Talk:Oort cloud

Contents

1 Diagram. 2 Milky way/solar system. 3 Sedna. 4 Oort cloud formation 5 Elliptical orbits? 6 Inner cloud disc. 7 Comets.

Diagram.

Milky way/solar system.

"In 1932 Ernst Öpik, an Estonian astronomer, proposed that comets originate in an orbiting cloud situated at the outermost edge of the Milky Way."

Shouldn't that be "solar system?"

Fixed.

Sedna.

I brought this over from the Kuiper belt table, since it's actually a member of the Oort cloud:

Sedna (2003 VB16)

<1800, >1250

~67

2004

Mike Brown, Chad Trujillo, David Rabinowitz

thermal

A member, I should note, of the exciting new just-discovered inner Oort cloud. :) More details here: [1] (http://www.gps.caltech.edu/~mbrown/sedna/) but I don't have time to work them into the article right now. I'll do it in about six hours if nobody beats me to it. Bryan 01:33, 15 Mar 2004 (UTC)

EDIT Great job Brian-- I updated the table to reflect the discovery date of 2003, not 2004 (since it was only announced in 2004). I forgot to put a summary though for my edit, which is why I'm commenting here.

--Celerityfm 20:10, 15 Mar 2004 (UTC)

Oort cloud formation

"The most widely-accepted theory of its formation is that the Oort cloud's objects initially formed much closer to the Sun as part of the same process that formed the planets and asteroids, but that gravitational interaction with young gas giants such as Jupiter ejected them into extremely long parabolic orbits. This process also served to scatter the objects out of the ecliptic plane, explaining the cloud's spherical distribution. While on the distant outer regions of these orbits, gravitational interaction with nearby stars further modified their orbits to make them more circular."

I think something is being confused here. Is this perhaps talking about the inner oort cloud? Do you have a link? Anthony DiPierro 14:33, 17 Mar 2004 (UTC)

"This has been proposed as possible evidence that the Sun initially formed as part of a dense cluster of stars; with closer neighbors during Oort cloud formation, objects ejected by gas giants would have their orbits circularized closer to the Sun than was predicted for situations with more distant neighbors."

I'm going to add this part back, but a cite would still be nice. Anthony DiPierro 14:33, 17 Mar 2004 (UTC)

I first read it at http://www.gps.caltech.edu/~mbrown/sedna/ under the section "What is the Oort cloud and what is its relationship to Sedna?": "Early in the history of the solar system many many small icy bodies were orbiting the sun and getting sling-shot out by close encounters with planets. As they were travelling further and further from the sun, the orbits of these bodies were affected by distant stars, causing them to slow down and stay attached to the sun. Sedna probably suffered a similar fate, except the stars which affected it must have been much much closer than previously expected. We believe that this is evidence that the sun formed in a tight-knit group along with many other stars." Bryan 15:39, 17 Mar 2004 (UTC)

OK. This looks good as at least "a theory". I'll restore it as was and look into some other links. Thanks. Anthony DiPierro 15:55, 17 Mar 2004 (UTC)

I think that something is mildly wrong here. There is talk about the "inner Oort Cloud" being something that is "newly-discovered", and therefore we need new theories to explain it (as is cited in the article). However, I am positive that the inner Oort Cloud was theorized at least as early as 1996, if not earlier. It was clearly marked on this (http://zebu.uoregon.edu/~js/ast121/images/oort_cloud.gif) common graphic from 1996 or earlier (the copy on that server was last modified in 1996, and I haven't found any older copies). I also have read some papers that theorized that the Kuiper Belt was connected directly to the Oort Cloud, a theory that is very closely related the inner Oort Cloud. Ctachme 03:46, 8 Apr 2004 (UTC)

Elliptical orbits?

gravitational interaction with young gas giants such as Jupiter ejected them into extremely long elliptical or parabolic orbits... While on the distant outer regions of these orbits, gravitational interaction with nearby stars further modified their orbits to make them more circular.

The recent addition of "elliptical" orbits make me wonder. I think the term "nearly parabolic" might be better in this context, since no real orbit is exactly parabolic. But calling an orbit way far out an "ellipse" seems wrong since if it is that far out it is affected enough by nearby stars that it is really an n-body orbit that isn't even conic. Similarly, when objects are ejected in strongly hyperbolic orbits I'm guessing that the nearby stars can't stop it and it cruses on like voyager I and II. Of course, checking references would be the best approach, but I suspect that the word eliptical is inappropriate here. I suspect that applies to the inner oort cloud described later on also, but the case for "elliptical" may be a bit stronger there NealMcB 00:42, 2004 May 16 (UTC)

As the one who added elliptical, I think "nearly parabolic" is indeed probably better. That includes both highly elongated elliptical orbits (at least in terms of simplistic orbital element analysis, discounting the n-body caveat you mention) and not-very-extreme hyperbolic ones, both of which I imagine would be common for this process. Bryan 00:56, 16 May 2004 (UTC)

Inner cloud disc.

What does this mean? "The Oort cloud would have its inner disk at the ecliptic from the Kuiper belt." That sentence doesn't parse for me. How can a sphere have an "inner disk"? Also, does the Kuiper belt lie exactly in the ecliptic? Molinari 21:49, 29 Oct 2004 (UTC)

See this Southwest Research Institute image (http://spaceflightnow.com/news/n0308/08comets/oortcloud.jpg). — Jeandré, 2004-10-30t20:12z

Comets.

Oort Clouds are mainly 'clouds' that 'spit out' comets into space, as comets are actually (dirty) snowballs, and the Oort cloud is an area that has a very low temperature. I am amazed by this 'formation'! -- An 11 year-old named Tan Shao Yun of Singapore.

Oort Clouds have funny names, like 90377 Sedna and something else. I wish to bring up a special question: If the Oort Cloud sends a comet crashing onto Halley's comet, would that affect research? And also: If the Oort Cloud sends out too many comets, won't the Solar system be chaotic? -- Asked by Tan Shao Jie, Brother of Tan Shao Yun.

First off, the Oort Cloud has no volition, so the anthropomorphisation above is a bit much. Random gravitational disturbances, typically due to passing nearby stars (and hence occurring millions of years apart), are what trigger the occasional comet to zip by the inner solar system. As for two comets hitting each other, the odds of that ever happening are very, very small, because comets are so small and space so big. Astronomers would love to observe such an event, however!

Urhixidur 11:49, 2005 May 19 (UTC)