Our solar system is not made up of just a star around which eight planets and their hundreds of satellites and countless asteroids and comets revolve. Beyond that, there are some structures for which our solar family has found perfection. One of the largest such structures is the Kuiper Belt.
The location of the Kuiper Belt is outside Neptune's orbit. It is actually a ring of rocky asteroids of several thousand different sizes. Its location is from 30 AU to 55 A.U. from the sun (AU or Astronomical Unit: The average distance between Sun and Earth). However, it is wrong if anyone thinks that after 55 AU the Kuiper Belt comes to an end. Combined with the Kuiper Belt, there is a belt, known as Scattered Belt. It is originally known as the source of Short-Period Comets (Short-Period Comets: Comets, that take 200 years or less to orbit the Sun once are called Short-Period Comets). During the formation of the solar family, this region was formed with the remains of various planets and satellites. One thing to keep in mind, however, the Kuiper Belt and the Oort cloud are not same. The Oort cloud is located farther outside the solar system and is 20 times wider in diameter than the Kuiper Belt and 20 to 200 times larger in mass. (Oort Cloud: From the distance of 2,000 to 2,00,000 AU from the Sun, the belt of rotating asteroids and comets which has no evidence of its existence but claims the presence of this zone on the basis of theories, hypothesis and surrounding situations)
The
Kuiper belt is named after Dutch astronomer Gerard Kuiper. After the discovery
of Pluto by Clyde Tombaugh in 1930, various scientists have been expressing
their views on the presence of this region. The reason for this is the odd
orbit of Pluto. In fact, Clyde Tombaugh opened the way for the possibility of a
new world. Scientist Frederick Leonard was the first to make public the
possibility of the belt's presence. This idea was supported by the scientist
Armin Leuschner. In 1943, scientist Kenneth Edgeworth in his research paper
mentioned the presence of this region. In 1951, Gerard Kuiper, in his research
paper, hypothesized a disc outside the solar system formed at the beginning of
the evolution of the solar system. But he did not realize how realistic his
assumptions were. Scientist Al Cameron estimated a massive structure filled
with tiny elements on the outskirts of the solar system. In 1987, scientist
David Jewitt and his prospective student Jane Luu first observed and studied it
from Kitt Peak National Observatory in Arizona, the Cerro Tololo Inter-American
Observatory in Chile, and finally the Mauna Kea Observatory in Hawaii. Finally,
on 30th August 1992, they proved the existence and veracity of the belt.
In
1992, 15760Albion was discovered as the second Kuiper Belt object after Pluto.
In its 10 years, more than 100 objects have been discovered in the region.
Scientists estimate that there are currently more than 1,00,000 objects in the
Kuiper Belt.
After
the discovery of this region, a controversy arose over its naming. Some called
it the Edgeworth-Kuiper Belt. Many did not want to accept that. Some call it
the Trans-Neptuneian Object (TNO). However, there has been a problem. This name
captures all of the objects, orbiting the Sun outside Neptune's orbit. At
present, however, this region is most commonly recognized as the Kuiper Belt
and the objects within it as the Kuiper Belt Object (KBO).
It has already been said that the Kuiper Belt is
located between 30 AU to AU, excluding the Scattered Disc. However, the densest
region of the Kuiper belt is between 39.5 AU to 48 AU. It is true that the
force of gravity of Neptune in the Kuiper Belt works strongly. Even Neptune's
largest satellite Triton was not a member of our original solar system. It was
actually part of the Kuiper Belt. But the intense attraction
force of Neptune has made Triton Neptune's satellite. This satellite, 14
percent larger than Pluto, bears a striking resemblance to Pluto's surface. But
this effect of Neptune is not so much seen in objects located between 42 AU to
48 AU. Hence they are called the Classical Kuiper Belt Objects. They also have
another name, Cubewans. These objects occupy two-thirds of the space in the
Kuiper Belt. This Classical Kuiper Belt Objects is divided into two classes,
namely, the Dynamically Cold Region and the Dynamically Hot Region. Such naming
is not due to any temperature difference. The difference between mobility of
the molecules of the object forming material of two regions at equal
temperatures is the cause of different naming. There are also some other differences
such that the material in the Dynamically Cold Region is of a slightly brighter
nature than the material in the Dynamically Hot Region. Again, the mass of
matter in Dynamically Hot Region is 30 times greater than that of matter in the
Dynamically Cold Region. So it can be said that the orbits and sources of
matter in both regions are of course different.
The
first object discovered in the Kuiper Belt was Pluto. Later, when Pluto was
studied, it was found that Pluto's orbit had somewhat overlapped Neptune's
orbit. Based on a few other factors, it was decided in 2006 to move Pluto from
a planet to a dwarf planet. Not just Pluto, but at least 200 Pluto-like objects
have been found that have moved into Neptune's orbit. All these objects are
called Plutinos. We know that Neptune has considerable influence on the objects
in the Kuiper Belt. But since Neptune and Plutinos are on different planes,
there is no possibility of a collision between them.
The
complex structure of the Kuiper Belt and its origins is an undisclosed fact to
scientists today. According to them, in the early stages of planetary formation
in the solar system, some of the tiny objects or Planetesimals that could not
come together to form a planet formed an Asteroid Belt in the solar system, the
rest came out completely and formed a Kuiper Belt. If Neptune's distance from
the Kuiper Belt had been a little longer, all these objects could have come
together to form another planet. Scientists have created many artificial models
to explain the Kuiper Belt, the most acceptable being the Nice Model (Named
after the French city, Nice) although this model is unable to accurately
explain many of the events in the Kuiper Belt. Scientists rely on some
long-term research results to explain these unresolved issues.
The
Kuiper Belt is assumed to remain the same over time due to its position at the
edge of solar system. Therefore, this region can be a reliable source of
information to know the initial state of the solar system in more detail. But
there are two problems. Firstly, their size is very small and secondly, they
are located at a great distance from the earth. However, scientists are
continuing to try in different ways to explore them.
It
is now understood that the average temperature in this region is only 50 Kelvin
or -223 degrees Celsius. It has been possible to measure the diameter and
density of very few objects here. It has been found that low density objects
have more ice and high density objects have less ice. This ice usually consists
of water, ammonia and compounds such as methane. Scientists are currently
focusing more on spectral analysis methods. It has been found that the
substances in this region are usually grey to red in color. From which
scientists estimate that all these objects may contain various metal compounds
and organic compounds. All these organic compounds or hydrocarbons can contain
methane, ethane, ethylene, acetylene etc. In addition, under the influence of
sunlight, those organic compounds may have modified forms of thollins. Another
compound scientists have expected for is hydrogen sulfide.
We
have learned some more information from the long search. For example, in 1996,
a group of scientists led by Robert Brown discovered that Pluto had a lot in
common with the Kuiper Belt object called 1993SC. The ice of this object has
been found to be similar to the ice of methane in the satellite Triton of
Neptune. Large amounts of volatile methane, nitrogen, and carbon monoxide have
been found on the surface of the objects of Kuiper Belt much similar to that of
Pluto or Quaoar. At very low temperatures (30 Kelvin to 50 Kelvin or -243
degree Celsius to -223 degree Celsius) they sometimes evaporate and come down
again like snowfall. The existence of solid forms of water ice has also been
found in objects such as 1996TO, 3626 Huya or 20000Varuna and the existence of
solid forms of ammonia solution has been found in 50000quaoar. The smallest
Kuiper object may be less than 1 km in diameter. In 2009, the Hubble Space
Telescope discovered objects that could be between 460 meter to 1,160 meter in
diameter. It is virtually impossible to observe all the objects in the Kuiper
Belt because they are so small in size, they are not easy to see at first, and
secondly their distance from the earth is huge that is why they seem
unimportant. So even if it covers a large area, the total mass of the Kuiper Belt
could be as much as 0.03 percent of the Earth's mass, or as much as 1 percent.
Another
100 AU wide area is almost merged with the Kuiper Belt. This area is called
Scattered Disc due to the restless nature of the members of the area. The
orbits of objects in this region are quite elliptical and it is the source of
many short-period comets. In this region, scientists have found a dwarf planet
named Eris. Many refer to objects in this region as Scattered Kuiper Belt
objects. Again, many do not want to see the region separately, but rather as
part of the Kuiper Belt. There is still a debate among scientists around the
world about this, as a result of which we still do not have a universally
accepted definition of the Kuiper Belt.
Regardless
of the controversy, some of the most famous objects in the region (including
the year of their discovery) are Pluto (1930), 20000Varuna (2000), 2696Ixion
(2001), 50000Quaoar (2003), Makemake (2005) and Haumae (2005). These include
one or more satellites of Pluto, Makemake, Haumaea, 50000Quaoar, Eris, 22506Ganggong.
Larger objects usually have satellites and smaller ones have no satellites. It
seems that the process of formation of these objects is completely different.
Talking about these satellites, scientists have given completely new
information. Eleven percent of the objects in this Kuiper Belt are binary,
meaning that two objects of approximate same mass are orbiting each other with
a center-of-mass such as Pluto and Charon.
At
least four man-made spacecraft have reached or passed the Kuiper Belt in the
past such as Pioneer-10, Pioneer-11, Voyager-1 and Voyager-2. But they were not
used for observation in this area. Finally, the only spacecraft sent to the
region for observation was launched on January 19, 2006. The name of that
spacecraft is New Horizon. This made its flyby on Pluto on July 14, 2015
(Flyby: According to the space science, the shortest distance, at the time of
observation, between observation space vehicle and the planet or satellite.).
New Horizon selected three more objects for observation which includes the 2014
MU69 or Arrokoth. The spacecraft made its flyby on that object on 1st January 2019.
All of the objects, that the spacecraft chose to observe, are between 30 km to
50 km in diameter and located between 43 AU and 44 AU. Many say spacecraft
should be launched to know about Quaoar, especially for Heliopause, should make
flyby on Makemake, Haumae and Ixion. (Heliopause: It is a hypothetical outline
after which no solar wind or solar particle is possible) The Kuiper belt is
considered by many to be the boundary of the solar system, but many scientists
consider the Heliopause to be the boundary of the solar system, located 50,000
AU or 2 light years away from the Sun.
(Light year: Light travels as much distance in a year) They want to
determine the trajectory of the spacecraft, proposed by the scientists, in such
a way that the spacecraft also observes Uranus and Neptune during its journey.
If the mission starts in 2039, the spacecraft will reach its destination 17
years later in 2056. Apart from this, if interstellar (Interstellar: The
unaffected space, located between two or more stars.) missions
occur in the future, the spacecraft must cross the Kuiper Belt and observe.
Only
a fraction of the mass of the Kuiper Belt, which was once 10 times the mass of
the Earth, remains today. Behind this, influences of giant planets are
responsible. Yet the Kuiper Belt is slowly eroding. The objects in this region
are colliding with each other and breaking into fragments and turning into
comets. The rest of the dust is going out of the solar system under the
influence of solar wind. Many of the comets of the past came to the solar
system under the attraction of Jupiter or Neptune and later ignited completely
and are now orbiting the Earth near or far like asteroids.
In
the case of nine more stars besides our Sun, regions such as the Kuiper Belt,
20 to 50 AU wide, have been found. The more research is done on these regions,
the more new information will come up and the mystery covered in the darkness
of the universe will step towards the light little by little.
