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Edwin E. Salpeter
Edwin Ernest Salpeter (3 December 1924 – 26 November 2008,) was an Austrian–Australian–American astrophysicist. Life Born in Vienna to a Jewish family, Salpeter emigrated from Austria to Australia while in his teens to escape the Nazis. He attended Sydney Boys High School (1939–40) and Sydney University, where he obtained his bachelor's degree in 1944 and his master's degree in 1945. In the same year he was awarded an overseas scholarship and attended the University of Birmingham, England, where he earned his doctorate in 1948 under the supervision of Sir Rudolf Peierls. He spent the remainder of his career at Cornell University, where he was the James Gilbert White Distinguished Professor of the Physical Sciences. Salpeter died of leukemia at his home in Ithaca, New York on 26 November 2008. Scientific contributions In 1951 Salpeter suggested that stars could burn helium-4 into carbon-12 with the Triple-alpha process not directly, but through an intermediate metastable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vienna
Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. Its larger metropolitan area has a population of nearly 2.9 million, representing nearly one-third of the country's population. Vienna is the Culture of Austria, cultural, Economy of Austria, economic, and Politics of Austria, political center of the country, the List of cities in the European Union by population within city limits, fifth-largest city by population in the European Union, and the most-populous of the List of cities and towns on the river Danube, cities on the river Danube. The city lies on the eastern edge of the Vienna Woods (''Wienerwald''), the northeasternmost foothills of the Alps, that separate Vienna from the more western parts of Austria, at the transition to the Pannonian Basin. It sits on the Danube, and is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beryllium-8
Beryllium-8 (8Be, Be-8) is a radionuclide with 4 neutrons and 4 protons. It is an unbound resonance and nominally an isotope of beryllium. It has a half-life on the order of 8.19 seconds, decaying into two alpha particles. This has important ramifications in stellar nucleosynthesis as it creates a bottleneck in the creation of heavier chemical elements. The properties of 8Be have also led to speculation on the fine tuning of the universe, and theoretical investigations on cosmological evolution had 8Be been stable. Discovery The discovery of beryllium-8 occurred shortly after the construction of the first particle accelerator in 1932. Physicists John Douglas Cockcroft and Ernest Walton performed their first experiment with their accelerator at the Cavendish Laboratory in Cambridge, in which they irradiated lithium-7 with protons. They reported that this populated a nucleus with ''A'' = 8 that near-instantaneously decays into two alpha particles. This activi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurobiologist
A neuroscientist (or neurobiologist) is a scientist specializing in neuroscience that deals with the anatomy and function of neurons, neural circuits, and glia, and their behavioral, biological, and psychological roles in health and disease. Neuroscientists generally work as researchers within a college, university, government agency, or private industry setting. In research-oriented careers, neuroscientists design and conduct scientific experiments on the nervous system and its functions. They can engage in basic or applied research. Basic research seeks to expand current understanding of the nervous system, whereas applied research seeks to address a specific problem, such as developing a treatment for a neurological disorder. Neuroscientists have numerous career opportunities outside of academic research, including careers in industry, science writing, government program management, science advocacy, and education. A neuroscientist commonly holds a doctorate in a medica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miriam Salpeter
Miriam (Mika) Salpeter (née Mark; April 8, 1929 – October 24, 2000) was an American academic. As professor of neurobiology at Cornell University, she developed quantitative electron microscopic autoradiography as a means to investigate the neuromuscular junction. The Society for Neuroscience created the Mika Salpeter Lifetime Achievement Award in her honour. Early life and education Salpeter was born in Riga. Her father was a Yiddish scholar and Salpeter was fluent in Yiddish. During the rise of Nazi Germany Salpeter emigrated from Latvia to Canada, before moving to the United States in 1945. Salpeter attended high school in New York City. She was an undergraduate student at Hunter College, where she was a member of Phi Beta Kappa and graduated ''summa cum laude''. Salpeter moved to Cornell University for her doctoral studies, where she earned a PhD under the supervision of Howard Liddell. She spent a year at the Australian National University before returning to Cornell Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relativistic Jet
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as extended beams along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within accretion disks, whose active processes are commonly connected with compact central objects such as black holes, neutron stars or pulsars. One explanation is that tangled magnetic fields are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a general relativity effect known as frame-dragging. Most of the largest and most active jets are created by supermassive black holes (SMBH) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such excess, non-stellar emissions have been observed in the radio waves, radio, microwave, infrared, visible spectrum, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an active galaxy. The non-stellar radiation from an AGN is theorized to result from the accretion (astrophysics), accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe and, as such, can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on cosmology, models of the cosmos. The observed characteristics of an AGN depend on several properties s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasar
A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous Accretion disk, accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosity, luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of Expansion of the universe, cosmological origin. The term originated as a Contraction (grammar), contraction of "quasi-stellar ''[star-like]'' radio source"—because they were first identified during the 1950s as sources of radio-wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Hole
A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary (topology), boundary of no escape is called the event horizon. A black hole has a great effect on the fate and circumstances of an object crossing it, but has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with thermal radiation, the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the Orders of magnitude (temperature), order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretion Disc
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 disks ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich
Yakov Borisovich Zeldovich (, ; 8 March 1914 – 2 December 1987), also known as YaB, was a leading Soviet physicist of Belarusian origin, who is known for his prolific contributions in physical cosmology, physics of thermonuclear reactions, combustion, and hydrodynamical phenomena. From 1943, Zeldovich, a self-taught physicist, started his career by playing a crucial role in the development of the former Soviet program of nuclear weapons. In 1963, he returned to academia to embark on pioneering contributions on the fundamental understanding of the thermodynamics of black holes and expanding the scope of physical cosmology. Biography Early life and education Yakov Zeldovich was born into a Belarusian Jewish family in his grandfather's house in Minsk. However, in mid-1914, the Zeldovich family moved to Saint Petersburg. They resided there until August 1941, when the family was evacuated together with the faculty of the Institute of Chemical Physics to Kazan to avoid the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Field Theory
In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines Field theory (physics), field theory and the principle of relativity with ideas behind quantum mechanics. QFT is used in particle physics to construct physical models of subatomic particles and in condensed matter physics to construct models of quasiparticles. The current standard model of particle physics is based on QFT. History Quantum field theory emerged from the work of generations of theoretical physicists spanning much of the 20th century. Its development began in the 1920s with the description of interactions between light and electrons, culminating in the first quantum field theory—quantum electrodynamics. A major theoretical obstacle soon followed with the appearance and persistence of various infinities in perturbative calculations, a problem only resolved in the 1950s with the invention of the renormalization procedure. A second major barrier came with QFT's apparent inabili ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elementary Particle
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number: electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles. Ordinary matter is composed of atoms, themselves once thought to be indivisible elementary particles. The name ''atom'' comes from the Ancient Greek word ''ἄτομος'' ( atomos) which means ''indivisible'' or ''uncuttable''. Despite the theories about atoms that had existed for thousands of years, the factual existence of ato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
