121-467: Epsilon Eridani ( Latinized from ε Eridani ), proper name Ran , is a star in the southern constellation of Eridanus . At a declination of −9.46°, it is visible from most of Earth's surface. Located at a distance 10.5 light-years (3.2 parsecs ) from the Sun , it has an apparent magnitude of 3.73, making it the third-closest individual star (or star system ) visible to the naked eye . The star
242-571: A heliometer at the Royal Observatory at the Cape of Good Hope , South Africa, to compare the position of Epsilon Eridani with two nearby stars. From these observations, a parallax of 0.14 ± 0.02 arcseconds was calculated. By 1917, observers had refined their parallax estimate to 0.317 arcseconds. The modern value of 0.3109 arcseconds is equivalent to a distance of about 10.50 light-years (3.22 pc). Based on apparent changes in
363-536: A 1964 RAND Corporation study by space scientist Stephen H. Dole, the probability of a habitable planet being in orbit around Epsilon Eridani were estimated at 3.3%. Among the known nearby stars, it was listed with the 14 stars that were thought most likely to have a habitable planet. William I. McLaughlin proposed a new strategy in the search for extraterrestrial intelligence ( SETI ) in 1977. He suggested that widely observable events such as nova explosions might be used by intelligent extraterrestrials to synchronise
484-542: A 20 year period, which is much higher than the measurement uncertainty of 3 m s . This makes interpretation of periodicities in the radial velocity of Epsilon Eridani, such as those caused by an orbiting planet, more difficult. Epsilon Eridani is classified as a BY Draconis variable because it has regions of higher magnetic activity that move into and out of the line of sight as it rotates. Measurement of this rotational modulation suggests that its equatorial region rotates with an average period of 11.2 days, which
605-427: A central sacred tree , Yggdrasil . Units of time and elements of the cosmology are personified as deities or beings. Various forms of a creation myth are recounted, where the world is created from the flesh of the primordial being Ymir , and the first two humans are Ask and Embla . These worlds are foretold to be reborn after the events of Ragnarök when an immense battle occurs between the gods and their enemies, and
726-553: A cloud of exozodiacal dust . The latter is an analogue of the zodiacal dust that occupies the plane of the Solar System . One belt sits at approximately the same position as the one in the Solar System, orbiting at a distance of 3.00 ± 0.75 au from Epsilon Eridani, and consists of silicate grains with a diameter of 3 μm and a combined mass of about 10 kg. If the planet Epsilon Eridani b exists then this belt
847-507: A combined total of 0.962 arcseconds per year. The star has a radial velocity of +15.5 km/s (35,000 mph) (away from the Sun). The space velocity components of Epsilon Eridani in the galactic co-ordinate system are (U, V, W) = (−3, +7, −20) km/s , which means that it is travelling within the Milky Way at a mean galactocentric distance of 28.7 kly (8.79 kiloparsecs) from
968-558: A distance of 10.50 ly (3.22 parsecs), Epsilon Eridani is the 13th-nearest known star (and ninth nearest solitary star or stellar system ) to the Sun as of 2014. Its proximity makes it one of the most studied stars of its spectral type . Epsilon Eridani is located in the northern part of the constellation Eridanus, about 3° east of the slightly brighter star Delta Eridani . With a declination of −9.46°, Epsilon Eridani can be viewed from much of Earth's surface, at suitable times of year. Only to
1089-455: A female being of the same name , may be ferried away by valkyries to Odin's martial hall Valhalla , or may be chosen by the goddess Freyja to dwell in her field Fólkvangr . The goddess Rán may claim those that die at sea, and the goddess Gefjon is said to be attended by virgins upon their death. Texts also make reference to reincarnation . Time itself is presented between cyclic and linear, and some scholars have argued that cyclic time
1210-462: A new edition of Lalande's catalogue was published by Francis Baily, containing the majority of its observations, in which the stars were numbered in order of right ascension . Because every observation of each star was numbered and Epsilon Eridani was observed three times, it got three numbers: 6581, 6582 and 6583. (Today numbers from this catalogue are used with the prefix "Lalande", or "Lal".) Lalande assigned Epsilon Eridani magnitude 3. Also in 1801 it
1331-511: A paucity of volatile-bearing comets and icy planetesimals compared to the Kuiper belt. The JCMT images show signs of clumpy structure in the belt that may be explained by gravitational perturbation from a planet, dubbed Epsilon Eridani c. The clumps in the dust are theorised to occur at orbits that have an integer resonance with the orbit of the suspected planet. For example, the region of the disk that completes two orbits for every three orbits of
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#17327803508381452-450: A planet is in a 3:2 orbital resonance . The planet proposed to cause these perturbations is predicted to have a semimajor axis of between 40 and 50 au. However, the brightest clumps have since been identified as background sources and the existence of the remaining clumps remains debated. Dust is also present closer to the star. Observations from NASA's Spitzer Space Telescope suggest that Epsilon Eridani actually has two asteroid belts and
1573-453: A planet orbiting just inside the dust ring. In 1987, the detection of an orbiting planetary object was announced by Bruce Campbell, Gordon Walker and Stephenson Yang. From 1980 to 2000, a team of astronomers led by Artie P. Hatzes made radial velocity observations of Epsilon Eridani, measuring the Doppler shift of the star along the line of sight . They found evidence of a planet orbiting
1694-463: A region in the center of the cosmos. Outside of the gods, humanity, and the jötnar, these Nine Worlds are inhabited by beings, such as elves and dwarfs . Travel between the worlds is frequently recounted in the myths, where the gods and other beings may interact directly with humanity. Numerous creatures live on Yggdrasil, such as the insulting messenger squirrel Ratatoskr and the perching hawk Veðrfölnir . The tree itself has three major roots, and at
1815-487: A region of the outer atmosphere just above the light emitting photosphere , the abundance of iron is estimated at 74% of the Sun's value. The proportion of lithium in the atmosphere is five times less than that in the Sun. Epsilon Eridani's K-type classification indicates that the spectrum has relatively weak absorption lines from absorption by hydrogen ( Balmer lines ) but strong lines of neutral atoms and singly ionized calcium (Ca II). The luminosity class V (dwarf)
1936-529: A sixth of the mass of the Moon, with individual dust grains exceeding 3.5 μm in size at a temperature of about 55 K. This dust is being generated by the collision of comets, which range up to 10 to 30 km in diameter and have a combined mass of 5 to 9 times that of Earth. This is similar to the estimated 10 Earth masses in the primordial Kuiper belt. The disk around Epsilon Eridani contains less than 2.2 × 10 kg of carbon monoxide . This low level suggests
2057-486: A variety of formats for rendering Greek and Greek shorthand using Latin letters. Examples include "8elo" and "thelw" for θέλω , "3ava" for ξανά , and "yuxi" for ψυχή . Owing to the difficulties encountered in transliterating and transcribing both ancient and modern Greek into the Latin alphabet, a number of regulatory bodies have been established. The Hellenic Organization for Standardization (ELOT), in cooperation with
2178-615: A variety of romanizations for names and placenames in the 19th and 20th century. The Hellenic Organization for Standardization (ELOT) issued its system in cooperation with the International Organization for Standardization (ISO) in 1983. This system was adopted (with minor modifications) by the United Nations ' Fifth Conference on the Standardization of Geographical Names at Montreal in 1987, by
2299-560: Is (1.65 ± 0.30) × 10 tesla , which is more than forty times greater than the (5–40) × 10 T magnetic-field strength in the Sun's photosphere. The magnetic properties can be modelled by assuming that regions with a magnetic flux of about 0.14 T randomly cover approximately 9% of the photosphere, whereas the remainder of the surface is free of magnetic fields. The overall magnetic activity of Epsilon Eridani shows co-existing 2.95 ± 0.03 and 12.7 ± 0.3 year activity cycles. Assuming that its radius does not change over these intervals,
2420-504: Is Njörðr's unnamed sister (her name is unprovided in the source material). However, there is more information about his pairing with the skiing and hunting goddess Skaði . Their relationship is ill-fated, as Skaði cannot stand to be away from her beloved mountains, nor Njörðr from the seashore. Together, Freyja, Freyr, and Njörðr form a portion of gods known as the Vanir . While the Aesir and
2541-576: Is 30 times higher than the Sun's. This stellar wind generates the astrosphere that spans about 8,000 au (0.039 pc) and contains a bow shock that lies 1,600 au (0.0078 pc) from Epsilon Eridani. At its estimated distance from Earth, this astrosphere spans 42 arcminutes, which is wider than the apparent size of the full Moon. Epsilon Eridani has a high proper motion , moving −0.976 arcseconds per year in right ascension (the celestial equivalent of longitude) and 0.018 arcseconds per year in declination (celestial latitude), for
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#17327803508382662-407: Is 5,084 K. With a stellar classification of K2 V, it is the second-nearest K-type main-sequence star (after Alpha Centauri B). Since 1943 the spectrum of Epsilon Eridani has served as one of the stable anchor points by which other stars are classified. Its metallicity , the fraction of elements heavier than helium , is slightly lower than the Sun's. In Epsilon Eridani's chromosphere ,
2783-543: Is a candidate member of the Ursa Major moving group of stars, which share a similar motion through the Milky Way , implying these stars shared a common origin in an open cluster . Periodic changes in Epsilon Eridani's radial velocity have yielded evidence of a giant planet orbiting it, designated Epsilon Eridani b . The discovery of the planet was initially controversial, but most astronomers now regard
2904-408: Is assigned to stars that are undergoing thermonuclear fusion of hydrogen in their core. For a K-type main-sequence star, this fusion is dominated by the proton–proton chain reaction , in which a series of reactions effectively combines four hydrogen nuclei to form a helium nucleus. The energy released by fusion is transported outward from the core through radiation , which results in no net motion of
3025-410: Is common to mark the long vowels with macrons over the Latin letters and to leave the short vowels unmarked; such macrons should not be confused or conflated with those used by some systems to mark eta and omega as distinct from epsilon , iota , and omicron . Greece's early Attic numerals were based on a small sample of letters (including heta ) arranged in multiples of 5 and 10, likely forming
3146-526: Is engineered by Loki , and Baldr thereafter resides in Hel , a realm ruled over by an entity of the same name . Odin must share half of his share of the dead with a powerful goddess, Freyja . She is beautiful, sensual, wears a feathered cloak, and practices seiðr . She rides to battle to choose among the slain and brings her chosen to her afterlife field Fólkvangr . Freyja weeps for her missing husband Óðr and seeks after him in faraway lands. Freyja's brother,
3267-521: Is estimated to be less than a billion years old. This relative youth gives Epsilon Eridani a higher level of magnetic activity than the Sun , with a stellar wind 30 times as strong. The star's rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a lower level of elements heavier than helium . It is a main-sequence star of spectral class K2, with an effective temperature of about 5,000 K (8,500 °F ), giving it an orange hue. It
3388-480: Is less than half of the rotation period of the Sun. Observations have shown that Epsilon Eridani varies as much as 0.050 in V magnitude due to starspots and other short-term magnetic activity. Photometry has also shown that the surface of Epsilon Eridani, like the Sun, is undergoing differential rotation i.e. the rotation period at equator differs from that at high latitude . The measured periods range from 10.8 to 12.3 days. The axial tilt of Epsilon Eridani toward
3509-604: Is more luminous in X-rays than the Sun at peak activity . The source for this strong X-ray emission is Epsilon Eridani's hot corona. Epsilon Eridani's corona appears larger and hotter than the Sun's, with a temperature of 3.4 × 10 K , measured from observation of the corona's ultraviolet and X-ray emission. It displays a cyclical variation in X-ray emission that is consistent with the magnetic activity cycle. The stellar wind emitted by Epsilon Eridani expands until it collides with
3630-603: Is primarily attested in dialects of Old Norse , a North Germanic language spoken by the Scandinavian people during the European Middle Ages and the ancestor of modern Scandinavian languages . The majority of these Old Norse texts were created in Iceland , where the oral tradition stemming from the pre-Christian inhabitants of the island was collected and recorded in manuscripts. This occurred primarily in
3751-682: Is shaped like the Latinate semicolon . Greek punctuation which has been given formal romanizations include: There are many archaic forms and local variants of the Greek alphabet . Beta , for example, might appear as round Β or pointed [REDACTED] throughout Greece but is also found in the forms [REDACTED] (at Gortyn ), [REDACTED] and [REDACTED] ( Thera ), [REDACTED] ( Argos ), [REDACTED] ( Melos ), [REDACTED] ( Corinth ), [REDACTED] ( Megara and Byzantium ), and even [REDACTED] ( Cyclades ). Well into
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3872-466: Is the same as Ptolemy's catalogue designation). In 1598 Epsilon Eridani was included in Tycho Brahe 's star catalogue, republished in 1627 by Johannes Kepler as part of his Rudolphine Tables . This catalogue was based on Tycho Brahe's observations of 1577–1597, including those on the island of Hven at his observatories of Uraniborg and Stjerneborg . The sequence number of Epsilon Eridani in
3993-497: Is the star's Bayer designation . Despite being a relatively bright star, it was not given a proper name by early astronomers. It has several other catalogue designations . Upon its discovery, the planet was designated Epsilon Eridani b, following the usual designation system for extrasolar planets . The planet and its host star were selected by the International Astronomical Union (IAU) as part of
4114-472: Is unlikely to have had a source outside the orbit of the planet, so the dust may have been created by fragmentation and cratering of larger bodies such as asteroids . The second, denser belt, most likely also populated by asteroids, lies between the first belt and the outer comet disk. The structure of the belts and the dust disk suggests that more than two planets in the Epsilon Eridani system are needed to maintain this configuration. In an alternative scenario,
4235-599: The Chinese name for ε Eridani itself is 天苑四 ( Tiān Yuàn sì , the Fourth [Star] of Celestial Meadows.) Epsilon Eridani has been known to astronomers since at least the 2nd century AD, when Claudius Ptolemy (a Greek astronomer from Alexandria , Egypt ) included it in his catalogue of more than a thousand stars. The catalogue was published as part of his astronomical treatise the Almagest . The constellation Eridanus
4356-579: The Christianization of Scandinavia as the Nordic folklore of the modern period. The northernmost extension of Germanic mythology and stemming from Proto-Germanic folklore , Norse mythology consists of tales of various deities, beings, and heroes derived from numerous sources from both before and after the pagan period, including medieval manuscripts, archaeological representations, and folk tradition. The source texts mention numerous gods such as
4477-915: The English letter B ( /b/ ) was written as β in ancient Greek but is now written as the digraph μπ , while the modern β sounds like the English letter V ( /v/ ) instead. The Greek name Ἰωάννης became Johannes in Latin and then John in English, but in modern Greek has become Γιάννης ; this might be written as Yannis , Jani, Ioannis, Yiannis, or Giannis, but not Giannes or Giannēs as it would be for ancient Greek. The word Άγιος might variously appear as Hagiοs, Agios, Aghios, or Ayios, or simply be translated as " Holy " or " Saint " in English forms of Greek placenames . Traditional English renderings of Greek names originated from Roman systems established in antiquity. The Roman alphabet itself
4598-517: The Greek alphabet to groups of stars belonging to the same visual magnitude class in each constellation, beginning with alpha (α) for a star in the brightest class. Bayer made no attempt to arrange stars by relative brightness within each class. Thus, although Epsilon is the fifth letter in the Greek alphabet, the star is the tenth-brightest in Eridanus . In addition to the letter ε, Bayer had given it
4719-543: The International Organization for Standardization (ISO), released a system in 1983 which has since been formally adopted by the United Nations , the United Kingdom and United States. The following tables list several romanization schemes from the Greek alphabet to modern English. Note, however, that the ELOT, UN, and ISO formats for Modern Greek intend themselves as translingual and may be applied in any language using
4840-482: The Latin alphabet . The American Library Association and Library of Congress romanization scheme employs its "Ancient or Medieval Greek" system for all works and authors up to the Fall of Constantinople in 1453, although Byzantine Greek was pronounced distinctly and some have considered "Modern" Greek to have begun as early as the 12th century. For treatment of polytonic Greek letters —for example, ᾤ —see also
4961-519: The NameExoWorlds competition for giving proper names to exoplanets and their host stars, for some systems that did not already have proper names. The process involved nominations by educational groups and public voting for the proposed names. In December 2015, the IAU announced the winning names were Ran for the star and AEgir [ sic ] for the planet. Those names had been submitted by
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5082-624: The Tatel Telescope to search for such signals from the nearby Sun-like stars Epsilon Eridani and Tau Ceti . The systems were observed at the emission frequency of neutral hydrogen , 1,420 MHz (21 cm). No signals of intelligent extraterrestrial origin were detected. Drake repeated the experiment in 2010, with the same negative result. Despite this lack of success, Epsilon Eridani made its way into science fiction literature and television shows for many years following news of Drake's initial experiment. In Habitable Planets for Man ,
5203-625: The first letter of the pair indicates vowels which should be taken (and romanized) separately. Although the second vowel is not marked with a superfluous diaeresis in Greek, the first-edition ELOT 743 and the UN systems place a diaeresis on the Latin vowel for the sake of clarity. Apart from the diacritical marks native to Greek itself or used to romanize its characters, linguists also regularly mark vowel length with macrons ( ¯ ) marking long vowels and rounded breves ( ˘ ) marking short vowels . Where these are romanized, it
5324-419: The interstellar medium (out of which stars form) is steadily enriched by heavier elements produced by older generations of stars. This anomaly might be caused by a diffusion process that has transported some of the heavier elements out of the photosphere and into a region below Epsilon Eridani's convection zone . The X-ray luminosity of Epsilon Eridani is about 2 × 10 erg ·s ( 2 × 10 W ). It
5445-593: The radial velocity method is difficult, because the stellar activity may create signals that mimic the presence of planets. Searches for exoplanets around Epsilon Eridani with direct imaging have been unsuccessful. Infrared observation has shown there are no bodies of three or more Jupiter masses in this system, out to at least a distance of 500 au from the host star. Planets with similar masses and temperatures as Jupiter should be detectable by Spitzer at distances beyond 80 au. One roughly Jupiter-sized long-period planet has been detected and characterized by both
5566-516: The section on romanizing Greek diacritical marks below. ELOT approved in 1982 the ELOT 743 standard, revised in 2001, whose Type 2 (Greek: Τύπος 2 , romanized: Typos 2 ) transcription scheme has been adopted by the Greek and Cypriot governments as standard for romanization of names on Greek and Cypriot passports . It also comprised a Type 1 (Greek: Τύπος 1 , romanized: Typos 1 ) transliteration table, which
5687-410: The transcriptions of Modern Greek into Latin letters used by ELOT, UN and ISO are essentially equivalent, while there remain minor differences in how they approach reversible transliteration . The American Library Association and Library of Congress romanization scheme employs its "Modern Greek" system for all works and authors following the Fall of Constantinople in 1453. In the table below,
5808-575: The 13th century by Snorri and Gesta Danorum , composed in Latin by Saxo Grammaticus in Denmark in the 12th century, are the results of heavy amounts of euhemerization. Numerous additional texts, such as the sagas , provide further information. The saga corpus consists of thousands of tales recorded in Old Norse ranging from Icelandic family histories ( Sagas of Icelanders ) to Migration period tales mentioning historic figures such as Attila
5929-813: The 13th century. These texts include the Prose Edda , composed in the 13th century by the Icelandic scholar, lawspeaker , and historian Snorri Sturluson , and the Poetic Edda , a collection of poems from earlier traditional material anonymously compiled in the 13th century. The Prose Edda was composed as a prose manual for producing skaldic poetry—traditional Old Norse poetry composed by skalds . Originally composed and transmitted orally, skaldic poetry utilizes alliterative verse , kennings , and several metrical forms. The Prose Edda presents numerous examples of works by various skalds from before and after
6050-754: The Christianization process and also frequently refers back to the poems found in the Poetic Edda . The Poetic Edda consists almost entirely of poems, with some prose narrative added, and this poetry— Eddic poetry—utilizes fewer kennings . In comparison to skaldic poetry, Eddic poetry is relatively unadorned. The Prose Edda features layers of euhemerization , a process in which deities and supernatural beings are presented as having been either actual, magic-wielding human beings who have been deified in time or beings demonized by way of Christian mythology . Texts such as Heimskringla , composed in
6171-617: The Hun ( legendary sagas ). Objects and monuments such as the Rök runestone and the Kvinneby amulet feature runic inscriptions —texts written in the runic alphabet , the indigenous alphabet of the Germanic peoples —that mention figures and events from Norse mythology. Objects from the archaeological record may also be interpreted as depictions of subjects from Norse mythology, such as amulets of
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#17327803508386292-656: The Norwegian woman Ragnhild Tregagås —convicted of witchcraft in Norway in the 14th century—and spells found in the 17th century Icelandic Galdrabók grimoire also sometimes make references to Norse mythology. Other traces, such as place names bearing the names of gods may provide further information about deities, such as a potential association between deities based on the placement of locations bearing their names, their local popularity, and associations with geological features. Central to accounts of Norse mythology are
6413-412: The Sun, including an excess infrared emission from Epsilon Eridani. The observations indicated a disk of fine-grained cosmic dust was orbiting the star; this debris disk has since been extensively studied. Evidence for a planetary system was discovered in 1998 by the observation of asymmetries in this dust ring. The clumping in the dust distribution could be explained by gravitational interactions with
6534-676: The United Kingdom's Permanent Committee on Geographical Names for British Official Use (PCGN) and by the United States' Board on Geographic Names (BGN) in 1996, and by the ISO itself in 1997. Romanization of names for official purposes (as with passports and identity cards) were required to use the ELOT system within Greece until 2011, when a legal decision permitted Greeks to use irregular forms (such as " Demetrios " for Δημήτριος ) provided that official identification and documents also list
6655-546: The Vanir retain distinct identification, they came together as the result of the Aesir–Vanir War . While they receive less mention, numerous other gods and goddesses appear in the source material. (For a list of these deities, see List of Germanic deities .) Some of the gods heard less of include the apple-bearing goddess Iðunn and her husband, the skaldic god Bragi ; the gold-toothed god Heimdallr , born of nine mothers ;
6776-662: The ancient god Týr , who lost his right hand while binding the great wolf Fenrir ; and the goddess Gefjon , who formed modern-day Zealand , Denmark . Various beings outside of the gods are mentioned. Elves and dwarfs are commonly mentioned and appear to be connected, but their attributes are vague and the relation between the two is ambiguous. Elves are described as radiant and beautiful, whereas dwarfs often act as earthen smiths. A group of beings variously described as jötnar , thursar , and trolls (in English these are all often glossed as " giants ") frequently appear. These beings may either aid, deter, or take their place among
6897-530: The base of one of these roots live the Norns , female entities associated with fate. Elements of the cosmos are personified, such as the Sun ( Sól , a goddess), the Moon ( Máni , a god), and Earth ( Jörð , a goddess), as well as units of time, such as day ( Dagr , a god) and night ( Nótt , a jötunn). The afterlife is a complex matter in Norse mythology. The dead may go to the murky realm of Hel —a realm ruled over by
7018-548: The belt is located 70 au from the star with a width of just 11 au. The disc is inclined 33.7° from face-on, making it appear elliptical. Dust and possibly water ice from this belt migrates inward because of drag from the stellar wind and a process by which stellar radiation causes dust grains to slowly spiral toward Epsilon Eridani, known as the Poynting–Robertson effect . At the same time, these dust particles can be destroyed through mutual collisions. The time scale for all of
7139-411: The best fit to the observations occurs when a mix of ice and silicate dust is assumed. Inside this radius, the dust must consist of silicate grains that lack volatiles . The inner region around Epsilon Eridani, from a radius of 2.5 AU inward, appears to be clear of dust down to the detection limit of the 6.5 m MMT telescope . Grains of dust in this region are efficiently removed by drag from
7260-719: The circumstellar disk orbiting Epsilon Eridani. Epsilon Eridani made its closest approach to the Sun about 105,000 years ago, when they were separated by 7 ly (2.1 pc). Based upon a simulation of close encounters with nearby stars, the binary star system Luyten 726-8 , which includes the variable star UV Ceti , will encounter Epsilon Eridani in approximately 31,500 years at a minimum distance of about 0.9 ly (0.29 parsecs). They will be less than 1 ly (0.3 parsecs) apart for about 4,600 years. If Epsilon Eridani has an Oort cloud , Luyten 726-8 could gravitationally perturb some of its comets with long orbital periods . An infrared excess around Epsilon Eridani
7381-436: The classical Greek alphabet such as heta ( Ͱ & ͱ ), meanwhile, usually take their nearest English equivalent (in this case, h ) but are too uncommon to be listed in formal transliteration schemes. Uncommon Greek letters which have been given formal romanizations include: The sounds of Modern Greek have diverged from both those of Ancient Greek and their descendant letters in English and other languages. This led to
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#17327803508387502-485: The constellation Eridanus was 10, and it was designated Quae omnes quatuor antecedit ( Latin for 'which precedes all four'); the meaning is the same as Ptolemy's description. Brahe assigned it magnitude 3. Epsilon Eridani's Bayer designation was established in 1603 as part of the Uranometria , a star catalogue produced by German celestial cartographer Johann Bayer . His catalogue assigned letters from
7623-480: The core along an orbit that has an eccentricity of 0.09. The position and velocity of Epsilon Eridani indicate that it may be a member of the Ursa Major Moving Group , whose members share a common motion through space. This behaviour suggests that the moving group originated in an open cluster that has since diffused. The estimated age of this group is 500±100 million years, which lies within
7744-490: The cosmological tree Yggdrasil to gain knowledge of the runic alphabet, which he passed on to humanity, and is associated closely with death, wisdom, and poetry. Odin is portrayed as the ruler of Asgard , and leader of the Aesir . Odin's wife is the powerful goddess Frigg who can see the future but tells no one, and together they have a beloved son, Baldr . After a series of dreams had by Baldr of his impending death, his death
7865-492: The dust in the disk to be cleared away by these processes is less than Epsilon Eridani's estimated age. Hence, the current dust disk must have been created by collisions or other effects of larger parent bodies, and the disk represents a late stage in the planet-formation process. It would have required collisions between 11 Earth masses' worth of parent bodies to have maintained the disk in its current state over its estimated age. The disk contains an estimated mass of dust equal to
7986-491: The evidence is sufficiently compelling that they regard the discovery as confirmed. The discovery was questioned in 2013 because a search program at La Silla Observatory did not confirm it exists. Further studies since 2018 have gradually reaffirmed the planet's existence through a combination of radial velocity and astrometry. Published sources remain in disagreement as to the planet's basic parameters. Recent values for its orbital period range from 7.3 to 7.6 years, estimates of
8107-399: The exozodiacal dust may be generated in the outer belt. This dust is then transported inward past the orbit of Epsilon Eridani b. When collisions between the dust grains are taken into account, the dust will reproduce the observed infrared spectrum and brightness. Outside the radius of ice sublimation , located beyond 10 au from Epsilon Eridani where the temperatures fall below 100 K,
8228-652: The first of the four in the apparent daily motion of the sky from east to west. Modern scholars of Ptolemy's catalogue designate its entry as "P 784" (in order of appearance) and "Eri 13" . Ptolemy described the star's magnitude as 3. Epsilon Eridani was included in several star catalogues of medieval Islamic astronomical treatises, which were based on Ptolemy's catalogue: in Al-Sufi 's Book of Fixed Stars , published in 964, Al-Biruni 's Mas'ud Canon , published in 1030, and Ulugh Beg 's Zij-i Sultani , published in 1437. Al-Sufi's estimate of Epsilon Eridani's magnitude
8349-404: The first rather than the second vowel letter, or by having a diaeresis ( ¨ ) over the second letter. For treatment of accents and diaereses —for example, ϊ —also see the section on romanizing Greek diacritical marks below. The traditional polytonic orthography of Greek uses several distinct diacritical marks to render what was originally the pitch accent of Ancient Greek and
8470-418: The formula m sin i , where m is the mass of the planet and i is the orbital inclination . Estimates for the value of m sin i ranged from 0.60 Jupiter masses to 1.06 Jupiter masses, which sets the lower limit for the mass of the planet (because the sine function has a maximum value of 1). Taking m sin i in the middle of that range at 0.78, and estimating the inclination at 30° as
8591-486: The god Freyr , is also frequently mentioned in surviving texts, and in his association with the weather, royalty, human sexuality, and agriculture brings peace and pleasure to humanity. Deeply lovesick after catching sight of the beautiful jötunn Gerðr , Freyr seeks and wins her love, yet at the price of his future doom. Their father is the powerful god Njörðr . Njörðr is strongly associated with ships and seafaring, and so also wealth and prosperity. Freyja and Freyr's mother
8712-503: The god Thor's hammer Mjölnir found among pagan burials and small silver female figures interpreted as valkyries or dísir , beings associated with war, fate or ancestor cults. By way of historical linguistics and comparative mythology , comparisons to other attested branches of Germanic mythology (such as the Old High German Merseburg Incantations ) may also lend insight. Wider comparisons to
8833-459: The gods. The Norns , dísir , and aforementioned valkyries also receive frequent mention. While their functions and roles may overlap and differ, all are collective female beings associated with fate. In Norse cosmology , all beings live in Nine Worlds that center around the cosmological tree Yggdrasil . The gods inhabit the heavenly realm of Asgard whereas humanity inhabits Midgard ,
8954-594: The inspiration for the later Etruscan and Roman numerals . This early system was replaced by Greek numerals which employed the entire alphabet, including the nonstandard letters digamma , stigma , or sigma-tau (placed between epsilon and zeta), koppa (placed between pi and rho), and sampi (placed after omega). As revised in 2001, ELOT 743 provides for the uncommon characters to be given (in Greek) as $ for stigma, + for koppa, and / for sampi. These symbols are not given lower-case equivalents. When used as numbers,
9075-763: The letters are used in combination with the upper keraia numeral sign ⟨ ʹ ⟩ to denote numbers from 1 to 900 and in combination with the lower keraia ⟨ ͵ ⟩ to denote multiples of 1000. ( For a full table of the signs and their values, see Greek numerals .) These values are traditionally romanized as Roman numerals , so that Αλέξανδρος Γ' ο Μακεδών would be translated as Alexander III of Macedon and transliterated as Aléxandros III o Makedṓn rather than Aléxandros G' or Aléxandros 3 . Greek laws and other official documents of Greece which employ these numerals, however, are to be formally romanized using "decimal" Arabic numerals . Ancient Greek text did not mark word division with spaces or interpuncts , instead running
9196-461: The line of sight from Earth is highly uncertain: estimates range from 24° to 72°. The high levels of chromospheric activity, strong magnetic field, and relatively fast rotation rate of Epsilon Eridani are characteristic of a young star. Most estimates of the age of Epsilon Eridani place it in the range from 200 million to 800 million years. The low abundance of heavy elements in the chromosphere of Epsilon Eridani usually indicates an older star, because
9317-408: The long-term variation in activity level appears to produce a temperature variation of 15 K, which corresponds to a variation in visual magnitude (V) of 0.014. The magnetic field on the surface of Epsilon Eridani causes variations in the hydrodynamic behaviour of the photosphere. This results in greater jitter during measurements of its radial velocity . Variations of 15 m s were measured over
9438-535: The modern period, classical and medieval Greek was also set using a wide array of ligatures , symbols combining or abbreviating various sets of letters, such as those included in Claude Garamond 's 16th-century grecs du roi . For the most part, such variants—as ϖ and [REDACTED] for π , ϛ for σ τ , and ϗ for και —are just silently emended to their standard forms and transliterated accordingly. Letters with no equivalent in
9559-615: The modern period, the Romanticist Viking revival re-awoke an interest in the subject matter, and references to Norse mythology may now be found throughout modern popular culture . The myths have further been revived in a religious context among adherents of Germanic Neopaganism . The historical religion of the Norse people is commonly referred to as Norse mythology . Other terms are Scandinavian mythology , North Germanic mythology or Nordic mythology . Norse mythology
9680-535: The most likely cause. This discovery was supported by astrometric measurements of Epsilon Eridani made between 2001 and 2003 with the Hubble Space Telescope , which showed evidence for gravitational perturbation of Epsilon Eridani by a planet. In 1960, physicists Philip Morrison and Giuseppe Cocconi proposed that extraterrestrial civilisations might be using radio signals for communication. Project Ozma , led by astronomer Frank Drake , used
9801-463: The mythology of other Indo-European peoples by scholars has resulted in the potential reconstruction of far earlier myths. Only a tiny amount of poems and tales survive of the many mythical tales and poems that are presumed to have existed during the Middle Ages, Viking Age, Migration Period, and before. Later sources reaching into the modern period, such as a medieval charm recorded as used by
9922-436: The mythology, Thor lays waste to numerous jötnar who are foes to the gods or humanity, and is wed to the beautiful, golden-haired goddess Sif . The god Odin is also frequently mentioned in surviving texts. One-eyed, wolf - and raven -flanked, with a spear in hand, Odin pursues knowledge throughout the nine realms. In an act of self-sacrifice, Odin is described as having hanged himself upside-down for nine days and nights on
10043-631: The names of exoplanets and their host stars that were produced by the competition. Epsilon Eridani is now listed as Ran in the IAU Catalog of Star Names. Professional astronomers have mostly continued to refer to the star as Epsilon Eridani. In Chinese , 天苑 ( Tiān Yuàn ), meaning Celestial Meadows , refers to an asterism consisting of ε Eridani, γ Eridani , δ Eridani , π Eridani , ζ Eridani , η Eridani , π Ceti , τ Eridani , τ Eridani , τ Eridani , τ Eridani , τ Eridani , τ Eridani , τ Eridani , τ Eridani and τ Eridani . Consequently,
10164-456: The north of latitude 80° N is it permanently hidden below the horizon. The apparent magnitude of 3.73 can make it difficult to observe from an urban area with the unaided eye, because the night skies over cities are obscured by light pollution . Epsilon Eridani has an estimated mass of 0.82 solar masses and a radius of 0.738 solar radii . It shines with a luminosity of only 0.34 solar luminosities . The estimated effective temperature
10285-425: The number 13 (the same as Ptolemy's catalogue number, as were many of Bayer's numbers) and described it as Decima septima ( Latin for 'the seventeenth'). Bayer assigned Epsilon Eridani magnitude 3. In 1690 Epsilon Eridani was included in the star catalogue of Johannes Hevelius . Its sequence number in constellation Eridanus was 14, its designation was Tertia ( Latin for 'the third'), and it
10406-399: The planet as confirmed. In 2015 the planet was given the proper name AEgir [ sic ]. The Epsilon Eridani planetary system also includes a debris disc consisting of a Kuiper belt analogue at 70 au from the star and warm dust between about 3 au and 20 au from the star. The gap in the debris disc between 20 and 70 au implies the likely existence of outer planets in
10527-513: The planet's orbital eccentricity are needed to explain the dust distribution. Epsilon Eridani is a target for planet finding programs because it has properties that allow an Earth-like planet to form. Although this system was not chosen as a primary candidate for the now-canceled Terrestrial Planet Finder , it was a target star for NASA's proposed Space Interferometry Mission to search for Earth-sized planets. The proximity, Sun-like properties and suspected planets of Epsilon Eridani have also made it
10648-605: The plights of the gods and their interaction with various other beings, such as with the jötnar , who may be friends, lovers, foes, or family members of the gods. Numerous gods are mentioned in the source texts. As evidenced by records of personal names and place names, the most popular god among the Scandinavians during the Viking Age was Thor the thunder god , who is portrayed as unrelentingly pursuing his foes, his mountain-crushing, thunderous hammer Mjölnir in hand. In
10769-448: The position of Epsilon Eridani between 1938 and 1972, Peter van de Kamp proposed that an unseen companion with an orbital period of 25 years was causing gravitational perturbations in its position. This claim was refuted in 1993 by Wulff-Dieter Heintz and the false detection was blamed on a systematic error in the photographic plates . Launched in 1983, the space telescope IRAS detected infrared emissions from stars near to
10890-418: The presence or absence of word-initial /h/ . In 1982, monotonic orthography was officially introduced for modern Greek. The only diacritics that remain are the acute accent (indicating stress) and the diaeresis (indicating that two consecutive vowels should not be combined). When a Greek diphthong is accented, the accent mark is placed over the second letter of the pair. This means that an accent over
11011-493: The proposed asteroid belt at a distance of 3 au. If the eccentricity was this high, the planet would pass through the asteroid belt and clear it out within about ten thousand years. If the belt has existed for longer than this period, which appears likely, it imposes an upper limit on Epsilon Eridani b's eccentricity of about 0.10–0.15. If the dust disk is instead being generated from the outer debris disk, rather than from collisions in an asteroid belt, then no constraints on
11132-517: The pupils of the 8th Grade at Mountainside Middle School in Colbert, Washington , United States. Both names derive from Norse mythology : Rán is the goddess of the sea and Ægir , her husband, is the god of the ocean. In 2016, the IAU organised a Working Group on Star Names (WGSN) to catalogue and standardise proper names for stars. In its first bulletin of July 2016, the WGSN explicitly recognised
11253-482: The radial velocity and astrometry methods. Planets more than 150% as massive as Jupiter can be ruled out at the inner edge of the debris disk at 30–35 au. Referred to as Epsilon Eridani b , this planet was announced in 2000, but the discovery remained controversial over roughly the next two decades. A comprehensive study in 2008 called the detection "tentative" and described the proposed planet as "long suspected but still unconfirmed". Many astronomers believed
11374-475: The range of the age estimates for Epsilon Eridani. During the past million years, three stars are believed to have come within 7 ly (2.1 pc) of Epsilon Eridani. The most recent and closest of these encounters was with Kapteyn's Star , which approached to a distance of about 3 ly (0.92 pc) roughly 12,500 years ago. Two more distant encounters were with Sirius and Ross 614 . None of these encounters are thought to have been close enough to affect
11495-546: The second edition of his star catalogue (its first edition was published in 1803), based on observations during 1792–1813, in which more than 7000 stars were grouped into 24 hours (0–23). Epsilon Eridani is number 89 in hour 3. Piazzi assigned it magnitude 4. In 1918 Epsilon Eridani appeared in the Henry Draper Catalogue with the designation HD 22049 and a preliminary spectral classification of K0. Based on observations between 1800 and 1880, Epsilon Eridani
11616-402: The size of its elliptical orbit—the semimajor axis —range from 3.38 au to 3.53 au, and approximations of its orbital eccentricity range from 0.055 to 0.26. Initially, the planet's mass was unknown, but a lower limit could be estimated based on the orbital displacement of Epsilon Eridani. Only the component of the displacement along the line of sight to Earth was known, which yields a value for
11737-547: The sound: ⟨th⟩, ⟨ph⟩, ⟨rh⟩, and ⟨ch⟩. Because English orthography has changed so much from the original Greek , modern scholarly transliteration now usually renders ⟨κ⟩ as ⟨k⟩ and the diphthongs ⟨αι, οι, ει, ου⟩ as ⟨ai, oi, ei, ou⟩. " Greeklish " has also spread within Greece itself, owing to the rapid spread of digital telephony from cultures using the Latin alphabet . Since Greek typefaces and fonts are not always supported or robust, Greek email and chatting has adopted
11858-427: The special rules for vowel combinations ( αι, αυ, ει, ευ, ηυ, οι, ου, ωυ ) only apply when these letters function as digraphs . There are also words where the same letters stand side by side incidentally but represent separate vowels. In these cases each of the two letters is transcribed separately according to the normal rules for single letters. Such cases are marked in Greek orthography by either having an accent on
11979-657: The standard forms (as, for example, "Demetrios OR Dimitrios"). Other romanization systems still encountered are the BGN/PCGN's earlier 1962 system and the system employed by the American Library Association and the United States' Library of Congress . Norse mythology Norse , Nordic , or Scandinavian mythology , is the body of myths belonging to the North Germanic peoples , stemming from Old Norse religion and continuing after
12100-456: The star with a period of about seven years. Although there is a high level of noise in the radial velocity data due to magnetic activity in its photosphere , any periodicity caused by this magnetic activity is expected to show a strong correlation with variations in emission lines of ionized calcium (the Ca II H and K lines ). Because no such correlation was found, a planetary companion was deemed
12221-472: The stellar wind, while the presence of a planetary system may also help keep this area clear of debris. Still, this does not preclude the possibility that an inner asteroid belt may be present with a combined mass no greater than the asteroid belt in the Solar System. As one of the nearest Sun-like stars, Epsilon Eridani has been the target of many attempts to search for planetary companions. Its chromospheric activity and variability mean that finding planets with
12342-412: The subject of multiple studies on whether an interstellar probe can be sent to Epsilon Eridani. Romanization of Greek Romanization of Greek is the transliteration ( letter -mapping) or transcription ( sound -mapping) of text from the Greek alphabet into the Latin alphabet . The conventions for writing and romanizing Ancient Greek and Modern Greek differ markedly. The sound of
12463-437: The surrounding interstellar medium of diffuse gas and dust, resulting in a bubble of heated hydrogen gas (an astrosphere , the equivalent of the heliosphere that surrounds the Sun). The absorption spectrum from this gas has been measured with the Hubble Space Telescope , allowing the properties of the stellar wind to be estimated. Epsilon Eridani's hot corona results in a mass loss rate in Epsilon Eridani's stellar wind that
12584-410: The surrounding plasma. Outside of this region, in the envelope, energy is carried to the photosphere by plasma convection , where it then radiates into space. Epsilon Eridani has a higher level of magnetic activity than the Sun, and thus the outer parts of its atmosphere (the chromosphere and corona ) are more dynamic. The average magnetic field strength of Epsilon Eridani across the entire surface
12705-646: The system as a plausible target for interstellar travel . The following year, the British Interplanetary Society suggested Epsilon Eridani as one of the targets in its Project Daedalus study. The system has continued to be among the targets of such proposals, such as Project Icarus in 2011. Based on its nearby location, Epsilon Eridani was among the target stars for Project Phoenix , a 1995 microwave survey for signals from extraterrestrial intelligence. The project had checked about 800 stars by 2004 but had not yet detected any signals. At
12826-489: The system. As one of the nearest Sun-like stars , Epsilon Eridani has been the target of several observations in the search for extraterrestrial intelligence . Epsilon Eridani appears in science fiction stories and has been suggested as a destination for interstellar travel . From Epsilon Eridani, the Sun would appear as a star in Serpens , with an apparent magnitude of 2.4. ε Eridani , Latinised to Epsilon Eridani ,
12947-401: The thunder-god Thor , the raven -flanked god Odin , the goddess Freyja , and numerous other deities . Most of the surviving mythology centers on the plights of the gods and their interaction with several other beings, such as humanity and the jötnar , beings who may be friends, lovers, foes, or family members of the gods. The cosmos in Norse mythology consists of Nine Worlds that flank
13068-494: The transmission and reception of their signals. This idea was tested by the National Radio Astronomy Observatory in 1988, which used outbursts of Nova Cygni 1975 as the timer. Fifteen days of observation showed no anomalous radio signals coming from Epsilon Eridani. Because of the proximity and Sun-like properties of Epsilon Eridani, in 1985 physicist and author Robert L. Forward considered
13189-469: The words together ( scripta continua ). In the Hellenistic period, a variety of symbols arose for punctuation or editorial marking ; such punctuation (or the lack thereof) are variously romanized, inserted, or ignored in different modern editions. Modern Greek punctuation generally follows French with the notable exception of Greek's use of a separate question mark , the erotimatiko , which
13310-524: The world is enveloped in flames, only to be reborn anew. There the surviving gods will meet, and the land will be fertile and green, and two humans will repopulate the world. Norse mythology has been the subject of scholarly discourse since the 17th century when key texts attracted the attention of the intellectual circles of Europe. By way of comparative mythology and historical linguistics , scholars have identified elements of Germanic mythology reaching as far back as Proto-Indo-European mythology . During
13431-567: Was 3. Al-Biruni quotes magnitudes from Ptolemy and Al-Sufi (for Epsilon Eridani he quotes the value 4 for both Ptolemy's and Al-Sufi's magnitudes; original values of both these magnitudes are 3). Its number in order of appearance is 786. Ulugh Beg carried out new measurements of Epsilon Eridani's coordinates in his observatory at Samarkand , and quotes magnitudes from Al-Sufi (3 for Epsilon Eridani). The modern designations of its entry in Ulugh Beg's catalogue are "U 781" and "Eri 13" (the latter
13552-611: Was a form of the Cumaean alphabet derived from the Euboean script that valued Χ as / k s / and Η as / h / and used variant forms of Λ and Σ that became L and S . When this script was used to write the classical Greek alphabet, ⟨κ⟩ was replaced with ⟨c⟩, ⟨αι⟩ and ⟨οι⟩ became ⟨æ⟩ and ⟨œ⟩, and ⟨ει⟩ and ⟨ου⟩ were simplified to ⟨i⟩ (more rarely—corresponding to an earlier pronunciation—⟨e⟩) and ⟨u⟩. Aspirated consonants like ⟨θ⟩, ⟨φ⟩, initial-⟨ρ⟩, and ⟨χ⟩ simply wrote out
13673-754: Was assigned magnitude 3 or 4 (sources differ). The star catalogue of English astronomer John Flamsteed , published in 1712, gave Epsilon Eridani the Flamsteed designation of 18 Eridani, because it was the eighteenth catalogued star in the constellation of Eridanus by order of increasing right ascension . In 1818 Epsilon Eridani was included in Friedrich Bessel 's catalogue, based on James Bradley 's observations from 1750–1762, and at magnitude 4. It also appeared in Nicolas Louis de Lacaille 's catalogue of 398 principal stars, whose 307-star version
13794-585: Was detected by IRAS indicating the presence of circumstellar dust. Observations with the James Clerk Maxwell Telescope (JCMT) at a wavelength of 850 μm show an extended flux of radiation out to an angular radius of 35 arcseconds around Epsilon Eridani, resolving the debris disc for the first time. Higher resolution images have since been taken with the Atacama Large Millimeter Array , showing that
13915-475: Was extensively modified in the second edition of the standard. International versions of ELOT 743, with an English language standard document, were approved by the UN (V/19, 1987) and the British and American governments. The ISO approved in 1997 its version, ISO 843 , with a different Type 1 transliteration system, which was adopted four years later by ELOT itself, while the U.N. did not update its version. So
14036-490: Was found to have a large proper motion across the celestial sphere , which was estimated at three arcseconds per year ( angular velocity ). This movement implied it was relatively close to the Sun, making it a star of interest for the purpose of stellar parallax measurements. This process involves recording the position of Epsilon Eridani as Earth moves around the Sun, which allows a star's distance to be estimated. From 1881 to 1883, American astronomer William L. Elkin used
14157-426: Was included in the catalogue of Johann Bode , in which about 17,000 stars were grouped into 102 constellations and numbered (Epsilon Eridani got the number 159 in the constellation Eridanus). Bode's catalogue was based on observations of various astronomers, including Bode himself, but mostly on Lalande's and Lacaille's (for the southern sky). Bode assigned Epsilon Eridani magnitude 3. In 1814 Giuseppe Piazzi published
14278-523: Was named by Ptolemy – Ποταμού ( Ancient Greek for 'River'), and Epsilon Eridani was listed as its thirteenth star. Ptolemy called Epsilon Eridani ό τών δ προηγούμενος ( Ancient Greek for 'a foregoing of the four') (here δ is the number four). This refers to a group of four stars in Eridanus: γ , π , δ and ε (10th–13th in Ptolemy's list). ε is the most western of these, and thus
14399-768: Was published in 1755 in the Ephémérides des Mouvemens Célestes, pour dix années, 1755–1765 , and whose full version was published in 1757 in Astronomiæ Fundamenta , Paris. In its 1831 edition by Francis Baily , Epsilon Eridani has the number 50. Lacaille assigned it magnitude 3. In 1801 Epsilon Eridani was included in Histoire céleste française , Joseph Jérôme Lefrançois de Lalande 's catalogue of about 50,000 stars, based on his observations of 1791–1800, in which observations are arranged in time order. It contains three observations of Epsilon Eridani. In 1847,
14520-412: Was suggested by Hubble astrometry, this yields a value of 1.55 ± 0.24 Jupiter masses for the planet's mass. More recent astrometric studies have found lower masses, ranging from 0.63 to 0.78 Jupiter masses. Of all the measured parameters for this planet, the value for orbital eccentricity is the most uncertain. The eccentricity of 0.7 suggested by some older studies is inconsistent with the presence of
14641-483: Was the original format for the mythology. Various forms of a cosmological creation story are provided in Icelandic sources, and references to a future destruction and rebirth of the world— Ragnarok —are frequently mentioned in some texts. According to the Prose Edda and the Poetic Edda poem, Völuspá , the first human couple consisted of Ask and Embla ; driftwood found by a trio of gods and imbued with life in
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