Theory The Kuiper Belt Objects

An artist view of a space mission overhanging our distant solar system. picture site 'Amateur Astronomy'

Beginning in 1992, the astronomers turned to study in depth a vast zone of leftovers of the solar system's formation, the Kuiper Belt, which had been previously thought to exist. The Kuiper Belt is a vast reservoir of leftover frozen material from the construction of our solar system 4.5 billion years ago and home to several dwarf planets. The so-called cold 'classical region' of the Kuiper Belt is believed to contain some of the oldest, most prehistoric material in the solar system. Such a ring of leftovers is now thought to be the source for the short-period comets which orbit in the solar system. Further still, the Oort Cloud is the other zone of leftovers. It is of a spherical shape and containing billions of comets and providing this time for long-period ones. As the Kuiper Belt is extending from beyond Neptune (about 2.8 billion miles -4.5 billion km) to 28.6 billion miles (46 billion km, or 500 AU), the Oort cloud is stretching from where the Kuiper Belt ends to about 1, or maybe 2 light-years. The Kuiper Belt, or Edgworth-Kuiper Belt has been found to harbour various and numerous bodies, of them 70,000 with a diameter of some 100 km (some 62 miles) as over 1,000 Kuiper Belt Objects, or KBOs have been cataloged so far. Such bodies may be of the comet or asteroid sort, as, through the collisions between them, further, they have yielded large fragments and dust! Small objects, smaller than one-mile diameter, are much rare in the Kuiper Belt than previously thought, hinting to that the Kuiper Belt either in its formation or evolution, or both, were somewhat different than that of the Asteroid Belt between Mars and Jupiter, and allowing less collisions. Those objects are named Kuiper Belt Objects (KBOs) or Edgeworth-Kuiper Belt Objects (EKOs). While rare in the asteroid belt, comets as large as half the mass of the asteroid Ceres are thought to be common in the icy Kuiper belt. A small fraction of these objects, on the other hand, are over the 620 miles in diameter mark (1,000 km). This last class of objets have risen the question of where the limits are between such large KBOs and the ultimate planet of the solar system, Pluto. A broader view of such a question is to turn to the exoplanets' search, which, since some years, is showing how diverse and varied solar systems may be, with hot Jupiter, usual rocky planets, far-away worlds with elongated orbits and leftovers of the primitive protoplanetary disk. It seems likely that our own solar system, with its orderly 9 planets, and the Kuiper Belt and the Oort cloud, is a form of a solar system. The distance to the Sun, in our solar system, might be the criterium for the planets, with Pluto being a planet and farther objects, whatever their size, KBOs or inner Oort Cloud objects only. The discovery of new, large KBOs, regularly leads to the announcement that the 10th planet of the solar system has been found... Most recent observations by the Hubble Space Telescope are showing that the Kuiper Belt, over the course of billion years, has had its bodies endure numerous collisions between themselves, leading to that, beyond that the belt contains medium-sized bodies, it also eventually yielded unnumerable small bodies, in the order of the 3,000-ft, cometary bodies that is. Other source are stating dimensions between 25 to 62 miles in diameter (40-100 km) as their orbits might extend either side of the ecliptic. Some Kuiper Belt objects are double ones with two objects orbiting about eachother, a reminder of sort of the double system between Pluto-Charon. The finds at Pluto and Charon, by the New Horizons mission in 2015 have led scientists to doubt a longstanding model that all Kuiper Belt objects formed by accumulating much smaller objects -less than a-mile (1.609-km) wide. The absence of small craters on Pluto and Charon support other models theorizing that Kuiper Belt objects tens of miles (kilometers) across may have formed directly, at their current -or close to current- size. Neptune may kick out KBOs -as some have their orbit perpendicular to the ecliptic- and then return back to it as the hypothetical Planet Nine, theorized by early 2016, as far as it is concerned, produces Sedna-like objects at the contrary by taking a standard KBO and slowly pulling it away into an orbit less connected to Neptune

A figuration of the distances at the far reaches of the solar system, with distances from the Sun in miles (non-clickable picture)

Oort Cloud objects formed in our own solar system, but were kicked out far beyond the planets by the immense gravity of Jupiter. After the discover of Sedna by 2004, at a perihelion of about 70 AU, 2012 VP113 as discovered in 2014 might hint to a hypothesizd inner Oort Cloud filled with bodies about 900 with orbits and a size like Sedna, and even hundreds of thousands smaller objects. Some of such celestial bodies could rival the size of Mars or even Earth. That could determine a area of rocky planets and asteroids of the Asteroids Belt at between .39 and 4.2 AU, gas giants at 5 and 30 AU, the Kuiper Belt at ranges from 30 to 50 AU as a inner Oort cloud belt could lie about 80 AU. The outer Oort cloud would remain the likely origin of some comets. A number of theoretical models are able to reproduce much of the structure seen in the Solar System. A important difference between these models is what they predict about the objects that make up the Oort Cloud. Different models predict significantly different ratios of icy to rocky objects. Astronomers further are wondering whether the inner Oort cloud objects might be influenced by the potential presence of a yet unseen planet perhaps up to 10 times the size of Earth. Since the end of the 19th century, astronomers considered that there might be a massive planet beyond gas giants. As a 'Planet X' was hypothesised by the turn of the 20th century, or that the idea tat a dwarf-star, called 'Nemesis' could come with the Sun in the 1980's, sky surveys since that time did not return any such presence (like the Infrared Astronomical Satellite (IRAS) which scanned the sky in the infrared, or NASA's Two Micron All-Sky Survey (2MASS)). By 1999 still unexplained anomalies in the orbit of comets brought to the idea of a gas giant named 'Tyche.' The recentest WISE mission found no any body as far away as 26,000 AU. Disturbances observed in the orbits of KBOs brought those ideas back to life by early 2016. One can theoretically accept the existence of a 'Planet Nine', likely a gas giant orbiting by 10 to 20,000 years at 2 billion miles (kilometers) beyond Neptune's orbit. There too however a observation of that planet is still missing. Sedna and other extreme objects in the solar system beyond Pluto are puzzling. They are thought to have formed closer to the Sun, along with planets, asteroids and other objects that coalesced from a primordial spinning disk of gas and dust. Some unknown factor later pushed a few of these objects out to extreme orbits. The combined gravity of extreme objects could provide a alternate explanation to the question of Planet Nine and its influence on the far reaches of the solar system

The Kuiper Belt likely is a more aged, leaner version of debris disks seen around stars like Vega and Fomalhaut. Kuiper Belt objects occasionally crash into each other, and this relentless bump-and-grind produces a flurry of icy grains. Through gravitational effects called resonances, Neptune wrangles nearby particles into preferred orbits. This is what creates the clear zone near the planet as well as dust enhancements that precede and follow it around the sun. In the past, the Kuiper Belt contained many more objects that crashed together more frequently, generating dust at a faster pace. With more dust particles came more frequent grain collisions, creating a dense, bright ring. By 15 million years of age, the Kuiper Belt was represented like a bright ring at the outskirts of the solar system, as 85 millions years later, dust grains already had migrated inside as at 700 million years into the solar sytem history, the belt had mostly turned to how it looks nowadays, keeping fading since and with Neptune coralling the particles. Asteroid belts generally should not be uncommon around other stars, both in their outer, cooler, and inner, warmer versions, matching, in proportions included, the Sun's Kuiper and Asteroid Belts, respectively. The gap found between both belt usually contains outer planets orbits. The dual belt structure further likely is maintained by planets orbiting inside. In our solar system, the Asteroid belt is maintained by the gravity of the terrestrial planets and the giant planets as the outer Kuiper belt is by giant planets. At other stars however, dust in the belts provided by comets and the collisions of rocky chunks is in far more quantity around young stars or stars which formed out of a massive interstellar cloud

A compared view of the outer and inner asteroid belts both around Vega and our Sun. courtesy site 'Amateur Astronomy'

Some objects' brightness makes them at reaches of the amateur astronomers. 2003 UB313 is currently in constellation Cetus, the Whale. Sedna is a very faint object at magnitude 20.5 and at the boundary of the high-end amateurs' instruments, as Quaoar is at the 18.6th magnitude as 2004 DW is at the 18.5th

check a table of the largest KBOs known