# Is there really a Planet 9 out there in the Kuiper Belt? **URL:** \ **Category:** Factual Questions\ **Created:** [January 29, 2021, 1:49pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771 "2021-01-29T13:49:54Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [January 29, 2021, 1:49pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/1 "2021-01-29T13:49:54Z")
Since this is a Science question, I put it in GQ, even though I expect that there may be differing opinions on this topic. I was watching an episode of _How the Universe Works_ and the very distinguished astronomers and physicists in the show seem to agree that there exists a planet, about 10 times the size of Earth, out in the Kuiper Belt. I may be leaving details out, but the premise seems to be that several objects in the Kuiper Belt have odd orbits that can only be explained by a massive object influencing them. Additionally, computer modeling of the creation of the Solar System, and the current orbits of the 8 known planets, only work with the existence of a 9th planet. Apparently, since the planet is estimated to have a very elliptical orbit, and at certain points is over 10 billion miles away from the sun (over 1,000 times the earth-sun distance), it is very difficult to locate. While I love the show, there are times that it is somewhat sensationalist, likely to attract more viewers. So, what is the opinion of our SDMB experts? ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [January 29, 2021, 1:55pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/2 "2021-01-29T13:55:50Z")
[![](https://img.youtube.com/vi/pe83T9hISoY/maxresdefault.jpg "Does Planet 9 Exist?") ](https://www.youtube.com/watch?v=pe83T9hISoY) ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [January 29, 2021, 2:01pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/3 "2021-01-29T14:01:38Z")
I was going to say “Astronomers aren’t putting their money on that yet”, but then I looked for a more qualified opinion and discovered that Phil Plait, my go to qualified opinion on astronomy, is in fact putting his (rhetorical) money on Planet 9. Still, in this 2019 post he isn’t saying that wouldn’t still be a gamble: [Does planet 9 exist?](https://www.syfy.com/syfywire/does-planet-9-exist) ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [January 29, 2021, 3:57pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/4 "2021-01-29T15:57:28Z")
If there is something there, can it be said to have cleared it’s area sufficiently to be a planet? ---
**Author:** ![pjd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pjd/32/3009_2.png) [@pjd](https://boards.straightdope.com/u/pjd)\ **Post date:** [January 29, 2021, 5:05pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/5 "2021-01-29T17:05:29Z")
You can help to find it ! > **[Zooniverse](https://www.zooniverse.org/projects/marckuchner/backyard-worlds-planet-9)** > > The Zooniverse is the world’s largest and most popular platform for people-powered research. ---
**Author:** ![Steve\_MB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steve_mb/32/5339_2.png) [@Steve\_MB](https://boards.straightdope.com/u/Steve_MB)\ **Post date:** [January 29, 2021, 5:12pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/6 "2021-01-29T17:12:14Z")
> [@Jackknifed\_Juggernaut](#): > > over 10 billion miles away from the sun (over 1,000 times the earth-sun distance) Er, you’re off an order of magnitude there. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [January 29, 2021, 7:55pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/7 "2021-01-29T19:55:51Z")
> **[Back In My Day We Had Nine Planets T-Shirt | SnorgTees](https://www.snorgtees.com/back-in-my-day-we-had-nine-planets)** > > Back In My Day We Had Nine Planets T-Shirt by SnorgTees. Men's and women's sizes available. Check out our full catalog for tons of funny t-shirts. ---
**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\ **Post date:** [January 29, 2021, 8:10pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/8 "2021-01-29T20:10:21Z")
There is a ninth planet. It’s called, “Pluto”. It even has a moon of its own, but those who callously gave Pluto the boot remain unmoved by that fact and the fact that it was a planet for 76 years. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 29, 2021, 8:21pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/9 "2021-01-29T20:21:05Z")
The real planets were the friends we made along the way ---
**Author:** ![Larry\_Borgia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/larry_borgia/32/156_2.png) [@Larry\_Borgia](https://boards.straightdope.com/u/Larry_Borgia)\ **Post date:** [January 29, 2021, 8:22pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/10 "2021-01-29T20:22:29Z")
There’s some speculation that planet nine is not a planet at all, but a black hole. > **[Is Planet Nine a black hole or a planet? Harvard scientists suggest a](https://astronomy.com/news/2020/07/is-planet-nine-a-black-hole-or-a-planet-harvard-scientists-suggest-a-way-to-find-out)** > > Scientists propose a method to determine, once and for all, if any planet-mass black holes are lurking in the outer solar system. ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [January 29, 2021, 8:28pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/11 "2021-01-29T20:28:53Z")
Indeed. Thanks. It’s clearly been many years since I passed the first two actuarial exams. ---
**Author:** ![Frodo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frodo/32/302_2.png) [@Frodo](https://boards.straightdope.com/u/Frodo)\ **Post date:** [January 29, 2021, 8:39pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/12 "2021-01-29T20:39:37Z")
Then Pluto is the 10th planet, the 5th planet is Ceres but those who callously gave Ceres the boot remain((ed) they are all dead by now) unmoved by the fact that it was a planet for 50 years. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [January 29, 2021, 8:47pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/13 "2021-01-29T20:47:28Z")
As you can see from Pluto’s quandary, it depends what you call a real planet. Is Ceres a planet? How big does it have to be? How circular/concentric does the orbit have to be? the article linked is not terribly clear what they mean by “aligned long axes” - I presume they mean the long axes are close to the same plane. That may be a very rare coincidence, but only if that’s the case for everything, not just for the few bodies selected. ---
**Author:** ![Two\_Many\_Cats2](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@Two\_Many\_Cats2](https://boards.straightdope.com/u/Two_Many_Cats2)\ **Post date:** [January 29, 2021, 8:50pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/14 "2021-01-29T20:50:16Z")
I don’t know about a Planet 9, but there definitely is a Plan 9. ---
**Author:** ![Frodo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frodo/32/302_2.png) [@Frodo](https://boards.straightdope.com/u/Frodo)\ **Post date:** [January 29, 2021, 8:50pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/15 "2021-01-29T20:50:33Z")
From where? ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [January 29, 2021, 8:50pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/16 "2021-01-29T20:50:43Z")
> [@Jasmine](#): > > There is a ninth planet. It’s called, “Pluto”. It even has a moon of its own… As far as Pluto being a planet because it has its own moon, meet [Ida](https://en.wikipedia.org/wiki/243_Ida): [![](https://upload.wikimedia.org/wikipedia/commons/8/89/243_ida_crop.jpg) ](https://upload.wikimedia.org/wikipedia/commons/8/89/243_ida_crop.jpg) Ida is less than 40 miles wide at its widest point, and I don’t think anyone would call it a “planet”. It very much looks like the sort of thing Han Solo would have to dodge out of the way of. But, see that smaller thing off to the right? That’s Ida’s moon, Dactyl. Turns out that asteroids with moons aren’t even all that uncommon–we’ve discovered [several hundred of them](https://en.wikipedia.org/wiki/Minor-planet_moon). ---
**Author:** ![Two\_Many\_Cats2](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@Two\_Many\_Cats2](https://boards.straightdope.com/u/Two_Many_Cats2)\ **Post date:** [January 29, 2021, 8:50pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/17 "2021-01-29T20:50:56Z")
Outer Space! ---
**Author:** ![Frodo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frodo/32/302_2.png) [@Frodo](https://boards.straightdope.com/u/Frodo)\ **Post date:** [January 29, 2021, 8:51pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/18 "2021-01-29T20:51:38Z")
Horrifying revelation! ---
**Author:** ![Two\_Many\_Cats2](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@Two\_Many\_Cats2](https://boards.straightdope.com/u/Two_Many_Cats2)\ **Post date:** [January 29, 2021, 8:52pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/19 "2021-01-29T20:52:24Z")
From sworn testimony! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 29, 2021, 9:12pm UTC](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771/20 "2021-01-29T21:12:45Z")
Yet another reason why I support classing objects as rockballs, gasballs, and iceballs, rather than lumping all three into one “planet” category. Mercury, Venus, Earth, Luna, Mars, and Ceres are all rockballs. Jupiter, Saturn, Uranus, and Neptune are all gasballs. Pluto is one of the largest iceballs (not the largest; Eros at least is larger, and probably several others as well that we haven’t discovered yet), but there are many, many other iceballs. [Next page](https://boards.straightdope.com/t/is-there-really-a-planet-9-out-there-in-the-kuiper-belt/931771.md?page=2)