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Walter Lewin
Walter Hendrik Gustav Lewin (born January 29, 1936) is a Dutch astrophysicist and retired professor of physics at the Massachusetts Institute of Technology. Lewin earned his doctorate in nuclear physics in 1965 at the Delft University of Technology and was a member of MIT's physics faculty for 43 years beginning in 1966 until his retirement in 2009. Lewin's contributions in astrophysics include the first discovery of a rotating neutron star through all-sky balloon surveys and research in X-ray detection in investigations through satellites and observatories. Lewin has received awards for teaching and is known for his lectures on physics and their publication online via YouTube, MIT OpenCourseWare and edX. In December 2014, MIT revoked Lewin's Professor Emeritus title after an MIT investigation determined that Lewin had violated university policy by sexually harassing an online student in an online MITx course he taught in fall 2013. Early life and education Lewin was born to W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Hague
The Hague ( ; nl, Den Haag or ) is a city and municipality of the Netherlands, situated on the west coast facing the North Sea. The Hague is the country's administrative centre and its seat of government, and while the official capital of the Netherlands is Amsterdam, The Hague has been described as the country's de facto capital. The Hague is also the capital of the province of South Holland, and the city hosts both the International Court of Justice and the International Criminal Court. With a population of over half a million, it is the third-largest city in the Netherlands, after Amsterdam and Rotterdam. The Hague is the core municipality of the Greater The Hague urban area, which comprises the city itself and its suburban municipalities, containing over 800,000 people, making it the third-largest urban area in the Netherlands, again after the urban areas of Amsterdam and Rotterdam. The Rotterdam–The Hague metropolitan area, with a population of approximately 2.6&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Associate Professor
Associate professor is an academic title with two principal meanings: in the North American system and that of the ''Commonwealth system''. Overview In the ''North American system'', used in the United States and many other countries, it is a position between assistant professor and a full professorship. In this system an associate professorship is typically the first promotion obtained after gaining a faculty position, and in the United States it is usually connected to tenure. In the '' Commonwealth system'' (Canada included), the title associate professor is traditionally used in place of reader in certain countries.UK Academic Job Titles Explained academicpositions.com Like the reader title it ranks above senior lecturer – which corresponds to associ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier 81
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of . Because of its relative proximity to the Milky Way galaxy, large size, and active galactic nucleus (which harbors a 70 million supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also makes it a popular target for amateur astronomers. In late February 2022, astronomers reported that M81 may be the source of FRB 20200120E, a repeating fast radio burst. Discovery Messier 81 was first discovered by Johann Elert Bode on 31 December 1774. Thus, it is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, hence listed it in the Messier Catalogue. Visibility The galaxy is to be found approximately 10° northwest of Alpha Ursae M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andromeda Galaxy
The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology. The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at . The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study that cited a lower estimate on the mass of the Andromeda Galaxy, combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way. The Andromeda Galaxy has a diameter of about , making it the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ROSAT
ROSAT (short for Röntgensatellit; in German X-rays are called Röntgenstrahlen, in honour of Wilhelm Röntgen) was a German Aerospace Center-led satellite X-ray telescope, with instruments built by West Germany, the United Kingdom and the United States. It was launched on 1 June 1990, on a Delta II rocket from Cape Canaveral, on what was initially designed as an 18-month mission, with provision for up to five years of operation. ROSAT operated for over eight years, finally shutting down on 12 February 1999. In February 2011, it was reported that the satellite was unlikely to burn up entirely while re-entering the Earth's atmosphere due to the large amount of ceramics and glass used in construction. Parts as heavy as could impact the surface. ROSAT eventually re-entered the Earth's atmosphere on 23 October 2011 over Bay of Bengal. Overview According to NASA, the Roentgensatellit (ROSAT) was a joint German, U.S. and British X-ray astrophysics project. ROSAT carried a Germa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ginga (satellite)
ASTRO-C, renamed Ginga (Japanese for 'galaxy'), was an X-ray astronomy satellite launched from the Kagoshima Space Center on 5 February 1987 using M-3SII launch vehicle. The primary instrument for observations was the Large Area Counter (LAC). Ginga was the third Japanese X-ray astronomy mission, following Hakucho and Tenma (also Hinotori satellite - which preceded Ginga - had X-ray sensors, but it can be seen as a heliophysics rather than X-ray astronomy mission). Ginga reentered the Earth's atmosphere on 1 November 1991. Instruments * Large Area Proportional Counter (LAC 1.5-37 keV) * All-Sky Monitor (ASM 1-20 keV) * Gamma-ray Burst Detector (GBD 1.5-500 keV) Highlights *Discovery of transient Black Hole Candidates and study of their spectral evolution. *Discovery of weak transients in the galactic ridge. *Detection of cyclotron features in 3 X-ray pulsars: 4U1538-522, V0332+53, and Cep X-4. *Evidence for emission and absorption Fe feature in Seyfert probing reproces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasi-periodic Oscillation
In X-ray astronomy, quasi-periodic oscillation (QPO) is the manner in which the X-ray light from an astronomical object flickers about certain frequencies. In these situations, the X-rays are emitted near the inner edge of an accretion disk in which gas swirls onto a compact object such as a white dwarf, neutron star, or black hole. The QPO phenomenon promises to help astronomers understand the innermost regions of accretion disks and the masses, radii, and spin periods of white dwarfs, neutron stars, and black holes. QPOs could help test Albert Einstein's theory of general relativity which makes predictions that differ most from those of Newtonian gravity when the gravitational force is strongest or when rotation is fastest (when a phenomenon called the Lense–Thirring effect comes into play). However, the various explanations of QPOs remain controversial and the conclusions reached from their study remain provisional. A QPO is identified by performing a power spectrum of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EXOSAT
The European X-ray Observatory Satellite (EXOSAT), originally named HELOS, was an X-ray telescope operational from May 1983 until April 1986 and in that time made 1780 observations in the X-ray band of most classes of astronomical object including active galactic nuclei, stellar coronae, cataclysmic variable In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae (), since ones with an outburst brightness visible to ...s, white dwarfs, X-ray binaries, cluster of galaxies, clusters of galaxies, and supernova remnants. This European Space Agency (ESA) satellite for direct-pointing and lunar-occultation observation of X-ray sources beyond the solar system was launched into a highly eccentric orbit (apogee 200,000 km, perigee 500 km) almost perpendicular to that of the moon on 26 May 1983. The instrumentation includes two low-energy im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white holes, quark stars, and strange stars), neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of and a mass of about 1.4 solar masses. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei. Once formed, they no longer actively generate heat, and cool over time; however, they may still evolve further through collision or accretion. Most of the basic models for these objects imply that neutron stars are composed almost entirely of neutrons (subatomic particles with no net electrical charge and with slightly larger mass than protons); the electro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hakucho
Hakucho (also known as CORSA-b before launch; CORSA stands for Cosmic Radiation Satellite) was Japan's first X-ray astronomy satellite, developed by the Institute of Space and Aeronautical Science (then a division of the University of Tokyo). It was launched from the Kagoshima Space Center by the ISAS M-3C rocket on the M-3C-4 mission on February 21, 1979 and reentered the atmosphere on April 15, 1985. Hakucho was a replacement for the CORSA satellite which failed to launch due to rocket failure on February 4, 1976. Highlights *Discovery of soft X-ray transient Cen X-4 and Aql X-1 *Discovery of many burst sources *Long-term monitoring of X-ray pulsar (e.g. Vela X-1) *Discovery of 2 Hz variability in the Rapid Burster later named Quasi Period Oscillation. See also * Timeline of artificial satellites and space probes This Timeline of artificial satellites and Space probe A space probe is an artificial satellite that travels through space to collect scientific data. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Energy Astronomy Observatory 1
HEAO-1 was an X-ray telescope launched in 1977. HEAO-1 surveyed the sky in the X-ray portion of the electromagnetic spectrum (0.2 keV – 10 MeV), providing nearly constant monitoring of X-ray sources near the ecliptic poles and more detailed studies of a number of objects by observations lasting 3–6 hours. It was the first of NASA's three High Energy Astronomy Observatories, HEAO 1, launched August 12, 1977 aboard an Atlas rocket with a Centaur upper stage, operated until 9 January 1979. During that time, it scanned the X-ray sky almost three times HEAO included four X-ray and gamma-ray astronomy instruments, known as A1, A2, A3, and A4, respectively (before launch, HEAO 1 was known as HEAO A). The orbital inclination was about 22.7 degrees. HEAO 1 re-entered the Earth's atmosphere on 15 March 1979. A1: Large-Area Sky Survey instrument The A1, or Large-Area Sky Survey (LASS) instrument, covered the 0.25–25 keV energy range, using seven large proportional counters. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Small Astronomy Satellite 3
The Small Astronomy Satellite 3 (SAS 3, also known as SAS-C before launch) was a NASA X-ray astronomy space telescope. It functioned from May 7, 1975 to April 1979. It covered the X-ray range with four experiments on board. The satellite, built by the Johns Hopkins University Applied Physics Laboratory (APL), was proposed and operated by MIT's Center for Space Research (CSR). It was launched on a Scout vehicle from the Italian San Marco launch platform near Mombasa, Kenya, into a low-Earth, nearly equatorial orbit. It was also known as Explorer 53, as part of NASA's Explorer program. The spacecraft was 3-axis stabilized with a momentum wheel that was used to establish stability about the nominal rotation, or z-axis. The orientation of the z-axis could be altered over a period of hours using magnetic torque coils that interacted with the Earth's magnetic field. Solar panels charged batteries during the daylight portion of each orbit, so that SAS 3 had essentially no expendab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
