|
Wojciech Krzemiński
Wojciech Krzemiński (20 May 1933 – 5 August 2017) was a Polish astronomer and a retired professor of Nicolaus Copernicus Astronomical Center of Polish Academy of Sciences. He worked many years for the Carnegie Institution for Science Observatories. Biography Wojciech Krzemiński was a student of professors Stefan Piotrowski and Włodzimierz Zonn. In the early 1960s he was active in Lick Observatory and Lowell Observatory in USA, and at the end of the 1960s he received a scholarship at Carnegie Institution. In 1973, he left – as the first Polish astronomer – to Las Campanas Observatory in Chile. In the 1970s Krzemiński actively collaborated with professors Bohdan Paczyński and Józef Smak. In the 1980s he received an offer to take over as administrator or "resident astronomer" of Las Campanas, position which he held for 16 years. He lived many years in La Serena in Chile and returned to Poland in 2011. Scientific achievements Wojciech Krzemiński was one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Warsaw
Warsaw, officially the Capital City of Warsaw, is the capital and List of cities and towns in Poland, largest city of Poland. The metropolis stands on the Vistula, River Vistula in east-central Poland. Its population is officially estimated at 1.86 million residents within a Warsaw metropolitan area, greater metropolitan area of 3.27 million residents, which makes Warsaw the List of cities in the European Union by population within city limits, 6th most-populous city in the European Union. The city area measures and comprises List of districts and neighbourhoods of Warsaw, 18 districts, while the metropolitan area covers . Warsaw is classified as an Globalization and World Cities Research Network#Alpha 2, alpha global city, a major political, economic and cultural hub, and the country's seat of government. It is also the capital of the Masovian Voivodeship. Warsaw traces its origins to a small fishing town in Masovia. The city rose to prominence in the late 16th cent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
La Serena, Chile
La Serena () is a List of cities in Chile, city and Communes of Chile, commune in northern Chile, capital of the Coquimbo Region. Founded in 1544, it is the country's second oldest city after the national capital, Santiago. As of 2012, it had a communal population of roughly 200,000, and was one of the fastest-growing areas of Chile. The city is an important tourist destination for Chileans and Argentines, especially during the summer, where people go to visit the beaches. It is the headquarters of the University of La Serena and also is home to the Roman Catholic Archdiocese of La Serena, one of five Catholic Archdioceses of the Catholic Church in Chile. History The sector is currently located where the city was inhabited by the pre-Hispanic village called Viluma or Vilumanque (Mapudungún Snakes and condors). La Serena was founded on the orders of the Spaniard Pedro de Valdivia in order to provide a sea link to maintain permanent contact between Santiago and Lima in the Vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Kraft (astronomer)
Robert Paul Kraft (June 16, 1927 – May 26, 2015) was an American astronomer. He performed pioneering work on Cepheid variables, stellar rotation, novae, and the chemical evolution of the Milky Way. His name is also associated with the Kraft break: the abrupt change in the average rotation rate of main sequence stars around spectral type F8. Career Kraft served as director of the Lick Observatory (1981–1991), president of the American Astronomical Society (1974–1976), and president of the International Astronomical Union (1997–2000). He received his B.S. at the University of Washington in 1947, M.S. in mathematics at the University of Washington in 1949, and PhD from the University of California, Berkeley. He died in 2015. Honors Awards * Helen B. Warner Prize for Astronomy (1962) *Henry Norris Russell Lectureship (1995) *Bruce Medal (2005) *National Academy of Sciences Named after him *Asteroid An asteroid is a minor planet—an object larger than a me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main Sequence
In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of stars on and off the band are believed to indicate their physical properties, as well as their progress through several types of star life-cycles. These are the most numerous true stars in the universe and include the Sun. Color-magnitude plots are known as Hertzsprung–Russell diagrams after Ejnar Hertzsprung and Henry Norris Russell. After condensation and ignition of a star, it generates thermal energy in its dense stellar core, core region through nuclear fusion of hydrogen into helium. During this stage of the star's lifetime, it is located on the main sequence at a position determined primarily by its mass but also based on its chemical composition and age. The cores of main-sequence stars are in hydros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roche Surface
F. Hoffmann-La Roche AG, commonly known as Roche (), is a Swiss multinational holding healthcare company that operates worldwide under two divisions: Pharmaceuticals and Diagnostics. Its holding company, Roche Holding AG, has shares listed on the SIX Swiss Exchange. The company headquarters are located in Basel. Roche is the fifth-largest pharmaceutical company in the world by revenue and the leading provider of cancer treatments globally. In 2023, the company’s seat in Forbes Global 2000 was 76. The company owns the American biotechnology company Genentech, which is a wholly owned independent subsidiary, and the Japanese biotechnology company Chugai Pharmaceuticals, as well as the United States–based companies Ventana and Foundation Medicine. Roche's revenues during fiscal year 2020, were 58.32 billion Swiss francs. Descendants of the founding Hoffmann and Oeri families own slightly over half of the bearer shares with voting rights (a pool of family shareholders 45%, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place in a white dwarf; what light it radiates is from its residual heat. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Jacob Luyten in 1922. White dwarfs are thought to be the final stellar evolution, evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the stars in the Milky Way. After the hydrogen-stellar nucleosynthesis, fusing period of a main sequence, main-sequence star of Stellar mass, lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U Geminorum
U Geminorum (''U Gem''), in the constellation Gemini, is an archetypal example of a dwarf nova. The binary star system consists of a white dwarf closely orbiting a red dwarf. Every few months it undergoes an outburst that greatly increases its brightness. The dwarf nova class of variable stars are often referred to as U Geminorum variables after this star. Discovery U Geminorum was discovered by J.R. Hind in 1855 who initially thought it was a nova; it quickly faded below his telescope's limiting magnitude. Its true nature was revealed three months later when it was re-observed in outburst by Pogson. The star has been monitored by amateur and professional astronomers ever since, though its location near the zodiac means that some outbursts are undoubtedly missed due to the seasonal gap. Orbit The U Geminorum binary has a very short orbital period of 4 hours and 11 minutes; this orbit alone makes the system variable, as the components transit and eclipse each other wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dwarf Novae
A dwarf nova (pl. novae), or U Geminorum variable, is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwarf novae are dimmer and repeat more often than "classical" novae. Overview The first one to be observed was U Geminorum in 1855; however, the mechanism was not known until 1974, when Brian Warner showed that the nova is due to the increase of the luminosity of the accretion disk. They are similar to classical novae in that the white dwarf is involved in periodic outbursts, but the mechanisms are different. Classical novae result from the fusion and detonation of accreted hydrogen on the primary's surface. Current theory suggests that dwarf novae result from instability in the accretion disk, when gas in the disk reaches a critical temperature that causes a change in viscosity, resulting in a temporary increase in mass flow through the disc, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars using a telescope, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough, they can gravitationally distort each other's outer stellar atmospheres. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lagrangian Point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium (mechanics), equilibrium for small-mass objects under the gravity, gravitational influence of two massive orbit, orbiting bodies. Mathematically, this involves the solution of the restricted three-body problem. Normally, the two massive bodies exert an unbalanced gravitational force at a point, altering the orbit of whatever is at that point. At the Lagrange points, the gravitational forces of the two large bodies and the centrifugal force balance each other. This can make Lagrange points an excellent location for satellites, as Orbital station-keeping, orbit corrections, and hence fuel requirements, needed to maintain the desired orbit are kept at a minimum. For any combination of two orbital bodies, there are five Lagrange points, L1 to L5, all in the orbital plane of the two large bodies. There are five Lagrange points for the Sun–Earth system, and five ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretion Disk
An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other forces induce instabilities causing orbiting material in the disk to spiral inward toward the central body. Gravitational and frictional forces compress and raise the temperature of the material, causing the emission of electromagnetic radiation. The frequency range of that radiation depends on the central object's mass. Accretion disks of young stars and protostars radiate in the infrared; those around neutron stars and black holes in the X-ray part of the spectrum. The study of oscillation modes in accretion disks is referred to as diskoseismology. Manifestations Accretion disks are a ubiquitous phenomenon in astrophysics; active galactic nuclei, protoplanetary disks, and gamma ray bursts all involve accretion disks. These di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Curve
In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis and with time on the ''x''-axis. The light is usually in a particular frequency interval or frequency band, band. Light curves can be periodic, as in the case of eclipsing binary, eclipsing binaries, Cepheid variables, other periodic variables, and Methods of detecting extrasolar planets#Transit photometry, transiting extrasolar planets; or aperiodic, like the light curve of a nova, cataclysmic variable star, supernova, gravitational microlensing, microlensing event, or binary as observed during occultation events. The study of a light curve and other observations can yield considerable information about the physical process that produces such a light curve, or constrain the physical theories about it. Variable stars Graphs of the ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
