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Answer: The Oort Cloud is a theorized giant spherical shell of icy objects surrounding the Sun, planets and Kuiper Belt. It is so far away that NASA has no direct images of it; its existence is inferred mainly from long-period comets.

The idea

In 1950, astronomer Jan Oort proposed that some comets come from a vast, distant spherical shell of icy bodies. Scientists picture it as a thick bubble around the solar system.

How far

It is the most distant region of our solar system, perhaps one-quarter to halfway from the Sun to the next star. For scale, Pluto orbits roughly 30 to 50 astronomical units (AU) from the Sun, while the Oort Cloud's inner edge is thought to be far beyond that. Voyager 1, moving about a million miles a day, will not enter it for about 300 years.

Why it matters

• It is a reservoir of long-period comets.
• Objects there are thought to be leftovers from the solar system's formation.

Limits of knowledge

Because nothing has been directly imaged, sizes and edges are estimates from models and comet orbits.

Claims

• id: C1 claim: Scientists think the Oort Cloud is a giant spherical shell surrounding the solar system. source: S1 evidence: "Scientists think the Oort Cloud is a giant spherical shell surrounding our solar system."
• id: C2 claim: NASA has no direct images of the Oort Cloud. source: S1 evidence: "Because it is so far away, NASA doesn't have direct images of the Oort Cloud."
• id: C3 claim: Jan Oort proposed the shell in 1950. source: S2 evidence: "In 1950, astronomer Jan Oort proposed that some comets come from a vast, extremely distant"
• id: C4 claim: It is the most distant region in our solar system. source: S2 evidence: "The Oort Cloud is the most distant region in our solar system"

Sources

• [S1] Oort Cloud. NASA. https://science.nasa.gov/solar-system/oort-cloud/ . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Oort Cloud: Facts. NASA. https://science.nasa.gov/solar-system/oort-cloud/facts/ . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_rj382058,
  author = {{iinventedlight}},
  title = {{The Oort Cloud: a distant shell of icy bodies}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/oort-cloud/},
  note = {Permanent ID iil:note:rj382058. License: CC-BY-4.0.},
}

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