The Kuiper belt [ kœypərɡʏʁtl̩ ] ( English Kuiper belt ) is a by Gerard Kuiper region named annular, relatively flat, which in the solar system outside the Neptun web in a distance of about 30 to 50 astronomical units near the (AE) ecliptic extends and Estimated to contain more than 70,000 objects more than 100 km in diameter as well as many smaller objects.
The objects in this area are as Kuiper Belt Objects (abbreviated KBO , of Engl. Kuiper Belt Objects , sometimes EKO of English. Edgeworth-Kuiper Belt called) and are among the trans-Neptunian objects (TNO).
It is believed that the majority of the medium period comets originated in the Kuiper Belt. While it used to be assumed that the cometary nuclei are KBOs that have been thrown out of their orbit almost unchanged, it is now true that they are fragments from collisions of KBOs.
Origin of name
The name Kuiper belt was coined by Scott Tremaine . In 1988 Tremaine used a computer simulation to check and confirm a theory by Julio Ángel Fernández from his publication On the existence of a comet belt beyond Neptune from 1980 and named the still hypothetical region Kuiper belt based on Fernández's publication, which is in the introduction based on a suspected comet belt and corresponding theories by Gerard Kuiper from 1951 and 1974.
The name is partly controversial because Kuiper's theory was neither the first of its kind nor is considered current. Therefore, the Edgeworth Belt (after the Irish astronomer Kenneth Edgeworth ) or Edgeworth-Kuiper Belt is sometimes also referred to , since both Edgeworth (1943 in Ireland) and Kuiper (1951 in the USA) had independently proposed the thesis that behind the orbit of Neptune is an area in which comets are formed from planetary material ( dust ).
The around 2000 known objects in this region up to now (2015) can be divided into several different groups based on their orbital elements :
- Classic KBOs (Classical Kuiper Belt Objects, CKBOs, or Cubewanos ) move with small eccentricities on almost circular paths between 41 and 50 AU with orbit inclinations of up to 30 °. The name Cubewano is derived from the provisional name (1992 QB 1 , pronounced Q B One ) of the asteroid (15760) Albion , which was the first of these objects to be discovered. Around two thirds of the known KBOs move on such a circular orbit around the sun.
- Resonant KBOs (Resonant Kuiper Belt Object, RKBOs) are objects that move on resonant orbits to Neptune and are thereby stabilized in their orbit (e.g. Plutinos with a 3: 2 resonance at around 40 AU or Twotinos with a 2 : 1 resonance at around 48 AU). Around a third of the KBOs known today are resonant KBOs.
- Scattered KBOs (Scattered Kuiper Belt Objects, SKBO, or Scattered disk objects , SDO) move with large eccentricities on paths with perihelion distances of close to 35 AU and aphelion distances of up to over 2000 AU. Up to now only a few of these scattered KBOs are known, e.g. B. (15874) 1996 TL 66 with a strongly elliptical orbit and an orbit inclination of 24 °. Depending on the author, the scattered disk is also viewed as a separate population rather than part of the Kuiper Belt.
Since 1978 it is known that Pluto with Charon a very large companion has, therefore we also speak of Pluto-Charon system . Between 1997 and 2001, eight more dual systems were found among the approximately 500 KBOs known to date, which are distributed across all three KBO groups.
Sub-regions of the Kuiper Belt (distances in AU):
The bars correspond to the latitude of the major semiaxes of the objects in the respective zones. The areas of the objects that are in orbit resonance with Neptune are shown in red. The Neptune Railway and the Neptune Trojans are shown for reference only and do not belong to the Kuiper Belt.
The KBOs presumably formed during planet formation near the region in which they are observed. While many planetesimals formed very quickly in the denser inner area and soon grew into planets, this process took place much more slowly in the thinner outer areas. The remnants are the observable KBOs.
The CKBOs move almost in a circle, as is to be expected for objects created in this area. However, the sometimes very large orbital slopes require a mechanism that deflects them from the ecliptic. This mechanism is not yet understood.
- One possibility is that Neptune scattered massive planetesimals (larger than Earth ) into the Kuiper Belt in the early stages of planetary evolution . These massive objects could explain the large orbital inclinations, but they would also have distracted the resonant KBOs more than what was observed.
- A star passing nearby caused the displacement from the ecliptic. This process would spare the resonant KBOs and also explain the outer edge of the Kuiper Belt at 50 AU, but the star should have approached the Sun within a few hundred AU.
The SKBOs were believed to have been scattered outward from the major planets during the formation of the planetary system. A part was captured by Neptune on orbits close to 35 AU perihelion distance, the rest was scattered further out and has probably partly left the solar system .
The educational processes of the dual systems are so far pure speculation. The main problem with most of the proposals is the large number of these systems made up of large KBOs.
Large Kuiper Belt Objects (KBOs)
As of 2016, eight KBOs are known with a diameter (with uncertainties of 10–15%) around 1000 km or more:
- CKBOs : (136472) Makemake (1500 × 1430 km), (136108) Haumea (1920 × 1540 × 990 km), (50000) Quaoar (1100 km), (20000) Varuna (668 km)
- RKBOs : (136108) Haumea (1920 × 1540 × 990 km)
- SKBOs : (136199) Eris (2326 km), (225088) Gonggong (1535 km), (55565) 2002 AW 197 (768 km)
- In 1930, Pluto, the first object in the region of the solar system later known as the Kuiper Belt, was discovered, but not yet recognized as such, but classified as a planet .
- In 1943, Kenneth Edgeworth sets up the theory of a collection of cosmic objects beyond the known planetary orbits.
- In 1951 Gerard Kuiper published a theory about objects beyond Pluto.
- In 1977 the centaur (2060) Chiron is discovered. According to current knowledge, it comes from the Kuiper belt.
- In 1978 the Pluto moon Charon is discovered.
- In January 1992 the second centaur (5145) Pholus is discovered.
- In 1992, (15760) Albion , known under the name 1992 QB 1 until it was named in January 2018 , was the first object to be discovered beyond Pluto's orbit.
- In 1993 the first Plutinos (after Pluto) were discovered, which also triggered a discussion about the planetary status of Pluto.
- In 1996, with (15874) 1996 TL 66, the first scattered KBO was discovered.
- In 1998 the centaur (52872) Okyrhoe was discovered, which some authors reclassified to the Jupiter family comet .
- In 1998 the second dual system (after Pluto) was discovered with 1998 WW 31 .
- In 2001 with (20000) Varuna the second TNO (after Pluto / Charon) with a size of (then estimated) about 1000 km is discovered.
- In 2002 (50,000) quaoar was discovered.
- In 2003 a TNO was discovered with (90377) Sedna , which so far did not fit into any scheme. It no longer seems to belong to the Kuiper Belt, but also not yet to the Oort Cloud .
- In 2005, with (136199) Eris, a TNO is discovered whose size exceeds that of Pluto according to initial estimates. As far as we know, Eris is a little shorter.
- In 2006, Pluto and Eris are officially declared as dwarf planets by the International Astronomical Union .
- In 2008, (136472) Makemake and (136108) Haumea were officially declared as dwarf planets by the International Astronomical Union.
- In 2015, New Horizons reached the Pluto system and in 2019 the object (486958) Arrokoth (then unofficially: Ultima Thule ). This is the first time that Kuiper belt objects are explored by a space probe.
Comparable planets are not to be expected in our solar system; their existence would be noticeable through a shift in the total center of gravity relative to the sun.
Zooniverse project IceHunters
As part of the Citizen Science project IceHunters , volunteers searched for objects in the Kuiper Belt to find a successor target for the New Horizons spacecraft . To do this, they evaluated images that were obtained from the subtraction of astronomical recordings taken at time intervals. Astronomical knowledge was not necessary for this activity.
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- Description on Centauri Dreams