Discovery [1] | |
---|---|
Discovered by | Spacewatch |
Discovery site | Kitt Peak National Observatory |
Discovery date | 11 April 1996 |
Designations | |
(65803) Didymos | |
Pronunciation | /ˈdɪdɪmɒs/ [2] |
Named after | Greek word for "Twin" [3] |
1996 GT | |
NEO · PHA Apollo (2022) [1] [lower-alpha 1] | |
Orbital characteristics [1] | |
Epoch 21 January 2022 (JD 2459600.5) | |
Uncertainty parameter 0 | |
Observation arc | 24.82 years (9,066 days) |
Aphelion | 2.2753 AU |
Perihelion | 1.0131 AU |
1.6442 AU | |
Eccentricity | 0.38385 |
2.11 yr (770 days) | |
232.01 | |
0° 28m 2.28s / day | |
Inclination | 3.4079° |
73.196° | |
319.32° | |
Known satellites | 1 (Dimorphos) |
Earth MOID | 0.0403 AU (15.7 LD) |
Mars MOID | 0.02 AU (7.8 LD) [4] |
Physical characteristics [5] | |
Dimensions | 851 × 849 × 620 m (± 15 × 15 × 15 m) |
Mean diameter | 765±15 m [lower-alpha 2] |
Mass | (5.4±0.4)×1011 kg (system) [6] ≈ 5.2×1011 kg (primary) [7] |
Mean density | 2.40±0.30 g/cm3 [5] |
2.2600±0.0001 [6] 2.2593±0.0002 h [8] | |
174°±20° [lower-alpha 3] | |
Pole ecliptic latitude | −84°±20° |
Pole ecliptic longitude | 310°±20° |
0.15±0.04 | |
S [6] [10] · SMASS = X k [1] · X [11] | |
18.0 [1] ·18.16 [11] [8] [12] 18.16±0.03 [13] | |
65803 Didymos (provisional designation 1996 GT) is a sub-kilometer asteroid and binary system that is classified as a potentially hazardous asteroid and near-Earth object of the Apollo group. [lower-alpha 1] The asteroid was discovered in 1996 by the Spacewatch survey at Kitt Peak, and its small 160-meter minor-planet moon, named Dimorphos, was discovered in 2003. Due to its binary nature, the asteroid was then named Didymos, the Greek word for 'twin'.
Didymos's moon, Dimorphos, was the target of the DART mission to test the viability of asteroid impact avoidance by collision with a spacecraft, while the impact was witnessed by LICIACube, a flyby CubeSat component of the mission.
Didymos was discovered on 11 April 1996 by the University of Arizona Steward Observatory's, and Lunar and Planetary Laboratory's, Spacewatch survey using its 0.9-meter telescope at Kitt Peak National Observatory in Arizona, United States. The binary nature of the asteroid was discovered by others; suspicions of binarity first arose in Goldstone delay-Doppler echoes, and these were confirmed with an optical lightcurve analysis, along with Arecibo radar imaging on 23 November 2003. [4]
Didymos orbits the Sun at a distance of 1.0–2.3 AU once every 770 days (2 years and 1 month). Its orbit has an eccentricity of 0.38 and an inclination of 3° with respect to the ecliptic. The minimum distance between the orbit of Earth and the orbit of Didymos is currently 0.04 AU (6.0 million km ), [1] but will change as the asteroid is perturbed. In November 2003 it passed 7.18 million km from Earth; it will not come that near again until November 2123, with a distance of 5.86 million km. Didymos also occasionally passes very close to Mars: it will fly by Mars at a distance of 4.68 million km in July 2144. [1] Even the Earth approach of October 2184 is still listed with an uncertainty region of roughly ±1343 km. [14]
In the SMASS classification, Didymos was classified as an Xk-type asteroid, which transitions from the X-type to the rare K-type asteroids. [1] Subsequent visible and near-infrared spectroscopy showed it to be silicate in nature, which also qualifies it as a stony S-type asteroid. [15] It rotates rapidly, with a period of 2.26 hours and a low brightness variation of 0.08 magnitude ( U=3/3 ), which indicates that the body has a nearly spheroidal shape. [11] [8] [16] Radar observations confirmed this spheroidal shape, showing it to be oblate due to its rapid rotation. [6]
Didymos is a binary asteroid with a satellite in its orbit. The minor-planet moon, named Dimorphos , [17] moves in a mostly circular retrograde orbit [18] with an orbital period of 11.9 hours. [11] [lower-alpha 4] It measures approximately 160 meters (520 ft) in diameter compared to 780 meters (2,560 ft) for its primary (a mean-diameter-ratio of 0.22). [19] It was previously known by its provisional designation S/2003 (65803) 1 and had been informally called "Didymoon" or "Didymos B". [20] [17]
This minor planet was named "Didymos", Greek for "twin", due to its binary nature. [3] The name was suggested by the discoverer, University of Arizona Lunar and Planetary Laboratory astronomer Joseph L. "Joe" Montani, who made the naming proposal to the International Astronomical Union after the binary nature of the object was detected. The approved naming citation was published on 13 July 2004 ( M.P.C. 52326). [21]
The proper name for the satellite Didymos B comes from the word "Dimorphos", Greek for "having two forms". [22] The meaning of the name represents how the form of Dimorphos's orbit will change after the collision with NASA’s Double Asteroid Redirection Test (DART) spacecraft, [17] though in fact the change will be only a very slight change in its orbital parameters. Appropriately, Dimorphos serves dual roles as both a test target and as a part of a blueprint for a modality for future planetary protection. [17] The name of the moon was suggested by planetary scientist Kleomenis Tsiganis at the Aristotle University of Thessaloniki, Greece. [23]
Two boulders (saxa) have been given names of traditional drums. [24]
Name | Pronunciation | Feature | Named after | Date approved [24] |
---|---|---|---|---|
Carillon Saxum | US: /ˈkærəlɒn/ UK: /kəˈrɪljən/ | boulder | carillon | 14 Nov 2023 |
Gong Saxum | /ˈɡɒŋ/ | boulder | gong | 14 Nov 2023 |
In the early 2010s, Didymos's moon, Dimorphos was to be the principal target of proposed robotic mission by the ESA and NASA, called the Asteroid Impact & Deflection Assessment (AIDA) mission. The ESA dropped out, and the mission did not proceed. [25] [26]
NASA redefined mission requirements and decided to proceed with a 2020s mission to visit Didymos with an impactor, which had been considered as a part of the earlier AIDA mission, named the Double Asteroid Redirection Test or DART. The NASA mission was intended to test whether a spacecraft impact could successfully deflect an asteroid on a collision course with Earth. The DART spacecraft was launched on 24 November 2021, and impacted Dimorphos on September 26, 2022. [27] [28] [29] It was accompanied by the Italian Space Agency's (ASI) six-unit LICIACube flyby Cubesat that was released 15 days before impact to observe the asteroid and DART's impact. [30]
DART was the first spacecraft to intentionally target and successfully visit an asteroid known to have a minor-planet moon (The binary asteroid 2000 DP107 was targeted by the PROCYON mission before it failed, 243 Ida was visited by the Galileo spacecraft but its moon was unknown until then, Pluto was considered a planet until a few months after the launch of New Horizons , and 3548 Eurybates's and 15094 Polymele's moons were not discovered until months before and after Lucy's launch, respectively). Didymos is the most easily reachable asteroid of its size from Earth, requiring a delta-v of only 5.1 km/s for a spacecraft to rendezvous, compared to 6.0 km/s to reach the Moon. [31]
After two weeks of analysis, NASA announced that the collision shortened Dimorphos's orbital period around Didymos by 32 minutes, [32] far more than the minimum requirement of 73 seconds and the success benchmark of 10 minutes. The measurement has an uncertainty of ±2 minutes. [33]
Another mission to Didymos was approved in November 2019 for a planned launch in 2024, to arrive at Didymos in January 2027. ESA's Hera mission is planning to survey the dynamical effects of the DART impact and measure the characteristics of the crater made by DART. [34]
An asteroid is a minor planet—an object that is neither a true planet nor a comet—that orbits within the inner Solar System. They are rocky, metallic, or icy bodies with no atmosphere. The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres, a dwarf planet almost 1000 km in diameter.
Asteroid impact avoidance comprises the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted away, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs would cause, depending on its impact location, massive tsunamis or multiple firestorms, and an impact winter caused by the sunlight-blocking effect of large quantities of pulverized rock dust and other debris placed into the stratosphere. A collision 66 million years ago between the Earth and an object approximately 10 kilometres wide is thought to have produced the Chicxulub crater and triggered the Cretaceous–Paleogene extinction event that is understood by the scientific community to have caused the extinction of all non-avian dinosaurs.
Don Quijote is a past space mission concept that has been studied from 2005 until 2007 by the European Space Agency, and which would investigate the effects of crashing a spacecraft into an asteroid to test whether a spacecraft could successfully deflect an asteroid on a collision course with Earth. The orbiter was designed to last for seven years. The mission did not proceed beyond initial studies.
Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss, but their orbits remain within Jupiter's orbit. These bodies were originally designated main-belt comets (MBCs) in 2006 by astronomers David Jewitt and Henry Hsieh, but this name implies they are necessarily icy in composition like a comet and that they only exist within the main-belt, whereas the growing population of active asteroids shows that this is not always the case.
(185851) 2000 DP107 is a sub-kilometer sized asteroid, classified as potentially hazardous asteroid and near-Earth object of the Apollo group that is notable because it provided evidence for binary asteroids in the near-Earth population. The PROCYON probe developed by JAXA and the University of Tokyo was intended to flyby this asteroid before its ion thruster failed and could not be restarted.
4029 Bridges, provisional designation 1982 KC1, is a stony asteroid and binary system from the middle regions of the asteroid belt, approximately 8 kilometers in diameter.
7088 Ishtar, provisional designation 1992 AA, is a synchronous binary asteroid and near-Earth object from the Amor group, approximately 1.3 kilometers in diameter. It was discovered on 1 January 1992, by American astronomer Carolyn Shoemaker at the Palomar Observatory in California. The relatively bright asteroid with an unknown spectral type has a rotation period of 2.7 hours. In December 2005, a 330-meter sized satellite was discovered, orbiting its primary every 20.65 hours.
(35107) 1991 VH is a binary near-Earth asteroid and potentially hazardous asteroid of the Apollo group. It was discovered on 9 November 1991, by Australian astronomer Robert McNaught at Siding Spring Observatory. This binary system is composed of a roughly-spheroidal primary body about one kilometre in diameter, and an elongated natural satellite less than half a kilometre in diameter. The 1991 VH system is unusual for its dynamically excited state; the satellite has a tumbling, non-synchronous rotation that chaotically exchanges energy and angular momentum with its precessing, eccentric orbit. This asteroid system was one of the two targets of NASA's upcoming Janus Mayhem mission, until the delay of the rocket launch made both targets inaccessible.
(175706) 1996 FG3 is a carbonaceous asteroid and binary system, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 1.7 kilometers (1.1 miles) in diameter. The primary has a spheroidal shape. Its minor-planet moon measures approximately 490 meters (1,600 feet) in diameter.
The Asteroid Impact and Deflection Assessment (AIDA) missions are a proposed pair of space probes which will study and demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon. The mission is intended to test and validate impact models of whether a spacecraft could successfully deflect an asteroid on a collision course with Earth.
(66063) 1998 RO1 is a stony near-Earth object of the Aten group on a highly-eccentric orbit. The synchronous binary system measures approximately 800 meters (0.50 miles) in diameter. It was discovered by astronomers of the Lincoln Near-Earth Asteroid Research at the Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, on 14 September 1998.
Double Asteroid Redirection Test (DART) was a NASA space mission aimed at testing a method of planetary defense against near-Earth objects (NEOs). It was designed to assess how much a spacecraft impact deflects an asteroid through its transfer of momentum when hitting the asteroid head-on. The selected target asteroid, Dimorphos, is a minor-planet moon of the asteroid Didymos; neither asteroid poses an impact threat to Earth, but their joint characteristics made them an ideal benchmarking target. Launched on 24 November 2021, the DART spacecraft successfully collided with Dimorphos on 26 September 2022 at 23:14 UTC about 11 million kilometers from Earth. The collision shortened Dimorphos' orbit by 32 minutes, greatly in excess of the pre-defined success threshold of 73 seconds. DART's success in deflecting Dimorphos was due to the momentum transfer associated with the recoil of the ejected debris, which was substantially larger than that caused by the impact itself.
The Planetary Missions Program Office is a division of NASA headquartered at the Marshall Space Flight Center, formed by the agency's Science Mission Directorate (SMD). Succeeding the Discovery and New Frontiers Program Office, it was established in 2014 to manage the Discovery and New Frontiers programs of low and medium-cost missions by third-party institutions, and the Solar System Exploration program of NASA-led missions that focus on prioritized planetary science objectives. The Discovery and New Frontiers programs were established in 1992 and 2001 respectively, and have launched fourteen primary missions together, along with two missions launched under the administration of the Planetary Missions Program Office. The Solar System Exploration Program was established alongside the office, with three missions planned for launch under the new program.
(164121) 2003 YT1, provisional designation 2003 YT1, is a bright asteroid and synchronous binary system on a highly eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 2 kilometers (1.2 miles) in diameter. It was discovered on 18 December 2003, by astronomers with the Catalina Sky Survey at the Catalina Station near Tucson, Arizona, in the United States. The V-type asteroid has a short rotation period of 2.3 hours. Its 210-meter sized minor-planet moon was discovered at Arecibo Observatory in May 2004.
Dimorphos is a natural satellite or moon of the near-Earth asteroid 65803 Didymos, with which it forms a binary system. The moon was discovered on 20 November 2003 by Petr Pravec in collaboration with other astronomers worldwide. Dimorphos has a diameter of 177 meters (581 ft) across its longest extent and it was the target of the Double Asteroid Redirection Test (DART), a NASA space mission that deliberately collided a spacecraft with the moon on 26 September 2022 to alter its orbit around Didymos. Before the impact by DART, Dimorphos had a shape of an oblate spheroid with a surface covered in boulders but virtually no craters. The moon is thought to have formed when Didymos shed its mass due to its rapid rotation, which formed an orbiting ring of debris that conglomerated into a low-density rubble pile that became Dimorphos today.
Light Italian CubeSat for Imaging of Asteroids is a six-unit CubeSat of the Italian Space Agency (ASI). LICIACube is a part of the Double Asteroid Redirection Test (DART) mission and carries out observational analysis of the Didymos asteroid binary system after DART's impact on Dimorphos. It communicates directly with Earth, sending back images of the ejecta and plume of DART's impact as well as having done asteroidal study during its flyby of the Didymos system from a distance of 56.7 km (35.2 mi), 165 seconds after DART's impact. LICIACube is the first purely Italian autonomous spacecraft in deep space. Data archiving and processing is managed by the Space Science Data Center (SSDC) of the ASI.
NEO-MAPP is a project for studying planetary defence and asteroid exploration.
Hera is a space mission in development at the European Space Agency in its Space Safety program. Its primary objective is to study the Didymos binary asteroid system that was impacted by DART and contribute to validation of the kinetic impact method to deviate a near-Earth asteroid in a colliding trajectory with Earth. It will measure the size and the morphology of the crater created by and momentum transferred by an artificial projectile impacting an asteroid, which will allow measuring the efficiency of the deflection produced by the impact. It will also analyze the expanding debris cloud caused by the impact.