137-570: New Earth may refer to: Books [ edit ] A New Earth: Awakening to Your Life's Purpose , a book by Eckhart Tolle "New Earth", the destination planet of Alpha Centauri featured in the sci-fi novel series First Ark to Alpha Centauri by A. Ahad Star Trek: New Earth , a series of Star Trek: The Original Series novels Media [ edit ] New Earth (film) (Dutch: Nieuwe Gronden ), 1934 documentary film by Joris Ivens New Earth (DC Comics) The current primary Earth in
274-402: A binary component. The AB designation, or older A×B , denotes the mass centre of a main binary system relative to companion star(s) in a multiple star system. AB-C refers to the component of Proxima Centauri in relation to the central binary, being the distance between the centre of mass and the outlying companion. Because the distance between Proxima (C) and either of Alpha Centauri A or B
411-597: A red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago. Sirius is colloquially known as the " Dog Star ", reflecting its prominence in its constellation , Canis Major (the Greater Dog). The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the " dog days " of summer for the ancient Greeks , while to
548-569: A bright giant). It is still around 25 times more luminous than the Sun. The closest large neighbouring star to Sirius is Procyon, 1.61 parsecs (5.24 ly) away. The Voyager 2 spacecraft, launched in 1977 to study the four giant planets in the Solar System, is expected to pass within 4.3 light-years (1.3 pc) of Sirius in approximately 296,000 years. Sirius is a binary star system consisting of two white stars orbiting each other with
685-555: A brilliant optical double star in the southern sky. It will then pass just north of the Southern Cross or Crux , before moving northwest and up towards the present celestial equator and away from the galactic plane . By about 26,700 CE , in the present-day constellation of Hydra , α Centauri will reach perihelion at 0.90 pc or 2.9 ly away, though later calculations suggest that this will occur in 27,000 AD. At its nearest approach, α Centauri will attain
822-468: A distance of 2.6 parsecs (8.6 ly), the Sirius system contains two of the eight nearest stars to the Sun, and it is the fifth closest stellar system to the Sun. This proximity is the main reason for its brightness, as with other near stars such as Alpha Centauri , Procyon and Vega and in contrast to distant, highly luminous supergiants such as Canopus, Rigel or Betelgeuse (although Canopus may be
959-476: A faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System . At a distance of 2.64 parsecs (8.6 ly ), the Sirius system is one of Earth's nearest neighbours . Sirius
1096-588: A few minutes. Some amateur and professional astronomers regularly monitor for outbursts using either optical or radio telescopes. In August 2015, the largest recorded flares of the star occurred, with the star becoming 8.3 times brighter than normal on 13 August, in the B ;band (blue light region) . Alpha Centauri may be inside the G-cloud of the Local Bubble , and its nearest known system
1233-411: A final summary in 1926. He cited not only Ptolemy but also the poet Aratus , the orator Cicero , and general Germanicus all calling the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus's poem Phaenomena . Seneca had described Sirius as being of a deeper red than Mars . It is therefore possible that the description as red
1370-492: A fraction of a degree since Ptolemy 's time due to proper motion .) In Ptolemy's time, Alpha Centauri was visible from Alexandria, Egypt , at 31° N, but, due to precession , its declination is now –60° 51′ South , and it can no longer be seen at that latitude. English explorer Robert Hues brought Alpha Centauri to the attention of European observers in his 1592 work Tractatus de Globis , along with Canopus and Achernar , noting: Now, therefore, there are but three Stars of
1507-399: A high proper motion. In this case, the apparent stellar motion was found using Nicolas Louis de Lacaille 's astrometric observations of 1751–1752, by the observed differences between the two measured positions in different epochs. Calculated proper motion of the centre of mass for α Centauri AB is about 3620 mas/y (milliarcseconds per year) toward the west and 694 mas/y toward
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#17327655218451644-877: A mass between that of Neptune and one-half that of Saturn, though it may be a dust disk or an artifact. The possibility of C1 being a background star has been ruled out. If this candidate is confirmed, the temporary name C1 will most likely be replaced with the scientific designation Alpha Centauri Ab in accordance with current naming conventions. GO Cycle 1 observations are planned for the James Webb Space Telescope (JWST) to search for planets around Alpha Centauri A, as well as observations of Epsilon Muscae . The coronographic observations, which occurred on July 26 and 27, 2023, were failures, though there are follow-up observations in March 2024. Pre-launch estimates predicted that JWST will be able to find planets with
1781-459: A mass of roughly 7 M E and orbits about 1.49 AU from Proxima Centauri with a period of 1,928 days (5.28 yr). In June 2020, a possible direct imaging detection of the planet hinted at the presence of a large ring system. However, a 2022 study disputed the existence of this planet. A 2020 paper refining Proxima b's mass excludes the presence of extra companions with masses above 0.6 M E at periods shorter than 50 days, but
1918-467: A maximum apparent magnitude of −0.86, comparable to present-day magnitude of Canopus , but it will still not surpass that of Sirius , which will brighten incrementally over the next 60,000 years, and will continue to be the brightest star as seen from Earth (other than the Sun) for the next 210,000 years. Alpha Centauri is a triple star system, with its two main stars, A and B, together comprising
2055-520: A paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credibility to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas J.J. See resurrected discussion on red Sirius with the publication of several papers in 1892, and
2192-404: A parallax of nearly 0.4 arcseconds . The Hipparcos parallax for Sirius is only accurate to about ± 0.04 light years , giving a distance of 8.6 light years . Sirius B is generally assumed to be at the same distance. Sirius B has a Gaia Data Release 3 parallax with a much smaller statistical margin of error, giving a distance of 8.709 ± 0.005 light years , but it
2329-601: A passing comet from his station in Puducherry . Alpha Centauri was only the third binary star to be discovered, preceded by Mizar AB and Acrux . The large proper motion of Alpha Centauri AB was discovered by Manuel John Johnson , observing from Saint Helena , who informed Thomas Henderson at the Royal Observatory, Cape of Good Hope of it. The parallax of Alpha Centauri was subsequently determined by Henderson from many exacting positional observations of
2466-424: A radius of 5 R 🜨 at 1–3 AU . Multiple observations every 3–6 months could push the limit down to 3 R 🜨 . Post-launch estimates based on observations of HIP 65426 b find that JWST will be able to find planets even closer to Alpha Centauri A and could find a 5 R 🜨 planet at 0.5–2.5 AU . Candidate 1 has an estimated radius between 3.3–11 R 🜨 and orbits at 1.1 AU . It
2603-410: A real change in the Sirius system over the past two millennia, of which the most widely discussed is the proposal that the white dwarf Sirius B was a red giant as recently as 2000 years ago. Extrinsic theories are concerned with the possibility of transient reddening in an intervening medium through which the star is observed, such as might be caused by dust in the interstellar medium , or by particles in
2740-439: A separation of about 20 AU (roughly the distance between the Sun and Uranus ) and a period of 50.1 years. The brighter component, termed Sirius A, is a main-sequence star of spectral type early A , with an estimated surface temperature of 9,940 K . Its companion, Sirius B, is a star that has already evolved off the main sequence and become a white dwarf. Currently 10,000 times less luminous in
2877-486: A terrestrial planet discovered in 2016 by astronomers at the European Southern Observatory (ESO). It has an estimated minimum mass of 1.17 M E ( Earth masses ) and orbits approximately 0.049 AU from Proxima Centauri, placing it in the star's habitable zone . The discovery of Proxima Centauri c was formally published in 2020 and could be a super-Earth or mini-Neptune . It has
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#17327655218453014-430: A third star or a planet. An apparent "third star" observed in the 1920s is now believed to be a background object. In 1915, Walter Sydney Adams , using a 60-inch (1.5 m) reflector at Mount Wilson Observatory , observed the spectrum of Sirius B and determined that it was a faint whitish star. This led astronomers to conclude that it was a white dwarf—the second to be discovered. The diameter of Sirius A
3151-401: A third star sufficiently luminous to affect the visible colour of the system in recent millennia is inconsistent with observational evidence. Intrinsic theories may therefore be disregarded. Extrinsic theories based on reddening by interstellar dust are similarly implausible. A transient dust cloud passing between the Sirius system and an observer on Earth would, indeed redden the appearance of
3288-518: Is Bram-bram-bult . To the naked eye, α Centauri AB appears to be a single star, the brightest in the southern constellation of Centaurus . Their apparent angular separation varies over about 80 years between 2 and 22 arcseconds (the naked eye has a resolution of 60 arcsec), but through much of the orbit, both are easily resolved in binoculars or small telescopes. At −0.27 apparent magnitude (combined for A and B magnitudes (see Apparent magnitude § Magnitude addition ) ), Alpha Centauri
3425-663: Is circumpolar and never sets below the horizon. North of about 29° N latitude, Alpha Centauri never rises. Alpha Centauri lies close to the southern horizon when viewed from the 29° North latitude to the equator (close to Hermosillo and Chihuahua City in Mexico ; Galveston, Texas ; Ocala, Florida ; and Lanzarote , the Canary Islands of Spain ), but only for a short time around its culmination . The star culminates each year at local midnight on 24 April and at local 9 p.m. on 8 June. As seen from Earth, Proxima Centauri
3562-638: Is 2.2° southwest from α Centauri AB ; this distance is about four times the angular diameter of the Moon . Proxima Centauri appears as a deep-red star of a typical apparent magnitude of 11.1 in a sparsely populated star field, requiring moderately sized telescopes to be seen. Listed as V645 Cen in the General Catalogue of Variable Stars , version 4.2, this UV Ceti star or "flare star" can unexpectedly brighten rapidly by as much as 0.6 magnitude at visual wavelengths, then fade after only
3699-457: Is 25,200 K. Because there is no internal heat source, Sirius B will steadily cool as the remaining heat is radiated into space over the next two billion years or so. A white dwarf forms after a star has evolved from the main sequence and then passed through a red giant stage. This occurred when Sirius B was less than half its current age, around 120 million years ago. The original star had an estimated 5 M ☉ and
3836-651: Is 35.6 AU (5.33 × 10 ^ km), about the distance between the Sun and Pluto. The most recent periastron was in August 1955 and the next will occur in May ;2035; the most recent apastron was in May 1995 and will next occur in 2075. Viewed from Earth, the apparent orbit of A and B means that their separation and position angle (PA) are in continuous change throughout their projected orbit. Observed stellar positions in 2019 are separated by 4.92 arcsec through
3973-453: Is Golius' latinisation of the Arabic name الظلمان al-Ẓulmān "the ostriches", the name of an asterism of which Alpha Centauri formed the main star. α Centauri C was discovered in 1915 by Robert T. A. Innes , who suggested that it be named Proxima Centaurus , from Latin 'the nearest [star] of Centaurus '. The name Proxima Centauri later became more widely used and
4110-502: Is a first-magnitude star and is fainter only than Sirius and Canopus . It is the outer star of The Pointers or The Southern Pointers , so called because the line through Beta Centauri (Hadar/Agena), some 4.5° west, points to the constellation Crux —the Southern Cross. The Pointers easily distinguish the true Southern Cross from the fainter asterism known as the False Cross . South of about 29° South latitude, α Cen
4247-401: Is a poetic metaphor for ill fortune. In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th-century Lombardic manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours . The Latin text taught readers how to determine the times of nighttime prayers from positions of the stars, and a bright star described as rubeola ("reddish")
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4384-482: Is a relatively low 16 km/s, which does not produce any significant flattening of its disk. This is at marked variance with the similar-sized Vega , which rotates at a much faster 274 km/s and bulges prominently around its equator. A weak magnetic field has been detected on the surface of Sirius A. Stellar models suggest that the star formed during the collapsing of a molecular cloud and that, after 10 million years, its internal energy generation
4521-516: Is about twice as massive as the Sun ( M ☉ ) and has an absolute visual magnitude of +1.43. It is 25 times as luminous as the Sun , but has a significantly lower luminosity than other bright stars such as Canopus, Betelgeuse , or Rigel . The system is between 200 and 300 million years old. It was originally composed of two bright bluish stars. The initially more massive of these, Sirius B, consumed its hydrogen fuel and became
4658-479: Is an approximation of the Arabic الظليمان aẓ-Ẓalīmān (in older transcription, aṭ-Ṭhalīmān ), meaning 'the (two male) Ostriches', an appellation Zakariya al-Qazwini had applied to the pair of stars Lambda and Mu Sagittarii ; it was often not clear on old star maps which name was intended to go with which star (or stars), and the referents changed over time. The name Toliman originates with Jacobus Golius ' 1669 edition of Al-Farghani 's Compendium . Tolimân
4795-524: Is approximately 511 000 +41 000 −30 000 years, with an eccentricity of 0.5, much more eccentric than Mercury 's. Proxima Centauri comes within 4100 +700 −600 AU of AB at periastron, and its apastron occurs at 12 300 +200 −100 AU . Asteroseismic studies, chromospheric activity , and stellar rotation ( gyrochronology ) are all consistent with the Alpha Centauri system being similar in age to, or slightly older than,
4932-481: Is classed as a type Am star , because the spectrum shows deep metallic absorption lines , indicating an enhancement of its surface layers in elements heavier than helium, such as iron. The spectral type has been reported as A0mA1 Va, which indicates that it would be classified as A1 from hydrogen and helium lines, but A0 from the metallic lines that cause it to be grouped with the Am ;stars. When compared to
5069-414: Is comparable to that of the Sun, showing coronal variability due to star spots , as modulated by the rotation of the star. However, since 2005 the activity level has fallen into a deep minimum that might be similar to the Sun's historical Maunder Minimum . Alternatively, it may have a very long stellar activity cycle and is slowly recovering from a minimum phase. Alpha Centauri B, also known as Toliman,
5206-515: Is depicted as a white horse. In Chinese astronomy Sirius is known as the star of the "celestial wolf" ( Chinese and Japanese : 天狼 Chinese romanization : Tiānláng; Japanese romanization : Tenrō; Korean and romanization: 천랑 /Cheonrang) in the Mansion of Jǐng (井宿). Many nations among the indigenous peoples of North America also associated Sirius with canines; the Seri and Tohono Oʼodham of
5343-416: Is different from Wikidata All article disambiguation pages All disambiguation pages Alpha Centauri Alpha Centauri ( α Centauri , α Cen , or Alpha Cen ) is a triple star system in the southern constellation of Centaurus . It consists of three stars: Rigil Kentaurus ( α Centauri A ), Toliman ( α Centauri B ), and Proxima Centauri ( α Centauri C ). Proxima Centauri
5480-454: Is flagged as having a very large value for astrometric excess noise, which indicates that the parallax value may be unreliable. In a letter dated 10 August 1844, the German astronomer Friedrich Wilhelm Bessel deduced from changes in the proper motion of Sirius that it had an unseen companion. On 31 January 1862, American telescope-maker and astronomer Alvan Graham Clark first observed
5617-458: Is gradually moving closer to the Solar System; it is expected to increase in brightness slightly over the next 60,000 years to reach a peak magnitude of −1.68. Coincidentally, at about the same time, Sirius will take its turn as the southern Pole Star, around the year 66,270 AD. In that year, Sirius will come to within 1.6 degrees of the south celestial pole. This is due to axial precession and proper motion of Sirius itself which moves slowly in
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5754-481: Is more magnetically active than Alpha Centauri A, showing a cycle of 8.2 ± 0.2 yr compared to 11 years for the Sun, and has about half the minimum-to-peak variation in coronal luminosity of the Sun. Alpha Centauri B has an apparent magnitude of +1.35, slightly dimmer than Mimosa . Alpha Centauri C, better known as Proxima Centauri, is a small main-sequence red dwarf of spectral class M6-Ve. It has an absolute magnitude of +15.60, over 20,000 times fainter than
5891-642: Is now listed by the International Astronomical Union (IAU) as the approved proper name; commonly, it is frequently abbreviated to Proxima . In 2016, the Working Group on Star Names of the IAU, having decided to attribute proper names to individual component stars rather than to multiple systems , approved the name Rigil Kentaurus ( / ˈ r aɪ dʒ əl k ɛ n ˈ t ɔːr ə s / ) as being restricted to α Centauri A and
6028-533: Is now so entered in the IAU Catalog of Star Names. Sirius has over 50 other designations and names attached to it. In Geoffrey Chaucer 's essay Treatise on the Astrolabe , it bears the name Alhabor and is depicted by a hound's head. This name is widely used on medieval astrolabes from Western Europe. In Sanskrit it is known as Mrgavyadha "deer hunter", or Lubdhaka "hunter". As Mrgavyadha,
6165-516: Is now sometimes known as Sirius A. Since 1894, some apparent orbital irregularities in the Sirius system have been observed, suggesting a third very small companion star, but this has never been confirmed. The best fit to the data indicates a six-year orbit around Sirius A and a mass of 0.06 M ☉ . This star would be five to ten magnitudes fainter than the white dwarf Sirius B, which would make it difficult to observe. Observations published in 2008 were unable to detect either
6302-415: Is part of the α Centauri system and slightly closer to Earth than α Centauri AB . As such, Innes concluded that Proxima Centauri was the closest star to Earth yet discovered. All components of α Centauri display significant proper motion against the background sky. Over centuries, this causes their apparent positions to slowly change. Proper motion was unknown to ancient astronomers. Most assumed that
6439-483: Is similar, the AB binary system is sometimes treated as a single gravitational object. The A and B components of Alpha Centauri have an orbital period of 79.762 years. Their orbit is moderately eccentric , as it has an eccentricity of almost 0.52; their closest approach or periastron is 11.2 AU (1.68 × 10 ^ km), or about the distance between the Sun and Saturn; and their furthest separation or apastron
6576-420: Is the closest star to the Sun at 4.2465 light-years (1.3020 pc ). α Centauri A and B are Sun-like stars ( class G and K , respectively) that together form the binary star system α Centauri AB . To the naked eye , these two main components appear to be a single star with an apparent magnitude of −0.27 . It is the brightest star in the constellation and the third-brightest in
6713-419: Is the binary brown dwarf system Luhman 16 , at 3.6 light-years (1.1 parsecs ) from Alpha Centauri. Alpha Centauri is listed in the 2nd century the star catalog appended to Ptolemy 's Almagest . He gave its ecliptic coordinates , but texts differ as to whether the ecliptic latitude reads 44° 10′ South or 41° 10′ South . (Presently the ecliptic latitude is 43.5° South , but it has decreased by
6850-695: Is the bright star, named Mirzam Al-Jawza' (Sirius), which a group of Arabs used to worship". The alternate name Aschere , used by Johann Bayer , is derived from this. In theosophy , it is believed the Seven Stars of the Pleiades transmit the spiritual energy of the Seven Rays from the Galactic Logos to the Seven Stars of the Great Bear , then to Sirius. From there is it sent via
6987-532: Is the principal member, or primary, of the binary system. It is a solar-like main-sequence star with a similar yellowish colour, whose stellar classification is spectral type G2-V; it is about 10% more massive than the Sun, with a radius about 22% larger. When considered among the individual brightest stars in the night sky, it is the fourth-brightest at an apparent magnitude of +0.01, being slightly fainter than Arcturus at an apparent magnitude of −0.05. The type of magnetic activity on Alpha Centauri A
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#17327655218457124-471: Is the secondary star of the binary system. It is a main-sequence star of spectral type K1-V, making it more an orange colour than Alpha Centauri A; it has around 90% of the mass of the Sun and a 14% smaller diameter. Although it has a lower luminosity than A, Alpha Centauri B emits more energy in the X-ray band. Its light curve varies on a short time scale, and there has been at least one observed flare . It
7261-412: Is therefore likely within the reach of JWST observations. The first claim of a planet around Alpha Centauri B was that of Alpha Centauri Bb in 2012, which was proposed to be an Earth-mass planet in a 3.2-day orbit. This was refuted in 2015 when the apparent planet was shown to be an artifact of the way the radial velocity data was processed. A search for transits of planet Bb was conducted with
7398-479: Is visible from almost everywhere on Earth, except latitudes north of 73° N , and it does not rise very high when viewed from some northern cities (reaching only 13° above the horizon from Saint Petersburg ). Because of its declination of roughly −17°, Sirius is a circumpolar star from latitudes south of 73° S . From the Southern Hemisphere in early July, Sirius can be seen in both
7535-625: The Bering Strait called it "Moon Dog". Several cultures also associated the star with a bow and arrows. The ancient Chinese visualized a large bow and arrow across the southern sky, formed by the constellations of Puppis and Canis Major. In this, the arrow tip is pointed at the wolf Sirius. A similar association is depicted at the Temple of Hathor in Dendera , where the goddess Satet has drawn her arrow at Hathor (Sirius). Known as "Tir",
7672-514: The Cape of Good Hope (4 seconds); by Piazzi (the same amount); using Lacaille's observations made at Paris , more numerous and certain than those made at the Cape (no sensible parallax); by Bessel (no sensible parallax). Scottish astronomer Thomas Henderson used his observations made in 1832–1833 and South African astronomer Thomas Maclear 's observations made in 1836–1837, to determine that
7809-706: The Centaur . The common name Rigil Kentaurus is a Latinisation of the Arabic translation رجل القنطورس Rijl al-Qinṭūrus, meaning "the Foot of the Centaur ". Qinṭūrus is the Arabic transliteration of the Greek Κένταυρος (Kentaurus). The name is frequently abbreviated to Rigil Kent ( / ˈ r aɪ dʒ əl ˈ k ɛ n t / ) or even Rigil , though the latter name is better known for Rigel ( β Orionis). An alternative name found in European sources, Toliman ,
7946-531: The Greek word Σείριος (Latin script: Seirios ), meaning lit. 'glowing' or 'scorching'. The star is designated α Canis Majoris , Latinized to Alpha Canis Majoris , and abbreviated α CMa or Alpha CMa . With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus , the next brightest star. Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1 , termed Sirius A, and
8083-713: The Hubble Space Telescope from 2013 to 2014. This search detected one potential transit-like event, which could be associated with a different planet with a radius around 0.92 R 🜨 . This planet would most likely orbit Alpha Centauri B with an orbital period of 20.4 days or less, with only a 5% chance of it having a longer orbit. The median of the likely orbits is 12.4 days. Its orbit would likely have an eccentricity of 0.24 or less. It could have lakes of molten lava and would be far too close to Alpha Centauri B to harbour life . If confirmed, this planet might be called Alpha Centauri Bc . However,
8220-520: The Hyades and the Pleiades , and each of these clusters consists of hundreds of stars. In 2017, a massive star cluster was discovered only 10 arcminutes from Sirius, making the two appear to be visually close to one other when viewed from the point of view of the Earth . It was discovered during a statistical analysis of Gaia data. The cluster is over a thousand times further away from us than
8357-824: The Marquesas Islands , Rehua in New Zealand, and Ta'urua-fau-papa "Festivity of original high chiefs" and Ta'urua-e-hiti-i-te-tara-te-feiai "Festivity who rises with prayers and religious ceremonies" in Tahiti. In 1717, Edmond Halley discovered the proper motion of the hitherto presumed fixed stars after comparing contemporary astrometric measurements with those from the second century AD given in Ptolemy's Almagest . The bright stars Aldebaran , Arcturus and Sirius were noted to have moved significantly; Sirius had progressed about 30 arcminutes (about
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#17327655218458494-647: The Polynesians , mostly in the Southern Hemisphere, the star marked winter and was an important reference for their navigation around the Pacific Ocean. As the brightest star in the night sky, Sirius appears in some of the earliest astronomical records. Its displacement from the ecliptic causes its heliacal rising to be remarkably regular compared to other stars, with a period of almost exactly 365.25 days holding it constant relative to
8631-422: The night sky , outshone by only Sirius and Canopus . α Centauri A (Rigil Kentaurus) has 1.1 times the mass and 1.5 times the luminosity of the Sun , while α Centauri B (Toliman) is smaller and cooler, at 0.9 solar mass and less than 0.5 solar luminosity. The pair orbit around a common centre with an orbital period of 79 years. Their elliptical orbit is eccentric , so that
8768-612: The sacred texts of the Avesta , the Avestan language Tishtrya followed by the version Tir in Middle and New Persian is also depicted in the Persian epic Shahnameh of Ferdowsi . Because of the concept of the yazatas , powers which are "worthy of worship", Tishtrya is a divinity of rain and fertility and an antagonist of apaosha , the demon of drought. In this struggle, Tishtrya
8905-495: The solar year . This rising occurs at Cairo on 19 July ( Julian ), placing it just before the onset of the annual flooding of the Nile during antiquity. Owing to the flood's own irregularity, the extreme precision of the star's return made it important to the ancient Egyptians , who worshipped it as the goddess Sopdet ( Ancient Egyptian : Spdt , "Triangle"; ‹See Tfd› Greek : Σῶθις }, Sō̂this ), guarantor of
9042-401: The terrestrial atmosphere . The possibility that stellar evolution of either Sirius A or Sirius B could be responsible for the discrepancy has been rejected on the grounds that the timescale of thousands of years is orders of magnitude too short and that there is no sign of the nebulosity in the system that would be expected had such a change taken place. Similarly, the presence of
9179-453: The "dog days", the hottest days of the summer. The Romans knew these days as dies caniculares , and the star Sirius was called Canicula, "little dog". The excessive panting of dogs in hot weather was thought to place them at risk of desiccation and disease. In extreme cases, a foaming dog might have rabies, which could infect and kill humans they had bitten. Homer , in the Iliad , describes
9316-509: The 7th century BC in Hesiod 's poetic work Works and Days . In 2016, 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 Sirius for the star α Canis Majoris A. It
9453-401: The AB system between April 1832 and May 1833. He withheld his results, however, because he suspected they were too large to be true, but eventually published them in 1839 after Bessel released his own accurately determined parallax for 61 Cygni in 1838. For this reason, Alpha Centauri is sometimes considered as the second star to have its distance measured because Henderson's work
9590-463: The Alpha Centauri system. Several established planet-hunting teams have used various radial velocity or star transit methods in their searches around these two bright stars. All the observational studies have so far failed to find evidence for brown dwarfs or gas giants . In 2009, computer simulations showed that a planet might have been able to form near the inner edge of Alpha Centauri B's habitable zone, which extends from 0.5–0.9 AU from
9727-552: The DC Comics Universe; see Multiverse (DC Comics) "New Earth" ( Doctor Who ) , an episode of Doctor Who The destination of the post-nuclear Earth colony in The Time Travelers (1964 film) Other uses [ edit ] Mass Effect: New Earth , amusement park ride at California's Great America New Earth (Christianity) New Earth Records , German record label Topics referred to by
9864-479: The Earth's atmosphere are better supported by available evidence. Scintillations caused by atmospheric turbulence result in rapid, transient changes in the apparent colour of the star, especially when observed near the horizon, although with no particular preference for red. However, systematic reddening of the star's light results from absorption and scattering by particles in the atmosphere, exactly analogous to
10001-1097: The Greek letter beta ( β ) and Latin ungula 'hoof', originally for Beta Centauri (the other hoof). In Chinese astronomy , 南門 Nán Mén , meaning Southern Gate , refers to an asterism consisting of Alpha Centauri and Epsilon Centauri . Consequently, the Chinese name for Alpha Centauri itself is 南門二 Nán Mén Èr , the Second Star of the Southern Gate. To the Indigenous Boorong people of northwestern Victoria in Australia, Alpha Centauri and Beta Centauri are Bermbermgle , two brothers noted for their courage and destructiveness, who speared and killed Tchingal "The Emu" (the Coalsack Nebula ). The form in Wotjobaluk
10138-637: The Hubble Space Telescope ruled out the existence of a stellar mass sized Sirius C, while still allowing a substellar mass candidate such as a lower mass Brown dwarf . The 1995 study predicted an astrometric movement of roughly 90 mas (0.09 arcsecond), but Hubble was unable to detect any location anomaly to an accuracy of 5 mas (0.005 arcsec). This ruled out any objects orbiting Sirius A with more than 0.033 solar mass (35 Jupiter masses) in 0.5 years, and 0.014 (15 Jupiter masses) in 2 years. The study
10275-658: The PA of 337.1°, increasing to 5.49 arcsec through 345.3° in 2020. The closest recent approach was in February 2016, at 4.0 arcsec through the PA of 300°. The observed maximum separation of these stars is about 22 arcsec, while the minimum distance is 1.7 arcsec. The widest separation occurred during February 1976, and the next will be in January 2056. Alpha Centauri C is about 13,000 AU (0.21 ly; 1.9 × 10 ^ km) from Alpha Centauri AB, equivalent to about 5% of
10412-645: The Polynesian night sky into two hemispheres. Just as the appearance of Sirius in the morning sky marked summer in Greece, it marked the onset of winter for the Māori , whose name Takurua described both the star and the season. Its culmination at the winter solstice was marked by celebration in Hawaii , where it was known as Ka'ulua , "Queen of Heaven". Many other Polynesian names have been recorded, including Tau-ua in
10549-635: The Roman period, mapped the stars in Books ;VII and VIII of his Almagest , in which he used Sirius as the location for the globe's central meridian. He described Sirius as reddish, along with five other stars, Betelgeuse , Antares , Aldebaran , Arcturus , and Pollux , all of which are at present observed to be of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker , squire of Lyndon Hall in Rutland , who prepared
10686-463: The SSW direction, so it will be visible from the southern hemisphere only. After that time, its distance will begin to increase, and it will become fainter, but it will continue to be the brightest star in the Earth's night sky for approximately the next 210,000 years, at which point Vega , another A-type star that is intrinsically more luminous than Sirius, becomes the brightest star. Sirius A
10823-554: The Solar System. This gives a speed with respect to the Sun of 32.4 km/s (20.1 mi/s), very close to the peak in the distribution of speeds of nearby stars. Since α Centauri AB is almost exactly in the plane of the Milky Way as viewed from Earth, many stars appear behind it. In early May 2028, α Centauri A will pass between the Earth and a distant red star, when there is a 45% probability that an Einstein ring will be observed. Other conjunctions will also occur in
10960-663: The Sun at 5 to 6 billion years, as derived by their mass and spectral characteristics. From the orbital elements , the total mass of Alpha Centauri AB is about 2.0 M ☉ – or twice that of the Sun. The average individual stellar masses are about 1.08 M ☉ and 0.91 M ☉ , respectively, though slightly different masses have also been quoted in recent years, such as 1.14 M ☉ and 0.92 M ☉ , totaling 2.06 M ☉ . Alpha Centauri A and B have absolute magnitudes of +4.38 and +5.71, respectively. Alpha Centauri A, also known as Rigil Kentaurus,
11097-589: The Sun to the god of Earth ( Sanat Kumara ), and finally through the seven Masters of the Seven Rays to the human race. The midnight culmination of Sirius in the northern hemisphere coincides with the beginning of the New Year of the Gregorian calendar during the decades around the year 2000. Over the years, its midnight culmination moves slowly, owing to the combination of the star's proper motion and
11234-415: The Sun's, has an age that is only half this, making it too young to belong to the group. Sirius may instead be a member of the proposed Sirius Supercluster, along with other scattered stars such as Beta Aurigae , Alpha Coronae Borealis , Beta Crateris , Beta Eridani and Beta Serpentis . This would be one of three large clusters located within 500 light-years (150 pc) of the Sun. The other two are
11371-419: The Sun, the proportion of iron in the atmosphere of Sirius A relative to hydrogen is given by [ Fe H ] = 0.5 , {\displaystyle \textstyle \ \left[{\frac {{\ce {Fe}}}{{\ce {H}}}}\right]=0.5\ ,} meaning iron is 316% as abundant as in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of
11508-484: The Sun. Asteroseismic analyses that incorporate tight observational constraints on the stellar parameters for the Alpha Centauri stars have yielded age estimates of 4.85 ± 0.5 Gyr, 5.0 ± 0.5 Gyr, 5.2 ± 1.9 Gyr, 6.4 Gyr, and 6.52 ± 0.3 Gyr. Age estimates for the stars based on chromospheric activity (Calcium H & K emission) yield 4.4 ± 2.1 Gyr, whereas gyrochronology yields 5.0 ± 0.3 Gyr. Stellar evolution theory implies both stars are slightly older than
11645-400: The Sun. Its mass is calculated to be 0.1221 M ☉ . It is the closest star to the Sun but is too faint to be visible to the naked eye. The Alpha Centauri system as a whole has two confirmed planets, both of them around Proxima Centauri. While other planets have been claimed to exist around all of the stars, none of the discoveries have been confirmed. Proxima Centauri b is
11782-410: The ancient Polynesians for navigation of the Pacific Ocean. They also served as latitude markers; the declination of Sirius matches the latitude of the archipelago of Fiji at 17°S and thus passes directly over the islands each sidereal day . Sirius served as the body of a "Great Bird" constellation called Manu , with Canopus as the southern wingtip and Procyon the northern wingtip, which divided
11919-476: The approach of Achilles toward Troy in these words: Sirius rises late in the dark, liquid sky On summer nights, star of stars, Orion's Dog they call it, brightest Of all, but an evil portent, bringing heat And fevers to suffering humanity. In a little-attested Greek myth, the star-god that personified Sirius fell in love with a fertility goddess named Opora , but he was unable to have her. Thus he began to burn hot, making humans suffer, who prayed to
12056-400: The authors detected a radial-velocity curve with a periodicity of 5.15 days, suggesting the presence of a planet with a mass of about 0.29 M E . This planet, Proxima Centauri d, was confirmed in 2022. In 2021, a candidate planet named Candidate 1 (or C1) was detected around Alpha Centauri A, thought to orbit at approximately 1.1 AU with a period of about one year, and to have
12193-405: The colour of Sirius preferentially when it was situated low in the sky (and therefore apparently red). In several Mediterranean cultures, the local visibility of Sirius at heliacal rising and setting (whether it appeared bright and clear or dimmed) was thought to have astrological significance and was thus subject to systematic observation and intense interest. Thus Sirius, more than any other star,
12330-445: The coming decades, allowing accurate measurement of proper motions and possibly giving information on planets. Based on the system's common proper motion and radial velocities, α Centauri will continue to change its position in the sky significantly and will gradually brighten. For example, in about 6,200 CE , α Centauri's true motion will cause an extremely rare first-magnitude stellar conjunction with Beta Centauri , forming
12467-451: The diameter of the Moon) to the southwest. In 1868, Sirius became the first star to have its velocity measured, the beginning of the study of celestial radial velocities . Sir William Huggins examined the spectrum of the star and observed a red shift . He concluded that Sirius was receding from the Solar System at about 40 km/s. Compared to the modern value of −5.5 km/s, this
12604-483: The distance between A and B varies from 35.6 astronomical units ( AU ), or about the distance between Pluto and the Sun, to 11.2 AU , or about the distance between Saturn and the Sun. α Centauri C , or more commonly, Proxima Centauri , is a small faint red dwarf ( class M ). Though not visible to the naked eye, Proxima Centauri is the closest star to the Sun at a distance of 4.24 ly (1.30 pc), slightly closer than α Centauri AB . Currently,
12741-418: The distance between Alpha Centauri AB and the Sun. Until 2017, measurements of its small speed and its trajectory were of too little accuracy and duration in years to determine whether it is bound to Alpha Centauri AB or unrelated. Radial velocity measurements made in 2017 were precise enough to show that Proxima Centauri and Alpha Centauri AB are gravitationally bound. The orbital period of Proxima Centauri
12878-416: The distance between Proxima Centauri and α Centauri AB is about 13,000 AU (0.21 ly), equivalent to about 430 times the radius of Neptune's orbit. Proxima Centauri has two confirmed planets: Proxima b or α Centauri Cb , an Earth-sized planet in the habitable zone discovered in 2016, and Proxima d ( α Centauri Cd ) , a candidate sub-Earth which orbits very closely to
13015-457: The entire star; rather the iron-peak and heavy metals are radiatively levitated towards the surface. Sirius B, also known as the Pup Star, is one of the most massive white dwarfs known. With a mass of 1.02 M ☉ , it is almost double the 0.5–0.6 M ☉ average. This mass is packed into a volume roughly equal to the Earth's. The current surface temperature
13152-538: The evening where it sets after the Sun and in the morning where it rises before the Sun. Along with Procyon and Betelgeuse , Sirius forms one of the three vertices of the Winter Triangle to observers in the Northern Hemisphere . Sirius can be observed in daylight with the naked eye under the right conditions. Ideally, the sky should be very clear, with the observer at a high altitude,
13289-553: The faint companion, which is now called Sirius B, or affectionately "the Pup". This happened during testing of an 18.5-inch (470 mm) aperture great refractor telescope for Dearborn Observatory , which was one of the largest refracting telescope lenses in existence at the time, and the largest telescope in the United States. Sirius B's sighting was confirmed on 8 March with smaller telescopes. The visible star
13426-472: The fertility of their land. The ancient Greeks observed that the appearance of Sirius as the morning star heralded the hot and dry summer and feared that the star caused plants to wilt, men to weaken, and women to become aroused. Owing to its brightness, Sirius would have been seen to twinkle more in the unsettled weather conditions of early summer. To Greek observers, this signified emanations that caused its malignant influence. Anyone suffering its effects
13563-592: The first magnitude that I could perceive in all those parts which are never seene here in England . The first of these is that bright Star in the sterne of Argo which they call Canobus [Canopus]. The second [Achernar] is in the end of Eridanus . The third [Alpha Centauri] is in the right foote of the Centaure . The binary nature of Alpha Centauri AB was recognized in December 1689 by Jean Richaud, while observing
13700-488: The gods. The god of the north wind, Boreas , solved the problem by ordering his sons to deliver Opora to Sirius, while he cooled down the earth with blasts of his own cold wind. In Iranian mythology, especially in Persian mythology and in Zoroastrianism , the ancient religion of Persia , Sirius appears as Tishtrya and is revered as the rain-maker divinity (Tishtar of New Persian poetry). Beside passages in
13837-407: The lack of any brown dwarfs or gas giants in close orbits around Alpha Centauri make the likelihood of terrestrial planets greater than otherwise. A theoretical study indicates that a radial velocity analysis might detect a hypothetical planet of 1.8 M E in Alpha Centauri B's habitable zone . Sirius Sirius is the brightest star in the night sky . Its name is derived from
13974-532: The mass of Jupiter at 1–2 AU distance, and down to around 4 times the mass of Jupiter at 10 AU distance. Similarly, Lucas and colleagues did not detect any companions around Sirius B. Sirius A, also known as the Dog Star, has a mass of 2.063 M ☉ . The radius of this star has been measured by an astronomical interferometer , giving an estimated angular diameter of 5.936±0.016 mas . The projected rotational velocity
14111-489: The name Proxima Centauri ( / ˈ p r ɒ k s ɪ m ə s ɛ n ˈ t ɔːr aɪ / ) for α Centauri C . On 10 August 2018, the IAU approved the name Toliman ( / ˈ t ɒ l ɪ m æ n / ) for α Centauri B . During the 19th century, the northern amateur popularist E.H. Burritt used the now-obscure name Bungula ( / ˈ b ʌ ŋ ɡ juː l ə / ). Its origin is not known, but it may have been coined from
14248-429: The name has not been used in the literature, as it is not a claimed discovery. Additional planets may exist in the Alpha Centauri system, either orbiting Alpha Centauri A or Alpha Centauri B individually, or in large orbits around Alpha Centauri AB. Because both stars are fairly similar to the Sun (for example, in age and metallicity ), astronomers have been especially interested in making detailed searches for planets in
14385-443: The north, giving an overall motion of 3686 mas/y in a direction 11° north of west. The motion of the centre of mass is about 6.1 arcmin each century, or 1.02 ° each millennium. The speed in the western direction is 23.0 km/s (14.3 mi/s) and in the northerly direction 4.4 km/s (2.7 mi/s). Using spectroscopy the mean radial velocity has been determined to be around 22.4 km/s (13.9 mi/s) towards
14522-441: The redness of the Sun at sunrise and sunset . Because the particles that cause reddening in the Earth's atmosphere are different (typically much smaller) than those that cause reddening in the interstellar medium, there is far less dimming of the starlight, and in the case of Sirius the change in colour can be seen without the aid of a telescope. There may be cultural reasons to explain why some ancient observers might have reported
14659-470: The relative places of the stars from a binary star ephemeris . Others, like D. Pourbaix (2002), have regularly refined the precision of new published orbital elements. Robert T. A. Innes discovered Proxima Centauri in 1915 by blinking photographic plates taken at different times during a proper motion survey. These showed large proper motion and parallax similar in both size and direction to those of α Centauri AB, which suggested that Proxima Centauri
14796-415: The same term [REDACTED] This disambiguation page lists articles associated with the title New Earth . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=New_Earth&oldid=1098981099 " Category : Disambiguation pages Hidden categories: Short description
14933-575: The southwest note the star as a dog that follows mountain sheep, while the Blackfoot called it "Dog-face". The Cherokee paired Sirius with Antares as a dog-star guardian of either end of the "Path of Souls". The Pawnee of Nebraska had several associations; the Wolf (Skidi) tribe knew it as the "Wolf Star", while other branches knew it as the "Coyote Star". Further north, the Alaskan Inuit of
15070-415: The star passing overhead, and the Sun low on the horizon. These observing conditions are more easily met in the Southern Hemisphere, owing to the southerly declination of Sirius. The orbital motion of the Sirius binary system brings the two stars to a minimum angular separation of 3 arcseconds and a maximum of 11 arcseconds. At the closest approach, it is an observational challenge to distinguish
15207-538: The star represents Rudra ( Shiva ). The star is referred to as Makarajyoti in Malayalam and has religious significance to the pilgrim center Sabarimala . In Scandinavia , the star has been known as Lokabrenna ("burning done by Loki", or "Loki's torch"). In the astrology of the Middle Ages , Sirius was a Behenian fixed star , associated with beryl and juniper . Its astrological symbol [REDACTED]
15344-629: The star system, but given its size it still appears at magnitude 8.3. The proper name "Sirius" comes from the Latin Sīrius , from the Ancient Greek Σείριος ( Seirios , "glowing" or "scorcher"). The Greek word itself may have been imported from elsewhere before the Archaic period , one authority suggesting a link with the Egyptian god Osiris . The name's earliest recorded use dates from
15481-427: The star to some degree, but reddening sufficient to cause it to appear similar in colour to intrinsically red bright stars such as Betelgeuse and Arcturus would also dim the star by several magnitudes, inconsistent with historical accounts: indeed, the dimming would be sufficient to render the colour of the star imperceptible to the human eye without the aid of a telescope. Extrinsic theories based on optical effects in
15618-617: The star was portrayed as the arrow itself in later Persian culture. Sirius is mentioned in Surah , An-Najm ("The Star"), of the Qur'an , where it is given the name الشِّعْرَى (transliteration: aš-ši'rā or ash-shira ; the leader). The verse is: " وأنَّهُ هُوَ رَبُّ الشِّعْرَى ", "That He is the Lord of Sirius (the Mighty Star)." (An-Najm:49) Ibn Kathir said in his commentary "that it
15755-446: The star, announced in 2022. The existence of Proxima c ( α Centauri Cc ) , a mini-Neptune 1.5 AU away discovered in 2019, is controversial. α Centauri A may have a Neptune-sized planet in the habitable zone, though it is not yet known with certainty to be planetary in nature and could be an artifact of the discovery mechanism. α Centauri B has no known planets: Planet α Cen Bb , purportedly discovered in 2012,
15892-436: The star. Certain special assumptions, such as considering that the Alpha Centauri pair may have initially formed with a wider separation and later moved closer to each other (as might be possible if they formed in a dense star cluster ), would permit an accretion-friendly environment farther from the star. Bodies around Alpha Centauri A would be able to orbit at slightly farther distances due to its stronger gravity. In addition,
16029-417: The stars were permanently fixed on the celestial sphere , as stated in the works of the philosopher Aristotle. In 1718, Edmond Halley found that some stars had significantly moved from their ancient astrometric positions. In the 1830s, Thomas Henderson discovered the true distance to α Centauri by analysing his many astrometric mural circle observations. He then realised this system also likely had
16166-510: The system, which is considered somewhat unusual for a binary star. The Chandra X-ray Observatory image shows Sirius B outshining its partner as an X-ray source. In 2015, Vigan and colleagues used the VLT Survey Telescope to search for evidence of substellar companions, and were able to rule out the presence of giant planets 11 times more massive than Jupiter at 0.5 AU distance from Sirius A, 6–7 times
16303-579: The two stars are believed to be too far apart for it to occur, even if Sirius A swells into a red giant . Novas , however, may be possible. Since 1894, irregularities have been tentatively observed in the orbits of Sirius A and B with an apparent periodicity of 6–6.4 years. A 1995 study concluded that such a companion likely exists, with a mass of roughly 0.05 solar mass—a small red dwarf or large brown dwarf , with an apparent magnitude of more than 15, and less than 3 arcseconds from Sirius A. In 2017, more accurate astrometric observations by
16440-410: The value of the parallax was 0.23 arcsecond , and error of the parallax was estimated not to exceed a quarter of a second, or as Henderson wrote in 1839, "On the whole we may conclude that the parallax of Sirius is not greater than half a second in space; and that it is probably much less." Astronomers adopted a value of 0.25 arcsecond for much of the 19th century. It is now known to have
16577-433: The visual spectrum, Sirius B was once the more massive of the two. The age of the system has been estimated at 230 million years. Early in its life, it is thought to have been two bluish-white stars orbiting each other in an elliptical orbit every 9.1 years. The system emits a higher than expected level of infrared radiation , as measured by IRAS space-based observatory. This might be an indication of dust in
16714-432: The white dwarf from its more luminous companion, requiring a telescope with at least 300 mm (12 in) aperture and excellent seeing conditions. After a periastron occurred in 1994, the pair moved apart, making them easier to separate with a telescope. Apoastron occurred in 2019, but from the Earth's vantage point, the greatest observational separation occurred in 2023, with an angular separation of 11.333″. At
16851-412: Was a B-type star (most likely B5V for 5 M ☉ ) when it was still on the main sequence, potentially burning around 600–1200 times more luminous than the sun. While it passed through the red giant stage, Sirius B may have enriched the metallicity of its companion, explaining the very high metallicity of Sirius A. This star is primarily composed of a carbon–oxygen mixture that
16988-657: Was a member of the Ursa Major Moving Group , based on his observations of the system's movements across the sky. The Ursa Major Group is a set of 220 stars that share a common motion through space. It was once a member of an open cluster , but has since become gravitationally unbound from the cluster. Analyses in 2003 and 2005 found Sirius's membership in the group to be questionable: the Ursa Major Group has an estimated age of 500 ± 100 million years, whereas Sirius, with metallicity similar to
17125-414: Was also able to rule out any companions to Sirius B with more than 0.024 solar mass (25 Jupiter masses) orbiting in 0.5 year, and 0.0095 (10 Jupiter masses) orbiting in 1.8 years. Effectively, there are almost certainly no additional bodies in the Sirius system larger than a small brown dwarf or large exoplanet. In 1909, Ejnar Hertzsprung was the first to suggest that Sirius
17262-551: Was an overestimate and had the wrong sign; the minus sign (−) means that it is approaching the Sun. In his 1698 book, Cosmotheoros , Christiaan Huygens estimated the distance to Sirius at 27,664 times the distance from the Earth to the Sun (about 0.437 light-year, translating to a parallax of roughly 7.5 arcseconds). There were several unsuccessful attempts to measure the parallax of Sirius: by Jacques Cassini (6 seconds); by some astronomers (including Nevil Maskelyne ) using Lacaille 's observations made at
17399-416: Was claimed to be Sirius. The authors proposed this as evidence that Sirius B had been a red giant at the time of observation. Other scholars replied that it was likely St. Gregory had been referring to Arcturus . It is notable that not all ancient observers saw Sirius as red. The 1st-century poet Marcus Manilius described it as "sea-blue", as did the 4th-century Avienius . Furthermore, Sirius
17536-491: Was consistently reported as a white star in ancient China: a detailed re-evaluation of Chinese texts from the 2nd century BC up to the 7th century AD concluded that all such reliable sources are consistent with Sirius being white. Nevertheless, historical accounts referring to Sirius as red are sufficiently extensive to lead researchers to seek possible physical explanations. Proposed theories fall into two categories: intrinsic and extrinsic. Intrinsic theories postulate
17673-469: Was derived entirely from nuclear reactions. The core became convective and used the CNO cycle for energy generation. It is calculated that Sirius A will have completely exhausted the store of hydrogen at its core within a billion (10 ) years of its formation, and will then evolve away from the main sequence. It will pass through a red giant stage and eventually become a white dwarf. Sirius A
17810-439: Was first measured by Robert Hanbury Brown and Richard Q. Twiss in 1959 at Jodrell Bank using their stellar intensity interferometer . In 2005, using the Hubble Space Telescope , astronomers determined that Sirius B has nearly the diameter of the Earth, 12,000 kilometres (7,500 mi), with a mass 102% of the Sun's. Around the year 150 AD, Claudius Ptolemy of Alexandria, an ethnic Greek Egyptian astronomer of
17947-449: Was generated by helium fusion in the progenitor star. This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity. The outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in its spectrum. Although Sirius A and B compose a binary system that is reminiscent of those that can undergo Type Ia supernova ,
18084-416: Was later disproven, and no other planet has yet been confirmed. α Centauri ( Latinised to Alpha Centauri ) is the system's designation given by J. Bayer in 1603. It belongs to the constellation Centaurus , named after the half human, half horse creature in Greek mythology. Hercules accidentally wounded the centaur and placed him in the sky after his death. Alpha Centauri marks the right front hoof of
18221-446: Was listed by Heinrich Cornelius Agrippa . Many cultures have historically attached special significance to Sirius, particularly in relation to dogs . It is often colloquially called the "Dog Star" as the brightest star of Canis Major , the "Great Dog" constellation. Canis Major was classically depicted as Orion 's dog. The Ancient Greeks thought that Sirius's emanations could affect dogs adversely, making them behave abnormally during
18358-480: Was misty or faint then it foretold (or emanated) pestilence. Coins retrieved from the island from the 3rd century BC feature dogs or stars with emanating rays, highlighting Sirius's importance. The Romans celebrated the heliacal setting of Sirius around 25 April, sacrificing a dog, along with incense, wine, and a sheep, to the goddess Robigo so that the star's emanations would not cause wheat rust on wheat crops that year. Bright stars were important to
18495-526: Was not fully acknowledged at first. (The distance of Alpha Centauri from the Earth is now reckoned at 4.396 light-years or 4.159 × 10 km.) Later, John Herschel made the first micrometrical observations in 1834. Since the early 20th century, measures have been made with photographic plates . By 1926, William Stephen Finsen calculated the approximate orbit elements close to those now accepted for this system. All future positions are now sufficiently accurate for visual observers to determine
18632-449: Was observed and recorded while close to the horizon. Other contemporary cultures, such as Chinese, lacking this tradition, recorded Sirius only as white. With an apparent magnitude of −1.46, Sirius is the brightest star in the night sky , almost twice as bright as the second-brightest star, Canopus . From Earth , Sirius always appears dimmer than Jupiter and Venus , and at certain times also dimmer than Mercury and Mars . Sirius
18769-503: Was said to be "star-struck" ( ἀστροβόλητος , astrobólētos ). It was described as "burning" or "flaming" in literature. The season following the star's reappearance came to be known as the "dog days". The inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes and would await the reappearance of the star in summer. If it rose clear, it would portend good fortune; if it
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