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112-429: An asterism is an observed pattern or group of stars in the sky . Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the 88 formally defined constellations . Constellations are based on asterisms, but unlike asterisms, constellations outline and today completely divide the sky and all its celestial objects into regions around their central asterisms. For example,

224-414: A common proper motion with Canopus. The projected separation of the M dwarf 2MASS J06234738-5351131 ("Canopus B") is approximately 1.9 parsecs. However, despite this large separation, it is still within the estimated tidal radius (2.9 parsecs) for the massive star Canopus. Since it is more luminous than any star closer to Earth, Canopus has been the brightest star in the night sky during three epochs over

336-565: A limb-darkened value of 6.86  mas , close to the accepted modern value. Very-long-baseline interferometry has been used to calculate Canopus' angular diameter at 6.9  mas . Combined with distance calculated from its Hipparcos parallax, this gives it a radius of 71 times that of the Sun . If it were at the centre of the Solar System, it would extend 90% of the way to the orbit of Mercury . The radius and temperature relative to

448-490: A neutrino telescope . Neutrino astronomy is motivated by the possibility of observing processes that are inaccessible to optical telescopes , such as the Sun's core . Gravitational wave detectors are being designed that may capture events such as collisions of massive objects such as neutron stars or black holes . Robotic spacecraft are also being increasingly used to make highly detailed observations of planets within

560-476: A science , the study of astronomy is somewhat hindered in that direct experiments with the properties of the distant universe are not possible. However, this is partly compensated by the fact that astronomers have a vast number of visible examples of stellar phenomena that can be examined. This allows for observational data to be plotted on graphs, and general trends recorded. Nearby examples of specific phenomena, such as variable stars , can then be used to infer

672-408: A broad spectrum. Later the grating spectrograph was developed, which reduced the amount of light loss compared to prisms and provided higher spectral resolution. The spectrum can be photographed in a long exposure, allowing the spectrum of faint objects (such as distant galaxies) to be measured. Stellar photometry came into use in 1861 as a means of measuring stellar colors . This technique measured

784-428: A changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence 'steadfast'. The south celestial pole can be approximately located using Canopus and two different bright stars. The first, Achernar , makes an equilateral triangle between the stars and the south pole. One can also locate the pole more roughly using an imaginary line between Sirius and Canopus; Canopus will be approximately at

896-405: A chemical film is much higher than any electronic detector yet constructed. Prior to the invention of photography, all astronomy was done with the naked eye. However, even before films became sensitive enough, scientific astronomy moved entirely to film, because of the overwhelming advantages: The blink comparator is an instrument that is used to compare two nearly identical photographs made of

1008-410: A cow, and ordered their medicine men to roll bone dice and read the fortune for the coming year. To the ǀXam -speaking Bushmen of South Africa, Canopus and Sirius signalled the appearance of termites and flying ants. They also believed that stars had the power to cause death and misfortune, and they would pray to Sirius and Canopus in particular to impart good fortune or skill. The ǃKung people of

1120-464: A critical role in observational astronomy for over a century, but in the last 30 years it has been largely replaced for imaging applications by digital sensors such as CCDs and CMOS chips. Specialist areas of astronomy such as photometry and interferometry have utilised electronic detectors for a much longer period of time. Astrophotography uses specialised photographic film (or usually a glass plate coated with photographic emulsion ), but there are

1232-413: A curved mirror, for example, require the surface to be within a fraction of a wavelength of light of a particular conic shape. Many modern "telescopes" actually consist of arrays of telescopes working together to provide higher resolution through aperture synthesis . Large telescopes are housed in domes, both to protect them from the weather and to stabilize the environmental conditions. For example, if

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1344-442: A few wavelength "windows") far infrared astronomy , so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays is a rapidly expanding branch of astronomy. For much of the history of observational astronomy, almost all observation was performed in the visual spectrum with optical telescopes . While

1456-524: A high number of cloudless days and generally possess good atmospheric conditions (with good seeing conditions). The peaks of the islands of Mauna Kea, Hawaii and La Palma possess these properties, as to a lesser extent do inland sites such as Llano de Chajnantor , Paranal , Cerro Tololo and La Silla in Chile . These observatory locations have attracted an assemblage of powerful telescopes, totalling many billion US dollars of investment. The darkness of

1568-510: A magnetic field that varies with the same period, detected by the Zeeman splitting of its spectral lines. Canopus is bright at microwave wavelengths, one of the few F-class stars to be detected by radio. The rotation period of the star is not accurately known, but may be over three hundred days. The projected rotational velocity has been measured at 9 km/s. An early interferometric measurement of its angular diameter in 1968 gave

1680-410: A number of drawbacks, particularly a low quantum efficiency , of the order of 3%, whereas CCDs can be tuned for a QE >90% in a narrow band. Almost all modern telescope instruments are electronic arrays, and older telescopes have been either been retrofitted with these instruments or closed down. Glass plates are still used in some applications, such as surveying, because the resolution possible with

1792-469: A paper dating Tasmanian Aboriginal oral tradition to the late Pleistocene, when Canopus was much closer to the South celestial pole . Canopus appears on the flag of Brazil , symbolising the state of Goiás . Two U.S. Navy submarine tenders have been named after Canopus, the first serving from 1922 to 1942 and the second serving from 1965 to 1994. The Royal Navy built nine Canopus-class ships of

1904-504: A similar brightness to each other. The larger brighter asterisms are useful for people who are familiarizing themselves with the night sky. The patterns of stars seen in asterisms are not necessarily a product of any physical association between the stars, but are rather the result of the particular perspectives of their observations. For example the Summer Triangle is a purely observational physically unrelated group of stars, but

2016-520: A star had been used. Canopus was little-studied by western scientists before the 20th century. It was given a spectral class of F in 1897, an early use of this extension to Secchi class I, applied to those stars where the hydrogen lines are relatively weak and the calcium K line relatively strong. It was given as a standard star of F0 in the Henry Draper Catalogue , with the spectral type F0 described as having hydrogen lines half

2128-573: Is almost exactly the latitude of Lick Observatory on Mt. Hamilton, California , from which it is readily visible because of the effects of elevation and atmospheric refraction , which add another degree to its apparent altitude. Under ideal conditions, it can be spotted as far north as latitude 37° 31′ from the Pacific coast. Another northernmost record of visibility came from Mount Nemrut in Turkey, latitude 37° 59′. It

2240-411: Is based on the region of the electromagnetic spectrum observed: In addition to using electromagnetic radiation, modern astrophysicists can also make observations using neutrinos , cosmic rays or gravitational waves . Observing a source using multiple methods is known as multi-messenger astronomy . Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere

2352-453: Is less yellow than Altair or Procyon , with indices measured as 0.22 and 0.42, respectively. Some observers may have perceived Canopus as yellow-tinged because it is low in the sky and hence subject to atmospheric effects. Patrick Moore said that it never appeared anything but white to him. The bolometric correction for Canopus is 0.00, indicating that the visual absolute magnitude and bolometric absolute magnitude are equal. Canopus

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2464-543: Is lined up on the pair and oriented using position wires that lie at right angles to the star separation. The movable wires are then adjusted to match the two star positions. The separation of the stars is then read off the instrument, and their true separation determined based on the magnification of the instrument. A vital instrument of observational astronomy is the spectrograph . The absorption of specific wavelengths of light by elements allows specific properties of distant bodies to be observed. This capability has resulted in

2576-488: Is more easily visible in places such as the Gulf Coast and Florida, and the island of Crete (Greece) where the best season for viewing it around 9 p.m. is during late January and early February. Canopus has a B–V color index of +0.15—where 0 is a blue-white—indicating it is essentially white, although it has been described as yellow-white. Canopus' spectral type has been given as F0 and the incrementally warmer A9. It

2688-529: Is relatively transparent at the wavelengths being detected. Observatories are usually located at high altitudes so as to minimise the absorption and distortion caused by the Earth's atmosphere. Some wavelengths of infrared light are heavily absorbed by water vapor , so many infrared observatories are located in dry places at high altitude, or in space. The atmosphere is opaque at the wavelengths used by X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for

2800-565: Is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus . The third is in the right foote of the Centaure ." In the Southern Hemisphere , Canopus and Sirius are both visible high in the sky simultaneously, and reach a meridian just 21 min apart. Brighter than first magnitude , Canopus can be seen by naked eye in the early twilight. Mostly visible in mid to late summer in

2912-719: Is used for other stars and constellations throughout Polynesia. Kapae-poto , "Short horizon", referred to it rarely setting as seen in New Zealand; Kauanga ("Solitary") was the name for Canopus only when it was the last star visible before sunrise. The people of the Society Islands had two names for Canopus, as did the Tuamotu people. The Society Islanders called Canopus Taurua-e-tupu-tai-nanu , "Festivity-whence-comes-the-flux-of-the-sea", and Taurua-nui-o-te-hiti-apatoa "Great-festivity-of-the-border-of-the-south", and

3024-680: The Alfonsine tables , Suhel ponderosus, a Latinization of Al Suhayl al Wazn . Its Greek name was revived during the Renaissance . The Arabic Muslim astronomer Ibn Rushd went to Marrakesh (in Morocco) to observe the star in 1153, as it was invisible in his native Córdoba , Al-Andalus . He used the different visibility in different latitudes to argue that the Earth is round , following Aristotle's argument which held that such an observation

3136-822: The Bright Star Catalogue as HR 2326, the Henry Draper Catalogue as HD 45348, and the Hipparcos catalogue as HIP 30438. Flamsteed did not number this southern star, but Benjamin Apthorp Gould gave it the number 7 (7 G. Carinae) in his Uranometria Argentina . An occasional name seen in English is Soheil , or the feminine Soheila; in Turkish is Süheyl , or the feminine Süheyla, from the Arabic name for several bright stars, سهيل suhayl , and Canopus

3248-544: The Gaia satellite and there is no published Gaia parallax for it. At present the star is drifting further away from the Sun with a radial velocity of 20 km/s. Some 3.1 million years ago it made the closest approach to the Sun at a distance of about 172 ly (53 pc). Canopus is orbiting the Milky Way with a heliocentric velocity of 24.5 km/s and a low eccentricity of 0.065. The absorption lines in

3360-485: The Galactic Center . Some asterisms refer to portions of traditional constellation figures. These include: Other asterisms are also composed of stars from one constellation, but do not refer to the traditional figures. Other asterisms that are formed from stars in more than one constellation. Asterisms range from the large and obvious to the small, and even telescopic. Observational astronomy As

3472-601: The International Astronomical Union organized a Working Group on Star Names (WGSN) 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 Canopus for this star. Canopus is now included in the IAU Catalog of Star Names . Canopus traditionally marked the steering oar of

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3584-892: The Kalahari Desert in Botswana held Canopus and Capella to be the horns of tshxum (the Pleiades), the appearance of all three marking the end of the dry season and start of the rainy season. The Navajo observed the star and named it Maʼii Bizòʼ , the “Coyote Star”. According to legend, Maʼii (Coyote) took part in the naming and placing of the star constellations during the creation of the universe. He placed Canopus directly south, naming it after himself. The Kalapalo people of Mato Grosso state in Brazil saw Canopus and Procyon as Kofongo "Duck", with Castor and Pollux representing his hands. The asterism's appearance signified

3696-723: The Shiji ( Records of the Grand Historian ) completed in 94 BC by Chinese historian Sima Qian . Drawing on sources from the Warring States period , he noted it to be the southern counterpart of Sirius , and wrote of a sanctuary dedicated to it established by Emperor Qin Shi Huang between 221 and 210 BC. During the Han dynasty , the star was auspicious, its appearance in the southern sky heralding peace and absence war. From

3808-598: The Solar System , so that the field of planetary science now has significant cross-over with the disciplines of geology and meteorology . The key instrument of nearly all modern observational astronomy is the telescope . This serves the dual purposes of gathering more light so that very faint objects can be observed, and magnifying the image so that small and distant objects can be observed. Optical astronomy requires telescopes that use optical components of great precision. Typical requirements for grinding and polishing

3920-414: The Sun , Canopus is a bright giant of spectral type A9 , so it is essentially white when seen with the naked eye. It has a luminosity over 10,000 times the luminosity of the Sun , is eight times as massive , and has expanded to 71 times the Sun's radius . Its enlarged photosphere has an effective temperature of around 7400 K . Canopus is undergoing core helium burning and is currently in

4032-470: The United Kingdom , this has led to campaigns for the reduction of light pollution . The use of hoods around street lights not only improves the amount of light directed toward the ground, but also helps reduce the light directed toward the sky. Atmospheric effects ( astronomical seeing ) can severely hinder the resolution of a telescope. Without some means of correcting for the blurring effect of

4144-470: The adaptive optics technology, image quality can approach the theoretical resolution capability of the telescope. Filters are used to view an object at particular frequencies or frequency ranges. Multilayer film filters can provide very precise control of the frequencies transmitted and blocked, so that, for example, objects can be viewed at a particular frequency emitted only by excited hydrogen atoms. Filters can also be used to partially compensate for

4256-408: The corona . With the discovery of radio waves, radio astronomy began to emerge as a new discipline in astronomy. The long wavelengths of radio waves required much larger collecting dishes in order to make images with good resolution, and later led to the development of the multi-dish interferometer for making high-resolution aperture synthesis radio images (or "radio maps"). The development of

4368-462: The main sequence . The position of Canopus in the H–R diagram indicates that it is currently in the core-helium burning phase. It is an intermediate mass star that has left the red-giant branch before its core became degenerate and is now in a blue loop . Models of stellar evolution in the blue loop phase show that the length of the blue loop is strongly affected by rotation and mixing effects inside

4480-649: The mythological Canopus , who was a navigator for Menelaus , king of Sparta . The acronycal rising marked the date of the Ptolemaia festival in Egypt. In ancient India, it was named Agastya after the revered Vedic sage. For Chinese astronomers, it was known as the Old Man of the South Pole . In Islamic astronomy , it is Suhail or Suhayl , a name that is also commonly used to imply rareness of appearance (as

4592-784: The Canopus infrequently appeared to a gazer at Middle Eastern latitutes) The name Canopus is a Latinisation of the Ancient Greek name Κάνωβος/Kanôbos, recorded in Claudius Ptolemy's Almagest (c.150 AD). Eratosthenes used the same spelling. Hipparchos wrote it as Κάνωπος. John Flamsteed wrote Canobus, as did Edmond Halley in his 1679 Catalogus Stellarum Australium . The name has two possible derivations, both listed in Richard Hinckley Allen 's seminal Star Names: Their Lore and Meaning . In 2016,

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4704-702: The Chinese capital of Chang'an . The Chinese astronomer Yi Xing had journeyed south to chart Canopus and other far southern stars in 724 AD. Its personification as the Old Man Star was popularised in the Tang dynasty , where it appeared often in poetry and memorials. Later still, during the Ming dynasty , the star was established as one of the Three Stars (Fu Lo Shou), appearing frequently in art and literature of

4816-434: The Earth's atmosphere is relatively transparent in this portion of the electromagnetic spectrum , most telescope work is still dependent on seeing conditions and air transparency, and is generally restricted to the night time. The seeing conditions depend on the turbulence and thermal variations in the air. Locations that are frequently cloudy or suffer from atmospheric turbulence limit the resolution of observations. Likewise

4928-512: The Elder mentions 72 asterisms in his book Naturalis Historia . A general list containing 48 constellations likely began to develop with the astronomer Hipparchus (c. 190 – c. 120 BCE). As constellations were considered to be composed only of the stars that constituted the figure, it was always possible to use any leftover stars to create and squeeze in a new grouping among the established constellations. Exploration by Europeans to other parts of

5040-482: The MK spectral classification scheme, Canopus was assigned class Iab indicating an intermediate luminosity supergiant. This was based on the relative strengths of certain spectral lines understood to be sensitive to the luminosity of a star. In the Bright Star Catalogue 5th edition it is given the spectral class F0II, the luminosity class indicating a bright giant . Balmer line profiles and oxygen line strengths indicate

5152-529: The Ptolemaia festival, which was held every four years, from 262 to 145 BC. The Greek astronomer Posidonius used observations of Canopus to calculate quite accurately the Earth's circumference , around 90 – 120 BC. In Indian Vedic literature , Canopus is associated with the sage Agastya , one of the ancient siddhars and rishis (the others are associated with the stars of the Big Dipper ). To Agastya,

5264-563: The Southern Hemisphere, Canopus culminates at midnight on December 27, and at 9 PM on February 11. When seen from latitudes south of 37° 18′ S, Canopus is a circumpolar star . Since Canopus is so far south in the sky, it never rises in mid- to far-northern latitudes; in theory the northern limit of visibility is latitude 37° 18′ north. This is just south of Athens , San Francisco , and Seoul , and very close to Seville and Agrigento . It

5376-570: The Sun means that it is 10,700 times more luminous than the Sun, and its position in the H-R diagram relative to theoretical evolutionary tracks means that it is 8.0 ± 0.3 times as massive as the Sun. Measurements of its shape find a 1.1° departure from spherical symmetry. Canopus is a source of X-rays , which are probably produced by its corona, magnetically heated to several million Kelvin . The temperature has likely been stimulated by fast rotation combined with strong convection percolating through

5488-565: The Tuamotu people called the star Te Tau-rari and Marere-te-tavahi , the latter said to be the true name for the former, "He-who-stands-alone". In the Guanche mythology of the island of Tenerife (Spain), the star Canopus was linked with the goddess Chaxiraxi . The Tswana people of Botswana knew Canopus as Naka . Appearing late in winter skies, it heralded increasing winds and a time when trees lose their leaves. Stock owners knew it

5600-415: The assumption of a very bright absolute magnitude for Canopus. Hipparcos established Canopus as being 310 light-years ( 95  parsecs ) from the Solar System ; this is based on its 2007 parallax measurement of 10.43 ± 0.53  mas . At 95 parsecs, the interstellar extinction for Canopus is low at 0.26 magnitudes. Canopus is too bright to be included in the normal observation runs of

5712-503: The asterism known as the Big Dipper or the Plough comprises the seven brightest stars in the constellation Ursa Major . Another asterism is the triangle , within the constellation of Capricornus . Asterisms range from simple shapes of just a few stars to more complex collections of many stars covering large portions of the sky. The stars themselves may be bright naked-eye objects or fainter, even telescopic, but they are generally all of

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5824-425: The behavior of more distant representatives. Those distant yardsticks can then be employed to measure other phenomena in that neighborhood, including the distance to a galaxy . Galileo Galilei turned a telescope to the heavens and recorded what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology. A traditional division of observational astronomy

5936-528: The body and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. The Hawaiian people called Canopus Ke Alii-o-kona-i-ka-lewa , "The chief of the southern expanse"; it was one of the stars used by Hawaiʻiloa and Ki when they traveled to the Southern Ocean . The Māori people of New Zealand/Aotearoa had several names for Canopus. Ariki ("High-born"),

6048-583: The brightest, and will remain so for a period of about 510,000 years. The southeastern wall of the Kaaba in Mecca is aligned with the rising point of Canopus, and is also named Janūb . The Bedouin people of the Negev and Sinai knew Canopus as Suhayl , and used it and Polaris as the two principal stars for navigation at night. Because it disappears below the horizon in those regions, it became associated with

6160-402: The coming of the rainy season and increase in manioc , a food staple fed to guests at feasts. Canopus is identified as the moiety ancestor Waa "Crow" to some Koori people in southeastern Australia. The Boorong people of northwestern Victoria recalled that War (Canopus) was the brother of Warepil (Sirius), and that he brought fire from the heavens and introduced it to humanity. His wife

6272-422: The discovery of the element of helium in the Sun's emission spectrum , and has allowed astronomers to determine a great deal of information concerning distant stars, galaxies, and other celestial bodies. Doppler shift (particularly " redshift ") of spectra can also be used to determine the radial motion or distance with respect to the Earth . Early spectrographs employed banks of prisms that split light into

6384-416: The distance, out to a limit imposed by the resolution of the instrument. The radial velocity of the star and changes in its position over time ( proper motion ) can be used to measure its velocity relative to the Sun. Variations in the brightness of the star give evidence of instabilities in the star's atmosphere, or else the presence of an occulting companion. The orbits of binary stars can be used to measure

6496-401: The distribution of stellar types. These tables can then be used to infer the age of the association. For distant galaxies and AGNs observations are made of the overall shape and properties of the galaxy, as well as the groupings where they are found. Observations of certain types of variable stars and supernovae of known luminosity , called standard candles , in other galaxies allows

6608-572: The earliest records are those of ancient India in the Vedanga Jyotisha and the Babylonians . Different cultures identified different constellations, although a few of the more obvious patterns tend to appear in the constellations of multiple cultures, such as those of Orion and Scorpius . As anyone could arrange and name a grouping of stars there was no distinct difference between a constellation and an asterism . For example, Pliny

6720-528: The effects of light pollution by blocking out unwanted light. Polarization filters can also be used to determine if a source is emitting polarized light, and the orientation of the polarization. Astronomers observe a wide range of astronomical sources, including high-redshift galaxies, AGNs , the afterglow from the Big Bang and many different types of stars and protostars. A variety of data can be observed for each object. The position coordinates locate

6832-451: The entire telescope to the same temperature as the surroundings. To prevent wind-buffet or other vibrations affecting observations, it is standard practice to mount the telescope on a concrete pier whose foundations are entirely separate from those of the surrounding dome and building. To do almost any scientific work requires that telescopes track objects as they wheel across the visible sky. In other words, they must smoothly compensate for

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6944-409: The evolution of galaxy forms. Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky . It is also designated α Carinae , which is romanized ( transliterated ) to Alpha Carinae . With a visual apparent magnitude of −0.74, it is outshone only by Sirius . Located around 310  light-years from

7056-492: The globe exposed them to stars previously unknown to them. Two astronomers particularly known for greatly expanding the number of southern constellations were Johann Bayer (1572–1625) and Nicolas Louis de Lacaille (1713–1762). Bayer had listed twelve figures made out of stars that were too far south for Ptolemy to have seen. Lacaille created 14 new groups, mostly for the area surrounding South Celestial Pole . Many of these proposed constellations have been formally accepted, but

7168-466: The horizon, while Eratosthenes and Ptolemy —observing from Alexandria —did, calling it Kanōbos . An Egyptian priestly poet in the time of Thutmose III mentions the star as Karbana, "the star which pours his light in a glance of fire, when he disperses the morning dew." Under the Ptolemies , the star was known as Ptolemaion ( Greek : Πτολεμαῖον) and its acronychal rising marked the date of

7280-440: The image nearly down to the level of individual photons , and can be designed to view in parts of the spectrum that are invisible to the eye. The ability to record the arrival of small numbers of photons over a period of time can allow a degree of computer correction for atmospheric effects, sharpening up the image. Multiple digital images can also be combined to further enhance the image, often known as "stacking". When combined with

7392-567: The imperial capital Chang'an , the star made a low transit across the southern sky, indicating true south to observers, and was often obscured by clouds. During this time it was also equated with Old Man of the South Pole (in Chinese : 南极老人 ; pinyin : Nanji Lǎorén ) Under this name, Canopus appears (albeit misplaced northwards) on the medieval Chinese manuscript the Dunhuang Star Chart , although it cannot be seen from

7504-490: The inference of the distance to the host galaxy. The expansion of space causes the spectra of these galaxies to be shifted, depending on the distance, and modified by the Doppler effect of the galaxy's radial velocity. Both the size of the galaxy and its redshift can be used to infer something about the distance of the galaxy. Observations of large numbers of galaxies are referred to as redshift surveys , and are used to model

7616-445: The launch of the Hipparcos satellite telescope, distance estimates for Canopus varied widely, from 96 light-years to 1200 light-years (or 30 to 370 parsecs). For example, an old distance estimate of 200 parsecs (652 light years) gave it a luminosity of 80,000  L ☉ , far higher than modern estimates. The closer distance was derived from parallax measurements of around 33  mas . The larger distance derives from

7728-479: The luminosity of the star as described by the Wilson-Bappu effect , but in the case of Canopus they indicate a luminosity much lower than that calculated by other methods. More detailed observations have shown that the emission line profiles are variable and may be due to plage areas on the surface of the star. Emission can also be found in other lines such as the h and k lines of ionised magnesium. Before

7840-450: The magnitude of a star at specific frequency ranges, allowing a determination of the overall color, and therefore temperature of a star. By 1951 an internationally standardized system of UBV- magnitudes ( U ltraviolet- B lue- V isual) was adopted. Photoelectric photometry using the CCD is now frequently used to make observations through a telescope. These sensitive instruments can record

7952-482: The microwave horn receiver led to the discovery of the microwave background radiation associated with the Big Bang . Radio astronomy has continued to expand its capabilities, even using radio astronomy satellites to produce interferometers with baselines much larger than the size of the Earth. However, the ever-expanding use of the radio spectrum for other uses is gradually drowning out the faint radio signals from

8064-450: The midpoint, being 36° one way to Sirius and 37° to the pole. Canopus's brightness and location well off the ecliptic make it useful for space navigation. Many spacecraft carry a special camera known as a "Canopus Star Tracker " plus a Sun sensor for attitude determination. Mariner 4 used Canopus for second axis stabilisation (after locking on the Sun) in 1964, the first time

8176-401: The night sky is an important factor in optical astronomy. With the size of cities and human populated areas ever expanding, the amount of artificial light at night has also increased. These artificial lights produce a diffuse background illumination that makes observation of faint astronomical features very difficult without special filters. In a few locations such as the state of Arizona and in

8288-483: The north foretell a mild winter. Food was offered to the star on its appearance. This name has several mythologies attached to it. One story tells of how Atutahi was left outside the basket representing the Milky Way when Tāne wove it. Another related myth about the star says that Atutahi was the first-born child of Rangi , who refused to enter the Milky Way and so turned it sideways and rose before it. The same name

8400-424: The object on the sky using the techniques of spherical astronomy , and the magnitude determines its brightness as seen from the Earth . The relative brightness in different parts of the spectrum yields information about the temperature and physics of the object. Photographs of the spectra allow the chemistry of the object to be examined. Parallax shifts of a star against the background can be used to determine

8512-791: The only such stars in their asterisms or constellations, with Canopus in the Argo Navis asterism south of Sirius, visually east of the Carina Nebula and near the Large Magellanic Cloud (both being first-magnitude deep-sky objects), Achernar in the Eridanus constellation east of Canopus, Fomalhaut in the Southern Fish constellation east of Achernar and Antares in the Scorpius constellation visually near

8624-411: The past four million years. Other stars appear brighter only during relatively temporary periods, during which they are passing the Solar System much closer than Canopus. About 90,000 years ago, Sirius moved close enough that it became brighter than Canopus, and that will remain so for another 210,000 years. But in 480,000 years, as Sirius moves further away and appears fainter, Canopus will once again be

8736-481: The precession of the Earth's axis the first rising of the star Canopus in Mesopotamia could be observed only from there at the southern meridian at midnight. Today, the star Sigma Sagittarii is known by the common name Nunki. Canopus was not visible to the mainland ancient Greeks and Romans ; it was, however, visible to the ancient Egyptians . Hence Aratus did not write of the star as it remained below

8848-447: The presence of the full Moon can brighten up the sky with scattered light, hindering observation of faint objects. For observation purposes, the optimal location for an optical telescope is undoubtedly in outer space . There the telescope can make observations without being affected by the atmosphere . However, at present it remains costly to lift telescopes into orbit . Thus the next best locations are certain mountain peaks that have

8960-442: The relative masses of each companion, or the total mass of the system. Spectroscopic binaries can be found by observing doppler shifts in the spectrum of the star and its close companion. Stars of identical masses that formed at the same time and under similar conditions typically have nearly identical observed properties. Observing a mass of closely associated stars, such as in a globular cluster , allows data to be assembled about

9072-669: The rest have remained as asterisms. In 1928, the International Astronomical Union (IAU) precisely divided the sky into 88 official constellations following geometric boundaries encompassing all of the stars within them. Any additional new selected groupings of stars or former constellations are often considered as asterisms. However, technical distinctions between the terms 'constellation' and 'asterism' often remain somewhat ambiguous. Some asterisms consist completely of bright first-magnitude stars , which mark out simple geometric shapes. Other asterisms consist partially of multiple first-magnitude stars. All other first-magnitude stars are

9184-462: The rotation of the Earth. Until the advent of computer controlled drive mechanisms, the standard solution was some form of equatorial mount , and for small telescopes this is still the norm. However, this is a structurally poor design and becomes more and more cumbersome as the diameter and weight of the telescope increases. The world's largest equatorial mounted telescope is the 200 inch (5.1 m) Hale Telescope , whereas recent 8–10 m telescopes use

9296-460: The same section of sky at different points in time. The comparator alternates illumination of the two plates, and any changes are revealed by blinking points or streaks. This instrument has been used to find asteroids , comets , and variable stars . The position or cross-wire micrometer is an implement that has been used to measure double stars . This consists of a pair of fine, movable lines that can be moved together or apart. The telescope lens

9408-450: The shifting atmosphere, telescopes larger than about 15–20 cm in aperture can not achieve their theoretical resolution at visible wavelengths. As a result, the primary benefit of using very large telescopes has been the improved light-gathering capability, allowing very faint magnitudes to be observed. However the resolution handicap has begun to be overcome by adaptive optics , speckle imaging and interferometric imaging , as well as

9520-400: The ship Argo Navis . German celestial cartographer Johann Bayer gave it—as the brightest star in the constellation—the designation of α Argus ( Latinised to Alpha Argus ) in 1603. In 1763, French astronomer Nicolas Louis de Lacaille divided the huge constellation into three smaller ones, and hence Canopus became α Carinae ( Latinised to Alpha Carinae ). It is listed in

9632-477: The size and luminosity of Canopus. When the effects of stellar rotation speed on spectral lines are accounted for, the MK spectral class of Canopus is adjusted to A9II. Its spectrum consists mostly of absorption lines on a visible continuum , but some emission has been detected. For example, the calcium K line has weak emission wings on each side of the strong central absorption line, first observed in 1966. The emission line profiles are usually correlated with

9744-537: The sky are also associated with states of being for some tribes; the Wailwun of northern New South Wales know Canopus as Wumba "deaf", alongside Mars as Gumba "fat" and Venus as Ngindigindoer "you are laughing". Tasmanian aboriginal lore holds that Canopus is Dromerdene , the brother of Moinee ; the two fought and fell out of the sky, with Dromerdene falling into Louisa Bay in southwest Tasmania. Astronomer Duane Hamacher has identified Canopus with Moinee in

9856-405: The so-called blue loop phase of its evolution , having already passed through the red-giant branch after exhausting the hydrogen in its core. Canopus is a source of X-rays , which are likely being emitted from its corona . The prominent appearance of Canopus means it has been the subject of mythological lore among many ancient peoples. Its proper name is generally considered to originate from

9968-413: The spectrum of Canopus shift slightly with a period of 6.9 d . This was first detected in 1906 and the Doppler variations were interpreted as orbital motion. An orbit was even calculated, but no such companion exists and the small radial velocity changes are due to movements in the atmosphere of the star. The maximum observed radial velocities are only 0.7 to 1.6  km/s . Canopus also has

10080-511: The star is said to be the 'cleanser of waters', and its rising coincides with the calming of the waters of the Indian Ocean . Canopus is described by Pliny the Elder and Gaius Julius Solinus as the largest, brightest and only source of starlight for navigators near Tamraparni island (ancient Sri Lanka) during many nights. Canopus was described as Shou Xing, the Star of Longevity, in

10192-498: The star's heliacal rising with ritual bathing and associated it with morning dew. Bright stars were important to the ancient Polynesians for navigation between the many islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations. Canopus served as the southern wingtip of a "Great Bird" constellation called Manu , with Sirius as

10304-480: The star's outer layers. The soft X-ray sub-coronal X-ray emission is much weaker than the hard X-ray coronal emission. The same behaviour has been measured in other F-class supergiants such as α Persei and is now believed to be a normal property of such stars. The spectrum of Canopus indicates that it spent some 30 million years of its existence as a blue-white main sequence star of around 10 solar masses, before exhausting its core hydrogen and evolving away from

10416-545: The star. It is difficult to determine whether a star is currently evolving towards hotter temperature or returning to cooler temperatures, since the evolutionary tracks for stars with different masses overlap during the blue loops. Canopus lies on the warm side of the instability strip and does not pulsate like Cepheid variables of a similar luminosity. However its atmosphere does appear to be unstable, showing strong signs of convection. Canopus may be massive enough to explode by an iron-core collapse supernova . Canopus

10528-678: The stars of Orion's Belt are all members of the Orion OB1 association and five of the seven stars of the Big Dipper are members of the Ursa Major Moving Group . Physical associations, such as the Hyades or Pleiades , can be asterisms in their own right and part of other asterisms at the same time. In many early civilizations, it was common to associate groups of stars in connect-the-dots stick-figure patterns. Some of

10640-473: The stars. For this reason, in the future radio astronomy might be performed from shielded locations, such as the far side of the Moon . The last part of the twentieth century saw rapid technological advances in astronomical instrumentation. Optical telescopes were growing ever larger, and employing adaptive optics to partly negate atmospheric blurring. New telescopes were launched into space, and began observing

10752-470: The strength of an A0 star and the calcium K line three times as strong as Hδ. American astronomer Jesse Greenstein was interested in stellar spectra and used the newly built Otto Struve Telescope at McDonald Observatory to analyze the star's spectrum in detail. In a 1942 paper, he reported that the spectrum is dominated by strong broad hydrogen lines. There are also absorption lines of carbon, nitrogen, oxygen, sulphur, iron, and many ionised metals. It

10864-705: The structurally better altazimuth mount , and are actually physically smaller than the Hale, despite the larger mirrors. As of 2006, there are design projects underway for gigantic alt-az telescopes: the Thirty Metre Telescope [1] , and the 100 m diameter Overwhelmingly Large Telescope . Amateur astronomers use such instruments as the Newtonian reflector , the Refractor and the increasingly popular Maksutov telescope . The photograph has served

10976-407: The temperature is different from one side of the telescope to the other, the shape of the structure changes, due to thermal expansion pushing optical elements out of position. This can affect the image. For this reason, the domes are usually bright white ( titanium dioxide ) or unpainted metal. Domes are often opened around sunset, long before observing can begin, so that air can circulate and bring

11088-716: The time. This symbolism spread into neighbouring cultures in Asia. In Japan, Canopus is known as Mera-boshi and Roujin-sei (the old man star), and in Mongolia, it was personified as the White Old Man. Although the link was known in Tibet, with names such as Genpo karpo ( Rgan po dkar po ) or Genkar ( Rgan dkar ) "White Old Man", the symbolism was not popular. Instead, Canopus was more commonly named Karma Rishi སྐར་མ་རི་ཥི། , derived from Indian mythology. Tibetans celebrated

11200-414: The triumphs of his general relativity theory). In addition to examination of the universe in the optical spectrum, astronomers have increasingly been able to acquire information in other portions of the electromagnetic spectrum. The earliest such non-optical measurements were made of the thermal properties of the Sun . Instruments employed during a solar eclipse could be used to measure the radiation from

11312-484: The universe in the infrared , ultraviolet , x-ray , and gamma ray parts of the electromagnetic spectrum, as well as observing cosmic rays . Interferometer arrays produced the first extremely high-resolution images using aperture synthesis at radio, infrared and optical wavelengths. Orbiting instruments such as the Hubble Space Telescope produced rapid advances in astronomical knowledge, acting as

11424-409: The use of space telescopes . Astronomers have a number of observational tools that they can use to make measurements of the heavens. For objects that are relatively close to the Sun and Earth, direct and very precise position measurements can be made against a more distant (and thereby nearly stationary) background. Early observations of this nature were used to develop very precise orbital models of

11536-399: The various planets, and to determine their respective masses and gravitational perturbations . Such measurements led to the discovery of the planets Uranus , Neptune , and (indirectly) Pluto . They also resulted in an erroneous assumption of a fictional planet Vulcan within the orbit of Mercury (but the explanation of the precession of Mercury's orbit by Einstein is considered one of

11648-603: The workhorse for visible-light observations of faint objects. New space instruments under development are expected to directly observe planets around other stars, perhaps even some Earth-like worlds. In addition to telescopes, astronomers have begun using other instruments to make observations. Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories, usually huge underground tanks. Nuclear reactions in stars and supernova explosions produce very large numbers of neutrinos , very few of which may be detected by

11760-467: Was Collowgullouric War ( Eta Carinae ). The Pirt-Kopan-noot people of western Victoria tell of Waa "Crow" falling in love with a queen, Gneeanggar "Wedge-tailed Eagle" (Sirius) and her six attendants (the Pleiades). His advances spurned, he hears that the women are foraging for grubs and so transforms himself into a grub. When the women dig him out, he changes into a giant and carries her off. The Kulin people know Canopus as Lo-an-tuka . Objects in

11872-405: Was known as Suhel / ˈ s uː h ɛ l / in medieval times. Alternative spellings include Suhail, Souhail, Suhilon, Suheyl, Sohayl, Suhayil, Shoel, Sohil, Soheil, Sahil, Suhayeel, Sohayil, Sihel, and Sihil. An alternative name was Wazn "weight" or Haḍar "ground" , implying the anchor stone used by ship, rather than being related to its low position near the horizon. Hence comes its name in

11984-454: Was known as a solitary star that appeared in the east, prompting people to weep and chant. They also named it Atutahi , Aotahi or Atuatahi , "Stand Alone". Its solitary nature indicates it is a tapu star, as tapu people are often solitary. Its appearance at the beginning of the Maruaroa season foretells the coming winter; light rays to the south indicate a cold wet winter, and to

12096-546: Was known to the ancient Mesopotamians and represented the city of Eridu in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. Canopus was called MUL.NUN by the Babylonians, which translates as "star of the city of Eridu". Eridu was the southernmost and one of the oldest Sumerian cities. From there is a good view to the south, so that about 6000 years ago due to

12208-466: Was only possible if the Earth was a relatively small sphere. English explorer Robert Hues brought Canopus to the attention of European observers in his 1592 work Tractatus de Globis , along with Achernar and Alpha Centauri , noting: "Now, therefore, there are but three Stars of the first magnitude that I could perceive in all those parts which are never seene here in England. The first of these

12320-565: Was previously proposed to be a member of the Scorpius–Centaurus association , however it is not located near the subgroups of that association, and has not been included as a Sco-Cen member in kinematic studies that used Hipparcos astrometric data. Canopus is not thought to be a member of any nearby young stellar groups. In 2014, astronomer Eric Mamajek reported that an extremely magnetically active M dwarf (having strong coronal X-ray emission), 1.16 degrees south of Canopus, appears to share

12432-442: Was studied in the ultraviolet by an early astronomical satellite, Gemini XI in 1966. The UV spectra were considered to be consistent with an F0 supergiant having a temperature of 6,900 K , the accepted parameters for Canopus at the time. New Zealand-based astronomers John Hearnshaw and Krishna Desikachary examined the spectrum in greater detail, publishing their results in 1982. When luminosity classes were added to

12544-650: Was time to put their sheep with rams. In southern Africa, the Sotho, Tswana and Venda people called Canopus Naka or Nanga , “the Horn Star”, while the Zulu and Swazi called it inKhwenkwezi "Brilliant star". It appears in the predawn sky in the third week of May. According to the Venda, the first person to see Canopus would blow a phalaphala horn from the top of a hill, getting a cow for a reward. The Sotho chiefs also awarded

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