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1 Hydrae
This is the list of notable star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...s in the constellation Hydra, sorted by decreasing brightness. See also * List of stars by constellation References Bibliography * * * * * {{Stars of Hydra *List Hydra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye, all within the Milky Way galaxy. A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Its total mass is the main factor determining its evolution and eventual fate. A star shines for most of its active life due t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alphard
Alphard , designated Alpha Hydrae (α Hydrae, abbreviated Alpha Hya, α Hya), is the brightest star in the constellation of Hydra. It is a single giant star, cooler than the Sun but larger and more luminous. It is about 177 light-years away. Nomenclature ''α Hydrae'' ( Latinised to ''Alpha Hydrae'') is the star's Bayer designation. The traditional name ''Alphard'' is from the Arabic الفرد (''al-fard''), "the individual", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', it was designated ''Soheil al Fard'', which was translated into Latin as ''Soheil Solitarius'', meaning ''the bright solitary one''. 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 ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upsilon1 Hydrae
Upsilon1 Hydrae (υ1 Hydrae, abbreviated Ups1 Hya, υ1 Hya), also named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12. Based upon an annual parallax shift of 12.36 mas as seen from Earth, it is located about 264 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −14.34 km/s. In 2005 it was announced that it had a substellar companion. Nomenclature ''υ1 Hydrae'' ( Latinised to ''Upsilon1 Hydrae'') is the star's Bayer designation. In Chinese, (), meaning '' Extended Net'', refers to an asterism consisting of Upsilon1 Hydrae, Lambda Hydrae, Mu Hydrae, HD 87344, Kappa Hydrae and Phi1 Hydrae. Consequently, Upsilon1 Hydrae itself is known as (), "the First Star of Extended Net". [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
30 Monocerotis
30 Monocerotis is a single star in the equatorial constellation of Hydra, located 122 light years away from the Sun. It has the Bayer designation C Hydrae; ''30 Monocerotis'' is the Flamsteed designation and was assigned when it belonged to the Monoceros constellation. The object is visible to the naked eye as a white-hued star with an apparent visual magnitude of 3.90. It is moving away from the Earth with a heliocentric radial velocity of +10 km/s. This is an A-type main-sequence star with a stellar classification of A0 Va. It is around 162 million years old with a high rate of spin, showing a projected rotational velocity of 129 km/s. The star has 2.36 times the mass of the Sun and about 2.7 times the Sun's radius. It is radiating 40 times the luminosity of the Sun from its photosphere at an effective temperature of 10,281 K. A statistically significant infrared excess has been detected, indicating a debris disk is orbiting from the hos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iota Hydrae
Iota Hydrae (ι Hydrae, abbreviated Iota Hya, ι Hya), formally named Ukdah , is a star in the constellation of Hydra, about 8° to the north-northwest of Alphard (Alpha Hydrae) and just to the south of the celestial equator. Visible to the naked eye, it is a suspected variable star with an apparent visual magnitude that ranges between 3.87 and 3.91. Based upon an annual parallax shift of 12.39 mas measured during the Hipparcos mission, it is located around 263 light-years from the Sun. Nomenclature ''ι Hydrae'' ( Latinised to ''Iota Hydrae'') is the star's Bayer designation. This star along with Tau¹ Hydrae, Tau² Hydrae and 33 Hydrae (A Hydrae), were Ptolemy's Καμπή (Kampē); but Kazwini knew them as عقدة ''ʽuqdah'' (or ''ʽuḳdah'') "knot". According to a 1971 NASA memorandum, ''Ukdah'' was the name of an asterism of four stars: Tau¹ Hydrae as ''Uḳdah I'', Tau² Hydrae as ''Uḳdah II'', 33 Hydrae as ''Uḳdah III'' and Iota Hydrae as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theta Hydrae
Theta Hydrae, Latinized from θ Hydrae, is a binary star system in the constellation Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.9. The star system has a high proper motion with an annual parallax shift of , indicating a distance of about . Theta Hydrae forms a double with a magnitude 9.9 star located at an angular separation of . The primary component of this system is a B-type main sequence star with a stellar classification of B9.5 V. It is a candidate Lambda Boötis star, indicating it displays an underabundance of iron peak elements. However, it is also underabundant in oxygen, a characteristic not shared by other Lambda Boötis stars. Instead, it may be a peculiar B star. An orbiting white dwarf companion was discovered in 1998 from its X-ray emission. This degenerate star must have evolved from a progenitor that was once more massive than the current primary. Burleigh and Barstow (1999) gave a mass estimate of 0.68 times th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mu Hydrae
μ Hydrae, Latinised as Mu Hydrae, is a solitary, orange-hued star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.83. Positioned just 1.8° to the south-southwest is the planetary nebula NGC 3242. Mu Hydrae has an annual parallax shift of 13.93 mas, which yields a distance estimate of 234 light years. This is an evolved K-type giant star with a stellar classification of K4 III, having used up its core hydrogen and has expanded to around 45 times the radius of the Sun. It is a suspected variable star, with a brightness that varies about 0.03 in magnitude. The relatively cool outer atmosphere has an effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ... of 3999 K. Refe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda Hydrae
λ Hydrae, Latinised as Lambda Hydrae, is a spectroscopic binary star in the constellation Hydra. Its apparent magnitude is 3.61 Located around distant. The spiral galaxy NGC 3145 is only away to the southwest. The primary is an orange giant of spectral type K0IIICN+1, a star that has used up its core hydrogen, left the main sequence, and expanded into a giant. It is considered to be a red clump giant, a cool horizontal branch The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha proce ... star that is burning helium in its core. λ Hydrae has two visual companions, components B and C, 11th and 13th magnitude stars respectively and away. References {{DEFAULTSORT:Lambda Hydrae K-type giants Horizontal-branch stars Spectroscopic binaries Hydra (constellation) Hydrae, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xi Hydrae
Xi Hydrae, Latinised from ξ Hydrae, is a solitary star in the equatorial constellation of Hydra. It was also given the Flamsteed designation 19 Crateris. This magnitude 3.54 star is situated 130 light-years from Earth and has a radius about 10 times that of the Sun. It is radiating 58 times as much luminosity as the Sun. Flamsteed gave Xi Hydrae the designation 19 Crateris. He included a number of stars now within the IAU boundaries of Hydra as part of a ''Hydra & Crater'' constellation overlapping parts of both modern constellations. The star Xi Hydrae is particularly interesting in the field of asteroseismology since it shows solar-like oscillations. Multiple frequency oscillations are found with periods between 2.0 and 5.5 hours. Xi Hydrae has left the main sequence, having exhausted the supply of hydrogen in its core. Its spectrum is that of a red giant. Modelling its physical properties against theoretical evolutionary tracks shows that it has just reached the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BY Draconis Variable
BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with starspots, and other chromospheric activity. Resultant brightness fluctuations are generally less than 0.5 magnitudes. Light curves of BY Draconis variables are quasiperiodic. The period is close to the star's mean rotational rate. The light curve is irregular over the duration of the period and it changes slightly in shape from one period to the next. For the star BY Draconis the shape of the light curve over a period remained similar for a month. Nearby K and M stars that are BY Draconis variables include Barnard's Star, Kapteyn's Star, 61 Cygni, Ross 248, Lacaille 8760, Lalande 21185, and Luyten 726-8. Ross 248 is the first discovered BY Draconis variable, the variability h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epsilon Hydrae
Epsilon Hydrae (ε Hydrae, abbreviated Epsilon Hya, ε Hya) is a multiple star system of a combined third magnitude in the constellation of Hydra. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly distant from the Sun. The system consists of a binary pair designated Epsilon Hydrae AB, whose two components are themselves designated Epsilon Hydrae A (formally named Ashlesha ) and B, orbited by a spectroscopic binary designated Epsilon Hydrae C. A possible fourth component, designated Epsilon Hydrae D, shares a common proper motion with the other components and thus is most likely a gravitationally-bound member of the system. Nomenclature ''ε Hydrae'' ( Latinised to ''Epsilon Hydrae'') is the system's Bayer designation. The designations of the three constituents as ''Epsilon Hydrae AB'', ''C'' and ''D'', and those of ''AB's'' components - ''Epsilon Hydrae A'' and ''B'' - derive from the convention used by the Washingto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Hydrae
Pi Hydrae, Latinized from π Hydrae, is a star in the constellation Hydra with an apparent visual magnitude of 3.3, making it visible to the naked eye. Parallax measurements put this star at a distance of about from the Earth. The spectrum of this star shows it to have a stellar classification of K1 III-IV, with the luminosity class of 'III-IV' suggesting it is in an evolutionary transition stage somewhere between a subgiant and a giant star. It has a low projected rotational velocity of 2.25 km s−1. Pi Hydrae is radiating energy from its outer envelope with an effective temperature of 4,670 K, giving it the orange hue of a K-type star. Pi Hydrae is a type of giant known as a cyanogen-weak star, which means that its spectrum displays weak absorption lines of CN− relative to the metallicity. (The last is a term astronomers use when describing the abundance of elements other than hydrogen and helium.) Otherwise, it appears to be a normal star of its ev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
