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Astronomy: The Oort Cloud
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The Oort Cloud is an immense spherical cloud surrounding our planetary system and extending approximately 3 light years, about 28 trillion km from the Sun, and about 100.000 times the distance between Earth and the Sun (100.000AU). This vast distance is considered the edge of the Sun's gravitational influence. The nearest star is 4,22 light years from the Sun and outside this range. Dutch astronomer Jan Oort studied where comets came from in 1950. He observed that comets seemed to come equally from all directions. Later this observation was corrected. By their paths, he found that comets should originate in a region 20.000 to 100.000AU. We have no observational data from the region to prove the Oort Cloud is real. But the idea raises many questions. 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. Planet X of NemesisDr John Murray recently went back through records of the paths of long period comets. He noticed that Jan Oort was wrong: comets don't come from all areas of the Oort Cloud equally.There is a region about 30,000 to 50,000AU away which produces more than its fair share of comets. He speculated that a Planet X might cause this, moving through The Oort Cloud about 40,000AU away scattering other Oort Cloud objects in all directions. Dr Murray thinks the planet should be 1 to 10 times the mass of Jupiter. However Dr John Matese came to the Planet X conclusion independently, and thinks the planet should be bigger - about the size of a brown dwarf (more than 10 times Jupiter's mass). If this is the case it raises interesting questions, including how did it get there? It is much too far out to have been formed the way the other planets were. The Nemesis theory was suggested to explain why comets get sent in toward the Sun. Most stars are part of a binary system, but is our Sun as well? Every 20 or 30 million years or so, mass extinctions seem to occur on Earth. Suppose the binary companion of the Sun is very faint and on a highly elliptical orbit, passing through The Oort Cloud every 20 million years, diverting comets into the inner Solar System, causing meteor bombardments on Earth and making species become extinct. This theory isn't widely accepted and highly speculative. At this time we know very little about the Oort Cloud. Related subjects>> Edgeworth-Kuiper Belt>> Comets >> Meteors >> Pluto >> Milky Way Galaxy |
 The Oort Cloud stretching over a vast distance, much wider than Pluto's orbit around the Sun. < JPG image 800 X 687 pixels > |
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