Английская Википедия:2017 YE5

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Шаблон:Use dmy dates Шаблон:Infobox planet

Шаблон:Mp is a binary pair of asteroids of approximately equal size and mass, each about Шаблон:Cvt in diameter. Classified as a near-Earth asteroid and potentially hazardous object of the Apollo group, Шаблон:Mp was discovered by amateur astronomer Claudine Rinner at the Oukaïmeden Observatory on 21 December 2017. On 21 June 2018, the pair of asteroids passed within 15.5 lunar distances or approximately Шаблон:Convert from Earth. During the close encounter, Шаблон:Mp was resolved in high detail by concurrent radar observations by the Arecibo and Green Bank observatories, along with individual observations by the Goldstone Solar System Radar. Шаблон:Mp is likely an extinct or dormant comet due to its distant elliptical orbit and dark red surface.[1]

Discovery

Шаблон:Mp was discovered on 21 December 2017, by French amateur astronomer Claudine Rinner at the Oukaïmeden Observatory in Marrakesh, Morocco.[2] The discovery formed part of the Morocco Oukaïmeden Sky Survey (MOSS) directed by Zouhair Benkhaldoun at the Cadi Ayyad University. The MOSS survey was designed for searching and characterizing the orbits of small Solar System bodies such as near-Earth asteroids and comets.[3] As the sixth near-Earth asteroid discovered by the MOSS survey,[4] Шаблон:Mp was found in images taken by the Oukaïmeden Observatory's 0.5-meter reflecting telescope, which was remotely operated by Rinner.[5][3] At the time of discovery, Шаблон:Mp was about Шаблон:Convert away from Earth, located in the constellation of Gemini at an apparent magnitude of 19.8.[6]Шаблон:Efn

Файл:2017YE5 PIA22558 crop.jpg
Шаблон:Mp imaged by the Oukaïmeden Observatory on 30 December 2018

The discovery of Шаблон:Mp was subsequently reported to the Minor Planet Center's Near-Earth Object Confirmation Page (NEOCP), where a preliminary orbit was calculated from additional observations conducted at multiple observatories.[7] Follow-up observations of Шаблон:Mp spanned six days starting from its discovery, and the object was formally announced in a Minor Planet Electronic Circular issued by the Minor Planet Center on 27 December 2017.[5]

Precovery observations of Шаблон:Mp were first identified and reported to the Minor Planet Center in February 2018. These observations were from the Mount Lemmon Survey, which had observed Шаблон:Mp on 14 December 2017, seven days prior to its discovery by the Oukaïmeden Observatory.[8][9] Earlier precovery observations by the Pan-STARRS1 survey on 12 December 2017 were later identified in May 2018, and are now known to be the earliest reported observations of Шаблон:Mp.[8][10]

Nomenclature

Upon discovery, the asteroid was given the temporary internal designation tltv005.[11][7] After follow up observations confirming the object, it was then given the provisional designation Шаблон:Mp by the Minor Planet Center on 27 December 2017.[5] The provisional designation signifies the object's discovery date and year, with the second letter and numbers indicating that it is the 130th object discovered during the second half of December 2017.[12]Шаблон:Efn Шаблон:Mp has not yet been issued a permanent minor planet number by the Minor Planet Center due to its short observation arc of 270 days, which is insufficient for an orbit to be accurately determined.[13][8] Шаблон:Mp is expected to receive a minor planet number once it has been observed for over at least four oppositions, which would take several years.[12] Once it receives a minor planet number, it will be eligible for naming.[12]

Orbit and classification

Шаблон:Mp orbits the Sun at an average distance of approximately Шаблон:Convert, taking 4.73 years to complete one orbit. The orbit of Шаблон:Mp is slightly inclined to the ecliptic plane by 6.2 degrees, with its farthest apsis oriented below the ecliptic. Шаблон:Mp has a highly elongated orbit with an orbital eccentricity of 0.71. Over the course of its orbit, Шаблон:Mp approaches 0.82 AU from the Sun at perihelion and recedes 4.82 AU from the Sun at aphelion, beyond the outer extent of the asteroid belt.[14]

Файл:PIA22560-Asteroid-2017-YE5-Orbit-20180712.gif
Animation of Шаблон:Mp's orbit during the 2018 close encounter with Earth, with the asteroid belt and orbits of the planets for scale

At aphelion, Шаблон:Mp approaches close to Jupiter's orbit, with a minimum orbital intersection distance (MOID) of 0.42 AU.[13][8] At such close proximity to Jupiter's orbit, Шаблон:Mp has likely been gravitationally perturbed by Jupiter, indicated by its Tisserand parameter of 2.877, which is considered to be characteristic of comets.[13][15] Because of its comet-like Tisserand parameter and relatively large orbit for a near-Earth object, Шаблон:Mp has been suspected to be an extinct or dormant Jupiter-family comet.[15] Additional evidence for its cometary origin was found by optical and infrared spectroscopy in 2018, which revealed a reddish and low-albedo surface, consistent with the D-type spectral classification.

As a near-Earth object, the orbit of Шаблон:Mp crosses that of Earth's, which leads to occasional close approaches to the planet. It has a semi-major axis (orbital distance) greater than 1 AU and a perihelion distance within that of Earth's, therefore it is formally classified under the Apollo group of near-Earth asteroids.[13][8] Шаблон:Mp's Earth MOID is approximately Шаблон:Convert, or about 8 lunar distances.[13] Given a small Earth MOID, Шаблон:Mp is considered a potentially hazardous asteroid (PHA) by the Minor Planet Center, under the definition that PHAs have Earth MOIDs less than 0.05 AU and absolute magnitudes brighter than 22.[8][16]

Despite being considered potentially hazardous, there is no risk of impact by Шаблон:Mp, as it will not make any close Earth encounters within 12 lunar distances or Шаблон:Convert over the next 200 years.[13] Шаблон:Mp was removed from the JPL Sentry Risk Table on 6 January 2018, after extensive observations and refinements of its orbit ruled out future possibilities of Earth impacts.[9][17]

2018 Earth approach

On 21 June 2018 at 20:53 UTC, Шаблон:Mp made its closest approach to Earth from a distance of Шаблон:Convert, or 15.52 lunar distances.[13] During the encounter, Шаблон:Mp approached Earth at a rate of Шаблон:Cvt and its apparent visual brightness peaked around magnitude 15, too faint to be seen with the naked eye.[13][15] At closest approach, Шаблон:Mp's apparent motion in the sky was 0.51 degrees per hour and was in the constellation of Andromeda, with an apparent magnitude of 16.6 and an angular separation of 66 degrees from the Sun.[18]Шаблон:Efn After the close encounter with Earth, Шаблон:Mp continued its approach to aphelion, passing by Mars from a distance of Шаблон:Convert on 30 July 2018.[13][2]

Observations

Файл:2017YE5 Goldstone radar summary 2x2.jpg
Collage of Goldstone delay-Doppler images of Шаблон:Mp during its close approach to Earth[15]

The June 2018 encounter with Шаблон:Mp provided an opportunity for radar observatories to study the asteroid's characteristics in detail.[15][19] On 17 June 2018, the first radar observations of Шаблон:Mp were attempted by the monostatic Goldstone Solar System Radar (GSSR) in California, but failed to detect the asteroid due to uncertainties in the radar pointing position. Шаблон:Mp was later successfully imaged and observed with the GSSR on 21 June 2018, revealing the asteroid's binary nature. Led by radar astronomer Marina Brozović, GSSR observations of Шаблон:Mp spanned four days, lasting until 24 June 2018.[15] During these observations, the GSSR's preliminary findings were alerted to astronomers at the Arecibo Observatory in Puerto Rico for further study.[20][2]

Arecibo radar observations of Шаблон:Mp began on 23 June 2018.[15] The Шаблон:Mp binary system was observed using a bistatic radar system where the Arecibo Observatory transmitted a radar signal to the pair of asteroids while the Green Bank Observatory in West Virginia received the signal reflected from the asteroids.[20][2] Led by Arecibo radar astronomers Anne Virkki, Flaviane Venditti, Sean Marshal, along with Patrick Taylor at the Green Bank Observatory, bistatic radar observations resolved Шаблон:Mp at a resolution of 7.5 meters per pixel.[21] Radar observations of Шаблон:Mp ended on 26 June 2018 after it had moved out of Arecibo's view.[15] Concurrently, optical observations were also carried out by various observatories in order to compile a light curve of the binary system.[2][22] Optical observations of Шаблон:Mp continued after the June 2018 encounter and detected possible mutual events or eclipses occurring between the components of the binary system.[23]

Future approaches

Over the course of its orbit in the next 200 years, Шаблон:Mp will continue to pass by Earth, though it will not make any approaches as close as the June 2018 encounter. The next Earth encounter by Шаблон:Mp will be on 15 April 2037, when it will pass by Earth from a nominal distance of approximately Шаблон:Convert.[13][2] In the next 100 years, Шаблон:Mp will make three Earth encounters within 0.2 AU (approximately 80 lunar distances), which will occur in February 2051, July 2088, and May 2107. The expected nominal approach distances for these dates are 0.123 AU, 0.179 AU, and 0.145 AU, respectively.[13]

Binary system

Шаблон:Infobox planet The secondary component of Шаблон:Mp was discovered in Goldstone radar observations conducted by Marina Brozović on 21 June 2018.[15] From the first Goldstone radar images, the two components appeared to be contact binary lobes as the components were viewed in front of each other. Additional radar observations by the Arecibo and Green Bank observatories resolved the Шаблон:Mp system in high resolution, confirming that the two components were indeed separate objects.[23] Under satellite naming conventions by the International Astronomical Union, the satellite would be provisionally designated Шаблон:Mpm-.[24]

Physical characteristics

Файл:PIA22556-BinaryAsteroid-2017-YE5-Animation-20180712.gif
Artist's rendering of the Шаблон:Mp binary system, with the contrasting surface brightnesses and shapes of each component

Шаблон:Mp is an equal-mass binary asteroid consisting of two components approximately Шаблон:Cvt in diameter. Equal-mass binary systems are relatively rare among the population of binary near-Earth asteroids as they constitute less than 1% of radar-observed near-Earth asteroids larger than Шаблон:Cvt in diameter.[23] Шаблон:Mp is one of only four systems of that kind known; the other three are Шаблон:Mpl, 69230 Hermes, and Шаблон:Mpl.[23]

From their mutual orbit and measured diameters, both components are calculated to have low bulk densities less than Шаблон:Val, indicating a significant macroporosity of their internal structures. Given their measured diameters and absolute magnitudes, the optical albedos of their surfaces are calculated to be as dark as charcoal, reflecting less than 3% of incident light.[23][2] Unlike other binary asteroid systems observed by radar, the components of Шаблон:Mp appear to display a distinct difference in their shape, surface brightness and radar reflectivity. These differences imply that the two components may also have different densities, compositions, and surface roughnesses.[20]

Orbit and rotation

Файл:2017 YE5 GSSR-movie 2018Jun23.gif
Animation of Goldstone radar images of Шаблон:Mp on 23 June 2018. The separation between the two components becomes more apparent as they move away from each other.

The pair of asteroids orbit each other around a common center of mass (barycenter) between them. Their mutual orbital period is Шаблон:Convert, with an orbital separation of Шаблон:Cvt or 4 times the component radii.[25] It is uncertain whether both components rotate synchronously with their mutual orbital period, as there is evidence of non-principal-axis rotation (or rotational precession) and axial misalignment of both components. Light curve measurements of Шаблон:Mp taken between June and August 2018 show a secondary period of 14.88 hours and radar images suggest that the obliquities of the components are misaligned by a few degrees.[23][1]

Notes

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References

Шаблон:Reflist

External links

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  1. ↑ 1,0 1,1 Ошибка цитирования Неверный тег <ref>; для сносок Monteiro2021 не указан текст
  2. ↑ 2,0 2,1 2,2 2,3 2,4 2,5 2,6 Ошибка цитирования Неверный тег <ref>; для сносок Davis2018b не указан текст
  3. ↑ 3,0 3,1 Ошибка цитирования Неверный тег <ref>; для сносок Davis2018a не указан текст
  4. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MOSS не указан текст
  5. ↑ 5,0 5,1 5,2 Ошибка цитирования Неверный тег <ref>; для сносок MPEC-2017-Y116 не указан текст
  6. ↑ Ошибка цитирования Неверный тег <ref>; для сносок NEODyS-Eph-Dis не указан текст
  7. ↑ 7,0 7,1 Ошибка цитирования Неверный тег <ref>; для сносок NEO-Exchange не указан текст
  8. ↑ 8,0 8,1 8,2 8,3 8,4 8,5 Ошибка цитирования Неверный тег <ref>; для сносок MPC-object не указан текст
  9. ↑ 9,0 9,1 Ошибка цитирования Неверный тег <ref>; для сносок MPS867675 не указан текст
  10. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MPS889315 не указан текст
  11. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MOSS-MPC-report не указан текст
  12. ↑ 12,0 12,1 12,2 Ошибка цитирования Неверный тег <ref>; для сносок Nomenclature не указан текст
  13. ↑ 13,00 13,01 13,02 13,03 13,04 13,05 13,06 13,07 13,08 13,09 13,10 Ошибка цитирования Неверный тег <ref>; для сносок jpldata не указан текст
  14. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Plait2018 не указан текст
  15. ↑ 15,0 15,1 15,2 15,3 15,4 15,5 15,6 15,7 15,8 Ошибка цитирования Неверный тег <ref>; для сносок Goldstone не указан текст
  16. ↑ Ошибка цитирования Неверный тег <ref>; для сносок PHA-def не указан текст
  17. ↑ Ошибка цитирования Неверный тег <ref>; для сносок CNEOS не указан текст
  18. ↑ Ошибка цитирования Неверный тег <ref>; для сносок NEODyS-Eph не указан текст
  19. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Bartels2018 не указан текст
  20. ↑ 20,0 20,1 20,2 Ошибка цитирования Неверный тег <ref>; для сносок NASA-20180711 не указан текст
  21. ↑ Ошибка цитирования Неверный тег <ref>; для сносок naic не указан текст
  22. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MPS900357 не указан текст
  23. ↑ 23,0 23,1 23,2 23,3 23,4 23,5 Ошибка цитирования Неверный тег <ref>; для сносок Taylor2019 не указан текст
  24. ↑ Ошибка цитирования Неверный тег <ref>; для сносок minorsats не указан текст
  25. ↑ Ошибка цитирования Неверный тег <ref>; для сносок johnston не указан текст
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