The Oort Cloud – where comets come from!

The solar system extends beyond the outermost planet, Pluto. Far from the planets, there’s thought to be a spherical shell of icy comets. Where did the Oort Cloud originate?

The Oort Cloud is thought to be the source of “long-period” comets — those needing more than two centuries to orbit the sun once. Some comets need more than a million years to orbit the sun! In 1950, Jan Oort of the Netherlands was trying to explain where these sorts of comets come from. Were they part of our solar system? Did they arrive from deep space?

Oort proposed that long-period comets are part of the solar system. He suggested they originate in a sort of “comet cloud” — a great sphere of icy bodies — surrounding our sun. No one has ever seen the Oort cloud. But astronomers consider it the best explanation so far for the source of long-period comets. So Rowena wants to know where the Oort Cloud came from. It’s thought to be a by-product of the process of planet formation . . .

That is, the planets are thought to have formed in a process whereby chunks of debris — in orbit around our sun — clumped together. Uranus, Neptune and Saturn formed in a region of icy debris. Their gravity might have slung smaller pieces in all directions. Some of this far-flung debris might ultimately have settled into orbits far from the sun — to become future comets in the Oort Cloud.

Additional Resources:

  1. John A. Wood, “Chapter 2 – Origin of the Solar System,” in J. Kelly Beatty, Carolyn Collins Petersen, and Andrew Chaikin, editors, The New Solar System, fourth edition, 1999, pp. 13-22.
  2. Paul R. Weissman, “Chapter 5 – Cometary Reservoirs,” in J. Kelly Beatty, Carolyn Collins Petersen, and Andrew Chaikin, editors, The New Solar System, fourth edition, 1999, pp. 59-68.
  3. John C. Brandt, “Chapter 24 – Comets,” in J. Kelly Beatty, Carolyn Collins Petersen, and Andrew Chaikin, editors, The New Solar System, fourth edition, 1999, pp. 321-335.
  4. “Oort Cloud” from James Schombert’s webpage at the University of Oregon
  5. “The Kuiper Belt and the Oort Cloud” from The Nine Planets
  6. Kuiper Belt Home Page (Institute for Astronomy, University of Hawaii)
  7. Oort Cloud Formation Simulations (Dept. of Space Studies, Southwest Research Center)
  8. The Bruce Medalists: Jan Oort (Sonoma State University)
  9. Jan Oort, Astronomer (Leiden University)

What you have in your mind?