162-423: Neptune has appeared in fiction since shortly after its 1846 discovery, albeit infrequently. It initially made appearances indirectly—e.g. through its inhabitants—rather than as a setting . The earliest stories set on Neptune itself portrayed it as a rocky planet rather than as having its actual gaseous composition ; later works rectified this error. Extraterrestrial life on Neptune is uncommon in fiction, though
324-451: A degree of the position predicted by Le Verrier. Its largest moon, Triton , was discovered shortly thereafter, though none of the planet's remaining moons were located telescopically until the 20th century. The planet's distance from Earth gives it a small apparent size , and its distance from the Sun renders it very dim, making it challenging to study with Earth-based telescopes. Only
486-520: 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
648-431: A depth of 7,000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. Scientists believe that this kind of diamond rain occurs on Jupiter, Saturn, and Uranus. Very-high-pressure experiments at Lawrence Livermore National Laboratory suggest that the top of the mantle may be an ocean of liquid carbon with floating solid 'diamonds'. The core of Neptune
810-468: 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
972-411: 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
1134-606: A frequency range of 50–12 kHz at magnetic latitudes 7–33˚. These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere. During Voyager 2 ’s closest approach to Neptune, the PWS instrument provided Neptune's first plasma wave detections at a sample rate of 28,800 samples per second. The measured plasma densities range from 10 – 10 cm . Neptunian lightning may occur in three cloud layers, with microphysical modelling suggesting that most of these occurrences happen in
1296-519: A higher proportion of ices such as water, ammonia and methane . Similar to Uranus, its interior is primarily composed of ices and rock; both planets are normally considered "ice giants" to distinguish them. Along with Rayleigh scattering , traces of methane in the outermost regions make Neptune appear faintly blue. In contrast to the strongly seasonal atmosphere of Uranus, which can be featureless for long periods of time, Neptune's atmosphere has active and consistently visible weather patterns. At
1458-410: A hot, dense supercritical fluid . This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean. The mantle may consist of a layer of ionic water in which the water molecules break down into a soup of hydrogen and oxygen ions , and deeper down superionic water in which the oxygen crystallizes but the hydrogen ions float around freely within the oxygen lattice. At
1620-485: A letter and urged Berlin Observatory astronomer Galle to search with the observatory's refractor . Heinrich d'Arrest , a student at the observatory, suggested to Galle that they could compare a recently drawn chart of the sky in the region of Le Verrier's predicted location with the current sky to seek the displacement characteristic of a planet , as opposed to a fixed star. On the evening of 23 September 1846,
1782-401: A low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1 bar (100 kPa ), the temperature is 72.00 K (−201.15 °C). Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from
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#17327653080031944-514: A new planet. In 1845–1846, Urbain Le Verrier , developed his own calculations independently from Adams, but aroused no enthusiasm among his compatriots. In June 1846, upon seeing Le Verrier's first published estimate of the planet's longitude and its similarity to Adams's estimate, Airy persuaded James Challis to search for the planet. Challis vainly scoured the sky throughout August and September. Challis had, in fact, observed Neptune
2106-520: 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
2268-404: 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
2430-609: A permanent home in John R. Pierce 's 1930 short story " The Relics from the Earth ". In the 1950s, the moon appeared in Margaret St. Clair 's 1950 short story " The Pillows " and Alfred Bester 's 1956 novel The Stars My Destination —albeit called "Lassell" in the latter, after its discoverer William Lassell . In the late 20th century it started receiving more attention from science fiction writers than Neptune itself. The main such work
2592-410: 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
2754-439: 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
2916-524: A star and puts it on a collision course with Earth. In Robert William Cole 's 1900 novel The Struggle for Empire: A Story of the Year 2236 , described by science fiction scholar E. F. Bleiler as the first space opera and by Westfahl as the first appearance of a galactic empire , the vicinity of Neptune is the site of a battle between the British Empire that has come to rule the Solar System and
3078-430: 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
3240-401: 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
3402-522: A voyage into Neptune's atmosphere and Alex Irvine 's 2003 short story " Shepherded by Galatea " features resource extraction in the atmosphere. In the 1969 novel Macroscope by Piers Anthony , Neptune is converted to a world ship , and in the 1997 film Event Horizon the titular spacecraft is adrift in Neptunian orbit. The planet also appears in Jack Williamson 's 1985 short story " At
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#17327653080033564-720: 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 the Polynesians , mostly in the Southern Hemisphere, the star marked winter and
3726-457: A year before the planet's subsequent discoverer, Johann Gottfried Galle , and on two occasions, 4 and 12 August 1845. However, his out-of-date star maps and poor observing techniques meant that he failed to recognize the observations as such until he carried out later analysis. Challis was full of remorse but blamed his neglect on his maps and the fact that he was distracted by his concurrent work on comet observations. Meanwhile, Le Verrier sent
3888-433: Is Samuel R. Delany 's 1976 novel Triton ( a.k.a. Trouble on Triton: An Ambiguous Heterotopia ) which depicts future societies living there. Gordon Eklund 's 1989 novel A Thunder on Neptune is partially set on Triton and features an exobiological expedition to Neptune. In the 1994 novel Neptune Crossing by Jeffrey Carver , an alien on Triton helps humanity avert an impact event . Neptune Neptune
4050-472: 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 a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between
4212-432: Is 10–100 times greater than at the poles. This is interpreted as evidence for upwelling at the equator and subsidence near the poles, as photochemistry cannot account for the distribution without meridional circulation. In 2007, it was discovered that the upper troposphere of Neptune's south pole was about 10 K warmer than the rest of its atmosphere, which averages about 73 K (−200 °C). The temperature differential
4374-443: 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 a red giant before shedding its outer layers and collapsing into its current state as
4536-457: 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
4698-422: Is 28.32°, which is similar to the tilts of Earth (23°) and Mars (25°). As a result, Neptune experiences seasonal changes similar to those on Earth. The long orbital period of Neptune means that the seasons last for forty Earth years. Its sidereal rotation period (day) is roughly 16.11 hours. Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year
4860-434: Is 29.81 AU, and the aphelion distance is 30.33 AU. Neptune's orbital eccentricity is only 0.008678, making it the planet in the Solar System with the second most circular orbit after Venus . The orbit of Neptune is inclined 1.77° compared to that of Earth. On 11 July 2011, Neptune completed its first full barycentric orbit since its discovery in 1846; it did not appear at its exact discovery position in
5022-401: 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")
Neptune in fiction - Misplaced Pages Continue
5184-482: 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
5346-518: Is banded by clouds of varying compositions depending on altitude. The upper-level clouds lie at pressures below one bar, where the temperature is suitable for methane to condense. For pressures between one and five bars (100 and 500 kPa), clouds of ammonia and hydrogen sulfide are thought to form. Above a pressure of five bars, the clouds may consist of ammonia, ammonium sulfide , hydrogen sulfide and water. Deeper clouds of water ice should be found at pressures of about 50 bars (5.0 MPa), where
5508-481: 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
5670-513: Is commonly used. In Māori , the planet is called Tangaroa , named after the Māori god of the sea . In Nahuatl , the planet is called Tlāloccītlalli , named after the rain god Tlāloc . In Thai , Neptune is referred to by the Westernised name Dao Nepchun/Nepjun ( ดาวเนปจูน ) but is also called Dao Ket ( ดาวเกตุ , lit. ' star of Ketu ' ), after Ketu ( केतु ),
5832-515: 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
5994-469: Is enough to let methane, which elsewhere is frozen in the troposphere, escape into the stratosphere near the pole. The relative "hot spot" is due to Neptune's axial tilt , which has exposed the south pole to the Sun for the last quarter of Neptune's year, or roughly 40 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the south pole will be darkened and the north pole illuminated, causing
6156-426: Is faintly blue in the optical spectrum , only slightly more saturated than the blue of Uranus's atmosphere. Early renderings of the two planets greatly exaggerated Neptune's colour contrast "to better reveal the clouds, bands and winds", making it seem deep blue compared to Uranus's off-white. The two planets had been imaged with different systems, making it hard to directly compare the resulting composite images . This
6318-449: Is favoured due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. The current most widely accepted explanation of the details of this hypothesis is known as the Nice model , which is a dynamical evolution scenario that explores the potential effect of a migrating Neptune and the other giant planets on the structure of
6480-454: 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
6642-519: Is harder to explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets. The average distance between Neptune and the Sun is 4.5 billion km (about 30.1 astronomical units (AU), the mean distance from the Earth to the Sun), and it completes an orbit on average every 164.79 years, subject to a variability of around ±0.1 years. The perihelion distance
Neptune in fiction - Misplaced Pages Continue
6804-876: Is in the 1930 novel Last and First Men by Olaf Stapledon , which outlines the future history of humanity through several billions of years and various sequential species from the First Men to the Eighteenth. In the story, Neptune becomes humanity's refuge in the far future when the Sun expands. This plot point would later reappear in the 1934 short story " Twilight " by John W. Campbell and its 1935 sequel " Night ". After this however, says Stableford, Neptune "retreated into obscurity again as pulp science fiction grew more sophisticated". [ Gardner Dozois ] didn't mind that there were elephants on Neptune, or that they breathed oxygen, or that they could speak English, or that they could forage and find food—but it bothered
6966-409: Is likely composed of iron, nickel and silicates , with an interior model giving a mass about 1.2x that of Earth. The pressure at the centre is 7 Mbar (700 GPa), about twice as high as that at the centre of Earth, and the temperature may be 5,400 K (5,100 °C; 9,300 °F). At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium . A trace amount of methane
7128-558: Is nearly four times that of Earth . Neptune, like Uranus , is an ice giant , a subclass of giant planet , because they are smaller and have higher concentrations of volatiles than Jupiter and Saturn. In the search for exoplanets , Neptune has been used as a metonym : discovered bodies of similar mass are often referred to as "Neptunes", just as scientists refer to various extrasolar bodies as "Jupiters". Neptune's internal structure resembles that of Uranus . Its atmosphere forms about 5 to 10% of its mass and extends perhaps 10 to 20% of
7290-426: Is not any more extreme. Because Neptune is not a solid body, its atmosphere undergoes differential rotation . The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in
7452-533: 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,
7614-516: 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
7776-407: Is present. Prominent absorption bands of methane exist at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by atmospheric methane is part of what gives Neptune its faint blue hue, which is more pronounced for Neptune's due to concentrated haze in Uranus's atmosphere. Neptune's atmosphere is subdivided into two main regions:
7938-471: Is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star . An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. This hypothesis of migration after formation
8100-695: 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
8262-490: Is the eighth and farthest known planet from the Sun . It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet . It is 17 times the mass of Earth . Compared to its fellow ice giant Uranus , Neptune is slightly more massive, but denser and smaller. Being composed primarily of gases and liquids, it has no well-defined solid surface, and orbits
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#17327653080038424-690: Is thought to be a " skin effect " and not due to any deeper atmospheric processes. At 70°S latitude, a high-speed jet travels at a speed of 300 m/s. Due to seasonal changes, the cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo . This trend was first seen in 1980. The long orbital period of Neptune results in seasons lasting 40 Earth years. Neptune differs from Uranus in its typical level of meteorological activity. Voyager 2 observed weather phenomena on Neptune during its 1989 flyby, but no comparable phenomena on Uranus during its 1986 flyby. The abundance of methane, ethane and acetylene at Neptune's equator
8586-479: 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
8748-625: 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",
8910-514: 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
9072-520: 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
9234-824: 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
9396-588: The dipole moment in strength. By contrast, Earth, Jupiter and Saturn have only relatively small quadrupole moments, and their fields are less tilted from the polar axis. The large quadrupole moment of Neptune may be the result of an offset from the planet's centre and geometrical constraints of the field's dynamo generator. Measurements by Voyager 2 in extreme-ultraviolet and radio frequencies revealed that Neptune has faint and weak but complex and unique aurorae ; however, these observations were limited in time and did not contain infrared. Subsequent astronomers using
9558-609: The orbit of Uranus . Subsequent observations revealed substantial deviations from the tables, leading Bouvard to hypothesize that an unknown body was perturbing the orbit through gravitational interaction. In 1843, John Couch Adams began work on the orbit of Uranus using the data he had. He requested extra data from Sir George Airy , the Astronomer Royal , who supplied it in February 1844. Adams continued to work in 1845–1846 and produced several different estimates of
9720-612: 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
9882-401: 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
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#173276530800310044-568: The tropopause layer. The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other, unknown mechanism. In 1989, Voyager 2 's Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7 × 10 J . A plasma wave system (PWS) detected 16 electromagnetic wave events with
10206-453: 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
10368-448: The 1930 short story " The Monsters of Neptune " by Henrik Dahl Juve , this time with a tropical climate. Alien life on Neptune, while uncommon, appears in some stories; "A Baby on Neptune" features gaseous lifeforms and "The Monsters of Neptune" grotesque creatures, while Neptune in the 1932 novel The Vanguard to Neptune by J. M. Walsh is populated by humanoids . In the 1930 short story " The Universe Wreckers " by Edmond Hamilton ,
10530-596: 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
10692-427: 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
10854-464: The French Bureau des Longitudes . In October, he sought to name the planet Le Verrier , after himself, and he had loyal support in this from the observatory director, François Arago . This suggestion met with stiff resistance outside France. French almanacs quickly reintroduced the name Herschel for Uranus, after that planet's discoverer Sir William Herschel , and Leverrier for
11016-637: The French and the British over who deserved credit for the discovery. Eventually, an international consensus emerged that Le Verrier and Adams deserved joint credit. Since 1966, Dennis Rawlins has questioned the credibility of Adams's claim to co-discovery, and the issue was re-evaluated by historians with the return in 1998 of the "Neptune papers" (historical documents) to the Royal Observatory, Greenwich . Shortly after its discovery, Neptune
11178-496: The Hubble Space Telescope have not glimpsed the aurorae, in contrast to the more well-defined aurorae of Uranus. Neptune's bow shock , where the magnetosphere begins to slow the solar wind , occurs at a distance of 34.9 times the radius of the planet. The magnetopause , where the pressure of the magnetosphere counterbalances the solar wind, lies at a distance of 23–26.5 times the radius of Neptune. The tail of
11340-562: 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
11502-577: The Human Limit ", Gregory Feeley 's 1986 short story " Neptune's Reach ", the adventures of comic book superhero Superman , the television series Doctor Who , and the video game Descent . Neptune's largest moon Triton was discovered less than a month after the planet. A few works in the 1930s depicted humans going to Triton, looking for minerals in Roman Frederick Starzl 's 1932 short story " The Power Satellite " and
11664-504: The Kuiper belt. Neptune's orbit has a profound impact on the region directly beyond it, known as the Kuiper belt . The Kuiper belt is a ring of small icy worlds, similar to the asteroid belt but far larger, extending from Neptune's orbit at 30 AU out to about 55 AU from the Sun. Much in the same way that Jupiter's gravity dominates the asteroid belt , Neptune's gravity dominates
11826-410: The Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in its structure. The region between 40 and 42 AU is an example. There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune's orbital period is a precise fraction of that of
11988-598: 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
12150-635: 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
12312-446: The Solar System, and it results in strong latitudinal wind shear. The formation of the ice giants, Neptune and Uranus, has been difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion , and various hypotheses have been advanced to explain their formation. One
12474-545: The Sun once every 164.8 years at an orbital distance of 30.1 astronomical units (4.5 billion kilometres; 2.8 billion miles). It is named after the Roman god of the sea and has the astronomical symbol [REDACTED] , representing Neptune's trident . Neptune is not visible to the unaided eye and is the only planet in the Solar System that was found from mathematical predictions derived from indirect observations rather than being initially observed by direct empirical observation , when unexpected changes in
12636-589: 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
12798-415: 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
12960-413: The Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C ; −361 °F ). Temperatures at the planet's centre are approximately 5,400 K (5,100 °C; 9,300 °F). Neptune has a faint and fragmented ring system (labelled "arcs"), discovered in 1984 and confirmed by Voyager 2 . Some of
13122-462: The Sun, making Neptune the ninth planet from the Sun during this period. The increasingly accurate estimations of Pluto's mass from ten times that of Earth's to far less than that of the Moon and the discovery of the Kuiper belt in 1992 led many astronomers to debate whether Pluto should be considered a planet or as part of the Kuiper belt. In 2006, the International Astronomical Union defined
13284-419: 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
13446-464: The Sun; whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. Neptune is over 50% farther from the Sun than Uranus and receives only ~40% of Uranus's amount of sunlight; however, its internal energy is still enough for the fastest planetary winds in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it
13608-565: The advent of the Hubble Space Telescope and of large ground-based telescopes with adaptive optics allowed for detailed observations. Neptune was visited by Voyager 2 , which flew by the planet on 25 August 1989; Voyager 2 remains the only spacecraft to have visited it. Like the gas giants ( Jupiter and Saturn ), Neptune's atmosphere is composed primarily of hydrogen and helium , along with traces of hydrocarbons and possibly nitrogen , but contains
13770-473: 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
13932-405: 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
14094-476: 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
14256-431: The cloud deck. These altitudes are in the layer where weather occurs, the troposphere. Weather does not occur in the higher stratosphere or thermosphere. In August 2023, the high-altitude clouds of Neptune vanished, prompting a study spanning thirty years of observations by the Hubble Space Telescope and ground-based telescopes. The study found that Neptune's high-altitude cloud activity is bound to Solar cycles , and not to
14418-405: 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,
14580-411: The day Galle received the letter, he discovered Neptune just northeast of Iota Aquarii , 1° from the " five degrees east of Delta Capricorn " position Le Verrier had predicted it to be, about 12° from Adams's prediction, and on the border of Aquarius and Capricornus according to the modern IAU constellation boundaries. In the wake of the discovery, there was a nationalistic rivalry between
14742-673: The descending lunar node , who plays a role in Hindu astrology . In Malay , the name Waruna , after the Hindu god of seas , is attested as far back as the 1970s, but was eventually superseded by the Latinate equivalents Neptun (in Malaysian ) or Neptunus (in Indonesian ). The usual adjectival form is Neptunian . The nonce form Poseidean ( / p ə ˈ s aɪ d i ən / ), from Poseidon , has also been used, though
14904-451: 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
15066-512: The earliest known telescopic observations ever, Galileo's drawings on 28 Dec. 1612 and 27 Jan. 1613 ( New Style ) contain plotted points that match what is now known to have been the positions of Neptune on those dates. Both times, Galileo seems to have mistaken Neptune for a fixed star when it appeared close—in conjunction —to Jupiter in the night sky . Hence, he is not credited with Neptune's discovery. At his first observation in Dec. 1612, Neptune
15228-402: The easterly direction to 325 m/s westward. At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles. Most of the winds on Neptune move in a direction opposite the planet's rotation. The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction
15390-457: 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
15552-538: 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,
15714-934: The exceptions have ranged from humanoids to gaseous lifeforms. Neptune's largest moon Triton has also appeared in fiction, especially in the late 20th century onwards. Neptune was discovered in 1846 and has only made occasional appearances in fiction since then; in the catalogue of early science fiction works compiled by E. F. Bleiler and Richard Bleiler in the reference works Science-Fiction: The Early Years from 1990 and Science-Fiction: The Gernsback Years from 1998, Neptune appears in 9 (out of 2,475) and 18 (out of 1,835) works respectively, compared to 194 for Mars in fiction and 131 for Venus in fiction in The Gernsback Years alone. Brian Ash writes in The Visual Encyclopedia of Science Fiction that "Neptune has been largely overlooked in
15876-553: 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
16038-445: The first ground-based observation of a dark spot on Neptune was announced. Neptune's dark spots are thought to occur in the troposphere at lower altitudes than the brighter cloud features, so they appear as holes in the upper cloud decks. As they are stable features that can persist for several months, they are thought to be vortex structures. Often associated with dark spots are brighter, persistent methane clouds that form around
16200-400: The forces of a rival empire centered on Sirius . Early works incorrectly depicted Neptune as a solid planet , and several stories thus include human expeditions to its surface. The earliest story where Neptune itself directly appears as a setting is the 1929 short story " A Baby on Neptune " by Clare Winger Harris and Miles J. Breuer , where the planet is covered in ice. It also appears in
16362-480: The former inhabitants of Neptune have left the planet for its moon Triton due to environmental changes . The concept of Neptune turning into a star from "The Star" was reused in the 1932 short story " Raiders of the Universes " by Donald Wandrei , although in this case it then proceeds to leave the Solar System rather than heading towards its center. The most significant appearance of Neptune in fiction in this era
16524-720: The genre", and Richard L. McKinney describes it as "unexplored territory" in The Greenwood Encyclopedia of Science Fiction and Fantasy . The Encyclopedia of Science Fiction attributes this in part to its relatively late date of discovery, Brian Stableford writes in Science Fact and Science Fiction: An Encyclopedia that its remote location was a significant factor, and science fiction scholar Gary Westfahl posits in Science Fiction Literature through History: An Encyclopedia that
16686-488: 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
16848-547: The hell out of him that I'd given Neptune a solid surface when everyone knows it's a gas giant, so I had to insert a sentence explaining that. Mike Resnick , on selling the 2002 short story " The Elephants on Neptune " to Asimov's Science Fiction Once more became known about Neptune through advances in planetary science , fiction writers began portraying it more accurately as a gaseous planet . Thus Alexei Panshin 's 1969 short story " One Sunday in Neptune " depicts
17010-495: The largest of the known Kuiper belt objects, Pluto , is among them. Although Pluto crosses Neptune's orbit regularly, the 2:3 resonance makes it so that they can never collide. The 3:4, 3:5, 4:7 and 2:5 resonances are less populated. Sirius Sirius is the brightest star in the night sky . Its name is derived from the Greek word Σείριος (Latin script: Seirios ), meaning lit. 'glowing' or 'scorching'. The star
17172-453: The lower troposphere , where temperature decreases with altitude, and the stratosphere , where temperature increases with altitude. The boundary between the two, the tropopause , lies at a pressure of 0.1 bars (10 kPa). The stratosphere then gives way to the thermosphere at a pressure lower than 10 to 10 bars (1 to 10 Pa). The thermosphere gradually transitions to the exosphere . Models suggest that Neptune's troposphere
17334-405: The magnetic equator of Neptune is about 14 microteslas (0.14 G ). The dipole magnetic moment of Neptune is about 2.2 × 10 T·m (14 μT· R N , where R N is the radius of Neptune). Neptune's magnetic field has a complex geometry that includes relatively large contributions from non-dipolar components, including a strong quadrupole moment that may exceed
17496-401: The magnetic fields of the two planets, scientists now think the extreme orientation may be characteristic of flows in the planets' interiors. This field may be generated by convective fluid motions in a thin spherical shell of electrically conducting liquids (probably a combination of ammonia, methane and water), resulting in a dynamo action. The dipole component of the magnetic field at
17658-403: The magnetosphere extends out to at least 72 times the radius of Neptune, and likely much farther. Neptune's weather is characterized by extremely dynamic storm systems, with winds reaching speeds of almost 600 m/s (2,200 km/h; 1,300 mph)—exceeding supersonic flow. More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in
17820-532: 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
17982-600: The methane release to shift to the north pole. In 1989, the Great Dark Spot , an anticyclonic storm system spanning 13,000 km × 6,600 km (8,100 mi × 4,100 mi), was discovered by NASA 's Voyager 2 spacecraft. The storm resembled the Great Red Spot of Jupiter. Some five years later, on 2 November 1994, the Hubble Space Telescope did not see the Great Dark Spot on
18144-561: The new planet. Struve came out in favour of the name Neptune on 29 December 1846, to the Saint Petersburg Academy of Sciences , after the colour of the planet as viewed through a telescope. Soon, Neptune became the internationally accepted name. In Roman mythology , Neptune was the god of the sea, identified with the Greek Poseidon . The demand for a mythological name seemed to be in keeping with
18306-450: 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 the SSW direction, so it will be visible from
18468-401: The nomenclature of the other planets, all of which were named for deities in Greek and Roman mythology. Most languages today use some variant of the name "Neptune" for the planet. In Chinese, Vietnamese, Japanese, and Korean, the planet's name was translated as "sea king star" ( 海王星 ). In Mongolian , Neptune is called Dalain van ( Далайн ван ), reflecting its namesake god's role as
18630-404: The object, such as 1:2, or 3:4. If, say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit by the time Neptune returns to its original position. The most heavily populated resonance in the Kuiper belt, with over 200 known objects, is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because
18792-463: 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 the fertility of their land. The ancient Greeks observed that
18954-404: The orbit of Uranus led Alexis Bouvard to hypothesise that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard's death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier . Neptune was subsequently directly observed with a telescope on 23 September 1846 by Johann Gottfried Galle within
19116-512: The planet visits Earth. Neptune was usually omitted in the subgenre of works visiting multiple locations in the Solar System that appeared in this time, though it did make some indirect appearances in works not otherwise set there. Supernatural communication with its inhabitants appears in Marie Corelli 's 1892 novel The Soul of Lilith . In the 1897 short story " The Star " by H. G. Wells , an impact event causes Neptune to turn into
19278-429: The planet's seasons. Neptune's spectra suggest that its lower stratosphere is hazy due to condensation of products of ultraviolet photolysis of methane, such as ethane and ethyne . The stratosphere is home to trace amounts of carbon monoxide and hydrogen cyanide . The stratosphere of Neptune is warmer than that of Uranus due to the elevated concentration of hydrocarbons. For reasons that remain obscure,
19440-576: The planet's thermosphere is at an anomalously high temperature of about 750 K (477 °C; 890 °F). The planet is too far from the Sun for this heat to be generated by ultraviolet radiation. One candidate for a heating mechanism is atmospheric interaction with ions in the planet's magnetic field . Other candidates are gravity waves from the interior that dissipate in the atmosphere. The thermosphere contains traces of carbon dioxide and water, which may have been deposited from external sources such as meteorites and dust. Neptune's atmosphere
19602-477: The planet. Instead, a new storm similar to the Great Dark Spot was found in Neptune's northern hemisphere. The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when they were observed moving at speeds faster than the Great Dark Spot (and images acquired later would subsequently reveal
19764-476: The presence of clouds moving even faster than those that had initially been detected by Voyager 2 ). The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It was initially completely dark, but as Voyager 2 approached the planet, a bright core developed, which can be seen in most of the highest-resolution images. In 2018, a newer main dark spot and smaller dark spot were identified and studied. In 2023,
19926-399: The presumed-harsh environmental conditions of the planet made it unappealing for writers to use it as a setting . The first time Neptune was mentioned in a work of fiction—then called "Leverrier's planet" after astronomer Urbain Le Verrier whose orbital calculations led to the planet's discovery —was in the 1848 novel The Triumphs of Woman by Charles Rowcroft where an inhabitant of
20088-441: 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
20250-638: The ruler of the sea. In modern Greek , the planet is called Poseidon ( Ποσειδώνας , Poseidonas ), the Greek counterpart of Neptune. In Hebrew , Rahab ( רהב ), from a Biblical sea monster mentioned in the Book of Psalms , was selected in a vote managed by the Academy of the Hebrew Language in 2009 as the official name for the planet, even though the existing Latin term Neptun ( נפטון )
20412-448: The sky because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July, Neptune was not at its exact discovery position in relation to the Sun—if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011. The axial tilt of Neptune
20574-481: 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 is about twice as massive as the Sun ( M ☉ ) and has an absolute visual magnitude of +1.43. It
20736-575: 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
20898-415: 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
21060-538: 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]
21222-629: 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
21384-427: 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
21546-617: 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
21708-510: 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
21870-406: The temperature reaches 273 K (0 °C; 32 °F). Underneath, clouds of ammonia and hydrogen sulfide may be found. High-altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are high-altitude cloud bands that wrap around the planet at constant latitudes. These circumferential bands have widths of 50–150 km and lie about 50–110 km above
22032-492: The time of the Voyager ;2 flyby in 1989, the planet's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. In 2018, a newer main dark spot and smaller dark spot were identified and studied. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, as high as 2,100 km/h (580 m/s; 1,300 mph). Because of its great distance from
22194-579: 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
22356-417: 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 is gradually moving closer to the Solar System; it is expected to increase in brightness slightly over
22518-442: The usual adjectival form of Poseidon is Poseidonian ( / ˌ p ɒ s aɪ ˈ d oʊ n i ən / ). From its discovery in 1846 until the discovery of Pluto in 1930, Neptune was the farthest known planet. When Pluto was discovered, it was considered a planet, and Neptune thus became the second-farthest known planet, except for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer than Neptune to
22680-410: 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
22842-433: 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
23004-476: The water clouds of the troposphere or the shallow ammonia clouds of the magnetosphere. Neptune is predicted to have 1/19 the lightning flash rate of Jupiter and to display most of its lightning activity at high latitudes. However, lightning on Neptune seems to resemble lightning on Earth rather than Jovian lightning. Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating . The upper regions of Neptune's troposphere reach
23166-399: The way towards the core. Pressure in the atmosphere reaches about 10 GPa , or about 10 atmospheres. Increasing concentrations of methane , ammonia and water are found in the lower regions of the atmosphere. The mantle is equivalent to 10 to 15 Earth masses and is rich in water, ammonia and methane. As is customary in planetary science, this mixture is called icy even though it is
23328-432: 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
23490-492: The word "planet" for the first time, reclassifying Pluto as a " dwarf planet " and making Neptune once again the outermost-known planet in the Solar System. Neptune's mass of 1.0243 × 10 kg is intermediate between Earth and the larger gas giants : it is 17 times that of Earth but just 1/19th that of Jupiter . Its gravity at 1 bar is 11.15 m/s , 1.14 times the surface gravity of Earth, and surpassed only by Jupiter. Neptune's equatorial radius of 24,764 km
23652-412: 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
23814-657: 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
23976-517: Was almost stationary in the sky because it had just turned retrograde that day. This apparent backward motion is created when Earth's orbit takes it past an outer planet. Because Neptune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with Galileo's small telescope. In 2009, a study suggested that Galileo was at least aware that the "star" he had observed had moved relative to fixed stars. In 1821, Alexis Bouvard published astronomical tables of
24138-414: 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
24300-472: 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 the solar year . This rising occurs at Cairo on 19 July ( Julian ), placing it just before
24462-551: 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
24624-416: 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
24786-491: 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
24948-469: 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
25110-439: 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
25272-449: 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 ,
25434-446: 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
25596-480: 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
25758-449: 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
25920-410: Was referred to simply as "the planet exterior to Uranus" or as "Le Verrier's planet". The first suggestion for a name came from Galle, who proposed the name Janus . In England, Challis put forward the name Oceanus . Claiming the right to name his discovery, Le Verrier quickly proposed the name Neptune for this new planet, though falsely stating that this had been officially approved by
26082-483: Was revisited with the colour normalised over time, most comprehensively in late 2023. Neptune's magnetosphere consists of a magnetic field that is strongly tilted relative to its rotational axis at 47° and offset of at least 0.55 radius (~13,500 km) from the planet's physical centre—resembling Uranus's magnetosphere. Before the arrival of Voyager 2 to Neptune, it was hypothesised that Uranus's sideways rotation caused its tilted magnetosphere. In comparing
26244-503: 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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