retrieved 2012-07-17. 
  107. 107.0 107.1 "DY Persei variable, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 17, 2013. Retrieved 2013-03-27. 
  108. "DY Persei, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 18, 2013. Retrieved 2013-03-27. 
  109. 109.0 109.1 109.2 109.3 "R Coronae Borealis variable, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. March 18, 2013. Retrieved 2013-03-27. 
  110. Tisserand; Clayton; Welch; Pilecki; Wyrzykowski; Kilkenny (2012). The ongoing pursuit of R Coronae Borealis stars: ASAS-3 survey strikes again. https://books.google.com/books?isbn=3527655204. 
  111. Please use work-specific template. See Template:Cite for more information.
  112. 112.0 112.1 112.2 H. Nieuwenhuijzen & C. de Jager (January 2000). "Checking the yellow evolutionary void. Three evolutionary critical Hypergiants: HD 33579, HR 8752 & IRC +10420". Astronomy and Astrophysics 353 (1): 163-76. 
  113. 113.0 113.1 113.2 "Yellow hypergiant, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. January 19, 2012. Retrieved 2012-07-17. 
  114. "Astronomy, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. June 7, 2012. Retrieved 2012-06-09. 

Further reading[edit]

External links[edit]

{{Astronomy resources}}{{Principles of radiation astronomy}}