Orange astronomy

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An orange sunset in the Mahim Bay is shown around the Haji Ali Dargah in India. Credit: Humayunn Peerzaada.

Orange astronomy is astronomy applied to the various extraterrestrial orange 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) orange astronomy.

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Seeing an orange Sun due to atmospheric effects and feeling the warmth of its rays is probably a student's first encounter with an apparent astronomical orange radiation source. This may occur at a secondary educational level.

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There are orange objects and emission lines in the orange portion of the visible spectrum from 590 to 620 nm in wavelength.

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Contents

[edit] Notation

Notation: let the symbol Def. indicate that a definition is following.

[edit] Universals

To help with definitions, their meanings and intents, there is the learning resource theory of definition.

Def. "[t]he colour of a ripe orange (the fruit); a color midway between red and yellow", per Wiktionary orange, is called orange.

From the Wikipedia article spectral bands, "Band spectra [are] the combinations of many different spectral lines, resulting from rotational, vibrational and electronic transition."

[edit] Doppler broadening

Per the Wikipedia article, Doppler broadening, "Doppler broadening is the broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules. Different velocities of the emitting particles result in different (Doppler) shifts, the cumulative effect of which is the line broadening.[1]"

[edit] Stark broadening

"Linear Stark broadening occurs via the linear Stark effect which results from the interaction of an emitter with an electric field, which causes a shift in energy which is linear in the field strength. (\Delta E \sim 1/r^2)" from the Wikipedia entry spectral line.

"Quadratic Stark broadening occurs via the quadratic Stark effect which results from the interaction of an emitter with an electric field, which causes a shift in energy which is quadratic in the field strength. (\Delta E \sim 1/r^4)" per the Wikipedia entry spectral line.

[edit] van der Waals broadening

Notation: "van der Waals profile" appears as lowercase in almost all sources

"Van der Waals broadening occurs when the emitting particle is being perturbed by van der Waals forces. For the quasistatic case, a van der Waals profile[2][3] is often useful in describing the profile. The energy shift as a function of distance is given in the wings by e.g. the Lennard-Jones potential (\Delta E \sim 1/r^6)." from the Wikipedia entry spectral line.

[edit] Temperatures

"Temperatures [are] estimated from intensity ratios of atomic lines (used mainly for early C stars), color in the orange region of the spectrum, strength of the Na D-lines, and C2 band intensity gradients."[4]

[edit] Carbon

There is a C2 band at 619.1 nm.[5] Sometimes there is a hint of 13C12C at 618.8 nm.[5]

[edit] Lithium

Lithium I has an orange line at 610.3 nm. In some 824 red giant stars, the Li I 670.78 nm line was detected in several stars, "but only the five objects ... presented a strong line. Indeed, the Li subordinate line at 6103.6 Å was detected in these stars only."[6]

[edit] Spite plateau

"The Spite plateau (or Spite lithium plateau) is a baseline in the abundance of lithium found in old stars orbiting the galactic halo." from the Wikipedia entry about the Spite plateau.

"[T]he curve on a graph of the abundance of lithium versus effective surface temperature formed a plateau among old halo stars for effective temperatures below about:

log Teff ~ 3.75

or roughly 5,600 K. This suggested that the plateau represented the primordial abundance level of lithium in the Milky Way ... [with an estimate] that the abundance of lithium at the beginning of the galaxy was:

NLi = (11.2 ± 3.8) × 10−11 NH

where NH is the abundance of hydrogen.[7]" after the Wikipedia entry about the Spite plateau.

"Lithium depletion through atomic diffusion has been suggested as a solution to the discrepancy between the Spite plateau abundance and the predicted value of the primordial lithium abundance"[8].

[edit] Orange system

The orange system is a number of emission lines very close together forming a band in the orange portion of the visible spectrum. These lines are usually associated with particular molecular species, including ScO, YO, and TiO.[9] The emission features for ScO (the 0-0 band) are near 603.6 and 607.9 nm.[9] There is also a 1-1 band at 607.2 and 611.5 nm.[9]

There may be a TiO band present at 615.8 nm, which "suggests that the star may be a late K or early M star."[5]

The orange band from molecular CaCl is "observed in the spectra of many carbon stars."[10] "[T]he concentration of CaCl is strongly temperature and pressure dependent, but almost independent of the C/O ratio at a fixed pressure."[11] "The probable absence of CaCl bands in spectra of carbon stars with C/O ≫ 1 can be explained by CN opacity effects near 6000 Å, ... whereas the absence of CaCl bands in spectra of the coolest M and S stars can probably be attributed largely to molecular band masking."[11] "[T]he CaCl bands are a useful, but not infallible, temperature criteria."[12]

"The YO bands at 6132 [the 0-0 emission band] and 5972 Å appear only in the cooler stars, but in MS stars and weak S stars they are so sensitive to heavy-element abundance that they are not very useful as temperature indicators."[12]

[edit] Optical astronomy

Optical astronomy includes those portions of ultraviolet, visual, and infrared astronomy that benefit from the use of quartz crystal or silica glass telescope components.

Per the Wikipedia article telescope: "An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum (although some work in the infrared and ultraviolet)."[13]

[edit] Visual astronomy

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

From the Wikipedia article visible spectrum: "The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm.[14] In terms of frequency, this corresponds to a band in the vicinity of 400–790 THz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function)."

[edit] Stellar classification

"Most stars are currently classified using the letters O, B, A, F, G, K, and M ..., where O stars are the hottest and the letter sequence indicates successively cooler stars up to the coolest M class. ... K stars [are] "orange", ... even though the actual star colors perceived by an observer may deviate from these colors depending on visual conditions and individual stars observed." from the Wikipedia article stellar classification.

The Secchi Class III consists of "orange to red stars with complex band spectra," per the Wikipedia article stellar classification.

From the Wikipedia article stellar classification, "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:"

Class Temperature[15]
K		 Conventional color Apparent color[16][17][18] Mass[15]
(solar masses, Mʘ)		 Radius[15]
(solar radii, Rʘ)		 Luminosity[15]
(bolometric, Lʘ)		 Hydrogen
lines		 Fraction of all
main sequence stars[19]
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%

[edit] Orange giants

Arcturus (α Bootes) is an orange (K-type) giant.[20]

[edit] Orange stars

This is a visual image in real color of SY Persei (an orange star). Credit: Aladin at SIMBAD.

The variability of BD +50 961 (SY Persei, an orange star) is confirmed.[21]

[edit] Brown dwarfs

This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. The brown dwarf, called Gliese 229B, is about 20 to 50 times the mass of Jupiter. Credit: .

"Brown dwarfs are sub-stellar objects ... [that] have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest-mass stars; this upper limit is between 75[1] and 80 Jupiter masses (M_J)." per the Wikipedia article about the brown dwarf.

[edit] Sub-brown dwarf

"A sub-brown dwarf is an astronomical object of planetary mass that is not orbiting a star and is not considered to be a brown dwarf because its mass is below the limiting mass ... [of] about 13 Jupiter masses).[22] ... Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud (perhaps with the help of photo-erosion), and not through accretion or core collapse from a circumstellar disc [although] not universally agreed upon; astronomers are divided into two camps as whether to consider the formation process of a planet as part of its division in classification.[23] ... The smallest mass of gas cloud that could collapse to form a sub-brown dwarf is about 1 MJ.[24] This is because to collapse by gravitational contraction requires radiating away energy as heat and this is limited by the opacity of the gas.[25]" after the Wikipedia article about a sub-brown dwarf.

[edit] Jupiter

Cloud bands are clearly visible on Jupiter. Credit: .

"[O]range [is] the color of Jupiter"[26].

"The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons.[27][28] These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.[29]" from the Wikipedia entry Jupiter.

[edit] See also

[edit] References

  1. ↑ Siegman, AE (1986). Lasers. http://books.google.dk/books?id=1BZVwUZLTkAC&lpg=PA1184&ots=6xdm1N2jLf&dq=doppler%20broadening%20Siegman&hl=en&pg=PA1184#v=onepage&q=doppler%20broadening%20Siegman&f=false. 
  2. ↑ Statistical mechanics of the liquid surface by Clive Anthony Croxton, 1980, A Wiley-Interscience publication, ISBN 0-471-27663-4, 9780471276630, [1]
  3. ↑ Journal of technical physics, Volume 36, by Instytut Podstawowych Problemów Techniki (Polska Akademia Nauk), publisher: Państwowe Wydawn. Naukowe., 1995, [2]
  4. ↑ John M. Scalo (December 1973). "Opacity effects and the classification of carbon stars". The Astrophysical Journal 186 (12): 967-78. Bibcode: 1973ApJ...186..967S. Retrieved on 2012-02-01. 
  5. ↑ 5.0 5.1 5.2 Harvey B. Richer (February 1981). "Observations of a complete sample of carbon stars in the Large Magellanic Cloud". The Astrophysical Journal 243 (2): 744-55. doi:10.1086/158642. Bibcode: 1981ApJ...243..744R. Retrieved on 2012-02-01. 
  6. ↑ L. Monaco, S. Villanova, C. Moni Bidin, G. Carraro, D. Geisler, P. Bonifacio, O. A. Gonzalez, M. Zoccali and L. Jilkova (May 2011). "Lithium-rich giants in the Galactic thick disk". Astronomy & Astrophysics 529 (5): 10. doi:10.1051/0004-6361/201016285. Bibcode: 2011A&A...529A..90M. Retrieved on 2012-04-16. 
  7. ↑ F. Spite, M. Spite (November 1982). "Abundance of lithium in unevolved halo stars and old disk stars - Interpretation and consequences". Astronomy and Astrophysics 115 (2): 357–366. Bibcode: 1982A&A...115..357S. 
  8. ↑ K. Lind, M. Asplund, P. S. Barklem (August 2009). "Departures from LTE for neutral Li in late-type stars". Astronomy and Astrophysics 503 (2): 541-4. doi:10.1051/0004-6361/200912221. Bibcode: 2009A&A...503..541L. Retrieved on 2012-04-16. 
  9. ↑ 9.0 9.1 9.2 G. H. Herbig (March 1974). "VY Canis Majoris. IV. The emission bands of ScO". The Astrophysical Journal 188 (3): 533-8. doi:10.1086/152744. Bibcode: 1974ApJ...188..533H. Retrieved on 2012-02-01. 
  10. ↑ J. E. Littleton and Sumner P. Davis (October 1988). "Transition strength data for the orange and red bands of CaCl". The Astrophysical Journal 333 (10): 1026-34. doi:10.1086/166809. Bibcode: 1988ApJ...333.1026L. Retrieved on 2012-02-01. 
  11. ↑ 11.0 11.1 R. Clegg and S. Wyckoff (May 1977). "Calcium chloride in cool stars". Monthly Notices of the Royal Astronomical Society 179: 417-32. Bibcode: 1977MNRAS.179..417C. Retrieved on 2012-02-01. 
  12. ↑ 12.0 12.1 Philip C. Keenan and Patricia C. Boeshaar (July 1980). "Spectral types of S and SC stars on the revised MK system". The Astrophysical Journal Supplement Series 43 (7): 379-91. doi:10.1086/190673. Bibcode: 1980ApJS...43..379K. Retrieved on 2012-02-01. 
  13. ↑ Barrie William Jones. The search for life continued: planets around other stars. p. 111. http://books.google.com/books?id=5wX9aHqfBS0C&pg=PA111&dq=%22optical+telescope+is%22&lr=&cd=55#v=onepage&q=%22optical%20telescope%20is%22&f=false. 
  14. ↑ Cecie Starr (2005). Biology: Concepts and Applications. Thomson Brooks/Cole. ISBN 053446226X. http://books.google.com/?id=RtSpGV_Pl_0C&pg=PA94. 
  15. ↑ 15.0 15.1 15.2 15.3 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.
  16. ↑ The Guinness book of astronomy facts & feats, Patrick Moore, 1992, 0-900424-76-1
  17. ↑ The Colour of Stars. Australia Telescope Outreach and Education (2004-12-21). Retrieved on 2007-09-26. — Explains the reason for the difference in color perception.
  18. ↑ What color are the stars?, Mitchell Charity. Accessed online March 19, 2008.
  19. ↑ 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. Bibcode: 2001JRASC..95...32L. 
  20. ↑ [3], entry in SIMBAD, accessed April 17, 2012.
  21. ↑ T. W. Backhouse (July 1899). "Confirmed or New Variable Stars". The Observatory 22 (281): 275-6. Bibcode: 1899Obs....22..276. Retrieved on 2012-02-01. 
  22. ↑ Working Group on Extrasolar Planets - Definition of a "Planet" POSITION STATEMENT ON THE DEFINITION OF A "PLANET" (IAU)
  23. ↑ Fresh Debate over First Photo of Extrasolar Planet, by Robert Roy Britt, 30 April 2005
  24. ↑ Nomenclature: Brown Dwarfs, Gas Giant Planets, and ?, Brown Dwarfs, Proceedings of IAU Symposium #211, held 20–24 May 2002 at University of Hawaii, Honolulu, Boss, A. P., Basri, G., Kumar, S. S., Liebert, J., Martín, E. L., Reipurth, B
  25. ↑ SUBSTELLAR OBJECTS IN NEARBY YOUNG CLUSTERS (SONYC): THE BOTTOM OF THE INITIAL MASS FUNCTION IN NGC 1333, Alexander Scholz, Vincent Geers, Ray Jayawardhana, Laura Fissel, Eve Lee, David Lafreni`ere, Motohide Tamura
  26. ↑ Faber Birren (Summer 1983). "Color and human response". Color Research and Application 8 (2): 75-81. doi:10.1002/col.5080080204. Retrieved on 2012-04-23. 
  27. ↑ Elkins-Tanton, Linda T. (2006). Jupiter and Saturn. New York: Chelsea House. ISBN 0-8160-5196-8. 
  28. ↑ Strycker, P. D.; Chanover, N.; Sussman, M.; Simon-Miller, A. (2006). A Spectroscopic Search for Jupiter's Chromophores. American Astronomical Society. Bibcode: 2006DPS....38.1115S. 
  29. ↑ Gierasch, Peter J.; Nicholson, Philip D. (2004). Jupiter. World Book @ NASA. Retrieved on 2006-08-10.

[edit] Further reading

[edit] External links


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