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88-423: The Baptistina family ( FIN : 403 ) is an asteroid family of more than 2500 members that was probably produced by the breakup of an asteroid 170 km (110 mi) across 80 million years ago following an impact with a smaller body. The two largest presumed remnants of the parent asteroid are main-belt asteroids 298 Baptistina and 1696 Nurmela . The Baptistina family is part of the larger Flora clan . It

176-543: A 1.6% chance of Earth impact in April 2029. As observations were collected over the next three days, the calculated chance of impact increased to as high as 2.7%, then fell back to zero, as the uncertainty zone for this close approach no longer included the Earth. There was still some uncertainty about potential impacts during later close approaches, however, as the precision of orbital calculations improved due to additional observations,

264-522: A global catastrophe, was met by 2011. In later years, the survey effort was expanded to include smaller objects which have the potential for large-scale, though not global, damage. NEOs have low surface gravity, and many have Earth-like orbits that make them easy targets for spacecraft. As of April 2024 , five near-Earth comets and six near-Earth asteroids, one of them with a moon, have been visited by spacecraft. Samples of three have been returned to Earth, and one successful deflection test

352-635: A large differentiated parent body. Asteroid families are thought to have lifetimes of the order of a billion years, depending on various factors (e.g. smaller asteroids are lost faster). This is significantly shorter than the Solar System's age, so few if any are relics of the early Solar System. Decay of families occurs both because of slow dissipation of the orbits due to perturbations from Jupiter or other large bodies, and because of collisions between asteroids which grind them down to small bodies. Such small asteroids then become subject to perturbations such as

440-540: A network of infrasound sensors designed to detect the detonation of nuclear devices. Asteroid impact prediction remains in its infancy and successfully predicted asteroid impacts are rare. The vast majority of impacts recorded by IMS are not predicted. Observed impacts aren't restricted to the surface and atmosphere of Earth. Dust-sized NEOs have impacted man-made spacecraft, including the space probe Long Duration Exposure Facility , which collected interplanetary dust in low Earth orbit for six years from 1984. Impacts on

528-582: A new crater 40 m (130 ft) across, was the largest ever observed as of July 2019 . Through human history, the risk that any near-Earth object poses has been viewed having regard to both the culture and the technology of human society . Through history, humans have associated NEOs with changing risks, based on religious, philosophical or scientific views, as well as humanity's technological or economical capability to deal with such risks. Thus, NEOs have been seen as omens of natural disasters or wars; harmless spectacles in an unchanging universe;

616-642: A plan to deflect the asteroid with rockets in case it was found to be on a collision course with Earth. Project Icarus received wide media coverage, and inspired the 1979 disaster movie Meteor , in which the US and the USSR join forces to blow up an Earth-bound fragment of an asteroid hit by a comet. The first astronomical program dedicated to the discovery of near-Earth asteroids was the Palomar Planet-Crossing Asteroid Survey . The link to impact hazard,

704-498: A potential 2028 close approach 0.00031 AU (46,000 km) from the Earth, well within the orbit of the Moon, but with a large error margin allowing for a direct hit. Further data allowed a revision of the 2028 approach distance to 0.0064 AU (960,000 km), with no chance of collision. By that time, inaccurate reports of a potential impact had caused a media storm. In 1998, the movies Deep Impact and Armageddon popularised

792-523: A restriction that applies to comets in particular, but this approach is not universal. Some authors further restrict the definition to orbits that are at least partly further than 0.983 AU away from the Sun. NEOs are thus not necessarily currently near the Earth, but they can potentially approach the Earth relatively closely. Many NEOs have complex orbits due to constant perturbation by the Earth's gravity, and some of them can temporarily change from an orbit around

880-411: A result, the ratio of the known and the estimated total number of near-Earth asteroids larger than 1 km in diameter rose from about 20% in 1998 to 65% in 2004, 80% in 2006, and 93% in 2011. The original Spaceguard goal has thus been met, only three years late. As of March 2024 , 861 NEAs larger than 1 km have been discovered. In 2005, the original USA Spaceguard mandate was extended by

968-516: A space mission to avert the threat. REP. STEWART: ... are we technologically capable of launching something that could intercept [an asteroid]? ... DR. A'HEARN: No. If we had spacecraft plans on the books already, that would take a year ... I mean a typical small mission ... takes four years from approval to start to launch ... The ATLAS project, by contrast, aims to find impacting asteroids shortly before impact, much too late for deflection maneuvers but still in time to evacuate and otherwise prepare

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1056-526: A swarm of asteroids that are much smaller. Some families (e.g. the Flora family ) have complex internal structures which are not satisfactorily explained at the moment, but may be due to several collisions in the same region at different times. Due to the method of origin, all the members have closely matching compositions for most families. Notable exceptions are those families (such as the Vesta family ) which formed from

1144-545: A theory that Noah's flood in the Bible was caused by a comet impact. Human perception of near-Earth asteroids as benign objects of fascination or killer objects with high risk to human society has ebbed and flowed during the short time that NEAs have been scientifically observed. The 1937 close approach of Hermes and the 1968 close approach of Icarus first raised impact concerns among scientists. Icarus earned significant public attention due to alarmist news reports. while Hermes

1232-848: A workshop at Vulcano , Italy in 1995, and set up The Spaceguard Foundation also in Italy a year later. In 1998, the United States Congress gave NASA a mandate to detect 90% of near-earth asteroids over 1 km (0.62 mi) diameter (that threaten global devastation) by 2008. Several surveys have undertaken " Spaceguard " activities (an umbrella term), including Lincoln Near-Earth Asteroid Research (LINEAR), Spacewatch , Near-Earth Asteroid Tracking (NEAT), Lowell Observatory Near-Earth-Object Search (LONEOS), Catalina Sky Survey (CSS), Campo Imperatore Near-Earth Object Survey (CINEOS), Japanese Spaceguard Association , Asiago-DLR Asteroid Survey (ADAS) and Near-Earth Object WISE (NEOWISE). As

1320-529: Is assessed at 1 in 34,000. The corresponding Palermo scale value of −2.05 is still the second highest for all objects on the Sentry List Table. On December 24, 2004, 370 m (1,210 ft) asteroid 99942 Apophis (at the time known only by its provisional designation 2004 MN 4 ) was assigned a 4 on the Torino scale, the highest rating given to date, as the information available at the time translated to

1408-478: Is detected, like all other small Solar System bodies, its positions and brightness are submitted to the (IAU's) Minor Planet Center (MPC) for cataloging. The MPC maintains separate lists of confirmed NEOs and potential NEOs. The MPC maintains a separate list for the potentially hazardous asteroids (PHAs). NEOs are also catalogued by two separate units of the Jet Propulsion Laboratory (JPL) of NASA :

1496-418: Is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Earth. Asteroids as small as 20 metres (66 ft) in diameter can cause significant damage to the local environment and human populations. Larger asteroids penetrate the atmosphere to the surface of the Earth, producing craters if they impact a continent or tsunamis if they impact

1584-584: Is the basis of the age determinations. It is supposed that many very old families have lost all the smaller and medium-sized members, leaving only a few of the largest intact. A suggested example of such old family remains are the 9 Metis and 113 Amalthea asteroid pair . Further evidence for a large number of past families (now dispersed) comes from analysis of chemical ratios in iron meteorites . These show that there must have once been at least 50 to 100 parent bodies large enough to be differentiated, that have since been shattered to expose their cores and produce

1672-464: The George E. Brown, Jr. Near-Earth Object Survey Act, which calls for NASA to detect 90% of NEOs with diameters of 140 m (460 ft) or greater, by 2020. In January 2020, it was estimated that less than half of these have been found, but objects of this size hit the earth only about once in 2000 years. In December 2023, the ratio of discovered NEOs with diameters of 140 m (460 ft) or greater

1760-563: The K–T impactor was part of this family of asteroids, as it typically takes many tens of millions of years for an asteroid to reach a resonance with Earth and then collide, much more than the 15 million between this breakup and the collision of the K–T impactor. "As a result of the WISE science team's investigation, the demise of the dinosaurs remains in the cold case files," said Lindley Johnson, program executive for

1848-600: The Near Earth Object Observation Program. Family identification number Large prominent families contain several hundred recognized asteroids (and many more smaller objects which may be either not-yet-analyzed, or not-yet-discovered). Small, compact families may have only about ten identified members. About 33% to 35% of asteroids in the main belt are family members. There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in

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1936-692: The Nubian Desert in Sudan. It was the first time that an asteroid was observed and its impact was predicted prior to its entry into the atmosphere as a meteor . 10.7 kg of meteorites were recovered after the impact. As of September 2024 , nine impacts have been predicted, all of them small bodies that produced meteor explosions, with some impacts in remote areas only detected by the Comprehensive Nuclear-Test-Ban Treaty Organization 's International Monitoring System (IMS) ,

2024-468: The Rocky Mountains from the U.S. Southwest to Canada. It passed within 58 km (36 mi) of the Earth's surface. On October 13, 1990, Earth-grazing meteoroid EN131090 was observed above Czechoslovakia and Poland, moving at 41.74 km/s (25.94 mi/s) along a 409 km (254 mi) trajectory from south to north. The closest approach to the Earth was 98.67 km (61.31 mi) above

2112-456: The Yarkovsky effect that can push them towards orbital resonances with Jupiter over time. Once there, they are relatively rapidly ejected from the asteroid belt. Tentative age estimates have been obtained for some families, ranging from hundreds of millions of years to less than several million years as for the compact Karin family . Old families are thought to contain few small members, and this

2200-510: The above table ), as well as non-asteroid families include: Near Earth Object 34,000+ known NEOs, divided into several orbital subgroups 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

2288-412: The hierarchical clustering method ( HCM ), which looks for groupings with small nearest-neighbour distances in orbital element space, and wavelet analysis, which builds a density-of-asteroids map in orbital element space, and looks for density peaks. The boundaries of the families are somewhat vague because at the edges they blend into the background density of asteroids in the main belt. For this reason

2376-497: The main asteroid belt , although several family-like groups such as the Pallas family , Hungaria family , and the Phocaea family lie at smaller semi-major axis or larger inclination than the main belt. One family has been identified associated with the dwarf planet Haumea . Some studies have tried to find evidence of collisional families among the trojan asteroids , but at present

2464-473: The 1980s, with mounting evidence for the theory that the Cretaceous–Paleogene extinction event (in which the non-avian dinosaurs died out) 65 million years ago was caused by a large asteroid impact . On March 23, 1989, the 300 m (980 ft) diameter Apollo asteroid 4581 Asclepius (1989 FC) missed the Earth by 700,000 km (430,000 mi). If the asteroid had impacted it would have created

2552-400: The 2010s, each year, several mostly small NEOs pass Earth closer than the distance of the Moon. As astronomers became able to discover ever smaller and fainter and ever more numerous near-Earth objects, they began to routinely observe and catalogue close approaches. As of April 2024 , the closest approach without impact ever detected, other than meteors or fireballs that went through

2640-433: The 30 m (98 ft) asteroid 367943 Duende ( 2012 DA 14 ) passed approximately 27,700 km (17,200 mi) above the surface of Earth, closer than satellites in geosynchronous orbit. The asteroid was not visible to the unaided eye. This was the first sub-lunar close passage of an object discovered during a previous passage, and was thus the first to be predicted well in advance. Some small asteroids that enter

2728-452: The Baptistina family. Concerns were raised regarding the reputed link, in part because very few solid observational constraints existed of the asteroid or family. One year later, it was discovered that 298 Baptistina does not share the same chemical signature as the source of the Cretaceous–Paleogene boundary . Because of the timeframe, it had also been suggested that the impactor that produced

Baptistina family - Misplaced Pages Continue

2816-490: The Baptistina family. It was discovered on 9 September 1890 by Auguste Charlois at the Nice Observatory . The source of its name is unknown. It measures about 13 to 30 kilometres (8 to 19 mi) in diameter. Although it has an orbit similar to the Flora family asteroids, Baptistina is an unrelated interloper. Other members of the Baptistina family include 1696 Nurmela , 2858 Carlosporter , and (7255) 1993 VY1 . It

2904-651: The Earth dangerously closely and the estimated consequences that an impact would have if it occurs. Objects with both an Earth minimum orbit intersection distance (MOID) of 0.05 AU or less and an absolute magnitude of 22.0 or brighter (a rough indicator of large size) are considered PHAs. Objects that either cannot approach closer to the Earth than 0.05  AU (7,500,000 km; 4,600,000 mi), or which are fainter than H = 22.0 (about 140 m (460 ft) in diameter with assumed albedo of 14%), are not considered PHAs. The first near-Earth objects to be observed by humans were comets. Their extraterrestrial nature

2992-451: The Earth surface, while larger objects hit the water surface, forming tsunami waves, or the solid surface, forming impact craters . The frequency of impacts of objects of various sizes is estimated on the basis of orbit simulations of NEO populations, the frequency of impact craters on the Earth and the Moon, and the frequency of close encounters. The study of impact craters indicates that impact frequency has been more or less steady for

3080-400: The Moon can be observed as flashes of light with a typical duration of a fraction of a second. The first lunar impacts were recorded during the 1999 Leonid storm. Subsequently, several continuous monitoring programs were launched. A lunar impact that was observed on September 11, 2013, lasted 8 seconds, was likely caused by an object 0.6–1.4 m (2.0–4.6 ft) in diameter, and created

3168-421: The Moon. During this approach, Icarus became the first minor planet to be observed using radar . This was the first close approach predicted years in advance, since Icarus had been discovered in 1949. The first near-Earth asteroid known to have passed Earth closer than the distance of the Moon was 1991 BA , a 5–10 m (16–33 ft) body which passed at a distance of 170,000 km (110,000 mi). By

3256-532: The Palermo Scale. Observations during the August 2022 close approach were expected to ascertain whether the asteroid will impact or miss Earth in 2095. As of April 2024 , the risk of the 2095 impact was put at 1 in 10, still the highest, with a Palermo Scale rating of −2.98. A year before the 1968 close approach of asteroid Icarus, Massachusetts Institute of Technology students launched Project Icarus, devising

3344-436: The Sun to one around the Earth, but the term is applied flexibly for these objects, too. The orbits of some NEOs intersect that of the Earth, so they pose a collision danger. These are considered potentially hazardous objects (PHOs) if their estimated diameter is above 140 meters. PHOs include potentially hazardous asteroids (PHAs). PHAs are defined based on two parameters relating to respectively their potential to approach

3432-413: The Sun, passed Earth undetected at a distance of 0.0120 AU (4.65 LD) on June 12, 1999. In 1937, 800 m (2,600 ft) asteroid 69230 Hermes was discovered when it passed the Earth at twice the distance of the Moon . On June 14, 1968, the 1.4 km (0.87 mi) diameter asteroid 1566 Icarus passed Earth at a distance of 0.042 AU (6,300,000 km), or 16 times the distance of

3520-635: 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 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids , but about 0.35% are comets . There are over 34,000 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

3608-465: The Sun. This definition excludes larger bodies such as planets , like Venus ; natural satellites which orbit bodies other than the Sun, like Earth's Moon ; and artificial bodies orbiting the Sun. A small Solar System body can be an asteroid or a comet , thus an NEO is either a near-Earth asteroid (NEA) or a near-Earth comet (NEC). The organisations cataloging NEOs further limit their definition of NEO to objects with an orbital period under 200 years,

Baptistina family - Misplaced Pages Continue

3696-533: The actual meteorites (Kelley & Gaffey 2000). When the orbital elements of main belt asteroids are plotted (typically inclination vs. eccentricity , or vs. semi-major axis ), a number of distinct concentrations are seen against the rather uniform distribution of non-family background asteroids . These concentrations are the asteroid families (see above ) . Interlopers are asteroids classified as family members based on their so-called proper orbital elements but having spectroscopic properties distinct from

3784-526: The affected Earth region. Another project, the Zwicky Transient Facility (ZTF), which surveys for objects that change their brightness rapidly, also detects asteroids passing close to Earth. Scientists involved in NEO research have also considered options for actively averting the threat if an object is found to be on a collision course with Earth. All viable methods aim to deflect rather than destroy

3872-522: The asteroid was removed from the Sentry Risk Table entirely in February 2008. In 2021, 2010 RF 12 was listed with the highest chance of impacting Earth, at 1 in 22 on September 5, 2095. At only 7 m (23 ft) across, the asteroid however is much too small to be considered a potentially hazardous asteroid and it poses no serious threat: the possible 2095 impact therefore rated only −3.32 on

3960-605: The atmosphere (see #Earth-grazers below), was an encounter with asteroid 2020 VT 4 on November 14, 2020. The 5–11 m (16–36 ft) NEA was detected receding from Earth; calculations showed that on the day before, it had a close approach at about 6,750 km (4,190 mi) from the Earth's centre, or about 380 km (240 mi) above its surface. On November 8, 2011, asteroid (308635) 2005 YU 55 , relatively large at about 400 m (1,300 ft) in diameter, passed within 324,930 km (201,900 mi) (0.845 lunar distances ) of Earth. On February 15, 2013,

4048-562: The atomic bomb dropped on Hiroshima , approximately 15 kilotonnes of TNT) at five years, for asteroids 60 m (200 ft) across (an impact energy of 10 megatons , comparable to the Tunguska event in 1908) at 1,300 years, for asteroids 1 km (0.62 mi) across at 440 thousand years, and for asteroids 5 km (3.1 mi) across at 18 million years. Some other models estimate similar impact frequencies, while others calculate higher frequencies. For Tunguska-sized (10 megaton) impacts,

4136-511: The background (e.g. the Juno clump ). Clans are groupings which merge very gradually into the background density and/or have a complex internal structure making it difficult to decide whether they are one complex group or several unrelated overlapping groups (e.g. the Flora family has been called a clan). Tribes are groups that are less certain to be statistically significant against the background either because of small density or large uncertainty in

4224-582: The bulk of family members. A prominent example is 1 Ceres , the largest asteroid, which is an interloper in the family once named after it (the Ceres family , now the Gefion family ). Spectral characteristics can also be used to determine the membership (or otherwise) of asteroids in the outer regions of a family, as has been used e.g. for the Vesta family , whose members have an unusual composition. As previously mentioned, families caused by an impact that did not disrupt

4312-626: The bulk of the family, suggesting that they, contrary to the true family members, did not originate from the same parent body that once fragmented upon a collisional impact. Strictly speaking, families and their membership are identified by analysing the proper orbital elements rather than the current osculating orbital elements , which regularly fluctuate on timescales of tens of thousands of years. The proper elements are related constants of motion that remain almost constant for at least tens of millions of years, and perhaps longer. The Japanese astronomer Kiyotsugu Hirayama (1874–1943) pioneered

4400-425: The color of members of the Baptistina family, showing that a low albedo does not necessarily indicate the composition of the family. In 2007, it was proposed that chromium concentrations in 66-million-year-old sediment layers at the Cretaceous–Paleogene boundary (K–T boundary) on Earth suggested that the impactor that gouged out Chicxulub Crater and caused the Cretaceous–Paleogene extinction event belonged to

4488-544: The consequences of such an impact would be. Some NEOs have had temporarily positive Torino or Palermo scale ratings after their discovery. Since 1998, the United States, the European Union, and other nations have been scanning the sky for NEOs in an effort called Spaceguard . The initial US Congress mandate to NASA to catalog at least 90% of NEOs that are at least 1 kilometre (0.62 mi) in diameter, sufficient to cause

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4576-520: The estimates range from one event every 2,000–3,000 years to one event every 300 years. The second-largest observed event after the Tunguska meteor was a 1.1 megaton air blast in 1963 near the Prince Edward Islands between South Africa and Antarctica, which was detected only by infrasound sensors. However this may have been a nuclear test . The third-largest, but by far best-observed impact,

4664-406: The estimation of proper elements for asteroids, and first identified several of the most prominent families in 1918. In his honor, asteroid families are sometimes called Hirayama families . This particularly applies to the five prominent groupings discovered by him. Present day computer-assisted searches have identified more than a hundred asteroid families . The most prominent algorithms have been

4752-416: The evidence is inconclusive. The families are thought to form as a result of collisions between asteroids. In many or most cases the parent body was shattered, but there are also several families which resulted from a large cratering event which did not disrupt the parent body (e.g. the Vesta , Pallas , Hygiea , and Massalia families). Such cratering families typically consist of a single large body and

4840-469: The family were classified, and not even the albedo of the meteors was known at the time. Following the impact of the Chelyabinsk meteor in 2013, a paper published in the journal Icarus showed that shock produced during impact of a large asteroid can darken otherwise bright silicate material. Spectral analysis of the darkly-colored portions of the non-carbonaceous Chelyabinsk meteorite closely matched

4928-544: The first asteroid with a temporarily positive rating on the Torino Scale, with about a 1 in 9,300 chance of an impact in 2049. Additional observations reduced the estimated risk to zero, and the asteroid was removed from the Sentry Risk Table in April 2002. It is now known that within the next two centuries, 2002 CU 11 will pass the Earth at a safe closest distance (perigee) of 0.00425 AU (636,000 km; 395,000 mi) on August 31, 2080. Asteroid (29075) 1950 DA

5016-468: The general public. The simple Torino scale was established at an IAU workshop in Torino in June 1999, in the wake of the public confusion about the impact risk of 1997 XF 11 . It rates the risks of impacts in the next 100 years according to impact energy and impact probability, using integer numbers between 0 and 10: The more complex Palermo Technical Impact Hazard Scale , established in 2002, compares

5104-607: The largest explosion in recorded history, equivalent to 20,000 megatons of TNT . It attracted widespread attention because it was discovered only after the closest approach. From the 1990s, a typical frame of reference in searches for NEOs has been the scientific concept of risk . The awareness of the wider public of the impact risk rose after the observation of the impact of the fragments of Comet Shoemaker–Levy 9 into Jupiter in July 1994. In March 1998, early orbit calculations for recently discovered asteroid (35396) 1997 XF 11 showed

5192-600: The likelihood of an impact at a certain date to the probable number of impacts of a similar energy or greater until the possible impact, and takes the logarithm of this ratio. Thus, a Palermo scale rating can be any positive or negative real number, and risks of any concern are indicated by values above zero. Unlike the Torino scale, the Palermo scale is not sensitive to newly discovered small objects with an orbit known with low confidence. The National Aeronautics and Space Administration NASA maintains an automated system to evaluate

5280-526: The lunar crater Tycho 108 million years ago was also a member of the group, as well as the Venusian craters Mead , Isabella , Meitner , and Klenova. In 2011, data from the Wide-field Infrared Survey Explorer (WISE) revised the date of the proposed collision which broke up the Baptistina parent asteroid to about 80 million years ago. If correct, this data means it is very unlikely that

5368-613: The need for dedicated survey telescopes and options to head off an eventual impact were first discussed at a 1981 interdisciplinary conference in Snowmass, Colorado . Plans for a more comprehensive survey, named the Spaceguard Survey, were developed by NASA from 1992, under a mandate from the United States Congress . To promote the survey on an international level, the International Astronomical Union (IAU) organised

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5456-451: The newly discovered comet 55P/Tempel–Tuttle has the same orbit as the Leonids. The first near-Earth asteroid to be discovered was 433 Eros in 1898. The asteroid was subject to several extensive observation campaigns, primarily because measurements of its orbit enabled a precise determination of the then imperfectly known distance of the Earth from the Sun. If a near-Earth object is near

5544-400: The notion that near-Earth objects could cause catastrophic impacts. Also at that time, a scare arose about a supposed 2003 impact of a planet called Nibiru with Earth, which persisted on the internet as the predicted impact date was moved to 2012 and then 2017. There are two schemes for the scientific classification of impact hazards from NEOs, as a way to communicate the risk of impacts to

5632-492: The number of members even among discovered asteroids is usually only known approximately, and membership is uncertain for asteroids near the edges. Additionally, some interlopers from the heterogeneous background asteroid population are expected even in the central regions of a family. Since the true family members caused by the collision are expected to have similar compositions, most such interlopers can in principle be recognised by spectral properties which do not match those of

5720-543: The orbital parameters of the members. Among the many asteroid families, the Eos , Eunomia , Flora , Hungaria , Hygiea , Koronis , Nysa , Themis and Vesta families are the most prominent ones in the asteroid belt . For a complete list, see § All families . In 2015, a study identified 122 notable families with a total of approximately 100,000 member asteroids, based on the entire catalog of numbered minor planets , which consisted of almost 400,000 numbered bodies at

5808-495: The parent body but only ejected fragments are called cratering families . Other terminology has been used to distinguish various types of groups which are less distinct or less statistically certain from the most prominent "nominal families" (or clusters ). The term cluster is also used to describe a small asteroid family, such as the Karin cluster . Clumps are groupings which have relatively few members but are clearly distinct from

5896-598: The part of its orbit closest to Earth's at the same time Earth is at the part of its orbit closest to the near-Earth object's orbit, the object has a close approach, or, if the orbits intersect, could even impact the Earth or its atmosphere. As of May 2019 , only 23 comets have been observed to pass within 0.1 AU (15,000,000 km; 9,300,000 mi) of Earth, including 10 which are or have been short-period comets. Two of these near-Earth comets, Halley's Comet and 73P/Schwassmann–Wachmann , have been observed during multiple close approaches. The closest observed approach

5984-407: The past 3.5 billion years, which requires a steady replenishment of the NEO population from the asteroid main belt . One impact model based on widely accepted NEO population models estimates the average time between the impact of two stony asteroids with a diameter of at least 4 m (13 ft) at about one year; for asteroids 7 m (23 ft) across (which impacts with as much energy as

6072-604: The ratio to 76%. Given the rarity of impacts by objects this big mentioned above, there are probably no objects of 140 metres or larger that will hit the earth in the next few centuries. In January 2016, NASA announced the creation of the Planetary Defense Coordination Office (PDCO) to track NEOs larger than about 30–50 m (98–164 ft) in diameter and coordinate an effective threat response and mitigation effort. Survey programs aim to identify threats years in advance, giving humanity time to prepare

6160-559: The risk of impact at any date was completely eliminated by 2021. Consequently, Apophis was removed from the Sentry Risk Table. In February 2006, (144898) 2004 VD 17 , having a diameter around 300 metres, was assigned a Torino Scale rating of 2 due to a close encounter predicted for May 4, 2102. After additional observations allowed increasingly precise predictions, the Torino rating was lowered first to 1 in May 2006, then to 0 in October 2006, and

6248-454: The sea. Interest in NEOs has increased since the 1980s because of greater awareness of this risk. Asteroid impact avoidance by deflection is possible in principle, and methods of mitigation are being researched. Two scales, the simple Torino scale and the more complex Palermo scale , rate the risk presented by an identified NEO based on the probability of it impacting the Earth and on how severe

6336-461: The source of era-changing cataclysms or potentially poisonous fumes (during Earth's passage through the tail of Halley's Comet in 1910); and finally as a possible cause of a crater-forming impact that could even cause extinction of humans and other life on Earth. The potential of catastrophic impacts by near-Earth comets was recognised as soon as the first orbit calculations provided an understanding of their orbits: in 1694, Edmond Halley presented

6424-483: The surface. It was captured by two all-sky cameras of the European Fireball Network , which for the first time enabled geometric calculations of the orbit of such a body. When a near-Earth object impacts Earth, objects up to a few tens of metres across ordinarily explode in the upper atmosphere (usually harmlessly), with most or all of the solids vaporized and only small amounts of meteorites arriving to

6512-532: The threat from known NEOs over the next 100 years, which generates the continuously updated Sentry Risk Table . All or nearly all of the objects are highly likely to drop off the list eventually as more observations come in, reducing the uncertainties and enabling more accurate orbital predictions. A similar table is maintained on NEODyS (Near Earth Objects Dynamic Site) by the European Space Agency (ESA). In March 2002, (163132) 2002 CU 11 became

6600-525: The threatening NEO, because the fragments would still cause widespread destruction. Deflection, which means a change in the object's orbit months to years prior to the predicted impact , also requires orders of magnitude less energy. For a given amount of energy, a greater effect on the momentum of the object can be had by causing some of it to be blasted off it, as was done in the Double Asteroid Redirection Test (see below). When an NEO

6688-578: The time (see catalog index for a current listing of numbered minor planets) . The data has been made available at the "Small Bodies Data Ferret". The first column of this table contains the family identification number or family identifier number ( FIN ), which is an attempt for a numerical labeling of identified families, independent of their currently used name, as a family's name may change with refined observations, leading to multiple names used in literature and to subsequent confusion. Other asteroid families from miscellaneous sources (not listed in

6776-419: The upper atmosphere of Earth at a shallow angle remain intact and leave the atmosphere again, continuing on a solar orbit. During the passage through the atmosphere, due to the burning of its surface, such an object can be observed as an Earth-grazing fireball . On August 10, 1972, a meteor that became known as the 1972 Great Daylight Fireball was witnessed by many people and even filmed as it moved north over

6864-460: Was 0.0151 AU (5.88 LD) for Lexell's Comet on July 1, 1770. After an orbit change due to a close approach of Jupiter in 1779, this object is no longer an NEC. The closest approach ever observed for a current short-period NEC is 0.0229 AU (8.92 LD) for Comet Tempel–Tuttle in 1366. Orbital calculations show that P/1999 J6 (SOHO) , a faint sungrazing comet and confirmed short-period NEC observed only during its close approaches to

6952-452: Was added to the Sentry list in April 2002 as the first object with a Palermo scale value greater than zero. The then-calculated 1 in 300 maximum chance of impact and +0.17 Palermo scale value was roughly 50% greater than the background risk of impact by all similarly large objects until 2880. After additional radar and optical observations, as of April 2024 , the probability of this impact

7040-495: Was briefly speculated that the Chicxulub impactor was part of the Baptistina family of asteroids, but this was disproven in 2011 using data from the Wide-field Infrared Survey Explorer (WISE). The Baptistina family consists of darkly colored asteroids and meteoroids in similar orbits. Baptistina broke up into thousands of fragments about 80 million years ago. 298 Baptistina is the namesake asteroid and largest presumed remnant of

7128-514: Was conducted. Similar missions are in progress. Preliminary plans for commercial asteroid mining have been drafted by private startup companies, but few of these plans were pursued. Near-Earth objects (NEOs) are formally defined by the International Astronomical Union (IAU) as all small Solar System bodies with orbits around the Sun that are at least partially closer than 1.3 astronomical units (AU; Sun–Earth distance) from

7216-447: Was considered a threat because it was lost after its discovery; thus its orbit and potential for collision with Earth were not known precisely. Hermes, having a period of 2.13 years, was only re-discovered in 2003, and it is now known to be no threat for at least the next century. Scientists have recognised the threat of impacts that create craters much bigger than the impacting bodies and have indirect effects on an even wider area since

7304-510: Was estimated at 38%. The Chile-based Vera C. Rubin Observatory , which will survey the southern sky for transient events from 2025, is expected to increase the number of known asteroids by a factor of 10 to 100 and increase the ratio of known NEOs with diameters of 140 m (460 ft) or greater to at least 60%, while the NEO Surveyor satellite, to be launched in 2027, is expected to push

7392-560: Was lost after its 1950 discovery, since its observations over just 17 days were insufficient to precisely determine its orbit. It was rediscovered in December 2000 prior to a close approach the next year, when new observations, including radar imaging, allowed much more precise orbit calculations. It has a diameter of about a kilometer (0.6 miles), and an impact would therefore be globally catastrophic. Although this asteroid will not strike for at least 800 years and thus has no Torino scale rating, it

7480-410: Was originally thought that the Baptistina family may consist of uncommon carbonaceous chondrite . In 2006, nine asteroids within the Baptistina family were given known classifications: three are S-type asteroids , two are X-type asteroids , another two are A / R-type asteroids , one is C-type and one is V-type . However, any conclusions taken from this were highly speculative, as very few members in

7568-403: Was recognised and confirmed only after Tycho Brahe tried to measure the distance of a comet through its parallax in 1577 and the lower limit he obtained was well above the Earth diameter; the periodicity of some comets was first recognised in 1705, when Edmond Halley published his orbit calculations for the returning object now known as Halley's Comet . The 1758–1759 return of Halley's Comet

7656-559: Was the Chelyabinsk meteor of 15 February 2013. A previously unknown 20 m (66 ft) asteroid exploded above this Russian city with an equivalent blast yield of 400–500 kilotons. The calculated orbit of the pre-impact asteroid is similar to that of Apollo asteroid 2011 EO 40 , making the latter the meteor's possible parent body. On October 7, 2008, 20 hours after it was first observed and 11 hours after its trajectory has been calculated and announced, 4 m (13 ft) asteroid 2008 TC 3 blew up 37 km (23 mi) above

7744-412: Was the first comet appearance predicted. The extraterrestrial origin of meteors (shooting stars) was only recognised on the basis of the analysis of the 1833 Leonid meteor shower by astronomer Denison Olmsted . The 33-year period of the Leonids led astronomers to suspect that they originate from a comet that would today be classified as an NEO, which was confirmed in 1867, when astronomers found that

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