(486958) Arrokoth

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Asteroid
(486958) Arrokoth
Arrokoth, captured January 1, 2019 by New Horizons, 7 mins from closest approach.
Arrokoth, captured January 1, 2019 by New Horizons, 7 mins from closest approach.
Properties of the orbit ( animation )
Epoch:  April 27, 2019 ( JD 2,458,600.5)
Orbit type Cubewano
Major semi-axis 44.63  AU
eccentricity 0.051
Perihelion - aphelion 42.376 AU - 46.883 AU
Inclination of the orbit plane 2.45 °
Length of the ascending node 159 °
Argument of the periapsis 181.1 °
Time of passage of the perihelion December 20, 2059
Sidereal period 298 a 2 M
Mean orbital velocity 0.2 km / s
Physical Properties
Medium diameter 31.7 ± 0.5 km
19.5 km ("Ultima")
14.2 km ("Thule")
Albedo 0.04-0.10 
0.04-0.15 
Rotation period 15 ± 1 h
Absolute brightness 11.1 mag
history
Explorer Hubble Space Telescope
Date of discovery June 26, 2014
Another name 2014 MU 69
1110113Y
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(486958) Arrokoth , provisional designations 2014 MU 69 and Ultima Thule , is a trans-Neptunian object (TNO). It consists of two bodies that touch each other ( English contact binary ) and has an orbital period of about 298 years, the maximum diameter is 31.7 km, of which 19.5 km to the larger component Ultima and 14.2 km to the smaller Thule omitted; the apparent magnitude is 26.8 mag. The orbit is almost circular and only slightly inclined towards the ecliptic . Due to the characteristics of the railway, it is a cold, classic Kuiper belt object . Cold in this case does not refer to temperature, but to the fact that the orbit has hardly been disturbed since the formation of the solar system. On January 1, 2019, the New Horizons probe passed Arrokoth. It is the most distant object to date that has been examined at close range by a probe.

Discovery and naming

An animated version of the Discovery images, taken every 10 minutes. 2014 MU 69 is in the green circles.

At the beginning of the New Horizons mission , the object was not yet known. (486958) 2014 MU 69 was discovered on June 26, 2014 during a targeted search with the Hubble space telescope for possible further flyby targets for New Horizons and was initially designated 1110113Y . In October 2014 the property was announced as one of several possible destinations and selected in August 2015. The property received the official numbering 2014 MU 69 in May 2015 after the orbit data had been determined with sufficient accuracy. The minor planet number (486958) was assigned on March 12, 2017 in MPO 399075.

In addition to the numbering, the object was given a nickname that was proposed in a competition. In March 2018, the New Horizons team chose the name Ultima Thule ("beyond Thule ", in the sense of the known world) from the proposals . The final naming of the object should be determined after the flyby, taking into account whether the object is a multiple system. After the flyby it was clear that it was a system of two bodies in contact, and so the larger part was called Ultima and the smaller part Thule .

In November 2019, NASA announced the name Arrokoth for 2014 MU 69 with the approval of the IAU . Arrokoth means heaven in the extinct Powhatan language , an Algonquin language .

Earthbound Investigations

Wink-of-a-star-2.gif
20170808-MU69Chart.jpg


(486958) 2014 MU69 obscured the light of a star in the constellation Sagittarius on July 17, 2017. Five of the telescopes involved in the observation recorded the event; this showed an irregular outline.

On June 3 and July 10 and 17, 2017, three star occultations were expected by the object. Astronomers used this to get information in advance about the diameter and accompanying debris or a ring system. However, the occultations on June 3 and July 10 could not be determined from any of the observation points. The scientists concluded that the object is smaller than what Hubble's observations suggested, and that the size is rather below the originally assumed 20 to 40 km. The object had to reflect accordingly strongly, or it is a binary system or even a swarm of small objects that were left over from the creation of the solar system.

The coverage of July 17, 2017, which lasted only around 0.2 seconds, suggested that the object is less than 30 km in length and fairly elongated or possibly even a two-part system in which the individual parts are each 15–20 km in size are. Up until the encounter with New Horizons, the object was closely monitored by Hubble in order to obtain the most precise orbit data and information about the rotation possible. However, no rotation period could be determined.

Provisions of the diameter for Arrokoth (provisionally "Ultima Thule" )
year Dimensions km source
2014 30.0-45.0 Lakdawalla et al. a.
2014 25.0-45.0 Buie et al. a.
2019 31.7 + 00.5- 00.5 Star u. a.
The most precise determination is marked in bold .

Investigation by New Horizons

The New Horizons orbit to 2014 MU 69
Computer generated model of the shape from 2014 MU 69 . Above the originally assumed "snowman" shape, below the model revised with newer data.

(486958) Arrokoth is the first small and at the same time the most distant Kuiper Belt Object (KBO) that was examined more closely by a probe. It is assumed that the object has remained frozen in a state since the formation of the solar system about 4.6 billion years ago, and thus enables insights into the early phases of the formation of the solar system . On August 16, 2018, New Horizons took the first long-exposure images of Arrokoth (provisionally "Ultima Thule") from over 100 million kilometers away.

At the time of the January 1, 2019 encounter, the object was approximately 43.4 AU from the Sun. At a distance of 3000 km, the probe flew much closer than Pluto , all instruments were used, as in the observation of Pluto. The system consists of two bodies, which had slowly approached each other a long time ago and which have become a double system of two bodies.

Shortly after the flyby, a series of images of the asteroid was taken. Through the occultation of stars, the shape of Arrokoth could be better determined. If, in the first few days after the flyby, it was assumed that the asteroid was roughly the shape of a snowman made of two approximately spherical parts, the data transmitted up to February 2019 show that the larger part (provisionally referred to as the "Ultima") is considerably flatter than was initially assumed. It has the shape of a pancake , the smaller one (“Thule”) that of a dented walnut. No moons, accompanying debris, or a ring system could be found. The property has no detectable atmosphere. The color is distinctly red. The colors of the larger and smaller part hardly differ, while the object is significantly lighter at the contact line. At the time of the encounter, the axis of rotation pointed approximately towards the earth and the sun, so that the same part of the surface is always illuminated by the sun. This explains why no periodic changes in brightness for determining rotation could be found before. The transmission of the data is expected to take around 20 months until the end of 2020.

Individual evidence

  1. a b c d Emily Lakdawalla: Finally! New Horizons has a second target . In: Planetary Society blog . Planetary Society . October 15, 2014. Archived from the original on October 15, 2014.
  2. ^ A b c Marc William Buie : New Horizons HST KBO Search Results: Status Report . Space Telescope Science Institute . 15th October 2014.
  3. a b Far, Far Away in the Sky: New Horizons Kuiper Belt Flyby Object Officially Named 'Arrokoth'. In: NASA. November 12, 2019, accessed November 12, 2019 .
  4. : Orbits and Accessibility of Potential New Horizons KBO Encounter Targets . In: 46th Lunar and Planetary Science Conference (2015) ..
  5. ^ New Horizons extended mission target selected. In: www.planetary.org. Retrieved November 9, 2015 .
  6. tagesschau.de: “New Horizons” in “Ultima Thule” - A rendezvous on the edge of the solar system (accessed January 1, 2019).
  7. NASA's Hubble Telescope Finds Potential Kuiper Belt Targets for New Horizons Pluto Mission . In: HubbleSite . 15th October 2014.
  8. Mike Wall: Hubble Telescope Spots Post-Pluto Targets for New Horizons Probe . Space.com. October 15, 2014. Archived from the original on October 15, 2014.
  9. Amanda Barnett: Pluto probe gets new assignment. August 29, 2015, accessed August 30, 2015 .
  10. NASA's New Horizons Team Selects Potential Kuiper Belt Flyby Target . NASA . August 28, 2015.
  11. a b New Horizons. Accessed May 21, 2017 .
  12. ^ Tricia Talbert: New Horizons Chooses Nickname for 'Ultimate' Flyby Target. NASA, March 13, 2018, accessed March 15, 2018 .
  13. a b c S.A. Stern, JR Spencer et al .: Overview of initial results from the reconnaissance flyby of a Kuiper Belt planetesimal: 2014 MU69 . January 9, 2019, arxiv : 1901.02578v1 ( arxiv.org [PDF]).
  14. ^ New Horizons: New Mysteries Surround New Horizons' Next Flyby Target. Retrieved July 15, 2017 .
  15. ^ New Horizons' Next Target Just Got a Lot More Interesting. Retrieved August 6, 2017 .
  16. August 28, 2015 NASA's New Horizons Team Selects Potential Kuiper Belt Flyby Target
  17. ^ New Horizons first recording of Ultima Thule. Retrieved September 6, 2018 .
  18. Tricia Talbert: NASA's New Horizons Makes First Detection of Kuiper Belt . In: NASA . August 28, 2018 ( nasa.gov [accessed September 4, 2018]).
  19. New pictures of Ultima Thule leave researchers puzzled. Retrieved February 11, 2019 .
  20. New Horizons: News Article? Page = 20190208. Accessed February 11, 2019 .
  21. The PI's Perspective: We Did It - The Bullseye Flyby of Ultima Thule! Retrieved January 20, 2019 .
  22. NASA probe reaches "Ultima Thule" at the edge of our solar system In: Spiegel online from December 31, 2018.

Web links

Commons : 486958 Arrokoth  - Collection of Images, Videos and Audio Files