X-ray astronomy

X-ray emissionX-rayX-ray source
These three structures around Eta Carinae are thought to represent shock waves produced by matter rushing away from the superstar at supersonic speeds. The temperature of the shock-heated gas ranges from 60 MK in the central regions to 3 MK on the horseshoe-shaped outer structure. "The Chandra image contains some puzzles for existing ideas of how a star can produce such hot and intense X-rays," says Prof. Kris Davidson of the University of Minnesota. Davidson is principal investigator for the Eta Carina observations by the Hubble Space telescope. "In the most popular theory, X-rays are made by colliding gas streams from two stars so close together that they'd look like a point source to us.


planetariaand planetariumColombo Planetarium
This gives the operator great flexibility in showing not only the modern night sky as visible from Earth, but any other image they wish (including the night sky as visible from points far distant in space and time). A new generation of home planetaria was released in Japan by Takayuki Ohira in cooperation with Sega. Ohira is worldwide known as a mastermind for building portable planetaria used at exhibitions and events such as the Aichi World Expo in 2005. Later, the Megastar star projectors released by Takayuki Ohira were installed in several science museums around the world.

List of most luminous stars

most luminousmost luminous starsmost luminous stars known
Below is a list of stars arranged in order of decreasing luminosity (increasing bolometric magnitude). Accurate measurement of stellar luminosities is quite difficult in practice, even when the apparent magnitude is measured accurately, for four reasons:

Orbital period

periodsynodic periodsynodic
Opposition (astronomy). List of periodic comets.


Alpha Cygniα CygAlpha Cygni (Deneb)
It is generally the 19th brightest star in the night sky, with an average apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous stars. However, its exact distance (and hence luminosity) has been difficult to calculate; it is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun, rivalling Rigel A as the most inherently luminous first magnitude star. α Cygni (Latinised to Alpha Cygni) is the star's Bayer designation. The traditional name Deneb is derived from the Arabic word for "tail", from the phrase ذنب الدجاجة Dhanab al-Dajājah, or "tail of the hen".


In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the celestial equator, along the hour circle passing through the point in question. The root of the word declination (Latin, declinatio) means "a bending away" or "a bending down". It comes from the same root as the words incline ("bend toward") and recline ("bend backward"). In some 18th and 19th century astronomical texts, declination is given as North Pole Distance (N.P.D.), which is equivalent to 90 - (declination).

Joseph von Fraunhofer

FraunhoferJoseph FraunhoferFraunhofer refracting telescope
He found that the spectra of Sirius and other first-magnitude stars differed from the sun and from each other, thus founding stellar spectroscopy. These dark fixed lines were later shown to be atomic absorption lines, as explained by Kirchhoff and Bunsen in 1859. These lines are still called Fraunhofer lines in his honor; his discovery had gone far beyond the half-dozen apparent divisions in the solar spectrum that had previously been noted by Wollaston in 1802.

Radio astronomy

radio astronomerradioradioastronomy
Society of Amateur Radio Astronomers. Visualization of Radio Telescope Data Using Google Earth. UnwantedEmissions.com A general reference for radio spectrum allocations, including radio astronomy. Improving Radio Astronomy Images by Array Processing. What is Radio Astronomy – Radioastrolab.

Doppler effect

Dopplerdoppler shiftDoppler shifts
The use of the Doppler effect for light in astronomy depends on our knowledge that the spectra of stars are not homogeneous. They exhibit absorption lines at well defined frequencies that are correlated with the energies required to excite electrons in various elements from one level to another. The Doppler effect is recognizable in the fact that the absorption lines are not always at the frequencies that are obtained from the spectrum of a stationary light source. Since blue light has a higher frequency than red light, the spectral lines of an approaching astronomical light source exhibit a blueshift and those of a receding astronomical light source exhibit a redshift.

Stellar kinematics

space velocityrunaway starmoving group
Entry in the Encyclopedia of Astrobiology, Astronomy, and Spaceflight. Two Exiled Stars Are Leaving Our Galaxy Forever. Entry in the Encyclopedia of Astrobiology, Astronomy, and Spaceflight. Hypervelocity stars. I. The spectroscopic survey information on HV 6 & HV 7. Young stellar kinematic groups, David Montes, Departamento de Astrofísica, Universidad Complutense de Madrid.

McDonald Observatory

McDonaldMcDonald Obs.Fort Davis
The high and dry peaks of the Davis Mountains make for some of the darkest and clearest night skies in the region and provide excellent conditions for astronomical research. The Otto Struve Telescope, dedicated in 1939, was the first large telescope built at the observatory. It is located on Mt. Locke at an altitude of 2070 m. The summit of Mt. Locke, accessed by Spur 78, is the highest point on Texas highways. The Harlan J. Smith Telescope, also on Mt. Locke, was completed in 1968. The Hobby-Eberly Telescope (HET), dedicated in late 1997, is located on the summit of Mt. Fowlkes at 2030 m above sea level.

Bortle scale

dark suburban skiessuitably dark skiesbright enough
Amateur astronomy. Dark-sky movement. The End of Night (book). International Dark-Sky Association (IDA). Light pollution. Night sky. Sky brightness. Sky & Telescope (S&T). by Sky & Telescope. Interactive demo of the Bortle Scale. International Dark-Sky Association. ObservingSites.com (North American sites only).


astrophotographerastronomical photographyastrophotographers
Astronomical equipment companies also now offer a wide range of purpose-built astronomical CCD cameras complete with hardware and processing software. Many commercially available DSLR cameras have the ability to take long time exposures combined with sequential (time-lapse) images allowing the photographer to create a motion picture of the night sky. Both digital camera images and scanned film images are usually adjusted in image processing software to improve the image in some way. Images can be brightened and manipulated in a computer to adjust color and increase the contrast.

History of astrology

astrologicalancient beliefanciently developed
They were led by the constellation Sothis or Sirius. The risings of the decans in the night were used to divide the night into ‘hours’. The rising of a constellation just before sunrise (its heliacal rising) was considered the last hour of the night. Over the course of the year, each constellation rose just before sunrise for ten days. When they became part of the astrology of the Hellenistic Age, each decan was associated with ten degrees of the zodiac. Texts from the 2nd century BC list predictions relating to the positions of planets in zodiac signs at the time of the rising of certain decans, particularly Sothis.

Southern celestial hemisphere

southern skysouthern hemispheresouthern skies
In the context of astronomical discussions or writing about celestial mapping, it may also simply then be referred to as the Southern Hemisphere. For the purpose of celestial mapping, the sky is considered by astronomers as the inside of a sphere divided in two halves by the celestial equator. The Southern Sky or Southern Hemisphere is therefore that half of the celestial sphere that is south of the celestial equator. Even if this one is the ideal projection of the terrestrial equatorial onto the imaginary celestial sphere, the Northern and Southern celestial hemispheres must not be confused with descriptions of the terrestrial hemispheres of Earth itself.

Astrophysical X-ray source

X-ray sourceX-ray sourcesdiffuse cosmic X-ray background
A Chandra X-ray image of Sirius A and B shows Sirius B to be more luminous than Sirius A. Whereas in the visual range, Sirius A is the more luminous. Regarding Cassiopea A SNR, it is believed that first light from the stellar explosion reached Earth approximately 300 years ago but there are no historical records of any sightings of the progenitor supernova, probably due to interstellar dust absorbing optical wavelength radiation before it reached Earth (although it is possible that it was recorded as a sixth magnitude star 3 Cassiopeiae by John Flamsteed on August 16, 1680 ).

Hal Clement

ClementHarry StubbsClement, Hal
Enigma 88 - A small planet near η Carinae in Still River. The interior of the object is honeycombed with caves, due to evaporation of accreted ice-rich planetoids. Unusually for Clement, Enigma's structure is not fully consistent with the laws of physics. "Proof" (June 1942). Short story. Published in Astounding. Collected in The Essential Hal Clement Volume 2, Possible Worlds of Science Fiction (1951), SF: Author's Choice 2 (1970), Where Do We Go From Here? (1971), The Great SF Stories 4 (1942) (1980), First Voyages (1981), The Golden Years of Science Fiction (Second Series) (1983), Encounters (1988), Ascent of Wonder (1994) and Wondrous Beginnings (2003). Impediment (aug 1942).

Planets in science fiction

fictional planetfictionalfictional planets
In the system of Claudius Ptolemy (fl. c. 150), the Alexandrian astronomer whose works were the basis of all European astronomy throughout the Middle Ages and Renaissance, the planets were lights set into a series of transparent spheres turning around the Earth, which was the center of the one and only universe. Dante (1265–1321), in his Paradiso, describes the ascent of his narrator through the spheres of the Moon, the planets from Mercury to Saturn, and thence to the sphere of the fixed stars and the heavens of the angels. Dante implies that the light of the planets is a combination of light imparted by Divine will and the radiance of the blessed souls that inhabit the spheres.

Australian Aboriginal astronomy

KungkarungkaraSeven SistersAboriginal Astronomy
In 2010, astronomers Duane Hamacher and David Frew from Macquarie University in Sydney showed that the Boorong Aboriginal people of northwestern Victoria, Australia, witnessed the outburst of Eta Carinae in the 1840s and incorporated it into their oral traditions as Collowgulloric War, the wife of War (Canopus, the Crow – ). This is the only definitive indigenous record of Eta Carinae's outburst identified in the literature to date. Aboriginal calendar's tend to be different to European calendar's. Manee group's in Northern Staraleah use a calendar with six season's, and some group's mark the season's by the star's, which are visible during them.

Stars in astrology

fixed starsgreat significanceparanatellonta
Thus, for example, if Sirius was rising while Jupiter was at the midheaven, Sirius would be considered a paran of Jupiter and could influence the way the astrologer interpreted Jupiter in that horoscope. Astrologically, Aldebaran is a fortunate star, portending riches and honor. This star, named "Tascheter" by the Persians, is one of the four "royal stars" of the Persians from around 3000 BC. These stars were chosen in such way that they were approximately 6 hours apart in right ascension. Each of these stars was assigned to a season, Aldebaran was prominent in the March sky and as such, it was associated with the vernal equinox.

Betelgeuse in fiction

Betelgeuse may be referred to in fictional works for its metaphorical (meta) or mythological (myth) associations, or else as a bright point of light in the sky of the Earth, but not as a location in space or the center of a planetary system: There follow references to Betelgeuse as a location in space or the center of a planetary system, categorized by genre: Betelgeuse is referred to as a location in space or the center of a planetary system unusually often in fiction. For a list containing many stars and planetary systems that have a less extensive list of references, see Stars and planetary systems in fiction.

List of star extremes

most extreme stars
Some of these properties are considered extreme and sometimes disproportionate by astronomers. Star. Star system. Multiple star system. List of extremes in the sky. List of extrasolar planet extremes. Degenerate star. Apparent size. Proper motion. Radial velocity. Peculiar motion. Rotational speed.

List of proper names of stars

by constellationgiven a proper namein alphabetical order
These are the names of stars that have either been approved by the International Astronomical Union (its Working Group on Star Names has since 2016 been publishing a "List of IAU-approved Star Names", which as of June 2018 included a total of 330 proper names of stars ) or which have been in somewhat recent usage. See also the lists of stars by constellation, which give variant names, derivations, and magnitudes. Of the roughly 10,000 stars visible to the naked eye, only a few hundred have been given proper names in the history of astronomy. Traditional astronomy tends to group stars into asterisms, and give proper names to those, not to individual stars.


If You Could Hie to Kolob
Kolob, astronomy and book of Abraham. Anthony Larson correlates cosmology with global mythology and LDS doctrine. Kolob as Sirius.

Extraterrestrial skies

Mercurian daylunar skynight sky
However, there are some notable differences with the position of other nearby stars; for example, Sirius would appear about one degree from the star Betelgeuse in the constellation Orion. Also, Procyon would appear in the constellation Gemini, about 13 degrees below Pollux. A planet around either α Centauri A or B would see the other star as a very bright secondary.