What is Oort cloud: Definition and 26 Discussions

The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 au (0.03 to 3.2 light-years). It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud.
The outer limit of the Oort cloud defines the cosmographic boundary of the Solar System and the extent of the Sun's Hill sphere. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way itself. These forces occasionally dislodge comets from their orbits within the cloud and send them toward the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some short-period comets may have originated from the Oort cloud.Astronomers conjecture that the matter composing the Oort cloud formed closer to the Sun and was scattered far into space by the gravitational effects of the giant planets early in the Solar System's evolution. Although no confirmed direct observations of the Oort cloud have been made, it may be the source that replenishes most long-period and Halley-type comets entering the inner Solar System, and many of the centaurs and Jupiter-family comets as well.

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  1. sophiecentaur

    I Oort Cloud and Kuiper Belt: differences

    When I read about formation of solar systems it seems reasonable to me that most of the material would end up lying in a plane because the number of collisions and interactions would be least and the most stable situation in a common orbital plane in the long run. (Is this a far too simplistic...
  2. H

    I Oort Cloud Dynamics: Interaction, Composition, Hazards

    1. Assuming the Oort Cloud of the Solar System stretches 'almost' to our nearest Star neighbour, how would it interact with that Star's 'Oort Cloud'? I imagine objects constantly colliding between the two systems perhaps causing them to leave the cloud. 2. Does the Oort cloud form a ring of...
  3. J

    I Why hasn't the Oort cloud converged to a disk shape?

    The Oort cloud is often drawn as a sphere. Everything in it orbits the sun in circles or ellipses. Since the shape is not a disk, collisions are expected. Why hasn't the Oort cloud converged to the more stable, collision-free, disk shape?
  4. I

    I Energy of an Oort Cloud object

    I read that the the energy of an Oort cloud object is approximately zero, as in the potential energy plus the kinetic energy is equal to zero. I was also told that the radius was approximately infinite and the velocity is approximately zero. I understand why the radius is said to be infinite...
  5. jim mcnamara

    B Sholz's star entered the Oort cloud ~70kya

    https://phys.org/news/2018-03-evidence-star-disturbed-prehistory-solar.html https://academic.oup.com/mnrasl/article-abstract/476/1/L1/4840245?redirectedFrom=fulltext (abstract) R. de la Fuentes, S. J Aarseth Based on an earlier paper (E. Mamajek 2015) that indicated Sholz's star passed very...
  6. C

    B How Can Astronomy Even Occur? (Oort Cloud)

    I watched a show on TV about the Oort cloud, that featured a visual. I think it mentioned something like several trillions with a t objects surrounding the Sun outside the solar system. And the image showed just that, a cloud so dense and thick you couldn't see the sun. Combine that with all the...
  7. R

    I Exploring the Possibility of the Oort Cloud

    I know this has been suggested because of long period comets. Sort of a spherical asteroid belt at the very edge of where the Sun's gravity has any relevance. The inner asteroid belt, and the Kuiper belt though have many examples of objects which are proof that they exist. Is the Oort cloud any...
  8. B

    Could Planet 9 have caused the gap between the heliopause and the Oort cloud?

    The proposed orbit of Planet Nine looks like it falls in a gap between the heliopause and the Oort cloud; could planet Nine have caused the gap? Would Planet Nine get most of it's energy (electro-magnetic) from extra solar sources, since it is outside the heliopause?
  9. GiantSheeps

    Why isn't the Oort Cloud shaped like a disk?

    Why isn't the Oort Cloud shaped like a disk like the asteroid belts and how the planets orbit? Also, why exactly do the planets orbit in that flat disk shape?
  10. jim mcnamara

    Scholz's star passed through the Oort cloud

    Eric E. Mamajek, Scott A. Barenfeld, Valentin D. Ivanov, Alexei Y. Kniazev, Petri Väisänen, Yuri Beletsky, Henri M. J. Boffin. THE CLOSEST KNOWN FLYBY OF A STAR TO THE SOLAR SYSTEM. The Astrophysical Journal, 2015; 800 (1): L17 DOI: 10.1088/2041-8205/800/1/L17 The Science Daily article...
  11. S

    Could a universal Oort cloud structure cause expansive acceleration?

    Could a universal "Oort cloud" structure cause expansive acceleration? Could there be a giant sphere of invisible non-reactive matter (neutrinos?), left over from the big bang, so massive that it's gravity is pulling galaxies outward? I know the Oort cloud doesn't pull planets outward, but...
  12. J

    Oort Cloud Dynamics: Speculations on Origins in a Sci-Fi Novel

    In writing a science fiction novel, I set it against a backdrop of the Oort cloud and, as part of the plot, I needed to speculate on its origins. Recognising my limitations, I would like some expert feedback on my ideas. The first idea I use in my book is that Centaury A & B both developed...
  13. C

    How far away is the Oort Cloud?

    How far away is the Oort comet cloud? 1000 AU or 10,000 AU? c=10^10 cm/sec. for 10^8 sec/yr., gives 10^18 cm/lyr. Approximately then, is 1000 AU ~ .01 lyr? And 10,000 AU ~ .1 lyr? Would this be large enough to contain a multi-stellar system, since stars form in multiple? Hence a common Oort...
  14. M

    How do collisions affect the evolution of objects in the Oort cloud?

    How frequent are collisions in the ooort cloud? Are there any good reference in the literature about this topic?
  15. Loren Booda

    When will we be able to image the Oort cloud?

    I find interesting a significant nearby astronomical object whose existence is only inferred.
  16. R

    Comet Evaporation in Oort Cloud

    Interesting question to think about. We know that there are lots of comet bodies in the Oort cloud and we know that even in the near absolute zero temperatures evaporation does take place. Comets are usually covered in dust, which slows down this evaporation, but let's consider clear body...
  17. Loren Booda

    Oort cloud bodies and prevalence

    What is the largest astronomical body in the Oort cloud? Do such clouds exist for most solar systems?
  18. C

    Is Voyager 1 Approaching the Oort Cloud?

    Voyager 1 launched in 1977 is ~10^10 miles out, near heliopause. Continuing at it's current velocity (3x 10^8 mph), for 3300 yrs (100x current 33 yrs), then it will be out ~10^-2 lyrs; that is approaching Oort Cloud outer gravitation limits of our stellar system...
  19. J

    Newtonian mechanics & Oort Cloud Shell

    Last week there was a documentary program on Nat Geo I believe having to do with the composition and origins of comets. The narrative seemed to imply that comets originate within & are rather randomly dislodged from a spherical shell around the Solar System called the Oort cloud. This...
  20. S

    Jupiter-sized Planet Lurking in Oort Cloud?

    Lately I've read some articles about the possibility of a Jupiter-sized planet hidden in the Oort cloud. This assertion is based on analysis of cometary deflections and observations of Sedna. What is the likelihood of this? We all know that there must be lots of planet-sized stuff out...
  21. G

    Exploring Beyond the Oort Cloud: Resonance Orbits at 80 AU & 100,000 AU

    The Titus-Bode law (and Dermott's Law) hypothesizes resonances in certain orbits. In general, in our solar system, each planet is roughly twice as far out as the previous planet. This also seems to hold true for moons around their parent planets. 5.2 AU - Jupiter 9.5 AU - Saturn 19.2 AU...
  22. A

    Another Neptune in the Oort Cloud

    Dr Steinn Sigurðsson (Penn State) has been reporting findings announced at the Confererence on Extreme Solar Systems on his blog http://scienceblogs.com/catdynamics/2007/06/extreme_solar_systems_v_the_sa.php but amongst all the interesting discoveries is this idea raised by planetary dynamicist...
  23. C

    Oort Cloud Treat to Interstellar Space Travel

    A few quotes from various sources suggest there is quite a bit of material in the Oort Cloud, maybe enough to threaten interstellar space travel: “The Oort cloud is an immense spherical cloud surrounding the planetary system and extending approximately 3 light years, about 30 trillion...
  24. E

    Interstellar propulsion island hopping the Oort cloud

    Ahad's virtual bridge might have to charge a toll fee: http://www.astroscience.org/abdul-ahad/firstarktoalphacentauri/interstellar-propulsion.htm :!)
  25. wolram

    Oort Cloud: Confirmed or Hypothetical?

    can anyone tell me if the existence of the Oort Cloud has been confirmed, or is it still hypothetical?
  26. O

    How do Oort Cloud objects become short-period comets?

    Something I've thought about before but never asked anybody...The existence of short-period comets is a problem if one believes the solar system is 4 billion years old, because obviously after that length of time all of the short-period comets would have disintegrated. So, we need a way of...