A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so all of them disintegrate and never hit the Earth's surface. Intense or unusual meteor showers are known as meteor outbursts and meteor storms, which produce at least 1,000 meteors an hour, most notably from the Leonids; the Meteor Data Centre lists over 900 suspected meteor showers of which about 100 are well established. Several organizations point to viewing opportunities on the Internet; the first great meteor storm in the modern era was the Leonids of November 1833. One estimate is a peak rate of over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of two hundred thousand meteors during the 9 hours of storm, over the entire region of North America east of the Rocky Mountains.
American Denison Olmsted explained the event most accurately. After spending the last weeks of 1833 collecting information, he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, January 1836, he noted the shower was of short duration and was not seen in Europe, that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space. Work continued, yet coming to understand the annual nature of showers though the occurrences of storms perplexed researchers; the actual nature of meteors was still debated during the XIX century. Meteors were conceived as an atmospheric phenomenon by many scientists until the Italian astronomer Giovanni Schiaparelli ascertained the relation between meteors and comets in his work "Notes upon the astronomical theory of the falling stars". In the 1890s, Irish astronomer George Johnstone Stoney and British astronomer Arthur Matthew Weld Downing, were the first to attempt to calculate the position of the dust at Earth's orbit.
They studied the dust ejected in 1866 by comet 55P/Tempel-Tuttle in advance of the anticipated Leonid shower return of 1898 and 1899. Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of Earth's orbit; the same results were independently arrived at by Adolf Berberich of the Königliches Astronomisches Rechen Institut in Berlin, Germany. Although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle. A graph from it was re-published in Sky and Telescope, it showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. This showed that the meteoroids are behind and outside the path of the comet, but paths of the Earth through the cloud of particles resulting in powerful storms were near paths of nearly no activity.
In 1985, E. D. Kondrat'eva and E. A. Reznikov of Kazan State University first identified the years when dust was released, responsible for several past Leonid meteor storms. In 1995, Peter Jenniskens predicted the 1995 Alpha Monocerotids outburst from dust trails. In anticipation of the 1999 Leonid storm, Robert H. McNaught, David Asher, Finland's Esko Lyytinen were the first to apply this method in the West. In 2006 Jenniskens published predictions for future dust trail encounters covering the next 50 years. Jérémie Vaubaillon continues to update predictions based on observations each year for the Institut de Mécanique Céleste et de Calcul des Éphémérides; because meteor shower particles are all traveling in parallel paths, at the same velocity, they will all appear to an observer below to radiate away from a single point in the sky. This radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks.
Meteor showers are always named after the constellation from which the meteors appear to originate. This "fixed point" moves across the sky during the night due to the Earth turning on its axis, the same reason the stars appear to march across the sky; the radiant moves from night to night against the background stars due to the Earth moving in its orbit around the sun. See IMO Meteor Shower Calendar 2017 for maps of drifting "fixed points." When the moving radiant is at the highest point it will reach in the observer's sky that night, the sun will be just clearing the eastern horizon. For this reason, the best viewing time for a meteor shower is slightly before dawn — a compromise between the maximum number of meteors available for viewing, the lightening sky which makes them harder to see. Meteor showers are named after the nearest constellation or bright star with a Greek or Roman letter assigned, close to the radiant position at the peak of the shower, whereby the grammatical declension of the Latin possessive form is replaced by "id" or "ids".
Hence, meteors radiating from near the star delta Aquarii are called delta Aquariids. The International Astronomical Union's Task Group on Meteor Shower Nomenclature and the IAU's Meteor Data Center keep track of meteor shower nomenclature and which showers are e
Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century AD astronomer Ptolemy and it remains one of the 88 modern constellations today, its name is Latin for "twins," and it is associated with the twins Castor and Pollux in Greek mythology. Its symbol is. Gemini lies between Taurus to the west and Cancer to the east, with Auriga and Lynx to the north and Monoceros and Canis Minor to the south; the Sun resides in the astrological sign of Gemini from June 20 to July 20 each year. By mid-August, Gemini will appear along the eastern horizon in the morning sky prior to sunrise; the best time to observe Gemini at night is overhead during the months of February. By April and May, the constellation will be visible soon after sunset in the west; the easiest way to locate the constellation is to find its two brightest stars Castor and Pollux eastward from the familiar “V” shaped asterism of Taurus and the three stars of Orion’s belt. Another way is to mentally draw a line from the Pleiades star cluster located in Taurus and the brightest star in Leo, Regulus.
In doing so, an imaginary line, close to the ecliptic is drawn, a line which intersects Gemini at the midpoint of the constellation, just below Castor and Pollux. The constellation contains 85 stars visible to observation on Earth without a telescope; the brightest star in Gemini is Pollux, the second-brightest is Castor. Castor's Bayer designation as "Alpha" arose because Johann Bayer did not distinguish which of the two was the brighter when he assigned his eponymous designations in 1603.α Gem is a sextuple star system 52 light-years from Earth, which appears as a magnitude-1.6 blue-white star to the unaided eye. Two spectroscopic binaries are visible at magnitudes 3.0 with a period of 470 years. A wide-set red dwarf star is a part of the system. Β Gem is an orange-hued giant star of 34 light-years from Earth. Pollux has an extrasolar planet revolving around it, as do two other stars in Gemini, HD 50554, HD 59686. Γ Gem is a blue-white hued star of 105 light-years from earth. Δ Gem is a long-period binary star 59 light-years from Earth.
The primary is a white star of magnitude 3.5, the secondary is an orange dwarf star of magnitude 8.2. The period is over 1000 years. Ε Gem, a double star, includes a primary yellow supergiant of magnitude 3.1, nine hundred light-years from Earth. The optical companion, of magnitude 9.6, is visible in binoculars and small telescopes.ζ Gem is a double star, whose primary is a Cepheid variable star with a period of 10.2 days. It is a yellow supergiant, 1,200 light-years from Earth, with a radius, 60 times solar, making it 220,000 times the size of the Sun; the companion, a magnitude-7.6 star, is visible in small amateur telescopes. Η Gem is a binary star with a variable component. 380 light-years away, it has a period of 500 years and is only divisible in large amateur telescopes. The primary is a semi-regular red giant with a period of 233 days; the secondary is of magnitude 6.κ Gem is a binary star 143 light-years from Earth. The primary is a yellow giant of magnitude 3.6. The two are only divisible in larger amateur instruments because of the discrepancy in brightness.
Ν Gem is a double star divisible in small amateur telescopes. The primary is a blue giant of magnitude 4.1, 550 light-years from Earth, the secondary is of magnitude 8. 38 Gem, a binary star, is divisible in small amateur telescopes, 84 light-years from Earth. The primary is a white star of magnitude 4.8 and the secondary is a yellow star of magnitude 7.8. U Gem is a dwarf nova type cataclysmic variable discovered by J. R. Hind in 1855. Mu Gem is the Bayer designation for a star in the northern constellation of Gemini, it has the traditional name Tejat Posterior, which means back foot, because it is the foot of Castor, one of the Gemini twins. Since the sky area of Gemini is directed away from the Milky Way, there are comparatively few deep-sky objects of note. M35 is a large, elongated open cluster of magnitude 5, discovered in the year 1745 by Swiss astronomer Philippe Loys de Chéseaux, it has an area of 0.2 square degrees, the same size as the full moon. Its high magnitude means; the 200 stars of M35 are arranged in chains.
Another open cluster in Gemini is NGC 2158. Visible in large amateur telescopes and rich, it is more than 12,000 light-years from Earth; the Eskimo Nebula or Clown Face Nebula is a planetary nebula with an overall magnitude of 9.2, located 4,000 light-years from Earth. In a small amateur telescope, its 10th magnitude central star is visible, along with its blue-green elliptical disk, it is named for its resemblance to the head of a person wearing a parka. The Medusa Nebula is some 1,500 light-years distant. Geminga is a neutron star 550 light-years from Earth. Other objects include NGC 2129, NGC 2158, NGC 2266, NGC 2331, NGC 2355, NGC 2395; the Geminids are a bright meteor shower that peaks on December 13–14. It has a maximum rate of 100 meteors per hour, making it
Alabama is a state in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east and the Gulf of Mexico to the south, Mississippi to the west. Alabama is the 30th largest by area and the 24th-most populous of the U. S. states. With a total of 1,500 miles of inland waterways, Alabama has among the most of any state. Alabama is nicknamed the Yellowhammer State, after the state bird. Alabama is known as the "Heart of Dixie" and the "Cotton State"; the state tree is the longleaf pine, the state flower is the camellia. Alabama's capital is Montgomery; the largest city by population is Birmingham. The oldest city is Mobile, founded by French colonists in 1702 as the capital of French Louisiana. From the American Civil War until World War II, like many states in the southern U. S. suffered economic hardship, in part because of its continued dependence on agriculture. Similar to other former slave states, Alabamian legislators employed Jim Crow laws to disenfranchise and otherwise discriminate against African Americans from the end of the Reconstruction Era up until at least the 1970s.
Despite the growth of major industries and urban centers, white rural interests dominated the state legislature from 1901 to the 1960s. During this time, urban interests and African Americans were markedly under-represented. Following World War II, Alabama grew as the state's economy changed from one based on agriculture to one with diversified interests; the state's economy in the 21st century is based on management, finance, aerospace, mineral extraction, education and technology. The European-American naming of the Alabama River and state was derived from the Alabama people, a Muskogean-speaking tribe whose members lived just below the confluence of the Coosa and Tallapoosa rivers on the upper reaches of the river. In the Alabama language, the word for a person of Alabama lineage is Albaamo; the suggestion that "Alabama" was borrowed from the Choctaw language is unlikely. The word's spelling varies among historical sources; the first usage appears in three accounts of the Hernando de Soto expedition of 1540: Garcilaso de la Vega used Alibamo, while the Knight of Elvas and Rodrigo Ranjel wrote Alibamu and Limamu in transliterations of the term.
As early as 1702, the French called the tribe the Alibamon, with French maps identifying the river as Rivière des Alibamons. Other spellings of the name have included Alibamu, Albama, Alibama, Alabamu, Allibamou. Sources disagree on the word's meaning; some scholars suggest the word comes from amo. The meaning may have been "clearers of the thicket" or "herb gatherers", referring to clearing land for cultivation or collecting medicinal plants; the state has numerous place names of Native American origin. However, there are no correspondingly similar words in the Alabama language. An 1842 article in the Jacksonville Republican proposed it meant "Here We Rest." This notion was popularized in the 1850s through the writings of Alexander Beaufort Meek. Experts in the Muskogean languages have not found any evidence to support such a translation. Indigenous peoples of varying cultures lived in the area for thousands of years before the advent of European colonization. Trade with the northeastern tribes by the Ohio River began during the Burial Mound Period and continued until European contact.
The agrarian Mississippian culture covered most of the state from 1000 to 1600 AD, with one of its major centers built at what is now the Moundville Archaeological Site in Moundville, Alabama. This is the second-largest complex of the classic Middle Mississippian era, after Cahokia in present-day Illinois, the center of the culture. Analysis of artifacts from archaeological excavations at Moundville were the basis of scholars' formulating the characteristics of the Southeastern Ceremonial Complex. Contrary to popular belief, the SECC appears to have no direct links to Mesoamerican culture, but developed independently; the Ceremonial Complex represents a major component of the religion of the Mississippian peoples. Among the historical tribes of Native American people living in present-day Alabama at the time of European contact were the Cherokee, an Iroquoian language people. While part of the same large language family, the Muskogee tribes developed distinct cultures and languages. With exploration in the 16th century, the Spanish were the first Europeans to reach Alabama.
The expedition of Hernando de Soto passed through Mabila and other parts of the state in 1540. More than 160 years the French founded the region's first European settlement at Old Mobile in 1702; the city was moved to the current site of Mobile in 1711. This area was claimed by the French from 1702 to 1763 as part of La Louisiane. After the French lost to the British in the Seven Years' War, it became part of British West Florida from 1763 to 1783. After the United States victory in the American Revolutionary War, the territory was divided between the United States and Spain; the latter retained control of this western territory from 1783 until the surrender of the Spanish garrison at Mobile to U. S. forces on April 13, 1813. Thomas Bassett, a loyalist to the British monarchy during the Revolutionary era, was one of the earliest white settlers in the state
The Milky Way is the galaxy that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye; the term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος. From Earth, the Milky Way appears as a band. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610; until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies; the Milky Way is a barred spiral galaxy with a diameter between 200,000 light-years. It is estimated to contain 100 -- more than 100 billion planets; the Solar System is located at a radius of 26,490 light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust.
The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, assumed to be a supermassive black hole of 4.100 million solar masses. Stars and gases at a wide range of distances from the Galactic Center orbit at 220 kilometers per second; the constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much of the mass of the Milky Way is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This conjectural mass has been termed "dark matter"; the rotational period is about 240 million years at the radius of the Sun. The Milky Way as a whole is moving at a velocity of 600 km per second with respect to extragalactic frames of reference; the oldest stars in the Milky Way are nearly as old as the Universe itself and thus formed shortly after the Dark Ages of the Big Bang. The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, itself a component of the Laniakea Supercluster.
The Milky Way is visible from Earth as a hazy band of white light, some 30° wide, arching across the night sky. In night sky observing, although all the individual naked-eye stars in the entire sky are part of the Milky Way, the term “Milky Way” is limited to this band of light; the light originates from the accumulation of unresolved stars and other material located in the direction of the galactic plane. Dark regions within the band, such as the Great Rift and the Coalsack, are areas where interstellar dust blocks light from distant stars; the area of sky that the Milky Way obscures is called the Zone of Avoidance. The Milky Way has a low surface brightness, its visibility can be reduced by background light, such as light pollution or moonlight. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be visible. It should be visible if the limiting magnitude is +5.1 or better and shows a great deal of detail at +6.1. This makes the Milky Way difficult to see from brightly lit urban or suburban areas, but prominent when viewed from rural areas when the Moon is below the horizon.
Maps of artificial night sky brightness show that more than one-third of Earth's population cannot see the Milky Way from their homes due to light pollution. As viewed from Earth, the visible region of the Milky Way's galactic plane occupies an area of the sky that includes 30 constellations; the Galactic Center lies in the direction of Sagittarius. From Sagittarius, the hazy band of white light appears to pass around to the galactic anticenter in Auriga; the band continues the rest of the way around the sky, back to Sagittarius, dividing the sky into two equal hemispheres. The galactic plane is inclined by about 60° to the ecliptic. Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic, relative to the galactic plane; the north galactic pole is situated at right ascension 12h 49m, declination +27.4° near β Comae Berenices, the south galactic pole is near α Sculptoris.
Because of this high inclination, depending on the time of night and year, the arch of the Milky Way may appear low or high in the sky. For observers from latitudes 65° north to 65° south, the Milky Way passes directly overhead twice a day; the Milky Way is the second-largest galaxy in the Local Group, with its stellar disk 100,000 ly in diameter and, on average 1,000 ly thick. The Milky Way is 1.5 trillion times the mass of the Sun. To compare the relative physical scale of the Milky Way, if the Solar System out to Neptune were the size of a US quarter, the Milky Way would be the size of the contiguous United States. There is a ring-like filament of stars rippling above and below the flat galactic plane, wrapping around the Milky Way at a diameter of 150,000–180,000 light-years, which may be part of the Milky Way itself. Estimates of the mass of the Milky Way vary, depending upon the method and data used; the low end of the estimate range is 5.8×1011 solar masses, somewhat less than that of the Andromeda Galaxy.
Measurements using the Very Long Baseline Array in 2009 found
Orion is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most recognizable constellations in the night sky, it was named after a hunter in Greek mythology. Its brightest stars are a blue-white and a red supergiant, respectively; the earliest depiction, linked to the constellation of Orion is a prehistoric mammoth ivory carving found in a cave in the Ach valley in West Germany in 1979. Archaeologists have estimated it to have been fashioned 32,000 to 38,000 years ago; the distinctive pattern of Orion has been recognized in numerous cultures around the world, many myths have been associated with it. Orion has been used as a symbol in the modern world; the Babylonian star catalogues of the Late Bronze Age name Orion MULSIPA. ZI. AN. NA, "The Heavenly Shepherd" or "True Shepherd of Anu" – Anu being the chief god of the heavenly realms; the Babylonian constellation was sacred to Papshukal and Ninshubur, both minor gods fulfilling the role of'messenger to the gods'.
Papshukal was associated with the figure of a walking bird on Babylonian boundary stones, on the star map the figure of the Rooster was located below and behind the figure of the True Shepherd—both constellations represent the herald of the gods, in his bird and human forms respectively. In ancient Egypt, the stars of Orion were regarded as a god, called Sah; because Orion rises before Sirius, the star whose heliacal rising was the basis for the Solar Egyptian calendar, Sah was linked with Sopdet, the goddess who personified Sirius. The god Sopdu was said to be the son of Sopdet. Sah was syncretized with Osiris, while Sopdet was syncretized with Isis. In the Pyramid Texts, from the 24th and 23rd centuries BC, Sah was one of many gods whose form the dead pharaoh was said to take in the afterlife; the Armenians identified their legendary founder Hayk with Orion. Hayk is the name of the Orion constellation in the Armenian translation of the Bible; the Bible mentions Orion three times, naming it "Kesil".
Though, this name is etymologically connected with "Kislev", the name for the ninth month of the Hebrew calendar, which, in turn, may derive from the Hebrew root K-S-L as in the words "kesel, kisla", i.e. hope for winter rains.: Job 9:9, Job 38:31, Amos 5:8. In ancient Aram, the constellation was known as Nephîlā′, the Nephilim may have been Orion's descendants. Orion's current name derives from Greek mythology, in which Orion was a gigantic, supernaturally strong hunter of ancient times, born to Euryale, a Gorgon, Poseidon, god of the sea in the Graeco-Roman tradition. One myth recounts Gaia's rage at Orion, who dared to say that he would kill every animal on the planet; the angry goddess tried to dispatch Orion with a scorpion. This is given as the reason that the constellations of Scorpius and Orion are never in the sky at the same time. However, the Serpent Bearer, revived Orion with an antidote; this is said to be the reason that the constellation of Ophiuchus stands midway between the Scorpion and the Hunter in the sky.
The constellation is mentioned in Horace's Odes, Homer's Odyssey and Iliad, Virgil's Aeneid In medieval Muslim astronomy, Orion was known as al-jabbar, "the giant". Orion's sixth brightest star, Saiph, is named from the Arabic, saif al-jabbar, meaning "sword of the giant". In China, Orion was one of the 28 lunar mansions Sieu （宿）, it is known as Shen （參） meaning "three", for the stars of Orion's Belt. The Chinese character 參 meant the constellation Orion; the Rig Veda refers to the Orion Constellation as Mriga. It is said that two bright stars in the front and two bright stars in the rear are The hunting dogs, the one comparatively less bright star in the middle and ahead of two front dogs is The hunter and three aligned bright stars are in the middle of all four hunting dogs is The Deer and three little aligned but less brighter stars is The Baby Deer; the Mriga means Deer, locally known as Harnu in folk parlance. There are many folk songs narrating the Harnu; the Malay called Orion's Belt Bintang Tiga Beradik.
In India, Nataraja ‘the cosmic dancer’ is seen in the constellation called Orion. In old Hungarian tradition, "Orion" is known as Reaper. In rediscovered myths, he is called Nimrod, the greatest hunter, father of the twins "Hunor" and "Magor"; the "π" and "o" stars form together the lifted scythe. In other Hungarian traditions, "Orion's belt" is known as "Judge's stick". In Scandinavian tradition, "Orion's belt" was known as Freyja's distaff; the Finns call the stars below it Väinämöisen viikate. Another name for the asterism of Alnilam and Mintaka is Väinämöisen vyö and the stars "hanging" from the belt as Kalevanmiekka. In Siberia, the Chukchi people see Orion as a hunter.
Betelgeuse designated α Orionis, is on average the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. It is a distinctly reddish, semiregular variable star whose apparent magnitude varies between 0.0 and 1.3, the widest range of any first-magnitude star. Betelgeuse is one of three stars that make up the Winter Triangle asterism, it marks the center of the Winter Hexagon. If the human eye could view all wavelengths of radiation, Betelgeuse would be the brightest star in the night sky. Classified as a red supergiant of spectral type M1-2, the star is one of the largest stars visible to the naked eye. If Betelgeuse were at the center of the Solar System, its surface would extend past the asteroid belt engulfing the orbits of Mercury, Earth and Jupiter. However, there are several other red supergiants in the Milky Way that could be larger, such as Mu Cephei and VY Canis Majoris. Calculations of its mass range from under ten to a little over twenty times that of the Sun.
It is calculated to be 640 light-years away, yielding an absolute magnitude of about −6. Less than 10 million years old, Betelgeuse has evolved because of its high mass. Having been ejected from its birthplace in the Orion OB1 Association—which includes the stars in Orion's Belt—this runaway star has been observed moving through the interstellar medium at a speed of 30 km/s, creating a bow shock over four light-years wide. Betelgeuse is in a late stage of stellar evolution, it is expected to explode as a supernova within the next million years. In 1920, Betelgeuse became the first extrasolar star to have the angular size of its photosphere measured. Subsequent studies have reported an angular diameter ranging from 0.042 to 0.056 arcseconds, with the differences ascribed to the non-sphericity, limb darkening and varying appearance at different wavelengths. It is surrounded by a complex, asymmetric envelope 250 times the size of the star, caused by mass loss from the star itself; the angular diameter of Betelgeuse is only exceeded by the Sun.
Α Orionis is the star's designation given by Johann Bayer in 1603. The traditional name Betelgeuse is derived from the Arabic إبط الجوزاء Ibṭ al-Jauzā’, meaning "the underarm of Orion", or يد الجوزاء Yad al-Jauzā’, meaning "the hand of Orion". In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog and standardize proper names for stars; the WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Betelgeuse for this star. It is now so entered in the IAU Catalog of Star Names. Betelgeuse and its red coloration have been noted since antiquity. In the nineteenth century, before modern systems of stellar classification, Angelo Secchi included Betelgeuse as one of the prototypes for his Class III stars. By contrast, three centuries before Ptolemy, Chinese astronomers observed Betelgeuse as having a yellow coloration; the variation in Betelgeuse's brightness was first described in 1836 by Sir John Herschel, when he published his observations in Outlines of Astronomy.
From 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone Rigel in October 1837 and again in November 1839. A 10-year quiescent period followed. Observers recorded unusually high maxima with an interval of years, but only small variations from 1957 to 1967; the records of the American Association of Variable Star Observers show a maximum brightness of 0.2 in 1933 and 1942, a minimum of 1.2, observed in 1927 and 1941. This variability in brightness may explain why Johann Bayer, with the publication of his Uranometria in 1603, designated the star alpha as it rivaled the brighter Rigel. From Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the Inuit regarded it as brighter, one local name was Ulluriajjuaq "large star". In 1920, Albert Michelson and Francis Pease mounted a 6-meter interferometer on the front of the 2.5-meter telescope at Mount Wilson Observatory. Helped by John Anderson, the trio measured the angular diameter of Betelgeuse at 0.047", a figure which resulted in a diameter of 3.84 × 108 km based on the parallax value of 0.018".
However, limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements. The 1950s and 1960s saw two developments that would affect stellar convection theory in red supergiants: the Stratoscope projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of Martin Schwarzschild and his colleague at Princeton University, Richard Härm; this book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's turbulence, produced some of the finest images of solar granules and sunspots seen, thus confirming the existence of convection in the solar atmosphere. Astronomers in the 1970s saw some major advances in astronomical imaging technology beginning with Antoine Labeyrie's invention of speckle interferometry, a pr
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, moons and galaxies – in either observational or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies. Related but distinct subjects like physical cosmology. Astronomers fall under either of two main types: observational and theoretical. Observational astronomers analyze the data. In contrast, theoretical astronomers create and investigate models of things that cannot be observed; because it takes millions to billions of years for a system of stars or a galaxy to complete a life cycle, astronomers must observe snapshots of different systems at unique points in their evolution to determine how they form and die. They use these data to create models or simulations to theorize how different celestial objects work.
Further subcategories under these two main branches of astronomy include planetary astronomy, galactic astronomy, or physical cosmology. Astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws. Today, that distinction has disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are educated individuals who have a Ph. D. in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although they quite have other duties such as teaching, building instruments, or aiding in the operation of an observatory; the number of professional astronomers in the United States is quite small. The American Astronomical Society, the major organization of professional astronomers in North America, has 7,000 members; this number includes scientists from other fields such as physics and engineering, whose research interests are related to astronomy.
The International Astronomical Union comprises 10,145 members from 70 different countries who are involved in astronomical research at the Ph. D. beyond. Contrary to the classical image of an old astronomer peering through a telescope through the dark hours of the night, it is far more common to use a charge-coupled device camera to record a long, deep exposure, allowing a more sensitive image to be created because the light is added over time. Before CCDs, photographic plates were a common method of observation. Modern astronomers spend little time at telescopes just a few weeks per year. Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field.
Those who become astronomers have a broad background in maths and computing in high school. Taking courses that teach how to research and present papers are invaluable. In college/university most astronomers get a Ph. D. in astronomy or physics. While there is a low number of professional astronomers, the field is popular among amateurs. Most cities have amateur astronomy clubs that meet on a regular basis and host star parties; the Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. Like any hobby, most people who think of themselves as amateur astronomers may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to the ambitious, who own science-grade telescopes and instruments with which they are able to make their own discoveries and assist professional astronomers in research.
List of astronomers List of women astronomers List of Muslim astronomers List of French astronomers List of Hungarian astronomers List of Russian astronomers and astrophysicists List of Slovenian astronomers Dallal, Ahmad. "Science and Technology". In Esposito, John; the Oxford History of Islam. Oxford University Press, New York. ISBN 0-300-15911-0. Kennedy, E. S.. "A Survey of Islamic Astronomical Tables. 46. Philadelphia: American Philosophical Society. Toomer, Gerald. "Al-Khwārizmī, Abu Jaʿfar Muḥammad ibn Mūsā". In Gillispie, Charles Coulston. Dictionary of Scientific Biography. 7. New York: Charles Scribner's Sons. ISBN 0-684-16962-2. American Astronomical Society European Astronomical Society International Astronomical Union Astronomical Society of the Pacific Space's astronomy news