Oort Cloud

In 1950, Dutch astronomer Jan Oort (building on an idea originated by Ernst Opik) proposed that a hypothetical and massive cloud of comets that orbit far from the center of our solar system might explain why comets don’t seem to originate from deep space and often have an outer orbital edge about 20-50,000 AUs from the Sun.

Solar System orbit scale in Astronomical Units (AUs):
Sun 0
Earth 1
Mars 1.5
Asteroid belt 2.3 – 3.3
Jupiter 5
Neptune 30
Kuiper belt 30 – 55
Oort cloud 2,000 – 50,000

Note that the existence of the Oort Cloud is still a working hypothesis that is not generally considered to have been observationally confirmed yet.

The Oort Cloud – [solarviews.com]

The Oort cloud is an immense spherical cloud surrounding the planetary system and extending approximately 3 light years, about 30 trillion kilometers from the Sun. This vast distance is considered the edge of the Sun’s orb of physical, gravitational, or dynamical influence.

Within the cloud, comets are typically tens of millions of kilometers apart. They are weakly bound to the sun, and passing stars and other forces can readily change their orbits, sending them into the inner solar system or out to interstellar space. This is especially true of comets on the outer edges of the Oort cloud. The structure of the cloud is believed to consist of a relatively dense core that lies near the ecliptic plane and gradually replenishes the outer boundaries, creating a steady state. One sixth of an estimated six trillion icy objects or comets are in the outer region with the remainder in the relatively dense core.

SEE ALSO:
Asteroid Belt
Kuiper Belt

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