Keyzer and de Houtman assigned fifteen stars to the constellation in their Malay and Madagascan vocabulary, with a star that would be later designated as Alpha Hydri marking the head, Gamma the chest and a number of stars that were later allocated to Tucana, Reticulum, Mensa and Horologium marking the body and tail. Lacaille charted and designated 20 stars with the Bayer designations Alpha through to Tau in 1756. Of these, he used the designations Eta, Pi and Tau twice each, for three sets of two stars close together, and omitted Omicron and Xi. He assigned Rho to a star that subsequent astronomers were unable to find.
Stars
Hydrus
Hydrus | Stars
Beta Hydri, Alpha Hydri, etc. Alpha Hydri Beta Hydri, Alpha Hydri, Beta Centauri Alpha Hydri, Beta Hydri
what is hydrus?
user
Small constellation in the deep southern sky.
assistant
what are its characteristics?
user
Irregular in shape and its tail has been shortened to make space for this last constellation he had drawn up.
assistant
name a few stars in the constellation?
user
This is the list of notable stars in the constellation Hydrus, sorted by decreasing brightness.
List of stars in Hydrus | Introduction
Keyzer and de Houtman assigned fifteen stars to the constellation in their Malay and Madagascan vocabulary, with a star that would be later designated as Alpha Hydri marking the head, Gamma the chest and a number of stars that were later allocated to Tucana, Reticulum, Mensa and Horologium marking the body and tail. Lacaille charted and designated 20 stars with the Bayer designations Alpha through to Tau in 1756. Of these, he used the designations Eta, Pi and Tau twice each, for three sets of two stars close together, and omitted Omicron and Xi. He assigned Rho to a star that subsequent astronomers were unable to find.
Hydrus | Stars
Irregular in shape, Hydrus is bordered by Mensa to the southeast, Eridanus to the east, Horologium and Reticulum to the northeast, Phoenix to the north, Tucana to the northwest and west, and Octans to the south; Lacaille had shortened Hydrus' tail to make space for this last constellation he had drawn up. Covering 243 square degrees and 0.589% of the night sky, it ranks 61st of the 88 constellations in size. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Hyi". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 12 segments.
Hydrus | Characteristics
Thought to be between 6.4 and 7.1 billion years old, this star bears some resemblance to what the Sun may look like in the far distant future, making it an object of interest to astronomers. It is also the closest bright star to the south celestial pole. Located at the northern edge of the constellation and just southwest of Achernar is Alpha Hydri, a white sub-giant star of magnitude 2.9, situated 72 light-years from Earth. Of spectral type F0IV, it is beginning to cool and enlarge as it uses up its supply of hydrogen. It is twice as massive and 3.3 times as wide as our sun and 26 times more luminous.
Hydrus | Stars
A line drawn between Alpha Hydri and Beta Centauri is bisected by the south celestial pole.
Hydrus | Stars
Beta Hydri, the brightest star in Hydrus, is a yellow star of apparent magnitude 2.8, lying 24 light-years from Earth. It has about 104% of the mass of the Sun and 181% of the Sun's radius, with more than three times the Sun's luminosity. The spectrum of this star matches a stellar classification of G2 IV, with the luminosity class of 'IV' indicating this is a subgiant star. As such, it is a slightly more evolved star than the Sun, with the supply of hydrogen fuel at its core becoming exhausted. It is the nearest subgiant star to the Sun and one of the oldest stars in the solar neighbourhood.
Hydrus | Stars
Hydrus is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm (14 in) diameter celestial globe published in late 1597 (or early 1598) in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. Its name means "male water snake", as opposed to Hydra, a much larger constellation that represents a female water snake.
Hydrus | Introduction
Beta Hydri (β Hyi, β Hydri) is a star in the southern circumpolar constellation of Hydrus. (Note that Hydrus is not the same as Hydra.) With an apparent visual magnitude of 2.8, this is the brightest star in the constellation. Based upon parallax measurements the distance to this star is about . This star has about 104% of the mass of the Sun and 181% of the Sun's radius, with more than three times the Sun's luminosity. The spectrum of this star matches a stellar classification of G2 IV, with the luminosity class of 'IV' indicating this is a subgiant star.
Beta Hydri | Introduction
ν Hydri, Latinized as Nu Hydri, is a single star in the southern circumpolar constellation of Hydrus. It is orange-hued and faintly visible to the naked eye with an apparent visual magnitude of 4.76. This object is located approximately 331 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +3 km/s. It is a member of the Ursa Major Moving Group of stars that share a common motion through space. This is an aging giant star with a stellar classification of K3III. With the supply of hydrogen at its core exhausted, the star has expanded and cooled.
Nu Hydri | Introduction
The map of Chinese constellation in constellation Hydrus area consists of:
Hydrus in Chinese astronomy | Stars
The modern constellation Hydrus is not included in the Three Enclosures and Twenty-Eight Mansions system of traditional Chinese uranography because its stars are too far south for observers in China to know about them prior to the introduction of Western star charts. Based on the work of Xu Guangqi and the German Jesuit missionary Johann Adam Schall von Bell in the late Ming Dynasty, this constellation has been classified under the 23 "Southern Asterisms" (近南極星區, "Jìnnánjíxīngōu") with the names "Snake's Tail" (蛇尾, "Shéwěi"), "Snake's Abdomen" (蛇腹, "Shéfù"), "Snake's Head" (蛇首, "Shéshǒu") and "White Patched Nearby" (附白, "Fùbái"). The name of the western constellation in modern Chinese is 水蛇座 ("shuǐ shé zuò"), which means "the water snake constellation".
Hydrus in Chinese astronomy | Introduction
The constellation also contains a spiral galaxy, NGC 1511, which lies edge on to observers on Earth and is readily viewed in amateur telescopes. Located mostly in Dorado, the Large Magellanic Cloud extends into Hydrus. The globular cluster NGC 1466 is an outlying component of the galaxy, and contains many RR Lyrae-type variable stars. It has a magnitude of 11.59 and is thought to be over 12 billion years old. Two stars, HD 24188 of magnitude 6.3 and HD 24115 of magnitude 9.0, lie nearby in its foreground. NGC 602 is composed of an emission nebula and a young, bright open cluster of stars that is an outlying component on the eastern edge of the Small Magellanic Cloud, a satellite galaxy to the Milky Way.
Hydrus | Deep-sky objects
It remains below the horizon for most Northern Hemisphere observers. The brightest star is the 2.8-magnitude Beta Hydri, also the closest reasonably bright star to the south celestial pole. Pulsating between magnitude 3.26 and 3.33, Gamma Hydri is a variable red giant 60 times the diameter of our Sun. Lying near it is VW Hydri, one of the brightest dwarf novae in the heavens. Four star systems in Hydrus have been found to have exoplanets to date, including HD 10180, which could bear up to nine planetary companions.
Hydrus | Introduction
Hydrus was one of the twelve constellations established by the Dutch astronomer Petrus Plancius from the observations of the southern sky by the Dutch explorers Pieter Dirkszoon Keyser and Frederick de Houtman, who had sailed on the first Dutch trading expedition, known as the "Eerste Schipvaart", to the East Indies. It first appeared on a 35-cm (14 in) diameter celestial globe published in 1598 in Amsterdam by Plancius with Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in the German cartographer Johann Bayer's "Uranometria" of 1603. De Houtman included it in his southern star catalogue the same year under the Dutch name "De Waterslang", "The Water Snake", it representing a type of snake encountered on the expedition rather than a mythical creature.
Hydrus | History
Epsilon Hydri, Latinized from ε Hydri, is a single, blue-white hued star in the southern constellation of Hydrus. It is a faint star with an apparent visual magnitude of 4.12, but it can be seen with the naked eye. Measurements made by the Hipparcos spacecraft showed an annual parallax shift of 21.48 mas, which provides a distance estimate of 152 light years. The star is moving away from the Sun with a radial velocity of +13.6 km/s. It is a member of the Tucana-Horologium moving group, an association of stars that share a common motion through space. The stellar classification for this star is B9 Va, indicating that is it a B-type main-sequence star that is generating energy through hydrogen fusion at its core.
Epsilon Hydri | Introduction
This is the list of notable stars in the constellation Taurus, sorted by decreasing brightness.
List of stars in Taurus | Introduction
Hydrus is a small constellation in the southern sky. Hydrus may also refer to:
Hydrus (disambiguation) | Introduction
Alpha Hydri (α Hyi, α Hydri) is the second brightest star in the southern circumpolar constellation of Hydrus. It is readily visible to the naked eye with an apparent visual magnitude of +2.9. It is sometimes informally known as the Head of Hydrus. This should not be confused with Alpha Hydrae (Alphard) in the constellation Hydra. Alpha Hydri is one of only three stars in the constellation Hydrus that are above the fourth visual magnitude. This star can be readily located as it lies to the south and west of the prominent star Achernar in the constellation Eridanus. Based upon parallax measurements from the Hipparcos mission, Alpha Hydri is located at a distance of about from Earth.
Alpha Hydri | Introduction
However, this may have been based on a photographic plate that was later rejected. It is listed in the General Catalogue of Variable Stars, but marked as probably constant. The star is about 311 million years old and is radiating 91 times the luminosity of the Sun from its photosphere at an effective temperature of 9,816 K.
Eta1 Hydri | Introduction
This system appears among bright stars in a compact pentagon, resembling a quadrilateral due to the suggestive proximity (close arc distance) to Epsilon Hydrae (ε Hya). This shape in the Greco-Roman tradition, which draws on trading and navigation histories shared with nearby older-recorded astrologies is an asterism that represents the head of the water snake. This light source, along with comparable strength (apparent magnitude) Epsilon, δ Hya (Lisan al Sudja), ζ Hya, η Hya, and σ Hya (Minchir), were Ulug Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Min al Azʽal" or "Minazal" were the title for five stars: δ Hya as "Minazal I", η Hya as "Minazal II", ε Hya as "Minazal III", ρ Hya as "Minazal IV" and ζ Hya as "Minazal V" (exclude σ Hya).
Rho Hydrae | Name and etymology
Delta Hydri, Latinized from δ Hydri, is a single, white-hued star in the southern constellation of Hydrus. It is bright enough to be faintly visible to the naked eye with an apparent visual magnitude of 4.09. The distance to this star, based upon an annual parallax shift of 23.35 mas, is about 140 light years. It is moving away from the Sun with a radial velocity of +6 km/s. This is an ordinary A-type main-sequence star with a stellar classification of A2 V It is about 209 million years old and has a high rate of spin, showing a projected rotational velocity of 162 km/s.
Delta Hydri | Introduction
Eta Hydri (η Hyi, η Hydri), often catalogued as HD 11977, is a giant yellow star approximately 219 light-years away in the constellation of Hydrus. Based on its mass, it was probably a class A star (similar to Vega or Fomalhaut) when it was on the main sequence, though it is now in the giant stage of its evolution. It is thought to be around 1.3 billion years old and has expanded to 10 times the Sun's diameter, though is only around 1.8 times as massive as the Sun. As of 2005, an extrasolar planet was confirmed to be orbiting the star.
Eta2 Hydri | Introduction
This is the list of notable stars in the constellation Cepheus, sorted by decreasing brightness.
List of stars in Cepheus | Introduction
This is the list of notable stars in the constellation Eridanus, sorted by decreasing brightness.
List of stars in Eridanus | Introduction
This is the list of notable stars in the constellation Hercules, sorted by decreasing brightness.
List of stars in Hercules | Introduction
This is the list of notable stars in the constellation Circinus, sorted by decreasing brightness.
List of stars in Circinus | Introduction
This is the list of notable stars in the constellation Perseus, sorted by decreasing brightness.
List of stars in Perseus | Introduction
Most of the cloud is located in the neighbouring constellation Tucana.
Hydrus | Deep-sky objects
Theta Hydri, Latinized from θ Hydri, is the Bayer designation for a blue-white hued star in the southern constellation of Hydrus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.53. Based upon an annual parallax shift of 6.34 mas as seen from Earth, is located roughly 510 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction of 0.10 due to interstellar dust. It is moving away from the Sun with a radial velocity of +12.3 km/s. A stellar classification of B8 III/IV suggests it is an evolving B-type star showing mixed traits of a subgiant or giant star.
Theta Hydri | Introduction
Forming the profile of a Bull's face is a "V" or "K"-shaped asterism of stars. This outline is created by prominent members of the Hyades, the nearest distinct open star cluster after the Ursa Major Moving Group. In this profile, Aldebaran forms the bull's bloodshot eye, which has been described as "glaring menacingly at the hunter Orion", a constellation that lies just to the southwest. The Hyades span about 5° of the sky, so that they can only be viewed in their entirety with binoculars or the unaided eye. It includes a naked eye double star, Theta Tauri (the proper name of Theta Tauri is "Chakumuy"), with a separation of 5.6 arcminutes.
Taurus (constellation) | Features
As such, it is a slightly more evolved star than the Sun, with the supply of hydrogen at its core becoming exhausted. It is one of the oldest stars in the solar neighborhood. This star bears some resemblance to what the Sun might look like in the far distant future, making it an object of interest to astronomers.
Beta Hydri | Introduction
This is the list of notable stars in the constellation Pyxis, sorted by decreasing brightness.
List of stars in Pyxis | Introduction
This is the list of notable stars in the constellation Hydra, sorted by decreasing brightness.
List of stars in Hydra | Introduction
This is the list of notable stars in the constellation Sagittarius, sorted by decreasing brightness.
List of stars in Sagittarius | Introduction
This is the list of notable stars in the constellation Capricornus, sorted by decreasing brightness.
List of stars in Capricornus | Introduction
HD 114613 lies about eight arcminutes south-east of Iota Centauri, towards the middle of Centaurus. Though it is fairly easily observable with the naked eye, the star does not have a Bayer or Flamsteed designation as the constellation of Centaurus contains many brighter stars. The B-V colour and spectroscopic temperature of HD 114613 correspond with its spectral type of G4. This means that the star is only slightly cooler than the Sun, and has the yellow hue typical of G-type stars. On the Hertzsprung-Russell diagram (left) the star lies significantly above the main sequence, and is close to the subgiant branch; this means that HD 114613 has depleted the hydrogen in its core through nuclear fusion, and is increasing in radius while decreasing in temperature as it moves towards the giant branch.
HD 114613 | Stellar characteristics
The five brightest member stars of the Hyades have consumed the hydrogen fuel at their cores and are now evolving into giant stars. Four of these stars, with Bayer designations Gamma, Delta 1, Epsilon, and Theta Tauri, form an asterism that is traditionally identified as the head of Taurus the Bull. The fifth of these stars is Theta Tauri, a tight naked-eye companion to the brighter Theta Tauri. Epsilon Tauri, known as "Ain" (the "Bull's Eye"), has a gas giant exoplanet candidate, the first planet to be found in any open cluster. The age of the Hyades is estimated to be about 625 million years.
Hyades (star cluster) | Introduction
This is the list of notable stars in the constellation Corvus, sorted by decreasing brightness.
List of stars in Corvus | Introduction
γ Hydri, Latinised as Gamma Hydri, is a solitary, red-hued star in the constellation Hydrus. It has an apparent visual magnitude of 3.26, making it easily visible to the naked eye at night. Based upon an annual parallax shift of 15.24 mas as measured from Earth, the system is located about 214 light years from the Sun. This is an evolved red giant star with a stellar classification of M1 III, and is most like on the asymptotic giant branch of the HR diagram. It is a semiregular variable that pulsates between magnitudes 3.26 and 3.33, although its period is not known precisely.
Gamma Hydri | Introduction
This is the list of notable stars in the constellation Apus, sorted by decreasing brightness.
List of stars in Apus | Introduction
Eta Hydri, Latinized from η Hydri, is a blue-white hued star in the southern constellation of Hydrus. It has an apparent visual magnitude of 6.76, which may be too faint to be visible to the naked eye. Based upon an annual parallax shift of as measured from Earth, the system is located about 619 light years distant from the Sun. At that distance, the visual magnitude of the star is diminished by 0.10 magnitudes of extinction due to interstellar dust. The star is drifting further away with a heliocentric radial velocity of +15 km/s. This is a B-type main-sequence star with a stellar classification of B9 V that was suspected in 1939 by Herbert Schneller of being variable.
Eta1 Hydri | Introduction
Zeta Hydri, Latinized from ζ Hydri, is a single, white-hued star in the southern constellation of Hydrus. It is faintly visible to the naked eye with an apparent magnitude of 4.83. This distance to this star can be estimated from its annual parallax shift of 11.47 mas, showing it to be about 284 light years away. It is moving further away from the Sun with a radial velocity of +3.6 km/s. The spectrum of this star matches a stellar classification of A2 IV, suggesting it is a subgiant star that is in the process of evolving away from the main sequence as the supply of hydrogen at its core becomes exhausted.
Zeta Hydri | Introduction
This is the list of notable stars in the constellation Aquarius, sorted by decreasing brightness.
List of stars in Aquarius | Introduction
This is giving the star an oblate shape with an equatorial bulge that is 7% larger than the polar radius. The star has 2.25 times the mass of the Sun and 2.3 times the Sun's radius. It is radiating 39.5 times the Sun's luminosity from its photosphere at an effective temperature of around 9.880. Delta Hydri has been checked for an infrared excess, but none was found.
Delta Hydri | Introduction
H. A. Rey has suggested an alternative visualization in which the "Keystone" becomes Hercules's head. This quadrangle lies between two very bright stars: Vega in the constellation Lyra and α CrB (Alphecca) in the constellation Corona Borealis. The hero's right leg contains two bright stars of the third magnitude: α Her (Rasalgethi) and δ Her (Sarin). The latter is the right knee. The hero's left leg contains dimmer stars of the fourth magnitude which do not have Bayer designations but which do have Flamsteed numbers. The star β Her belongs to the hero's outstretched right hand, and is also called Kornephoros.
Hercules (constellation) | H.A. Rey
This is the list of notable stars in the constellation Equuleus, sorted by decreasing brightness.
List of stars in Equuleus | Introduction
This is the list of notable stars in the constellation Lyra, sorted by decreasing brightness.
List of stars in Lyra | Introduction
This is the list of notable stars in the constellation Grus, sorted by decreasing brightness.
List of stars in Grus | Introduction
HD 20003 is a star in the southern constellation Hydrus. With an apparent visual magnitude of 8.39, this yellow-hued star is much too faint to be visible to the naked eye. It is located at a distance of 136.6 light years from the Sun based on parallax. HD 20003 is drifting closer with a radial velocity of −16 km/s, and is predicted to come to within in around 1.4 million years from now. This object is an ordinary, G-type main-sequence star with a stellar classification of G8 V. It is around five billion years old with a magnetic activity cycle lasting about ten years and a projected rotational velocity of 2.2 km/s.
HD 20003 | Introduction
This is the list of notable stars in the constellation Cetus, sorted by decreasing brightness.
List of stars in Cetus | Introduction
The German cartographer Johann Bayer used the Greek letters Alpha through Eta to label the most prominent stars in the constellation. John Flamsteed gave nine stars Flamsteed designations, while one star he designated in the neighbouring constellation Crater—31 Crateris—lay within Corvus once the constellation boundaries were established in 1930. Within the constellation's borders, there are 29 stars brighter than or equal to apparent magnitude 6.5. Four principal stars, Delta, Gamma, Epsilon, and Beta Corvi, form a quadrilateral asterism known as "the "Spica's Spanker" or "the Sail". Although none of the stars are particularly bright, they lie in a dim area of the sky, rendering the asterism easy to distinguish in the night sky.
Corvus (constellation) | Stars
"Hydor" is from Greek Ὕδωρ "water", a name given by Proclus, according to Richard Hinckley Allen. Another Greek name for the star is "Ekkhysis", from εκχυσις "outpouring". In Chinese, (), meaning "Line of Ramparts", refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, λ Aquarii itself is (, .)
Lambda Aquarii | Naming
The stars were picked for the resemblance of their arrangement to the Hyades group which form the "head" of Taurus. Before the definition of Taurus Poniatovii, some of these had been part of the obsolete constellation River Tigris. The brightest of these stars is 72 Oph (3.7 magnitude) in the "horn" of Taurus Poniatovii. The "face" of Taurus Poniatovii is formed by 67 Oph (4.0), 68 Oph (4.4) and 70 Oph (4.0). The five brightest stars belong to loose open cluster Collinder 359 or Melotte 186. Barnard's star is also inside the boundaries of this former constellation. Some minor stars (5th and 6th magnitude) now in Aquila formed the "rear" of Taurus Poniatovii.
Taurus Poniatovii | The stars
HD 10180, also designated 2MASS J01375356-6030414, is a Sun-like star in the southern constellation Hydrus that is notable for its large planetary system. Since its discovery, at least seven planets, and possibly as many as nine, have been observed orbiting it, making it potentially the largest of all known planetary systems, including the Solar System. (Other stars with a large known number of planets include Kepler-90, TRAPPIST-1, Kepler-11, and 55 Cancri.)
HD 10180 | Introduction
This is the list of notable stars in the constellation Scorpius, sorted by decreasing brightness.
List of stars in Scorpius | Introduction
This is the list of notable stars in the constellation of Cygnus, sorted by decreasing apparent magnitude.
List of stars in Cygnus | Introduction
In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −57.85° and −82.06°. As one of the deep southern constellations, it remains below the horizon at latitudes north of the 30th parallel in the Northern Hemisphere, and is circumpolar at latitudes south of the 50th parallel in the Southern Hemisphere. Indeed, Herman Melville mentions it and Argo Navis in Moby Dick "beneath effulgent Antarctic Skies", highlighting his knowledge of the southern constellations from whaling voyages. A line drawn between the long axis of the Southern Cross to Beta Hydri and then extended 4.5 times will mark a point due south.
Hydrus | Characteristics
This is the list of notable stars in the constellation Camelopardalis, sorted by decreasing brightness.
List of stars in Camelopardalis | Introduction
This is the list of notable stars in the constellation Pegasus, sorted by decreasing brightness.
List of stars in Pegasus | Introduction
This is the list of notable stars in the constellation Delphinus, sorted by decreasing brightness.
List of stars in Delphinus | Introduction
HD 195564 is the Henry Draper Catalogue designation for a star in the southern constellation of Capricornus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.65. Parallax measurements from the Hipparcos spacecraft give us an estimate of its distance as around 80 light years. This appears to be a wide binary system as a faint companion star shares a common proper motion with the brighter primary component. Based upon the spectrum of light emitted by the primary, it has a stellar classification of G2 V. This indicates that it is a G-type main sequence star that is generating energy through the process of thermonuclear fusion in its core region.
HD 195564 | Introduction
HR 3384 (11 G. Pyxidis) is solitary star in the southern constellation of Pyxis. It has an apparent magnitude of 6.38, indicating it is faintly visible to the naked eye. Based on the Bortle scale, the star can be viewed from dark rural skies. Astrometric measurements of the star by the Hipparcos spacecraft, give an estimated distance of about from Earth. It is moving away from the Sun with a radial velocity of +81.91. This star is lower in mass than the Sun at around 75%, and has just 85% of the Sun's radius. The spectrum matches a spectral class G9V, indicating that this is a G-type main sequence star that is generating energy through the nuclear fusion of hydrogen at its core.
HR 3384 | Introduction
In the northeastern quadrant of the Taurus constellation lie the Pleiades (M45), one of the best known open clusters, easily visible to the naked eye. The seven most prominent stars in this cluster are at least visual magnitude six, and so the cluster is also named the "Seven Sisters". However, many more stars are visible with even a modest telescope. Astronomers estimate that the cluster has approximately 500-1,000 stars, all of which are around 100 million years old. However, they vary considerably in type. The Pleiades themselves are represented by large, bright stars; also many small brown dwarfs and white dwarfs exist.
Taurus (constellation) | Features
HD 28527 is a star in the constellation Taurus, and a member of the Hyades open cluster. It is faintly visible to the naked eye with an apparent visual magnitude of 4.78. The distance to this star, as determined from its parallax shift of , is . It is moving away from the Earth with a heliocentric radial velocity of . Based upon a stellar classification of A6 IV by Cowley et al. (1969), this is an A-type subgiant star that has consumed the hydrogen at its core and is evolving away from the main sequence. Older studies had it classed as an A-type main-sequence star with a class of A7 V.
HD 28527 | Introduction
This is the list of notable stars in the constellation Aries, sorted by decreasing brightness.
List of stars in Aries | Introduction
Epsilon Eridani (the proper name is Ran) is a star with one extrasolar planet similar to Jupiter. It is an orange-hued main-sequence star of magnitude 3.7, 10.5 light-years from Earth. Its one planet, with an approximate mass of one Jupiter mass, has a period of 7 years.
Eridanus (constellation) | Stars
Together with the other eye-catching open star cluster of the Pleiades the Hyades form the Golden Gate of the Ecliptic, which is known for several thousand years. In Greek mythology, the Hyades were the five daughters of Atlas and half-sisters to the Pleiades. After the death of their brother, Hyas, the weeping sisters were transformed into a cluster of stars that was afterwards associated with rain. As a naked-eye object, the Hyades cluster has been known since prehistoric times. It is mentioned by numerous Classical authors from Homer to Ovid. In Book 18 of the "Iliad" the stars of the Hyades appear along with the Pleiades, Ursa Major, and Orion on the shield that the god Hephaistos made for Achilles.
Hyades (star cluster) | History
The star is roughly six billion years old with slightly more mass than the Sun. With the supply of hydrogen at its core exhausted, it has expanded to nearly 12 times the Sun's radius. The star is radiating 57 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,569 K. This star, together with 93 Her, 95 Her, and 102 Her, were consist Cerberus, the obsolete constellation
109 Herculis | Introduction
This is the list of notable stars in the constellation Centaurus, sorted by decreasing brightness.
List of stars in Centaurus | Introduction
This is the list of notable stars in the constellation Andromeda, sorted by decreasing brightness.
List of stars in Andromeda | Introduction
At present it has 21 times the girth of the Sun. It is 2.4 billion years old with estimates of its mass ranging from 1.8 to 3.5 times the mass of the Sun. The star is radiating 184 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,612 K.
Nu Hydri | Introduction
HD 176527 is a single star in the northern constellation of Lyra, positioned near the southern constellation border with Vulpecula. It has an orange hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.26. This object is located at a distance of approximately 266 light years from the Sun based on parallax, and it has an absolute magnitude of 0.28. It is drifting closer with a radial velocity of −22.6 km/s. This is an aging giant star with a stellar classification of K2III, which indicates it has exhausted the supply of hydrogen at its core, then evolved away from the main sequence by cooling and expanding.
HD 176527 | Introduction
Algol (from the Arabic رأس الغول "Ra's al-Ghul", which means "The Demon's Head"), also known by its Bayer designation Beta Persei, is the best-known star in Perseus. Representing the head of the Gorgon Medusa in Greek mythology, it was called Horus in Egyptian mythology and "Rosh ha Satan" ("Satan's Head") in Hebrew. Located 92.8 light-years from Earth, it varies in apparent magnitude from a minimum of 3.5 to a maximum of 2.3 over a period of 2.867 days. The star system is the prototype of a group of eclipsing binary stars named Algol variables, though it has a third member to make up what is actually a triple star system.
Perseus (constellation) | Stars
HD 196761 is the Henry Draper Catalogue designation for a G-type main-sequence star in the constellation Capricornus. With an apparent magnitude of 6.37 it is near the limit of what can be seen with the naked eye, but according to the Bortle Scale it may be possible to view it at night from rural skies. Based upon parallax measurements by the Hipparcos spacecraft, it is located about 47 light years from the Solar System. It has a stellar classification of G8V with about 88% of the radius of the Sun and 81% of the Sun's mass. Compared to the Sun, this star has about half the proportion of elements other than hydrogen and helium.
HD 196761 | Introduction
The Hyades (; Greek Ὑάδες, also known as Caldwell 41, Collinder 50, or Melotte 25) is the nearest open cluster and one of the best-studied star clusters. Located about away from the Sun, it consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical characteristics, and motion through space. From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still-brighter Aldebaran. However, Aldebaran is unrelated to the Hyades, as it is located much closer to Earth and merely happens to lie along the same line of sight.
Hyades (star cluster) | Introduction
At its southern end is the magnitude 0.5 star Achernar, designated Alpha Eridani. It is a blue-white hued main sequence star 144 light-years from Earth, whose traditional name means "the river's end". Achernar is a very peculiar star because it is one of the flattest stars known. Observations indicate that its radius is about 50% larger at the equator than at the poles. This distortion occurs because the star is spinning extremely rapidly. There are several other noteworthy stars in Eridanus, including some double stars. Beta Eridani, traditionally called Cursa, is a blue-white star of magnitude 2.8, 89 light-years from Earth.
Eridanus (constellation) | Stars
It is now so entered in the IAU Catalog of Star Names. The European astronomer Tycho Brahe dubbed it "Cor Hydræ", Latin for 'the heart of Hydra'.
Alphard | Nomenclature
This is the list of notable stars in the constellation Ophiuchus, sorted by decreasing brightness. Although the Sun travels through Ophiuchus, it is not listed here because it does not stay in the constellation.
List of stars in Ophiuchus | Introduction
This is the list of notable stars in the constellation Horologium, sorted by decreasing brightness.
List of stars in Horologium | Introduction
This is the list of notable stars in the constellation Sextans, sorted by decreasing brightness.
List of stars in Sextans | Introduction
Hydrus contains only faint deep-sky objects. IC 1717 was a deep-sky object discovered by the Danish astronomer John Louis Emil Dreyer in the late 19th century. The object at the coordinate Dreyer observed is no longer there, and is now a mystery. It was very likely to have been a faint comet. PGC 6240, known as the White Rose Galaxy, is a giant spiral galaxy surrounded by shells resembling rose petals, located around 345 million light years from the Solar System. Unusually, it has cohorts of globular clusters of three distinct ages suggesting bouts of post-starburst formation following a merger with another galaxy.
Hydrus | Deep-sky objects
This is the list of notable stars in the constellation Lupus, sorted by decreasing brightness.
List of stars in Lupus | Introduction
There is a nearby companion star of class A0 IV located at an angular separation of 0.1 arc seconds along a position angle of 179°, as of 2002. Schöller et al. (2010) consider this to be a visual companion, although Eggleton and Tokovinin (2008) listed the pair as a probable binary star system.
Theta Hydri | Introduction
HD 28375 is a single star in the equatorial constellation of Taurus, near the southern constellation border with Eridanus. It was previously known by the Flamsteed designation 44 Eridani, although the name has fallen out of use because constellations were redrawn, placing the star out of Eridanus and into Taurus. The star is blue-white in hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.53. The distance to this star is approximately 480 light-years based on parallax. It is drifting further away with a radial velocity of 18 km/s, after having come to within an estimated some 3.7 million years ago.
HD 28375 | Introduction
HD 115337 is a cool supergiant star in the constellation Camelopardalis. It has an apparent magnitude of 6.272 so it is visible under very dark conditions. It is about 680 light-years or 210 parsecs away. It has a much fainter A8 main sequence companion.
HD 115337 | Introduction
Lambda Aquarii (λ Aqr, λ Aquarii), informally known as Hydor , is the Bayer designation for a star in the equatorial constellation of Aquarius. The apparent visual magnitude of this star is 3.722, which is bright enough to be visible with the naked eye. It is roughly from Earth.
Lambda Aquarii | Introduction
It is a young star, just 133 million years in age, and has a high rate of spin with a projected rotational velocity of 96 km/s. This is giving the star a mild oblate shape with an equatorial bulge that is 5% greater than the polar radius. Epsilon Hydri has an estimated 2.64 times the mass of the Sun and 2.2 times the Sun's radius. It is radiating 60 times the Sun's luminosity from its photosphere at an effective temperature of around 10,970 K.
Epsilon Hydri | Introduction
HD 12467 is a single star in the northern circumpolar constellation of Cepheus. It has a white hue and is barely visible to the naked eye with an apparent visual magnitude of 6.05. The distance to this object is 231 light years based on parallax, but it is drifting closer with a heliocentric radial velocity of −9 km/s. This object is an ordinary A-type main-sequence star with a stellar classification of A1.5V, which indicates it is generating energy through core hydrogen fusion. It is 254 million years old with a relatively high projected rotational velocity of 130 km/s. The star has 1.8 times the mass of the Sun and 1.9 times the Sun's radius.
HD 12467 | Introduction
45 Herculis is a solitary variable star in the northern constellation Hercules. It has the Bayer designation l Herculis and the variable star designation V776 Herculis. The Flamsteed designation for this star comes from the publication "Historia Coelestis Britannica" by John Flamsteed. It is the 45th star in Flamsteed list of stars in the constellation Hercules, and is visible to the naked eye with a baseline apparent visual magnitude of 5.22. Parallax measurements show this star to be about 400 light-years away from the Solar System. It is moving closer to the Earth with a heliocentric radial velocity of −16 km/s.
45 Herculis | Introduction
HD 12039 is a variable star in the constellation of Cetus at a distance of about . It is categorized as a BY Draconis variable because of luminosity changes caused by surface magnetic activity coupled with rotation of the star. The stellar classification G4V is similar to the Sun, indicating this is a main sequence star that is generating energy at its core through the thermonuclear fusion of hydrogen. The effective temperature of 5,585 K gives the star a yellow hue. It has about the same mass as the Sun, but only emits 89% of the Sun's luminosity. This is a young star with age estimates ranging from 7.5−8 million years to 30 million years.
HD 12039 | Introduction
The cluster is estimated to dissipate in another 250 million years. The Pleiades cluster is classified as a Shapley class c and Trumpler class I 3 r n cluster, indicating that it is irregularly shaped and loose, though concentrated at its center and detached from the star-field.
Taurus (constellation) | Features
Bayer catalogued many stars in the constellation, giving them the Bayer designations from Alpha to Omega and then using lowercase Roman letters to g. John Flamsteed added the Roman letters h, i, k, l and m (these stars were considered "informes" by Bayer as they lay outside the asterism of Cygnus), but were dropped by Francis Baily. There are several bright stars in Cygnus. Alpha Cygni, called Deneb, is the brightest star in Cygnus. It is a white supergiant star of spectral type A2Iae that varies between magnitudes 1.21 and 1.29, one of the largest and most luminous A-class stars known.
Cygnus (constellation) | Stars
It is a PGa star – a higher temperature variety of the class of chemically peculiar stars known as mercury-manganese stars (HgMn stars). That is, it displays a rich spectra of singly-ionized phosphorus and gallium, in addition to ionized mercury and manganese. As such, Theta Hydri forms a typical example of this type. The absorption lines for these ionized elements are found to vary, most likely as the result of uneven surface distribution combined with the star's rotation. It is a helium-weak star, having helium lines that are anomalously weak for its spectral type. A weak and variable longitudinal magnetic field has been detected.
Theta Hydri | Introduction
95 Herculis is a binary star divisible in small telescopes, 470 light-years from Earth. The primary is a silvery giant of magnitude 4.9, and the secondary is an old, reddish giant star of magnitude 5.2. The star HD164669 near the primary may be an optical double. 100 Herculis is a double star easily divisible in small amateur telescopes. Both components are magnitude 5.8 blue-white stars; they are 165 and 230 light-years from Earth. There are several dimmer variable stars in Hercules. 30 Herculis, also called g Herculis, is a semiregular red giant with a period of 3 months. 361 light-years from Earth, it has a minimum magnitude of 6.3 and a maximum magnitude of 4.3.
Hercules (constellation) | Stars
HD 162826 (HR 6669, HIP 87382) is a star in the constellation Hercules. It is about away from Earth. With an apparent magnitude of 6.46, the star can be found with binoculars or a low-power telescope by reference to nearby Vega in the constellation Lyra. It is very similar to the Sun; the Sun is a G2V star with a temperature of 5772 K and 4.6 billion years old while HD 162826 is a F8V star with a temperature of 6210 K, 4.5 billion years old, and is just 15% more massive than the Sun and 3% more abundant in metals.
HD 162826 | Introduction
HD 123569 is a single star in the southern constellation of Centaurus, positioned near the eastern constellation border with Lupus. This object has a yellowish hue and is visible to the naked eye with an apparent visual magnitude of 4.74. It is located at a distance of approximately 176 light years from the Sun based on parallax, and it has an absolute magnitude of +1.00. The star is drifting closer with a radial velocity of −17 km/s. O. J. Eggen flagged this star as a member of the Hyades Supercluster. This is an aging giant star with a stellar classification of G9-III, having exhausted the supply of hydrogen at its core then evolved off the main sequence by cooling and expanding.
HD 123569 | Introduction
HD 175740 is a single star in the northern constellation of Lyra. This object has an orange hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.46. It is located at a distance of approximately 266 light years from the Sun based on parallax, and has an absolute magnitude of 0.89. The star is drifting closer with a radial velocity of −9.5 km/s, and is predicted to come as close as in around 8 million years. This is an aging giant star with a stellar classification of K0III, having evolving off the main sequence after the supply of hydrogen at its core was exhausted.
HD 175740 | Introduction
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Lisan al Shudja", which was translated into Latin as "Lingua Hydri", meaning "the snake's tongue". This star, along with ε Hya, ζ Hya, η Hya, ρ Hya and σ Hya (Minchir), were Ulugh Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Min al Azʽal" or "Minazal" were the title for five stars :δ Hya as "Minazal I", η Hya as "Minazal II", ε Hya as "Minazal III", ρ Hya as "Minazal IV" and ζ Hya as "Minazal V" (exclude σ Hya) In Chinese, (), meaning "Willow (asterism)", refers to an asterism consisting of δ Hydrae, σ Hydrae, η Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae Consequently, δ Hydrae itself is known as (, .)
Delta Hydrae | Name and etymology
The Bayer designation Eta Hydri (η Hyi / η Hydri) is shared by two stars, in the constellation Hydrus:
Eta Hydri | Introduction
HD 215152 is the Henry Draper Catalogue designation for a star in the zodiac constellation of Aquarius. It has an apparent visual magnitude of 8.13, meaning it is too faint to be seen with the naked eye. Parallax measurements made by the Hipparcos and Gaia spacecraft provide distance estimates of around 70 light years. The star has a relatively high proper motion, moving across the sky at an estimated 0.328 arc seconds per year along a position angle of 205°. The survey in 2015 have ruled out the existence of any additional stellar companions at projected distances from 6 to 145 astronomical units.
HD 215152 | Introduction