“A red giant is a luminous giant star The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower. The appearance of the red giant is from yellow orange to red, including the spectral types K and M, but also class S stars and most carbon stars. The most common red giants are the so-called red giant branch stars (RGB stars). Another case of red giants are the asymptotic giant branch stars (AGB). To the AGB stars belong the carbon stars of type C-N and late C-R. The stellar limb of a red giant is not sharply-defined, as depicted in many illustrations. Instead, due to the very low mass density of the envelope, such stars lack a well-defined photosphere. The body of the star gradually transitions into a 'corona' with increasing radii.
"To date, all of the reported hypervelocity stars (HVSs), which are believed to be ejected from the Galactic center, are blue and therefore almost certainly young.”
Def. a high-velocity star moving through space with an abnormally high velocity relative to the surrounding interstellar medium is called a runaway star.
"Of particular importance has been access to high resolution R~40,000-100,000 echelle spectra providing an ability to study the dynamics of hot plasma and separate multiple stellar and interstellar absorption components."
At left is a radiated object, the binary star Mira, and its associated phenomena.
"Ultra-violet studies of Mira by NASA's Galaxy Evolution Explorer (Galex) space telescope have revealed that it sheds a trail of material from the outer envelope, leaving a tail 13 light-years in length, formed over tens of thousands of years. It is thought that a hot bow-wave of compressed plasma/gas is the cause of the tail; the bow-wave is a result of the interaction of the stellar wind from Mira A with gas in interstellar space, through which Mira is moving at an extremely high speed of 130 kilometres/second (291,000 miles per hour). The tail consists of material stripped from the head of the bow-wave, which is also visible in ultra-violet observations. Mira's bow-shock will eventually evolve into a planetary nebula, the form of which will be considerably affected by the motion through the interstellar medium (ISM).
At second right is the only available X-ray image, by the Chandra X-ray Observatory, of Mira A on the right and Mira B (left). "Mira A is losing gas rapidly from its upper atmosphere [apparently] via a stellar wind. [Mira B is asserted to be a white dwarf. In theory] Mira B exerts a gravitational tug that creates a gaseous bridge between the two stars. Gas from the wind and bridge accumulates in an accretion disk around Mira B and collisions between rapidly moving particles in the disk produce X-rays."
It is a type of stellar remnant [(a compact star)] that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons
Neutron stars are theorized as the radiation source for anomalous X-ray pulsars (AXPs), binary pulsars, high-mass X-ray binaries, intermediate-mass X-ray binaries, low-mass X-ray binaries (LMXB), pulsars, and soft gamma-ray repeaters (SGRs).
"The [image on the right] shows two observations of [the] neutron star [RX J0822-4300] obtained with the Chandra X-ray Observatory over the span of five years, between December 1999 [on the left] and April 2005 [on the right]. By combining how far it has moved across the sky with its distance from Earth [at about 7,000 light years], astronomers determined the cosmic cannonball is moving at over 3 million miles per hour, one of the fastest moving stars ever observed. At this rate, RX J0822-4300 [at (J2000) RA 08h 23m 08.16s Dec -42° 41' 41.40" in Puppis] is destined to escape from the Milky Way after millions of years, even though it has only traveled about 20 light years so far."
"IN the standard model for type Ia supernovae1, a massive white dwarf in a binary system accretes matter from the companion star until it reaches the Chandrasekhar mass (the stability limit for degenerate-electron stars, corresponding to ~1.4 solar masses), and a runaway thermonuclear explosion ensues."
"In the 1980s two early water-Cherenkov experiments were built. The Irvine-Michigan-Brookhaven detector in an Ohio salt mine and the Kamiokande detector in a Japanese zinc mine were tanks containing thousands of tons of purified water, monitored with phototubes. The two detectors launched the field of neutrino astronomy by detecting some 20 low-energy (about 10 MeV) neutrinos from Supernova 1987A—the first supernova since the 17th century that was visible to the naked eye."
"The water-based detectors Kamiokande II and IMB detected 11 and 8 antineutrinos of thermal origin, respectively, while the scintillator-based Baksan detector found 5 neutrinos (lepton number = 1) of either thermal or electron-capture origin, in a burst lasting less than 13 seconds.
"In 1987, astronomers counted 19 neutrinos from an explosion of a star in the nearby Large Magellanic Cloud, 19 out of the billion trillion trillion trillion trillion neutrinos that flew from the supernova."
Gamma-ray stars have surface temperatures starting at 300,000,000 K (300 MK) corresponding to a peak wavelength of 0.010 nm (10 pm) for the beginning of super soft gamma-ray sources.
X-ray stars have surface temperatures starting at 300,000 K corresponding to a peak wavelength of 10 nm for the beginning of super soft X-ray sources.
Stellar class O stars have surface temperatures high enough that most of their luminescence is in the ultraviolet.
"The “Purple Haze” is a diffuse blueish/purple glow within a few arcseconds of the central star in HST images of the Homunculus (Morse et al. 1998; Smith et al. 2000, 2004). This emission is seen in excess of violet starlight scattered by dust, and the strength of the excess increases into the far UV (Smith et al. 2004; hereafter Paper I)."
Notation: let the symbol LH stand for the Little Homunculus.
"The LH has no outstanding correspondence with any of the clumps and filaments seen in scattered light in normal UV or visual-wavelength images of η Car, although it does match the spatial extent of the "Purple Haze"". Bold added.
The Fe II emission line at 489.1 nm occurs in the Little Homunculus (Eta Carinae)
Mass "loss at the η Carinae rate produces considerable changes of Teff on a human timescale. As an example, for the 120 Mʘ model, a change from about 20,000 K to 34,000 K was obtained over a time of 50 yr as a result of the secular bluewards evolution following the rapid ejection."
Stars are often referred to by their predominant color. For example, blue stragglers are found among the galactic halo globular clusters. Blue main sequence stars, that are metal poor, ([Fe/H] ≤ -1.0) are most likely not analogous to blue stragglers.
Theta Ursae Majoris is a spectral type F7V star. It has a surface temperature of 6300 ± 33 K. Such an effective surface temperature has a Planckian black body peak wavelength of 476 nm which places this star at the high temperature end of the cyan band.
Capella B, the image at right, has a surface temperature of approximately 5700 K, a radius of approximately 9 solar radii, a mass of approximately 2.6 solar masses, and a luminosity, again measured over all wavelengths, approximately 78 times that of the Sun.
Capella B is spectral type G0III star and an X-ray source from the catalog [FS2003] 0255 by ROSAT. Its surface temperature has an uncertainty of 100 K. It is part of a binary star with Capella A a G8III. From SIMBAD, the orbital period is 104.0217 d with an eccentricity is 0.001 and inclination of 137.2° to the line of sight.
Although the binary star Capella is not an eclipsing binary, it is a RS Canum Venaticorum variable. These are close binary stars having active chromospheres which can cause large stellar spots. These spots are believed to cause variations in their observed luminosity. Systems can exhibit variations on timescales of years due to variation in the spot surface coverage fraction, as well as periodic variations which are, in general, close to the orbital period of the binary system. Typical brightness fluctuation is around 0.2 magnitudes.
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.
"Many subgiants are rich in metals, and commonly host orbiting planets.
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.
The variability of BD +50 961 (SY Persei, an orange star) is confirmed.
"ESO Photo Ambassador Babak Tafreshi snapped this remarkable image [at right] of the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA), set against the splendour of the Milky Way. The richness of the sky in this picture attests to the unsurpassed conditions for astronomy on the 5000-metre-high Chajnantor plateau in Chile’s Atacama region."
"This view shows the constellations of Carina (The Keel) and Vela (The Sails). The dark, wispy dust clouds of the Milky Way streak from middle top left to middle bottom right. The bright orange star in the upper left is Suhail in Vela, while the similarly orange star in the upper middle is Avior, in Carina. Of the three bright blue stars that form an “L” near these stars, the left two belong to Vela, and the right one to Carina. And exactly in the centre of the image below these stars gleams the pink glow of the Carina Nebula"
With respect to the color 'red', there are studies of the redness of objects such as the red dwarf AZ Cancri shown in the visual image at right. Cool stars of spectral class M appear red; they are (depending on their size) referred to as "red giants" or "red dwarfs".
"Ideally all intrinsic colours should be found from unreddened stars. This is possible for dwarf and giant stars later than about A0 (Johnson, 1964) ... However, it cannot be used for stars of other spectral classes since they are all relatively infrequent in space, and generally reddened."
A very important wavelength in this region is the Balmer alpha line, 656.28 nm. It is emitted or absorbed by hydrogen atoms when electrons move between the second and third electron shells. Other Balmer lines, known as beta, gamma and delta, have wavelengths of 486.13, 434.05 and 410.17 nm respectively; these are also in the visual range but are less important than the alpha line.
Stars "of spectral type S are characterized by unusual photospheric abundances which imply enrichment of the stellar surface by nucleosynthesis products. Spectroscopically, S stars are identified by bands of ZrO and LaO, replacing the TiO bands found in M stars. The spectra of S stars indicate strong enhancement of s-process elements in the photosphere (an accident of nomenclature - when the S spectral type was introduced, the slow neutron capture process was unknown). Abundance analyses show that in S stars, the C/O ratio is very close to unity [...], which also implies the presence of the products of nucleosynthesis at the stellar surface."
The "extrinsic S stars, includes stars which have elemental abundances which appear to have been altered by mass transfer from a binary companion."
The "intrinsic S stars, includes stars which have high luminosity and lie on the asymptotic giant branch (AGB). They show evidence that their compositional abnormalities are a result of nucleosynthesis and [perhaps] convective mixing to the surface. In particular, a defining characteristic which distinguishes the two types is that the intrinsic S stars contain technetium, while the extrinsic S stars do not."
"Both HCN and SiO have readily observable lines at 3 mm." χ Cyg is at a distance of 170 pc, but parallax measurements put it at D = 144 ± 25 pc (Stein 1991), parallax of 5.53 mas (198 ± 38) pc as of 2007 according to SIMBAD.
"All of these stars are bright at 2 µm and therefore have circumstellar dust [...] In one observing session, we obtained a 5 x 5 cross at HPBW spacings for the star χ Cyg in the CO J = 2-1 line. The data were relatively noisy because of limited integration time and weather conditions but do indicate that the envelope is extended with respect to the 25" telescope beam."
χ Cyg was "detected in the SiO v = 1 J = 2-1 maser emission line [...] χ Cyg has an unusually large dust/gas ratio of 9.0 x 10-3 [The dust-to-gas ratio for S stars detected in CO J = 1-0 is] 9.0 x 10-3 [...] For one star in our sample namely χ Cyg, the SiO J = 2-1, v = 0 emission has been mapped interferometrically [...] the SiO abundance at the base of the expanding envelope must be ~ 2 x 10-5 to explain the observed intensity distribution of the SiO emission. Thus, a substantial fraction (30%-50%) of all silicon atoms are in the form of gas phase SiO at the point where molecules are injected into the stellar wind. As the gas moves away from the star, the SiO is depleted from the gas, presumably by the process of grain formation, such that at radii of several x 1015 cm, the SiO gas phase abundance has fallen by > 90%. [...] χ Cyg, which has a relatively low mass-loss rate and hence low envelope opacity to UV photons."
- orange sphere of the sun
- Juna A. Kollmeier and Andrew Gould (July 20, 2007). "Where Are the Old-Population Hypervelocity Stars?". The Astrophysical Journal 664 (1): 343-8. doi:10.1086/518405. http://iopscience.iop.org/0004-637X/664/1/343. Retrieved 2012-03-05.
- Martin A. Barstow ; L. Binette ; Noah Brosch ; F.Z. Cheng ; Michel Dennefeld ; A.I. G. de Castro ; H. Haubold ; K.A. van der Hucht ; N. Kappelmann ; P. Martinez ; A. Moisheev ; I. Pagano ; Erez N. Ribak ; J. Sahade ; B. I. Shustov ; J.-E. Solheim ; W. Wamsteker ; K. Werner ; Helmut Becker-Ross ; Stefan Florek (February 26, 2003). J. Chris Blades; Oswald H. W. Siegmund, ed. The WSO: a world-class observatory for the ultraviolet, In: Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation. 4854. The International Society for Optical Engineering. doi:10.1117/12.459779. Retrieved 2013-07-15.CS1 maint: Multiple names: authors list (link)
- Martin, Christopher; Seibert, M; Neill, JD; Schiminovich, D; Forster, K; Rich, RM; Welsh, BY; Madore, BF et al. (August 17, 2007). "A turbulent wake as a tracer of 30,000 years of Mira's mass loss history". Nature 448 (7155): 780–783. doi:10.1038/nature06003. PMID 17700694.
- Minkel, JR."Shooting Bullet Star Leaves Vast Ultraviolet Wake", "The Scientific American", August 15, 2007 Accessed August 21, 2007.
- Wareing, Christopher; Zijlstra, A. A.; O'Brien, T. J.; Seibert, M. (November 6, 2007). "It's a wonderful tail: the mass-loss history of Mira". Astrophysical Journal Letters 670 (2): L125–L129. doi:10.1086/524407. http://www.iop.org/EJ/article/1538-4357/670/2/L125/22252.html.
- W. Clavin (August 15, 2007). GALEX finds link between big and small stellar blasts. California Institute of Technology. Archived from the original on 2007-08-27. Retrieved 2007-08-16.
- Christopher Wareing (December 13, 2008). "Wonderful Mira". Philosophical Transactions of the Royal Society A 366 (1884): 4429–40. doi:10.1098/rsta.2008.0167. PMID 18812301.
- M. Karovska; et al. (April 28, 2005). More Images of Mira. NASA/CXC/SAO/M. Karovska et al. Retrieved 2012-12-22.CS1 maint: Explicit use of et al. (link)
- Castelaz, Michael W.; Luttermoser, Donald G. (1997). "Spectroscopy of Mira Variables at Different Phases.". The Astronomical Journal 114: 1584–1591. doi:10.1086/118589.
- Woodruff, H. C.; Eberhardt, M.; Driebe, T.; Hofmann, K.-H.; Ohnaka, K.; Richichi, A.; Schert, D.; Schöller, M.; Scholz, M.; Weigelt, G.; Wittkowski, M.; Wood, P. R. (2004). "Interferometric observations of the Mira star o Ceti with the VLTI/VINCI instrument in the near-infrared" (PDF). Astronomy & Astrophysics 421 (2): 703–714. doi:10.1051/0004-6361:20035826. http://www.eso.org/~mwittkow/publications/conferences/SPIECWo5491199.pdf. Retrieved 2007-12-07.
- F. Winkler; et al. (21 December 1999). RX J0822-4300 in Puppis A: Chandra Discovers Cosmic Cannonball. 60 Garden Street, Cambridge, MA 02138 USA: Harvard-Smithsonian Center for Astrophysics. Retrieved 2016-12-16.CS1 maint: Explicit use of et al. (link)
- Pilar Ruiz-Lapuente, David J. Jeffery, Peter M. Challis, Alexei V. Filippenko, Robert P. Kirshner, Luis C. Ho, Brian P. Schmidt, Francisco Sanchez & Ramon Canal (21 October 1993). "A possible low-mass type Ia supernova". Nature 365 (6448): 728 - 730. doi:10.1038/365728a0. http://www.nature.com/nature/journal/v365/n6448/abs/365728a0.html. Retrieved 2017-05-02.
- Francis Halzen and Spencer R. Klein (May 2008). "Astronomy and astrophysics with neutrinos". Physics Today: 29-35. http://www.lbl.gov/today/2008/Jun/06-Fri/PTNuAstronomy.pdf. Retrieved 2012-07-28.
- A.K. Mann (1997). Shadow of a star: The neutrino story of Supernova 1987A. W. H. Freeman. p. 122. ISBN 0-7167-3097-9.
- KENNETH CHANG (April 26, 2005). Tiny, Plentiful and Really Hard to Catch, In: The New York Times. Retrieved 2011-06-16.
- Nathan Smith, Jon A. Morse, Nicholas R. Collins, and Theodore R. Gull (August 2004). "The Purple Haze of eta Carinae: Binary-induced Variability?". The Astrophysical Journal 610 (2): L105-8. doi:10.1086/423341.
- Nathan Smith (March 2005). "Doppler tomography of the Little Homunculus: High‐resolution spectra of [Fe II λ16 435 around Eta Carinae"]. Monthly Notices of the Royal Astronomical Society 357 (4): 1330-6. doi:10.1111/j.1365-2966.2005.08750.x. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2005.08750.x/full. Retrieved 2012-02-27.
- A. Maeder (April 1983). "Evolution of chemical abundances in massive stars. I - OB stars, Hubble-Sandage variables and Wolf-Rayet stars - Changes at stellar surfaces and galactic enrichment by stellar winds. II - Abundance anomalies in Wolf-Rayet stars in relation with cosmic rays and 22/Ne in meteorites". Astronomy and Astrophysics 120 (1): 113-35. http://adsabs.harvard.edu/full/1983A%26A...120..113M. Retrieved 2013-09-19.
- Too Close for Comfort. Hubble Site. NASA. August 7, 2003. Retrieved 2010-01-21.
- Preston, G. W.; Beers, T. C.; Shectman, S. A. (December 1993). "The Space Density and Kinematics of Metal-Poor Blue Main Sequence Stars Near the Solar Circle". Bulletin of the American Astronomical Society 25 (12): 1415.
- Helmut A. Abt (January 2009). "MK Classifications of Spectroscopic Binaries". The Astrophysical Journal Supplement 180 (1): 117–8. doi:10.1088/0067-0049/180/1/117.
- Tabetha S. Boyajian,; McAlister, Harold A.; van Belle, Gerard; Gies, Douglas R.; ten Brummelaar, Theo A.; von Braun, Kaspar; Farrington, Chris; Goldfinger, P. J. et al. (February 2012). "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars". The Astrophysical Journal 746 (1): 101. doi:10.1088/0004-637X/746/1/101. . See Table 10.
- C. A. Hummel et al. (May 1994). "Very high precision orbit of Capella by long baseline interferometry". The Astronomical Journal 107 (5): 1859–67. doi:10.1086/116995.
- Berdyugina 2.4 RS CVn stars
- T. W. Backhouse (July 1899). "Confirmed or New Variable Stars". The Observatory 22 (281): 275-6. http://adsabs.harvard.edu//abs/1899Obs....22..276. Retrieved 2012-02-01.
- Babak Tafreshi (May 28, 2012). The Southern Milky Way Above ALMA. Chajnantor plateau in Chile’s Atacama region. Retrieved 2014-03-01.
- M. Pim FitzGerald (February 1970). "The Intrinsic Colours of Stars and Two-Colour Reddening Lines". Astronomy and Astrophysics 4 (2): 234-43.
- John H. Bieging and William B. Latter (February 20, 1994). "A Millimeter-Wavelength Survey of S Stars for Mass Loss and Chemistry". The Astrophysical Journal 422 (2): 765-82. doi:10.1086/173769. http://adsabs.harvard.edu/full/1994ApJ...422..765B. Retrieved 2014-04-18.