What is Oort cloud and where is it located?

Oort cloud is considered as the most distant of the solar system. The nearest objects of the oort cloud are considered to be far from the sun when compared to the outer reaches of kuper belt. Unlike the orbits of the planets and the Kuiper Belt, which lie mostly in the same flat disk around the Sun, the Oort Cloud is believed to be a giant spherical shell surrounding the rest of the solar system. Because the orbits of long-period comets are so extremely long, scientists suspect that the Oort Cloud is the source of most of those comets. For example, comet C/2013 A1 Siding Spring, which made a very close pass by Mars in 2014, will not return to the inner solar system for about 740,000 years. The Oort Cloud is a large spherical cloud with a radius from 50,000 to 100,000 A.U. surrounding the Sun filled with billions to trillions of comets. It has not been directly observed. Its existence has been inferred from observations of long period comets. Long period comets have very elliptical orbits and come into the inner solar system from all different random angles, their orbits are so elliptical that they spend only 2 to 4 years in the inner part of the solar system where the planets are and most of their time at 50,000 to 100,000 A.U. This implies the existence of a large reservoir of comets. This was first noted by the Dutch astronomer Jan Oort in 1950 so the spherical comet reservoir was named after him. 

The distance from the Sun to the Oort Cloud is so enormous that it’s useful to describe it not in the more common units of miles or kilometres, but astronomical units. One astronomical unit (or AU) is the distance between Earth and the Sun. Pluto’s elliptical orbit carries it as close as 30 AU from the Sun, and as far as 50 AU. The inner edge of the Oort Cloud, however, is thought to be between 2,000 and 5,000 AU from the Sun. The outer edge might be 10,000 or even 100,000 AU from the Sun — that's one-quarter to halfway between the Sun and the nearest neighbouring star. Though lonThough long-period comets observed among the planets are thought to originate in the Oort Cloud, no object has been observed in the distant Oort Cloud itself, leaving it a theoretical concept for the time being. But it remains the most widely-accepted explanation for the origin of long-period comets. The Oort Cloud is lies far beyond Pluto and the most distant edges of the Kuiper Belt. While the planets of our solar system orbit in a flat plane, the Oort Cloud is believed to be a giant spherical shell surrounding the Sun, planets, and Kuiper Belt Objects. Objects in the Oort Cloud are also referred to as Trans-Neptunian objects. This name also applies to objects in the Kuiper Belt. Some astronomers theorise that the Sun may have captured Oort Cloud cometary material from the outer disks of other stars that were forming in the same nebula as our star. The Oort Cloud is a reserve of cometary nuclei that contain ices dating back to the origin of the solar system. This cloud of particles is theorized to be the remains of the disc of material that formed the Sun and planets. Astronomers now refer to those primeval objects as a protoplanetary disk. The most likely theory is that the material now in the Oort Cloud probably formed closer to the young Sun in the earliest epochs of solar system formation. As the planets grew, and in particular as Jupiter coalesced and migrated to its present position, its gravitational influence is thought to have scattered many icy objects out to their present position in the Oort cloud. The inner limits of the Oort Cloud begin at about 2,000 AU from the Sun. The cloud itself stretches out almost a quarter of the way to the nearest star, Proxima Centauri. It is spherically shaped and consists of an outer cloud and a torus (doughnut-shaped) inner cloud.

Discuss its properties and effects?

1. Mass of the Oort cloud of comets is less than 1 mass of the Earth (ME), probably not greater than 1/2 ME. 
2. Theoretical number of long-period comets with perihelion distance q < 5 AU is about 50-times greater than the conventional approach yields. Gravity of Jupiter was taken into account in finding this result. 
3. Semi-major axis a and period of oscillations P of eccentricity (and other orbital elements) are related as a3 P = 1 in natural units for a moving Solar System in the Galaxy. The natural unit for time is the orbital period of the Solar System revolution around the galactic center and the natural unit for measuring the semi-major axis is its maximum value for the half-radius of the Solar System corresponding to the half-radius of the Oort cloud. The relation holds for the cases when comets approach the inner part of the Solar System, e.g., perihelion distances are less than ≈ 100 AU. 
4. The magnitude of the change in perihelion distance per orbit, Δq, of a comet due to galactic tides is a strong function of semi-major axis a, proportional to a8.25.
5. Their alignments with the plane of the planet orbits is also different. The long period comet orbits are oriented in all different random angles while the short period comets orbits are within about 30 degrees of the solar system plane 

Kuiper Belt and Oort Cloud objects can exert gravitational effects on the planets, but the real question is whether such perturbations are detectable. Based on the observation that long-period comets can appear in any part of the sky, we generally think that the Oort Cloud of comets is a near-spherical structure surrounding the solar system at a distance of about 20,000 to 100,000 astronomical units from the star. The orbital characteristics point to two regions beyond the realm of the planets, Oort Cloud and the Kuiper Belt.