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1991 BA
1991 BA is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group that was first observed by Spacewatch on 18 January 1991, and passed within 160,000 km (100,000 mi) of Earth. This is a little less than half the distance to the Moon. With a 5-hour observation arc the asteroid has a poorly constrained orbit and is considered lost. It could be a member of the Beta Taurids.Peter Jenniskens Meteor Showers and their Parent Comets pg 463 fig 25.7 Description 1991 BA is approximately 5 to 10 meters (15 to 30 ft) in diameter and is listed on the Sentry Risk Table. It follows a highly eccentric (0.68), low-inclination (2.0°) orbit of 3.3 years duration, ranging between 0.71 and 3.7 AU from the Sun. 1991 BA was, at the time of its discovery, the smallest and closest confirmed asteroid outside of Earth's atmosphere. 1991 BA is too faint to be observed except during close approaches to Earth and is considered lost. Possible impact Virtual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacewatch
The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona, in the United States. The Spacewatch Project has been active longer than any other similar currently active programs. Spacewatch was founded in 1980 by Tom Gehrels and Robert S. McMillan, and is currently led by astronomer Melissa Brucker at the University of Arizona. Spacewatch uses several telescopes on Kitt Peak for follow-up observations of near-Earth objects. The Spacewatch Project uses three telescopes of apertures 0.9-m, 1.8-m, and 2.3-m. These telescopes are located on Kitt Peak mountain in Arizona, and the first two are dedicated to the purpose of locating Near-Earth Objects (NEOs). The 36 inch (0.9 meter) telescope on Kitt Peak has been in use by Spacewatch since 1984, and since 2000 the 72 inch (1.8 meter) Spacewatch telescope. The 36 inch te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sentry (monitoring System)
Sentry is a highly automated impact prediction system operated by the JPL Center for NEO Studies (CNEOS) since 2002. It continually monitors the most up-to-date asteroid catalog for possibilities of future impact with Earth over the next 100+ years. Whenever a potential impact is detected it will be analyzed and the results immediately published by the Center for Near-Earth Object Studies. However, several weeks of optical data are not enough to conclusively identify an impact years in the future. By contrast, eliminating an entry on the risk page is a negative prediction, a prediction of where it will ''not'' be. Scientists warn against worrying about the possibility of impact with an object based on only a few weeks of optical data that show a possible Earth encounter years from now. Sometimes, it cannot even be said for certain what side of the Sun such an object will be at the time of the listed virtual impactor date. For example, even though has a 1-in-500,000 chance of imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minor Planet Center
The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function The Minor Planet Center is the official worldwide organization in charge of collecting observational data for minor planets (such as asteroids), calculating their orbits and publishing this information via the '' Minor Planet Circulars''. Under the auspices of the International Astronomical Union (IAU), it operates at the Smithsonian Astrophysical Observatory, which is part of the Center for Astrophysics along with the Harvard College Observatory. The MPC runs a number of free online services for observers to assist them in observing minor planets and comets. The complete catalogue of minor planet orbits (sometimes referred to as the "Minor Planet Catalogue") may also be freely downloaded. In addition to astrometric data, the MPC collect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NEODyS
NEODyS (Near Earth Objects Dynamic Site) is an Italian service that provides information on near-Earth objects with a Web-based interface. It is based on a continually and (almost) automatically maintained database of near earth asteroid orbits. This site provides a number of services to the NEO community. The main service is an impact monitoring system (CLOMON2) of all near-Earth asteroids covering a period until the year 2100. Services * Risk Page: One of the most important services is the production of a Risk Page where 1128 NEOs with probabilities of hitting the Earth greater of 10−11 from now until 2100 are shown in a Risk list. In the table of the Risk list the NEOs are divided into "Special", as it is the case of 101955 Bennu; "Observable", objects which are presently observable and which critically need a follow up in order to improve their orbit; "Possible recovery", objects which are not visible at present, but which are possible to recover in the near future; "Lost", ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Unit
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once each year. The astronomical unit was originally conceived as the average of Earth's aphelion and perihelion; however, since 2012 it has been defined as exactly (see below for several conversions). The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec. History of symbol usage A variety of unit symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union (IAU) had used the symbol ''A'' to denote a length equal to the astronomical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curve Fitting
Curve fitting is the process of constructing a curve, or mathematical function, that has the best fit to a series of data points, possibly subject to constraints. Curve fitting can involve either interpolation, where an exact fit to the data is required, or smoothing, in which a "smooth" function is constructed that approximately fits the data. A related topic is regression analysis, which focuses more on questions of statistical inference such as how much uncertainty is present in a curve that is fit to data observed with random errors. Fitted curves can be used as an aid for data visualization, to infer values of a function where no data are available, and to summarize the relationships among two or more variables. Extrapolation refers to the use of a fitted curve beyond the range of the observed data, and is subject to a degree of uncertainty since it may reflect the method used to construct the curve as much as it reflects the observed data. For linear-algebraic analysis o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JPL Horizons
JPL Horizons On-Line Ephemeris System provides access to key Solar System data and flexible production of highly accurate ephemerides for Solar System objects. Osculating elements at a given epoch (such as produced by the JPL Small-Body Database) are always an approximation to an object's orbit (i.e. an unperturbed conic orbit or a " two-body" orbit). The real orbit (or the best approximation to such) considers perturbations by all planets, a few of the larger asteroids, a few other usually small physical forces, and requires numerical integration. Jet Propulsion Laboratory (JPL) ephemerides do not use things such as periods, eccentricities, etc. Instead, JPL integrates the equations of motion in Cartesian coordinates (x,y,z), and adjusts the initial conditions in order to fit modern, highly accurate measurements of planetary positions. Since August 2013, Horizons has been using ephemeris DE431. During the week of 12 April 2021, the Horizons ephemeris system was updated to r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sudan
Sudan ( or ; ar, السودان, as-Sūdān, officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a country in Northeast Africa. It shares borders with the Central African Republic to the southwest, Chad to the west, Egypt to the north, Eritrea to the northeast, Ethiopia to the southeast, Libya to the northwest, South Sudan to the south and the Red Sea. It has a population of 45.70 million people as of 2022 and occupies 1,886,068 square kilometres (728,215 square miles), making it Africa's List of African countries by area, third-largest country by area, and the third-largest by area in the Arab League. It was the largest country by area in Africa and the Arab League until the 2011 South Sudanese independence referendum, secession of South Sudan in 2011, since which both titles have been held by Algeria. Its Capital city, capital is Khartoum and its most populated city is Omdurman (part of the metropolitan area of Khar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strewn Field
The term strewn field indicates the area where meteorites from a single fall are dispersed. It is also often used for the area containing tektites produced by large meteorite impact.''Tektites in the geological record: showers of glass from the sky''. Gerald Joseph Home McCall. Geological Society of London, 2001page 10/ref> Formation There are two strewnfield formation mechanisms: # Mid-air fragmentation: when a large meteoroid enters the atmosphere it often fragments into many pieces before touching the ground due to thermal shock. This mid-air explosion disperses material over a large oval-shaped area. The long axis of this oval is along the flight path of the meteoroid. When multiple-explosions occur, the material can be found in several overlapping ovals. # Impact fragmentation: when there is almost no mid-air fragmentation the fragmentation can occur upon impact. In this case the strewnfield shape can be different, usually circular. (e.g. Canyon Diablo at Meteor Crater; Austra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fat Man
"Fat Man" (also known as Mark III) is the codename for the type of nuclear bomb the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the first being Little Boy, and its detonation marked the third nuclear explosion in history. It was built by scientists and engineers at Los Alamos Laboratory using plutonium from the Hanford Site, and it was dropped from the Boeing B-29 Superfortress '' Bockscar'' piloted by Major Charles Sweeney. The name Fat Man refers to the early design of the bomb because it had a wide, round shape. Fat Man was an implosion-type nuclear weapon with a solid plutonium core. The first of that type to be detonated was the Gadget in the Trinity nuclear test less than a month earlier on 16 July at the Alamogordo Bombing and Gunnery Range in New Mexico. Two more were detonated during the Operation Crossroads nuclear tests at Bikini Atoll in 1946, and some 120 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Weapon Yield
The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produce the same energy discharge), either in kilotonnes (kt—thousands of tonnes of TNT), in megatonnes (Mt—millions of tonnes of TNT), or sometimes in terajoules (TJ). An explosive yield of one terajoule is equal to . Because the accuracy of any measurement of the energy released by TNT has always been problematic, the conventional definition is that one kilotonne of TNT is held simply to be equivalent to 1012 calories. The yield-to-weight ratio is the amount of weapon yield compared to the mass of the weapon. The practical maximum yield-to-weight ratio for fusion weapons (thermonuclear weapons) has been estimated to six megatonnes of TNT per tonne of bomb mass (25 TJ/kg). Yields of 5.2 megatonnes/tonne and higher have been reported ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
