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99942
99942 Apophis (provisional designation ) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, that caused a brief period of concern in December 2004 when initial observations indicated a probability of 0.027 (2.7%) that it would hit Earth on Friday, April 13, 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth in 2029. A small possibility nevertheless remained that, during its 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole estimated to be 800 metres in diameter, which would have set up a future impact exactly seven years later on Easter Sunday, April 13, 2036. This possibility kept it at Level 1 on the 0 to 10 Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small and Apophis's rating on the Torino scale was lowere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yarkovsky Effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids (about 10 cm to 10 km in diameter), as its influence is most significant for these bodies. History of discovery The effect was discovered by the Polish-Russian civil engineer Ivan Osipovich Yarkovsky (1844–1902), who worked in Russia on scientific problems in his spare time. Writing in a pamphlet around the year 1900, Yarkovsky noted that the daily heating of a rotating object in space would cause it to experience a force that, while tiny, could lead to large long-term effects in the orbits of small bodies, especially meteoroids and small asteroids. Yarkovsky's insight would have been forgotten had it not been for the Estonian astronomer Ernst J. Öpik (1893–1985), who read Yarkovsky's pamphlet sometime around 1909. Decades later, Öpik, recallin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tumbling Asteroid
This is a list of tumblers, that is, small Solar System bodiess or moons that do not rotate in a fairly constant manner with a constant period. Instead of rotating around a constant axis or around an axis that itself moves evenly, they appear to tumble (see Poinsot's ellipsoid for an explanation). For true tumbling, the three moments of inertia must be different. If two are equal, then the axis of rotation will simply precess in a circle. As of 2018, there are 3 natural satellites and 198 confirmed or likely tumblers out of a total of nearly 800,000 discovered small Solar System bodies. The data is sourced from the "Lightcurve Data Base" (LCDB). The tumbling of a body can be caused by the torque from asymmetrically emitted radiation known as the YORP effect. Note that the rotation periods given below are apparent periods and are not constant for a tumbler. There is another definition of rotation, sometimes called rotation, intrinsic rotation, that relates to how the point on the obj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Keyhole
A gravitational keyhole is a tiny region of space where a planet's gravity would alter the orbit of a passing asteroid such that the asteroid would collide with that planet on a given future orbital pass. The word "keyhole" contrasts the large uncertainty of trajectory calculations (between the time of the observations of the asteroid and the first encounter with the planet) with the relatively narrow bundle(s) of critical trajectories. The term was coined by P. W. Chodas in 1999. It gained some public interest when it became clear, in January 2005, that the asteroid 99942 Apophis would miss the Earth in 2029 but may go through one or another keyhole leading to impacts in 2036 or 2037. Further research has since been done, however, which revealed the probability of Apophis passing through the keyhole was extremely low. Keyholes for the nearer or further future are named by the numbers of orbital periods of the planet and the asteroid, respectively, between the two encounters (for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fabrizio Bernardi
Fabrizio Bernardi (born 1972) is an Italian astronomer and discoverer of minor planets and comets, best known for the co-discovery of the near-Earth and potentially hazardous asteroid 99942 Apophis. He is a member of the IAU, and credited by the Minor Planet Center with the discovery of 7 numbered minor planets during 2002–2005, including 280244 Ati, another near-Earth object a member of the Amor group of asteroids, and , a trans-Neptunian object. In 2002, he discovered the outer main-belt asteroid 65001 Teodorescu at Campo Imperatore station, Gran Sasso, Italy, and named it after his former wife, the Romanian astronomer Ana Teodorescu. He was involved together with colleagues Marco Micheli and David Tholen, with observations of the Mars-crosser asteroid 2007 WD5 during his stay at the University of Hawaii observatory. While at the Mauna Kea Observatories in Hawaii, he discovered 268P/Bernardi, a Jupiter family comet. The main-belt asteroid 27983 Bernardi, discover ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palermo Scale
The Palermo scale or Palermo technical impact hazard scale is a logarithmic scale used by astronomers to rate the potential hazard of impact of a near-Earth object (NEO). It combines two types of data—probability of impact and estimated kinetic yield—into a single "hazard" value. A rating of 0 means the hazard is equivalent to the background hazard (defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact). A rating of +2 would indicate the hazard is 100 times as great as a random background event. Scale values less than −2 reflect events for which there are no likely consequences, while Palermo scale values between −2 and 0 indicate situations that merit careful monitoring. A similar but less complex scale is the Torino scale, which is used for simpler descriptions in the non-scientific media. , no asteroid has a cumulative rating for impacts above 0, and only two asteroids have ratings betwee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torino Scale
The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. It is intended as a communication tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value. The Palermo scale is a similar, but more complex scale. Near-Earth objects with a Torino scale of 1 are discovered several times a year, and may last a few weeks until they have a longer observation arc that eliminates any possibility of a collision. The only objects on the Torino scale that have ever ranked higher are asteroids 99942 Apophis, which had a rating of 4 for four days in late 2004, the highest recorded rating; , with a historical rating of 2 from February to May 2006; and , with a rating of 3 from January 27, 2025 to February 20, 2025. Overview The Torino scale uses an integer scale from 0 to 10. A 0 indicates an o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting radio waves or microwaves off target objects and analyzing their reflections. Radar astronomy differs from ''radio astronomy'' in that the latter is a passive observation (i.e., receiving only) and the former an active one (transmitting and receiving). Radar systems have been conducted for six decades applied to a wide range of Solar System studies. The radar transmission may either be pulsed or continuous. The strength of the radar return signal is radar#Radar range equation, proportional to the inverse fourth-power of the distance. Upgraded facilities, increased transceiver power, and improved apparatus have increased observational opportunities. Radar techniques provide information unavailable by other means, such as testing general relativity by observing Mercury (planet), Mercury and providing a refined value for the astronomical unit. Radar imaging, Radar images provide information about th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Near-Earth Object
A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit around the Sun, rather than its current position, thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses the Earth's orbit, and the object is larger than across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about a third of a percent are comets. There are over 37,000 known near-Earth asteroids (NEAs) and over 120 known short-period near-Earth comets (NECs). A number of solar-orbiting meteoroids were large enough to be tracked in space before striking Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apophis Symbol (bold)
Apophis (; ), also known as Apep () or Aphoph (, ) Erman, Adolf, and Hermann Grapow, eds. 1926–1953. ''Wörterbuch der aegyptischen Sprache im Auftrage der deutschen Akademien''. 6 vols. Leipzig: J. C. Hinrichs'schen Buchhandlungen. (Reprinted Berlin: Akademie-Verlag GmbH, 1971). is the ancient Egyptian deity who embodied darkness and disorder, and was thus the opponent of light and Maat (order/truth). Ra was the bringer of light and hence the biggest opposer of Apophis. Features Because Ra was the solar deity, bringer of light, and thus the upholder of Maat, Apophis was viewed as the greatest enemy of Ra, and thus was given the title ''Enemy of Ra'', and also "the Lord of Chaos". "The Lord of Chaos" was seen as a giant snake or serpent leading to such titles as ''Serpent from the Nile'' and ''Evil Dragon''. Some elaborations said that he stretched 16 yards in length and had a head made of flint. Presented on a Naqada I (c. 4000–3550 BCE) C-ware bowl (now in C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apep
Apophis (; ), also known as Apep () or Aphoph (, ) Erman, Adolf, and Hermann Grapow, eds. 1926–1953. ''Wörterbuch der aegyptischen Sprache im Auftrage der deutschen Akademien''. 6 vols. Leipzig: J. C. Hinrichs'schen Buchhandlungen. (Reprinted Berlin: Akademie-Verlag GmbH, 1971). is the ancient Egyptian deity who embodied darkness and disorder, and was thus the opponent of light and Maat (order/truth). Ra was the bringer of light and hence the biggest opposer of Apophis. Features Because Ra was the solar deity, bringer of light, and thus the upholder of Maat, Apophis was viewed as the greatest enemy of Ra, and thus was given the title ''Enemy of Ra'', and also "the Lord of Chaos". "The Lord of Chaos" was seen as a giant snake or serpent leading to such titles as ''Serpent from the Nile'' and ''Evil Dragon''. Some elaborations said that he stretched 16 yards in length and had a head made of flint. Presented on a Naqada I (c. 4000–3550 BCE) C-ware bowl (now ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goldstone Deep Space Communications Complex
The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in Fort Irwin in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its main purpose is to track and communicate with interplanetary space missions. It is named after Goldstone, California, a nearby gold-mining ghost town. The station is one of three satellite communication stations in the NASA Space Communications and Navigation (SCaN) program’s Deep Space Network (DSN), whose mission is to provide the vital two-way communications link that tracks and controls interplanetary spacecraft and receives the images and scientific information they collect. The others are the Madrid Deep Space Communications Complex in Spain and the Canberra Deep Space Communication Complex in Australia. These three stations are located at separations of approximately 120° longitude so that as the Earth rotates a spacecraf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, appears always relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer ( inferior) to the Sun than Earth. The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
