I did read several of the Oort Cloud questions/answers which I found very helpful and instructive, but this question still persists for me:

Is the Oort Cloud actually opaque, or is the "cloud" used euphemistically because minor planets inside of it are too dim to be seen?

  • 3
    $\begingroup$ You can see stars and galaxies through it, so it's not opaque. Not a euphemism, cloud is being used as in "a large number of things (such as insects) that move together through the air in a group" merriam-webster.com/dictionary/cloud $\endgroup$ Apr 1 '15 at 17:26
  • $\begingroup$ Excellent answer. You should upgrade it to one. $\endgroup$
    – pela
    Apr 1 '15 at 19:22
  • 1
    $\begingroup$ @WayfaringStranger: Except that it doesn't move "through the air". (Not all dictionary definitions are perfect.) $\endgroup$ Apr 1 '15 at 21:40
  • $\begingroup$ Luminiferous aether, air, tomato, tomahto. ;-) $\endgroup$ Apr 1 '15 at 22:11
  • $\begingroup$ Both answers are very helpful, (above and @rob jefries) expands my understanding much more! $\endgroup$
    – AOC
    Apr 2 '15 at 10:15

Well, given that we can see the stars and that the Oort "cloud" is closer than the nearest star, then the answer to your main question is obviously that the "cloud" is not opaque.

I think it is called a cloud because it consists of many individual, small "particles" that don't interact with each other. Also, the term cloud avoids giving the impression that the Oort objects are arranged in any disk-like configuration - they should be much more spherically symmetric. The word cloud also avoids giving the impression that the objects fall between two relatively tight orbital radius limits. i.e. The Oort cloud is not like the Kuiper belt.


"Cloud" distinguishes the Oort Cloud as a 3-dimensional sphere of objects and not a disk like the orbital plane of the planets.

  • 1
    $\begingroup$ This is kinda what Rob said in the last paragraph of his answer. $\endgroup$
    – HDE 226868
    Apr 2 '15 at 1:05

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