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Beta Cephei Variables
Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200,000 K in their interiors. These stars are usually hot blue-white stars of spectral class B and should not be confused with Cepheid variables, which are named after Delta Cephei and are luminous supergiant stars. Properties Beta Cephei variables are main-sequence stars of masses between about 7 and 20 M_\odot (that is, 7–20 times as massive as the Sun). Among their number are some of the brightest stars in the sky, such as Beta Crucis and Beta Centauri; Spica is also classified as a Beta Cephei variable but mysteriously stopped pulsating in 1970. Typically, they change in brightness by 0.01 to 0.3 magnitudes with periods of 0.1 to 0.3 days (2.4–7.2 hours). The prototype of these variable stars, Beta Cephei, shows variation in appare ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Stars
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. * Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. Of the modern astronomers, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edwin Brant Frost
Edwin Brant Frost II (July 14, 1866 – May 14, 1935) was an American astronomer. Biography He was born in Brattleboro, Vermont. His father, Carlton Pennington Frost, was dean of Dartmouth Medical School. Frost graduated from Dartmouth in 1886. He continued his education as a post-graduate student in chemistry and in 1887 became an instructor in physics while only 21 years old. In 1890 Frost went abroad to Europe and ended up researching stellar spectroscopy under Hermann Vogel in Potsdam. He returned to Dartmouth in 1892 as an assistant professor of astronomy. He was fond of the outdoors and enjoyed golf, swimming, and ice skating. He also enjoyed music and literature. In 1896 he married Mary E. Hazard. They had three children, Katharine, Frederick, and Benjamin. Frost joined the staff of Yerkes Observatory in 1898 and became its director in 1905 when George Hale resigned. Frost kept the position until his retirement in 1932. He was the editor of the ''Astrophys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Pegasi
Gamma Pegasi is a star in the constellation of Pegasus, located at the southeast corner of the asterism known as the Great Square. It has the formal name Algenib ; the Bayer designation Gamma Pegasi is Latinized from γ Pegasi and abbreviated Gamma Peg or γ Peg. The average apparent visual magnitude of +2.84 makes this the fourth-brightest star in the constellation. The distance to this star has been measured using the parallax technique, yielding a value of roughly . Nomenclature ''Gamma Pegasi'' is the star's Bayer designation. Although it also had the traditional name ''Algenib'', this name was also used for Alpha Persei. 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 ''Algenib'' for this star (Alpha Persei was given the name ''Mirfak''). The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nu Eridani
Nu Eridani (ν Eri) is a star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.93. The distance to this star is roughly 520 light years, based upon an annual parallax shift of 0.00625 arcseconds. If the star were from the Sun, it would be the brightest star in the night sky with an apparent magnitude of −2.84. (Currently, the brightest star is Sirius at magnitude −1.46.) This is a B-type subgiant star with a stellar classification of B1.5 IV. It is a hybrid pulsator variable, lying as it does on the overlapping instability strips for Beta Cephei variables and slowly pulsating B-type stars. The star shows at least fourteen pulsations frequencies, with nine that also display radial velocity variations. It has about nine times the mass of the Sun and six times the Sun's radius. Nu Eridani shines with 7,943 times the solar luminosity from its outer atmosphere at an effective temperature The effective ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
53 Piscium
53 Piscium, abbreviated as 53 Psc, is a star in the zodiac constellation of Pisces. With an apparent magnitude of about 5.9, it is just barely visible to the naked eye. parallax measurements made by the Hipparcos spacecraft place the star at a distance of about 930 light-years (284 parsecs) away. The spectral type of 53 Piscium is B2.5IV, meaning it is a B-type subgiant. It is 5.4 times more massive than the Sun, and has a luminosity of almost . Its surface temperature is over 17,000 K, typical of a B-type star. 53 Piscium is a Beta Cephei variable, varying by 0.01 magnitudes just under every two hours. For that reason it has been given the AG Piscium. It has also been found to have some variability in common with slowly pulsating B star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main-sequence stars of spect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iota Herculis
Iota Herculis (ι Herculis, ι Her) is a fourth-magnitude variable star system in the constellation Hercules, consisting of at least four stars all about away. The brightest is a β Cephei variable, a pulsating star. Visibility Iota Herculis is dim enough that in cities with a lot of light pollution it is unlikely to be visible with the naked eye. In rural areas it will usually be visible, and for much of the Northern Hemisphere the star is circumpolar and visible year around. Pole star As a visible star, the proximity of Iota Herculis to the precessional path the Earth's North Pole traces across the celestial sphere makes it a pole star, a title currently held by Polaris. In 10,000 BCE it was the pole star, and in the future it will be again. While Polaris is only 0.5° off the precessional path Iota Herculis is 4° off. Properties Iota Herculis is a B-type subgiant star that is at the end of its hydrogen fusion stage. With a stellar classification B3IV, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
16 Lacertae
16 Lacertae is a triple star system in the northern constellation of Lacerta, located about 1,580 light years from the Sun. It has the variable star designation EN Lacertae; ''16 Lacertae'' is the Flamsteed designation. This system is visible to the naked eye as a faint blue-white hued star with a maximum apparent visual magnitude of +5.587. It is moving closer to the Earth with a heliocentric radial velocity of –12 km/s. The binary nature of the brighter component was discovered in 1910 by astronomer Oliver J. Lee at Yerkes Observatory. The first orbital elements were published by Otto Struve and Nicholay T. Bobrovnikov in 1925. This is a single-lined spectroscopic binary with an orbital period of 12.1 days and a small eccentricity of 0.05. It forms an eclipsing binary variable, although only the eclipse of the primary component has been detected. This component is a Beta Cephei variable star with three dominant pulsation modes having frequencies of arou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Scuti Variable
A Delta Scuti variable (sometimes termed dwarf cepheid when the V-band amplitude is larger than 0.3 mag.) is a subclass of young pulsating star. These variables as well as classical cepheids are important standard candles and have been used to establish the distance to the Large Magellanic Cloud, globular clusters, open clusters, and the Galactic Center. The variables follow a period-luminosity relation in certain passbands like other standard candles such as Cepheids. SX Phoenicis variables are generally considered to be a subclass of Delta Scuti variables that contain old stars, and can be found in globular clusters. SX Phe variables also follow a period-luminosity relation. One last sub-class are the pre-main sequence (PMS) Delta Scuti variables. The OGLE and MACHO surveys have detected nearly 3000 Delta Scuti variables in the Large Magellanic Cloud. Typical brightness fluctuations are from 0.003 to 0.9 magnitudes in V over a period of a few hours, although the amplitude ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sergei Gaposchkin
Cecilia Payne-Gaposchkin (born Cecilia Helena Payne; – ) was a British-born American astronomer and astrophysicist who proposed in her 1925 doctoral thesis that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected because it contradicted the scientific wisdom of the time, which held that there were no significant elemental differences between the Sun and Earth. Independent observations eventually proved she was correct. Her work on the nature of variable stars was foundational to modern astrophysics. Early life Cecilia Helena Payne was one of three children born in Wendover in Buckinghamshire, England, to Emma Leonora Helena (née Pertz) and Edward John Payne, a London barrister, historian and musician who had been an Oxford fellow. Her mother came from a Prussian family and had two distinguished uncles, historian Georg Heinrich Pertz and the Swedenborgian writer James John Garth Wilkinson; her sister Florence was a pian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cecilia Payne-Gaposchkin
Cecilia Payne-Gaposchkin (born Cecilia Helena Payne; – ) was a British-born American astronomer and astrophysicist who proposed in her 1925 doctoral thesis that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected because it contradicted the scientific wisdom of the time, which held that there were no significant elemental differences between the Sun and Earth. Independent observations eventually proved she was correct. Her work on the nature of variable stars was foundational to modern astrophysics. Early life Cecilia Helena Payne was one of three children born in Wendover in Buckinghamshire, England, to Emma Leonora Helena (née Pertz) and Edward John Payne, a London barrister, historian and musician who had been an Oxford fellow. Her mother came from a Prussian family and had two distinguished uncles, historian Georg Heinrich Pertz and the Swedenborgian writer James John Garth Wilkinson; her sister Florence was a pi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Struve
Otto Struve (August 12, 1897 – April 6, 1963) was a Russian-American astronomer of Baltic German origins. In Russian, his name is sometimes given as Otto Lyudvigovich Struve (Отто Людвигович Струве); however, he spent most of his life and his entire scientific career in the United States. Otto was the descendant of famous astronomers of the Struve family; he was the son of Ludwig Struve, grandson of Otto Wilhelm von Struve and great-grandson of Friedrich Georg Wilhelm von Struve. He was also the nephew of Karl Hermann Struve. With more than 900 journal articles and books, Struve was one of the most distinguished and prolific astronomers of the mid-20th century. He served as director of Yerkes, McDonald, Leuschner and National Radio Astronomy Observatories and is credited with raising worldwide prestige and building schools of talented scientists at Yerkes and McDonald observatories. In particular, he hired Subrahmanyan Chandrasekhar and Gerhard Herzber ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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