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Fiery Phoenix
2016-Jan-20, 05:04 PM
This has been all over the news this morning. As of right now, the discovery remains indirect, but all signs point to it being a strong evidence. Here's Caltech's news release:


Caltech researchers have found evidence of a giant planet tracing a bizarre, highly elongated orbit in the outer solar system. The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of Earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average distance of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun.

...

Brown notes that the putative ninth planet—at 5,000 times the mass of Pluto—is sufficiently large that there should be no debate about whether it is a true planet. Unlike the class of smaller objects now known as dwarf planets, Planet Nine gravitationally dominates its neighborhood of the solar system. In fact, it dominates a region larger than any of the other known planets—a fact that Brown says makes it "the most planet-y of the planets in the whole solar system."

Also:


And indeed Planet Nine's existence helps explain more than just the alignment of the distant Kuiper Belt objects. It also provides an explanation for the mysterious orbits that two of them trace. The first of those objects, dubbed Sedna, was discovered by Brown in 2003. Unlike standard-variety Kuiper Belt objects, which get gravitationally "kicked out" by Neptune and then return back to it, Sedna never gets very close to Neptune. A second object like Sedna, known as 2012 VP113, was announced by Trujillo and Shepherd in 2014. Batygin and Brown found that the presence of Planet Nine in its proposed orbit naturally produces Sedna-like objects by taking a standard Kuiper Belt object and slowly pulling it away into an orbit less connected to Neptune.

Much more at the link here:

http://www.caltech.edu/news/caltech-researchers-find-evidence-real-ninth-planet-49523

For those of you wanting to read the original paper (which is as of yet unpublished as I understand), it can be found here:

http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22

So...! ;)

jokergirl
2016-Jan-20, 05:43 PM
I guess the Nibiru people are going wild. :lol:

Fiery Phoenix
2016-Jan-20, 06:04 PM
According to my calculations based on the article, the orbital distance is between 464 and 736 AU, which translates into an average of 600 AU.

Centaur
2016-Jan-20, 06:40 PM
The word planet comes from the pre-telescopic ancient Greek term "astēr planētēs" meaning "wandering star" which referred to the bright points of light in the sky which appeared to move relative to most of the others. Since this conjectured object cannot be seen by naked eyes, then by the original sense of the term it is not a planet. Of course, neither is the Earth. ;)

Swift
2016-Jan-20, 08:11 PM
I think some of the media coverage of this is starting to over-reach. For example, this from Laboratory Equipment magazine (http://www.laboratoryequipment.com/news/2016/01/planet-nine-outer-orbit-identified-caltech-researchers?et_cid=5066621&et_rid=54636800&type=image&et_cid=5066621&et_rid=54636800&linkid=http%3a%2f%2fwww.laboratoryequipment.com%2f news%2f2016%2f01%2fplanet-nine-outer-orbit-identified-caltech-researchers%3fet_cid%3d5066621%26et_rid%3d%%subscr iberid%%%26type%3dimage):


A far-off ninth planet, still unseen, has been identified by Caltech researchers.
To me, until it is actually seen and observed enough to confirm an orbit, it has not been identified. The abstract of the actual paper, which is at the second link Fiery Phoenix gave, makes it clear that the authors are proposing this as a hypothesis, and are not claiming either its identification or discovery.

I am not belittling the actual work. If shown to be true, this will be a terrific discovery. We just shouldn't put the sky chariot too far in front of the horses.

Fiery Phoenix
2016-Jan-20, 08:25 PM
To me, until it is actually seen and observed enough to confirm an orbit, it has not been identified. The abstract of the actual paper, which is at the second link Fiery Phoenix gave, makes it clear that the authors are proposing this as a hypothesis, and are not claiming either its identification or discovery.

I am not belittling the actual work. If shown to be true, this will be a terrific discovery. We just shouldn't put the sky chariot too far in front of the horses.
I agree. I imagine the paper will lead many other astronomers around the globe to point their telescopes to that direction, giving way to a possible confirmation. Apparently the planet is 'just small enough' for survey observatories like WISE to miss it.

Until then, I remain cautiously excited. (P.S. It appears there's already a Wiki entry (https://en.wikipedia.org/wiki/Planet_Nine) on this planet.)

Swift
2016-Jan-20, 08:41 PM
And just to add to my previous post, this headline from R&D magazine (http://www.rdmag.com/news/2016/01/pluto-killer-announces-evidence-ninth-planet?et_cid=5066817&et_rid=54636800&location=top&et_cid=5066817&et_rid=54636800&linkid=http%3a%2f%2fwww.rdmag.com%2fnews%2f2016%2f 01%2fpluto-killer-announces-evidence-ninth-planet%3fet_cid%3d5066817%26et_rid%3d%%subscriberi d%%%26location%3dtop) is just stupid:

Pluto Killer Announces Evidence of Ninth Planet

In 2006 Pluto took a hard hit. Not literally, but figuratively. That year, the International Astronomical Union came up with a new definition of the word “planet.” The move demoted Pluto to a “dwarf planet.”

Prof. Mike Brown, of the California Institute of Technology, was the man behind the research that led to the decision. And now he’s one of the men behind the announcement that a new ninth planet may be lurking beyond Neptune.

"Pluto Killer"? Really? Are the editors of R&D magazine planning to hold their breath until Pluto is made a planet again. :rolleyes:

Don Alexander
2016-Jan-20, 08:53 PM
Swift, Mike Brown's Twitter handle is @plutokiller...

https://twitter.com/plutokiller?lang=en

Anyway, I propose to name this planet, if it turns out to be real "Yuggoth on the Rim"!!

PetersCreek
2016-Jan-20, 08:55 PM
...and let the pun games begin: Planet 9 From Outer Space

Drummer62
2016-Jan-20, 09:10 PM
Fascinating discovery, provided it's confirmed.

What puzzles me is how this object (and at 10 times Earth mass it's not exactly very small) could have been missed so far?
I don't understand much about the organization and mechanics of astronomical observations and would be grateful if a professional could shed some light on this.

jokergirl
2016-Jan-20, 09:13 PM
Would it be possible to calculate the approximate orbital position from the perturbances and turn a telescope that way? Even so, it'd be hard to spot, I bet, and the math seems seriously complicated, but still?

Fiery Phoenix
2016-Jan-20, 09:17 PM
Would it be possible to calculate the approximate orbital position from the perturbances and turn a telescope that way? Even so, it'd be hard to spot, I bet, and the math seems seriously complicated, but still?
They seem to have a general target direction/orbital zone, but nothing exact. See here:

http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system

Don Alexander
2016-Jan-20, 09:22 PM
Let me try an analogy.

You're standing outside, looking toward a wall. You detect several splotches on the wall, which are quite grouped. You come to the conclusion: "Seems likely there is a paintball player behind me, aiming at the wall."

But it might not be a paintball player at all, the grouping could be by chance (reasonably unlikely, but hardly impossible), or perhaps caused by some other effect. The paintball explanation fits the data, yes, but it's hardly rock solid.

And in terms of the location of the paintball player? Well, "somewhere behind you." Oh, and he's TINY. And looks like a leaf. In front of an entire forest.

I haven't seen any values for rough observable magnitudes so far. My verrrry rough shot-in-the-dark guesstimate would be ~25 mag in the optical. Perhaps even several fainter? At this distance, it would essentially be a point source, and while the technology exists to detect it, you have literally millions upon millions of other sources that will confuse you. At these depths, you get loads of tiny galaxies that are all also essentially point sources. the great distance of ~500 - 1000 AU implies that both orbital motion as well as parallax will be smaller than for any known Solar System object.

It looks like they will start looking with Subaru's HyperSuprimeCam, but even this grand magnifying glass hardly puts a dent into the haystack that's hiding your needle...

slang
2016-Jan-20, 09:29 PM
Fascinating discovery, provided it's confirmed.

What puzzles me is how this object (and at 10 times Earth mass it's not exactly very small) could have been missed so far?
I don't understand much about the organization and mechanics of astronomical observations and would be grateful if a professional could shed some light on this.

I seem to remember that in one of the gazillion Planet X topics a study was shown that put limits on what size of planet could still be undiscovered within some named orbital distance. Perhaps someone remembers better. This one would be 20 times further out than Neptune? Perhaps we should tell New Horizons to start looking in 190 years.

Fiery Phoenix
2016-Jan-20, 09:41 PM
It looks like they will start looking with Subaru's HyperSuprimeCam, but even this grand magnifying glass hardly puts a dent into the haystack that's hiding your needle...
I suspect this is part of the reason Mike Brown estimates ~5 years before a detection can occur. It's a tough task, but nothing we haven't done before.


I seem to remember that in one of the gazillion Planet X topics a study was shown that put limits on what size of planet could still be undiscovered within some named orbital distance. Perhaps someone remembers better. This one would be 20 times further out than Neptune? Perhaps we should tell New Horizons to start looking in 190 years.
You may be thinking of the 2013 study which concluded that planets the size of Neptune Saturn or larger cannot exist within 10,000 AU of the Sun (as per WISE's observations). Since this potential planet is below this threshold, the current thinking is that WISE simply missed it.

Don Alexander
2016-Jan-20, 09:47 PM
@Fiery Phoenix: It was planets the size of Saturn. Big difference.

Furthermore, WISE was an all-sky survey, it did not miss anything unless it was too faint for detection (which can be due to an object being extremely cold).

Fiery Phoenix
2016-Jan-20, 09:49 PM
Apologies. Yes, I meant to say Saturn-sized. Thanks, Don!

Don Alexander
2016-Jan-20, 09:59 PM
The whole "it might take 5 years" thing makes me wonder if LSST has a chance. Not sure when that will have first light...

Fiery Phoenix
2016-Jan-20, 10:02 PM
The whole "it might take 5 years" thing makes me wonder if LSST has a chance. Not sure when that will have first light...
Well, apparently Brown and co. have already reserved telescope time with Subaru. That should hopefully suffice for the time being.

Drummer62
2016-Jan-20, 10:07 PM
Thanks, Don Alexander, for your analogy.
I understand that the object is tiny compared to its distance. I just thought (wrongly) that our observational capabilities were advanced enough to routinely catch objects of that size in our own solar system.

As far as "Planet X" or "Nibiru" is concerned I just read a wikipedia article (https://en.wikipedia.org/wiki/Nibiru_cataclysm) about it.
Let it be known that I don't believe in any doomsday conspiracies whatsoever (humans do a pretty good job of destroying our planet all by ourselves).

One of the arguments to reject the Nibiru myth was: "A planet such as Nibiru would create noticeable effects in the orbits of the outer planets." (from that wiki article, section "Scientific rejection").
That argument always made perfect sense to me. However, now not so much any more. Does not the discovery of "Planet 9" (if confirmed) falsify that argument? If we have missed this object, what else did we miss?

I am not trying to resurrect the Nibiru myth and I am not advocating any conspiracies associated with it. I am only interested in the validity of the original scientific rejection of Nibiru in the light of the new discovery (if confirmed).

ETA: According to Nancy Lieder (the somewhat disturbed original promoter of Nibiru) it was supposed to be "roughly four times the size of the Earth", significantly smaller than the proposed Planet 9.

Don Alexander
2016-Jan-20, 10:17 PM
I just thought (wrongly) that our observational capabilities were advanced enough to routinely catch objects of that size in our own solar system.
The problem here is aperature cost. Finding TNOs implies blind searches - even if you stay in the ecliptic, you have a complete band of sky to search. TNOs are almost always fainter than 20th magnitude. If you want to find any, you need to go wide, not deep, which implies quite dedicated telescopes, and such telescopes are small, and can't go deeper than 22nd, maybe 23rd magnitude. You are not going to get time at Big Glass with pencil-beam optics to just randomly stare somewhere multiple times in the hopes of finding something.

I am not trying to resurrect the Nibiru myth and I am not advocating any conspiracies associated with it. I am only interested in the validity of the original scientific rejection of Nibiru in the light of the new discovery (if confirmed).
P9, if real, lies in an orbit with even perihelion at ~200 AU. This is much further away than even Neptune/Pluto. A planet of P9's size would not measurably perturb the orbits of objects closer in than the Kuiper Belt.

efanton
2016-Jan-20, 10:49 PM
I wonder if the New Horizons mission would possibly be able to get a better view. Of course with such a huge orbit involved it would mean that a bit of luck would be required as both would have to be on the same side of the sun.

Drummer62
2016-Jan-20, 10:57 PM
The problem here is aperature cost. Finding TNOs implies blind searches - even if you stay in the ecliptic, you have a complete band of sky to search. TNOs are almost always fainter than 20th magnitude. If you want to find any, you need to go wide, not deep, which implies quite dedicated telescopes, and such telescopes are small, and can't go deeper than 22nd, maybe 23rd magnitude. You are not going to get time at Big Glass with pencil-beam optics to just randomly stare somewhere multiple times in the hopes of finding something.

P9, if real, lies in an orbit with even perihelion at ~200 AU. This is much further away than even Neptune/Pluto. A planet of P9's size would not measurably perturb the orbits of objects closer in than the Kuiper Belt.

Thanks again, Don Alexander, both explanations make sense to me.

Jens
2016-Jan-20, 10:58 PM
Also, I don't know if anyone is saying that an object with the orbital characteristics doesn't exist, but rather are saying that there is no evidence that it does, so therefore no reason to think it it exists anymore that an almost infinite number of other possible bodies. So it's really the claim that it exists that people dispute.

antoniseb
2016-Jan-20, 10:59 PM
I wonder if the New Horizons mission would possibly be able to get a better view. Of course with such a huge orbit involved it would mean that a bit of luck would be required as both would have to be on the same side of the sun.
New Horizons is about 40 AU out, and has a fairly small diameter camera. If this thing is 700 AU out, that 5% closer that NH might have won't help much.

Fiery Phoenix
2016-Jan-20, 11:07 PM
Yeah, New Horizons unfortunately doesn't have much chance here. We also don't know the orbital position of this potential planet.

efanton
2016-Jan-20, 11:11 PM
New Horizons is about 40 AU out, and has a fairly small diameter camera. If this thing is 700 AU out, that 5% closer that NH might have won't help much.

I tend to agree with you, but a terrestrial telescope has the atmosphere to deal with.

At those distances I would imagine it would have to have the albedo of a 100 watt bulb to see it with any telescope we currently have.

Fiery Phoenix
2016-Jan-20, 11:14 PM
I tend to agree with you, but a terrestrial telescope has the atmosphere to deal with.
Subaru is supposed to be able to detect it, assuming it is where/what we think it is. But it still won't be easy!

jokergirl
2016-Jan-20, 11:15 PM
They seem to have a general target direction/orbital zone, but nothing exact. See here:

http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system

Thanks. That's a fairly big chunk of the proposed orbit still. Maybe they can narrow it down if they find more of those tell-tale perturbances. Which I suspect they now will be looking for, to either prove or disprove what we know so far.

Swift
2016-Jan-21, 12:41 AM
Calling it "Planet X" seems wrong to me. First, if I understand correctly, when the idea of a then 10th planet was suggested, Pluto was still the 9th, and X stood for 10 (Roman numeral) and X as in unknown. But it would be the ninth planet now, not 10, and the term "Planet X" is too connected with Nibiru and Nancy Lieder and all that nonsense.

Somewhere I've also seen it referred to as "Planet 9" and that works fine for me.

01101001
2016-Jan-21, 12:49 AM
Percival Lowell hunted for Planet X, and Clyde Tombaugh found it in Pluto. The X was unknown, not 10, historically.

efanton
2016-Jan-21, 01:14 AM
Subaru is supposed to be able to detect it, assuming it is where/what we think it is. But it still won't be easy!

From Wikipedia


Subaru Coronagraphic Extreme Adaptive Optics system

The Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO) is a high-contrast imaging system for directly imaging of exoplanets. The coronagraph uses a Phase Induced Amplitude Apodization (PIAA) design which means it will be able to image planets closer to their stars than conventional Lyot type coronagraph designs. For example, at a distance of 100 pc, the PIAA coronagraph on SCExAO would be able to image from 4 AU outwards while Gemini Planet Imager and VLT-SPHERE from 12 AU outwards.[14] The system also has several other types of coronagraph: Vortex, Four-Quadrant Phase Mask and 8-Octant Phase Mask versions, and a shaped pupil coronagraph.[15] The phase I of construction is complete[16] and phase II construction to be complete by end of 2014[17] for science operations in 2015. SCExAO will initially use the HiCIAO camera but this will be replaced by CHARIS,[18] an integral field spectrograph, around 2016.

https://en.wikipedia.org/wiki/Subaru_Telescope#Subaru_Coronagraphic_Extreme_Adap tive_Optics_system

I didnt realise the full capabilities of Subaru until I read the wiki.

not so much Subaru Impreza more Subaru seriously Impressive :surprised:

Fiery Phoenix
2016-Jan-21, 01:15 AM
Planet Nine is what Brown and co. are calling it right now. I'm okay with that until we get a confirmation of something.

DonM435
2016-Jan-21, 01:18 AM
How about Planet Nine From (Really) Outer Space in honor of Edward D. Wood Jr.?

Jens
2016-Jan-21, 02:49 AM
Or Love Planet Number Nine?

Or, somewhat cryptically:

Turn Me On, Dead Man?

Fiery Phoenix
2016-Jan-21, 03:09 AM
I do love the irony of the so-called Pluto Killer now championing the existence of a 9th planet a decade later. Here's a cute tweet he just posted:

https://twitter.com/plutokiller/status/689998851080634368

Jens
2016-Jan-21, 04:40 AM
How about they call it Pluto, and rename the current Pluto to be Plutonetto? :)

KaiYeves
2016-Jan-21, 05:16 AM
I'm cautiously optimistic.

slang
2016-Jan-21, 05:44 AM
How about Planet Nine From (Really) Outer Space in honor of Edward D. Wood Jr.?

ToPetered (http://cosmoquest.org/forum/showthread.php?159863-Caltech-Researchers-Find-Evidence-of-a-Real-Ninth-Planet&p=2337378#post2337378). :) Oh, and ToSeeked (https://twitter.com/plutokiller/status/689834557374267392) too.

parallaxicality
2016-Jan-21, 09:43 AM
Planet X was originally the ninth planet. It only became "Planet Ten" after Charon was discovered and we learned how small Pluto actually was.

Anyhoo....

Mike, Mike Mike, why? Why are you going all Tyche on us now? I love you man but this is too much. It's not like you're the first person to propose this planet; it's been talked about for three years. Do you really have to go to the press with a snazzy name and a welcome wagon? Can't we just wait until an actual confirmation? Or do you really want to be the next Percival Lowell?

Jetlack
2016-Jan-21, 10:17 AM
Is this suspected planet actually in our solar system or outside it? As in outside or inside the heliosphere?

parallaxicality
2016-Jan-21, 10:18 AM
The heliosphere has been somewhat overrated as the "edge of the Solar System". Even Eris, let alone Sedna, is outside the heliosphere.

Jetlack
2016-Jan-21, 12:21 PM
The heliosphere has been somewhat overrated as the "edge of the Solar System". Even Eris, let alone Sedna, is outside the heliosphere.

Okay. I´m wondering how close it ever comes to inner solar system if it takes 10k-20k years to orbit the sun. Could it have some major impact on earth at its closest pass?

profloater
2016-Jan-21, 12:32 PM
It's a long way to the next star, Proximus, so the legrange point must be in the order of half way there, I don't know how far that is away but this ninth planet is surely well inside that limit.?

antoniseb
2016-Jan-21, 12:57 PM
It's a long way to the next star, Proximus, so the legrange point must be in the order of half way there, I don't know how far that is away but this ninth planet is surely well inside that limit.?
The distance to Proxima Centauri is about 250,000 AU. This possible planet would be a few tenths of a percent that far from the Sun... so that's not an issue.

- Jetlack -- Okay. I´m wondering how close it ever comes to inner solar system if it takes 10k-20k years to orbit the sun. Could it have some major impact on earth at its closest pass?
Well, it might be that its orbit takes it inward to the outer edge of the Kuiper belt, which might slightly increase the number of comets we see ... or more likely, the orbit doesn't get that close, so it seems unlikely that Earth is affected.

Don Alexander
2016-Jan-21, 01:47 PM
Okay, here's an official page with some answers:

http://www.findplanetnine.com/p/blog-page.html

- at perihelion, even if it is at the purported 200 AU (way outside the Kuiper Belt Cliff), it would be roughly 18th mag an easily detectable. So it's very unlikely to be that close.

- factoring in different sky surveys, it is quite likely to be near aphelion, at roughly 23rd magnitude - quite a bit brighter than I had expected! - and in front of the Milky Way. >_>

Jetlack
2016-Jan-21, 03:08 PM
Thanks for the answers. Pretty cool thinking there could be something this huge sort of lurking way out there.

Fiery Phoenix
2016-Jan-21, 03:09 PM
Is this suspected planet actually in our solar system or outside it? As in outside or inside the heliosphere?
It's in the Solar System (which is why this news is such a big deal in the first place), just way, way out there.

Don Alexander
2016-Jan-21, 04:24 PM
Indeed.

Please note the difference between Heliosphere (the region where space is filled by the solar wind) and the Sun's Hill sphere (the gravitational influence of the Sun, extending out about one light year!).

Fiery Phoenix
2016-Jan-21, 06:29 PM
Phil has an article:

http://www.slate.com/blogs/bad_astronomy/2016/01/21/evidence_found_of_a_possible_planet_in_the_outer_s olar_system.html

LookingSkyward
2016-Jan-21, 06:55 PM
Phil was on the local (Seattle) radio station - KIRO - this morning with a nice description of the evidence.

efanton
2016-Jan-21, 07:37 PM
Phil has an article:

http://www.slate.com/blogs/bad_astronomy/2016/01/21/evidence_found_of_a_possible_planet_in_the_outer_s olar_system.html

Love the top comment


If found they should name it Nibiru just to screw with the conspiracy theorists.

:D

Concerned
2016-Jan-21, 09:06 PM
Interesting news, very cool if confirmed.

selvaarchi
2016-Jan-22, 01:38 AM
Okay, here's an official page with some answers:

http://www.findplanetnine.com/p/blog-page.html

- at perihelion, even if it is at the purported 200 AU (way outside the Kuiper Belt Cliff), it would be roughly 18th mag an easily detectable. So it's very unlikely to be that close.

- factoring in different sky surveys, it is quite likely to be near aphelion, at roughly 23rd magnitude - quite a bit brighter than I had expected! - and in front of the Milky Way. >_>

If we assume it is now at aphelion then it would have been at perihelion around 1360AD. Could we see 18th mag objects those days?

Jens
2016-Jan-22, 01:59 AM
If we assume it is now at aphelion then it would have been at perihelion around 1360AD. Could we see 18th mag objects those days?

Considering that telescopes weren't invented until the 1960s, absolutely not.

George
2016-Jan-22, 02:00 AM
Just learned of this plausible hypothesis and was surprised to see it on the front cover of Scientific American. The AoP (argument of perihelion) for four, I think, objects at time article was written an eye opener and worth discussion. [plane departing]

selvaarchi
2016-Jan-22, 02:27 AM
Considering that telescopes weren't invented until the 1960s, absolutely not.

1960s seriously!!!

KaiYeves
2016-Jan-22, 03:07 AM
Considering that telescopes weren't invented until the 1960s, absolutely not.

That will come as news to a certain Mr. Harriot and a certain Mr. Galilei.

speach
2016-Jan-22, 03:17 AM
Caltech announced on the 20th of Jan that they have 'solid theoretical evidence' of a ninth planet. If it is there, why is it the 9th planet? The IAU, in there rules for a planets stated:-
•It needs to be in orbit around the Sun – Yes, so maybe Pluto is a planet.
•It needs to have enough gravity to pull itself into a spherical shape – Pluto…check
•It needs to have “cleared the neighborhood” of its orbit – Uh oh. Here’s the rule breaker. According to this, Pluto is not a planet.
At the moment we don't know about the 3rd point. So shouldn't we be calling it a large Kuiper belt object? And maybe the 2nd point too.

tony873004
2016-Jan-22, 04:06 AM
Here's a simulation of the theorized planet that's been making the news lately.
http://orbitsimulator.com/gravitySimulatorCloud/simulations/1453421668138_PlanetNine.html

https://twitter.com/tony873004/status/690383418610286593

Fiery Phoenix
2016-Jan-22, 04:09 AM
I think Jens might be referring to space telescopes? NASA was already experimenting with space telescopes by attaching cameras to satellites around that time period.


Here's a simulation of the theorized planet that's been making the news lately.
http://orbitsimulator.com/gravitySimulatorCloud/simulations/1453421668138_Planet Nine.html

https://twitter.com/tony873004/status/690383418610286593
The first link doesn't work, though I can access it through the tweet. You need to edit the hyperlink.

tony873004
2016-Jan-22, 04:14 AM
The first link doesn't work, though I can access it through the tweet. You need to edit the hyperlink.
Fixed. Thanks for pointing that out! How do I make a typo copying and pasting?.

Jens
2016-Jan-22, 04:27 AM
1960s seriously!!!

Sorry, 1600s.

Fiery Phoenix
2016-Jan-22, 04:56 AM
Fixed. Thanks for pointing that out! How do I make a typo copying and pasting?.
I've done worse! :p

Jens
2016-Jan-22, 06:03 AM
Caltech announced on the 20th of Jan that they have 'solid theoretical evidence' of a ninth planet. If it is there, why is it the 9th planet? The IAU, in there rules for a planets stated:-
•It needs to be in orbit around the Sun – Yes, so maybe Pluto is a planet.
•It needs to have enough gravity to pull itself into a spherical shape – Pluto…check
•It needs to have “cleared the neighborhood” of its orbit – Uh oh. Here’s the rule breaker. According to this, Pluto is not a planet.
At the moment we don't know about the 3rd point. So shouldn't we be calling it a large Kuiper belt object? And maybe the 2nd point too.

This should probably get merged to the existing thread in Astronomy. But just quickly, I think that an object that size would be sure tomorrow clear its orbit, and there is absolutely no possibility it would not be spherical.


Edited after moving from Q&A to Astronomy, and merging with this thread by tusenfem.

Hornblower
2016-Jan-22, 01:21 PM
Caltech announced on the 20th of Jan that they have 'solid theoretical evidence' of a ninth planet. If it is there, why is it the 9th planet? The IAU, in there rules for a planets stated:-
•It needs to be in orbit around the Sun – Yes, so maybe Pluto is a planet.
•It needs to have enough gravity to pull itself into a spherical shape – Pluto…check
•It needs to have “cleared the neighborhood” of its orbit – Uh oh. Here’s the rule breaker. According to this, Pluto is not a planet.
At the moment we don't know about the 3rd point. So shouldn't we be calling it a large Kuiper belt object? And maybe the 2nd point too.
In the article linked in the opening post, Mike Brown says that at 10 times Earth's mass, this object would be massive enough to dominate its orbital neighborhood. I presume that he has the mathematical orbital dynamics knowhow to back up that statement.

efanton
2016-Jan-22, 01:26 PM
In the article linked in the opening post, Mike Brown says that at 10 times Earth's mass, this object would be massive enough to dominate its orbital neighborhood. I presume that he has the mathematical orbital dynamics knowhow to back up that statement.

Surely it would unless there were other objects of a similar or greater size in the same orbital vicinity.
Why would this not be the case?

Nittany Lion
2016-Jan-22, 03:04 PM
I’m confused. Okay, it happens a lot.

I’ve read the original paper and several media summaries and some points don’t entirely make sense to me. For purposes of this post, let’s assume that all the objects relevant to the prediction of Planet Nine can be called “KBOs.”

(1) I had thought that Sedna and 2012 VP113 were special in that they both had perihelia greater than 30 and very large aphelia. Now dozens of such objects have been observed?

(2) The clustering of arguments of perihelion around zero indicates that these objects are at perihelion on their first “day” of their Spring?

(3) The term “argument of perihelion” seems to be being used in two different and confusing ways; one is relative to the KBO’s vernal equinox and one is relative to the Earth’s vernal equinox. Why isn’t the available more precise terminology being used?

(4) Taken together (2) and (3) imply that, for the KBOs under consideration, all their perihelia and all their vernal equinoxes lie in approximately the same direction as viewed from Earth?

(5) Since Sedna and 2012 VP113 have very different orbital periods and they are both currently near their perihelion, we can imply that there is a very large number of such bodies?

(6) The Batygin / Brown paper talks about possible “apsidally anti-aligned” objects which have not (yet) been observed. Does that mean their perihelia would be shifted 90 degrees, or 180 degrees along the ecliptic? (I’m not referring to the KBOs that have orbits at right angles to the ecliptic.)

Any help will be appreciated.

George
2016-Jan-22, 04:56 PM
In the article linked in the opening post, Mike Brown says that at 10 times Earth's mass, this object would be massive enough to dominate its orbital neighborhood. I presume that he has the mathematical orbital dynamics knowhow to back up that statement.

Using the math from December's Planet Definition (http://cosmoquest.org/forum/showthread.php?159097-New-quot-planet-quot-definition-proposed) paper, I get a minimum planetary mass of 1.6x Earth mass to clear a path at 600 AU.

Fiery Phoenix
2016-Jan-22, 05:38 PM
Apparently the planet has a Hill sphere that is larger than even Neptune's, which I suppose makes sense given its distance. It's why Mike Brown calls it the most 'planet-y' of all.

George
2016-Jan-22, 06:34 PM
Apparently the planet has a Hill sphere that is larger than even Neptune's, which I suppose makes sense given its distance. It's why Mike Brown calls it the most 'planet-y' of all. Yes, Hill Sphere is linear with distance so going out 20x that of Neptune's makes a huge difference. However, diffusion may be the better term for clearing out a path in order to meet the IAU definition of a planet. That thread's paper (Margot) I referenced combines, I think, the Hill Sphere, diffusion and time to establish a hard value for the minimum mass for clearing at a given distance for a given star. It is interesting that more mass is needed with increasing distance, using Margot's approach, in order to diffuse would-be satellites even though the Hill sphere increases with distance for a given mass.

tony873004
2016-Jan-22, 07:08 PM
I’m confused. Okay, it happens a lot.


(2) The clustering of arguments of perihelion around zero indicates that these objects are at perihelion on their first “day” of their Spring?

(3) The term “argument of perihelion” seems to be being used in two different and confusing ways; one is relative to the KBO’s vernal equinox and one is relative to the Earth’s vernal equinox. Why isn’t the available more precise terminology being used?


I noticed the same thing. In order to appear clustered as they do in the diagrams, it is the longitude of perihelion, not argument of perihelion that must be similar. Argument of perihelion is simply angular distance from their ascending node.

longitude of perihelion = argument of perihelion + longitude of ascending node.

publiusr
2016-Jan-22, 07:30 PM
This brings to mind the earlier news blurb about ALMA--the object named Gna:
http://gizmodo.com/could-there-be-massive-planets-in-the-far-reaches-of-ou-1747410400

Would that be a good fit?

Superluminal
2016-Jan-23, 01:47 AM
This graph from at the Planetary Society is all you need to know about Planet 9.
http://www.planetary.org/blogs/emily-lakdawalla/2016/0122-xkcd-possible-undiscovered-planets.html

Robert Tulip
2016-Jan-23, 10:43 AM
Here's a simulation of the theorized planet that's been making the news lately.
http://orbitsimulator.com/gravitySimulatorCloud/simulations/1453421668138_PlanetNine.html

https://twitter.com/tony873004/status/690383418610286593

Tony - can you explain this? Is planet 9 hypothesised as the orange ellipse? Is the red circle Neptune?

parallaxicality
2016-Jan-23, 11:44 AM
Judging by the shape of the orbit in the animated model, the red one is Pluto

DonM435
2016-Jan-23, 03:33 PM
So Planet IX is so eccentric it makes Pluto look conventional.

Fiery Phoenix
2016-Jan-23, 04:35 PM
So Planet IX is so eccentric it makes Pluto look conventional.
Yeah, the orbit is several orders of magnitude more eccentric. It's more comparable to certain exoplanets than Pluto.

tony873004
2016-Jan-23, 10:16 PM
Tony - can you explain this? Is planet 9 hypothesised as the orange ellipse? Is the red circle Neptune?
The red one is Pluto.
You can press "L" on your keyboard or check the "Labels" box up near the slider controls and it will tell you what each object is.
You can also use the sliders to view from different locations.

tony873004
2016-Feb-09, 11:05 PM
https://www.youtube.com/watch?v=YW0Zb5gY0HA
Here's a nice talk from Ann Marie Madigan during SETI talk. She explains the argument of perihelion distribution with an analogy to a boat rolling, pitching and yawing.

George
2016-Feb-13, 09:42 PM
https://www.youtube.com/watch?v=YW0Zb5gY0HA
Here's a nice talk from Ann Marie Madigan during SETI talk. She explains the argument of perihelion distribution with an analogy to a boat rolling, pitching and yawing.
Thanks! That was great! The greater mass effect at aphelion and the resulting torque effect from it to produce the clustering seen is very interesting. Looks like we have two very interesting hypotheses at hand. I think I favor hers, actually, though I am still rooting for #9 even if it sounds a bit backwards. [Anyone old enough for that last bit? ;)]

selvaarchi
2016-Mar-27, 01:06 PM
Here is an article in Forbes that put in layman terms the likely hood of Planet 9 existing.

http://www.forbes.com/sites/jillianscudder/2016/03/26/astroquizzical-ninth-planet-exist/#8bf476631dbb


So now the hunt is on to see if we can find it. An object ten times the mass of the Earth isn’t undetectable, and there’s a limited area of space in which it could be hiding. We can rule out some sections of that area already because it should have been spotted by surveys that have already looked at those patches of sky. There are also some new surveys starting observations soon, which should have the ability to spot Planet Nine, should it exist.

The other option, of course, is that the data will improve, and will instead fill out the distribution of distant objects so that they don’t look so clustered together. However, that would also require some weird biases to be present in the data we have now, and all four authors suggesting a distant planet have worked hard to understand the biases in their data. So we can’t say for sure if there really is a Planet Nine out there until we find it, but in the mean time we’ll be looking both for Planet Nine and for any discoveries that might remove our need for a distant planet to explain the data.

bknight
2016-Mar-27, 04:46 PM
It'll be interesting to find out what the planet formation guys will come up with how/why it got to be that big and that far from the sun.

tony873004
2016-Mar-29, 01:25 AM
It'll be interesting to find out what the planet formation guys will come up with how/why it got to be that big and that far from the sun.
Maybe it used to orbit another star, and was captured by the Sun. That's what these people propose: http://arxiv.org/abs/1603.07247

bknight
2016-Mar-29, 03:39 PM
Maybe it used to orbit another star, and was captured by the Sun. That's what these people propose: http://arxiv.org/abs/1603.07247

Capture is one possible explanation, BUT the planet had to be somewhere for it to accumulate sufficient material to become a planet.
Should it be discovered and then studied to identify its composition.

kzb
2016-Mar-29, 03:58 PM
Capture is one possible explanation, BUT the planet had to be somewhere for it to accumulate sufficient material to become a planet.
Should it be discovered and then studied to identify its composition.

Planet 9 would've formed much closer in than it is now. Even Neptune and Uranus could not have formed at their current distances. That is the current idea anyway.

In fact, I believe the latest models actually require a planet of this kind of mass being ejected to explain the current orbits of the known planets.

But it possibly will turn out that this planet was not quite ejected, just nearly so. It ended up still being just about gravitationally bound.

George
2016-Mar-29, 05:08 PM
Capture is one possible explanation, BUT the planet had to be somewhere for it to accumulate sufficient material to become a planet.
Should it be discovered and then studied to identify its composition.Capture from a passing star system is deemed unlikely due to the more circular orbits of the planets. [I think Tony's earlier Youtube reference presentation addresses this briefly, though I've seen it elsewhere.] This circularity also puts an upper limit on the likely number of stars in our original cluster, which I think is a number like 3,000 sister stars. Stars too close would have caused greater eccentricity in the orbit of our planets.

Ara Pacis
2016-Mar-29, 05:18 PM
Capture from a passing star system is deemed unlikely due to the more circular orbits of the planets. [I think Tony's earlier Youtube reference presentation addresses this briefly, though I've seen it elsewhere.] This circularity also puts an upper limit on the likely number of stars in our original cluster, which I think is a number like 3,000 sister stars. Stars too close would have caused greater eccentricity in the orbit of our planets.

Even if it was as distant from a previous star as it is from the sun now?

George
2016-Mar-29, 07:19 PM
Even if it was as distant from a previous star as it is from the sun now?Perhaps ~700 AU is distant enough, though the solar grip extends to over 60,000 AU -- I think it's ~ 90,000 AU. The disruption effect for all the other planets, however, would still be obvious, as I understand it, if previous stars were flying very close.

Ara Pacis
2016-Mar-30, 04:50 AM
Perhaps ~700 AU is distant enough, though the solar grip extends to over 60,000 AU -- I think it's ~ 90,000 AU. The disruption effect for all the other planets, however, would still be obvious, as I understand it, if previous stars were flying very close.

Dunno if it helps, but I recall reading about a star passing within that radius recently. Scholz's Star (https://en.wikipedia.org/wiki/Scholz's_star) reportedly came within 52,000 AU around 70 kya.

dtilque
2016-Mar-30, 09:11 AM
Dunno if it helps, but I recall reading about a star passing within that radius recently. Scholz's Star (https://en.wikipedia.org/wiki/Scholz's_star) reportedly came within 52,000 AU around 70 kya.

Stars passing within a lightyear (63,000 AU) or so seems to be a fairly common phenomenon in the galaxy and not just in star clusters. Other examples besides Scholz's Star include Luyten's Star, which is currently just over a lightyear from Procyon and moving away. It had its closest approach to Procyon a few hundred years ago. Another is Gliese 710, which will have a closest approach to the Sun at about a lightyear some 1.4m years from now.

kzb
2016-Mar-30, 12:14 PM
I think the most interesting possibility is that it started life as an inner planet that got thrown further out. This means it could be a rocky planet with a solid surface, and I think a super-Earth would be more interesting to us than another Neptune. This terrestrial composition is allowed within the mass range postulated.

After all, the most common planet size in the galaxy seems to be super-Earth to mini-Neptune, something that we don't have in our system. If Planet 9 turns out to really exist, then we'd have one, and we wouldn't be quite so unusual.

bknight
2016-Mar-30, 02:15 PM
Capture from a passing star system is deemed unlikely due to the more circular orbits of the planets. [I think Tony's earlier Youtube reference presentation addresses this briefly, though I've seen it elsewhere.] This circularity also puts an upper limit on the likely number of stars in our original cluster, which I think is a number like 3,000 sister stars. Stars too close would have caused greater eccentricity in the orbit of our planets.
There is still a possibility of capture, albeit small. My point was the planet, if it exists, had to be somewhere to accumulate the material to become a planet. IIRC both Saturn and Jupiter were accumulated much closer to the Sun and gravitational forces moved them to current orbits. It may be possible for a planet 9 to formed closer to the Sun and then by forced to a elliptical orbit beyond Neptune.

George
2016-Mar-30, 05:00 PM
Dunno if it helps, but I recall reading about a star passing within that radius recently. Scholz's Star (https://en.wikipedia.org/wiki/Scholz's_star) reportedly came within 52,000 AU around 70 kya. That's interesting, though it was close in mass to a brown dwarf, so it may not have had much disruptive effect on our orbits. But, more to your point no doubt, could Scholz's star have dropped off such a heavy cargo during the pass? Seems unlikely but could we say one way or another on it?

George
2016-Mar-30, 05:05 PM
There is still a possibility of capture, albeit small. My point was the planet, if it exists, had to be somewhere to accumulate the material to become a planet. IIRC both Saturn and Jupiter were accumulated much closer to the Sun and gravitational forces moved them to current orbits. It may be possible for a planet 9 to formed closer to the Sun and then by forced to a elliptical orbit beyond Neptune. I think that is the popular scenario. I think I saw that some think the proto-sun cloud may have been extensive enough during this time frame to cause such an outward-bound planet to slow and be contained. [Perhaps this point may, or may not, be an advantage to the alternate hypothesis stating that we should find about the same amount of mass found in multiple smaller objects, as per Tony's link presents.]

Ara Pacis
2016-Mar-30, 05:17 PM
That's interesting, though it was close in mass to a brown dwarf, so it may not have had much disruptive effect on our orbits. But, more to your point no doubt, could Scholz's star have dropped off such a heavy cargo during the pass? Seems unlikely but could we say one way or another on it?

I wasn't implying this star specifically, but wondering what sort of effect it or others would have had on masses in the solar system. Could the alignment of objects they see that they think is due to a planet have been caused by stellar passages?

George
2016-Mar-30, 05:36 PM
I wasn't implying this star specifically, but wondering what sort of effect it or others would have had on masses in the solar system. Could the alignment of objects they see that they think is due to a planet have been caused by stellar passages?Oh, I see. I believe it is held that this would not likely form the very similar orbital patterns found in the 6 or more objects found, so far, and more seems likely. It's this orbital grouping that has all the attention. In the case of Scholz's star for example, its 0.15 solar mass is equivalent to a one solar mass passing by at about 2 light years, and it would not have been around long enough, apparently, to see this pattern we see today, not that I am even remotely wise in celestial mechanics. I'm just going on bits and pieces.

selvaarchi
2016-Apr-01, 03:39 AM
More clues to the existence of planet 9

http://www.popularmechanics.com/space/news/a20139/planet-nine-theory-orbit/

The tiny planet called uo3L91 is so new it doesn't even have an official catalog name yet, let alone a fancy moniker picked from mythology. But it does offer something important for scientists: more evidence that a ninth planet is lurking in the far reaches of the solar system.

This world uo3L91 has an orbit that seems to slingshot it out to some of the most distant reaches of our solar system before swooping back in. There are five other objects just like it. What makes it so special is that this family of objects, which includes Sedna and 2012VP113 (aka "Biden"), seem to point out in the same direction, something that Caltech astronomer and dwarf planet expert Mike Brown believes to be a giant ninth planet.



Sent from my SM-G900F using Tapatalk

Swift
2016-Apr-04, 02:19 PM
I wonder if adding uo3L91 to their model can further narrow the volume of the sky to search for the possible ninth planet?

selvaarchi
2016-Apr-05, 10:42 AM
Now another theory. Could our sun have stolen Planet 9 from a passing star.

http://www.universetoday.com/128244/sun-steal-planet-nine/


One of the biggest new mysteries in our Solar System is the purported presence of a large and distant “Planet Nine,” traveling around the Sun in a twenty-thousand-year orbit far beyond Pluto. Although this far-flung world’s existence has yet to actually be confirmed (or even detected) some scientists are suggesting it might have originally been an exoplanet around a neighboring star, pilfered by our Sun during its impudent adolescence.

Fiery Phoenix
2016-Apr-06, 03:40 AM
This might be the most convincing case yet. Perturbation's in Cassini's orbit may prove Planet Nine's existence:


[...]So Fienga and her colleagues compared the updated model, which placed Planet Nine at various points in its hypothetical orbit, with the data. They found a sweet spot—with Planet Nine 600 astronomical units (about 90 billion kilometers) away toward the constellation Cetus—that can explain Cassini’s orbit quite well.

More here:

http://www.scientificamerican.com/article/mysterious-gravitational-tug-on-orbiter-may-help-find-planet-nine/

At this rate it's expected we will be able to detect it within's a year's time.

selvaarchi
2016-Apr-06, 05:44 AM
At this rate it's expected we will be able to detect it within's a year's time.

The paper you pointed to had the following "If Planet Nine is located toward the constellation Cetus, then it could be picked up by the Dark Energy Survey, a Southern Hemisphere observation project designed to probe the acceleration of the universe. "

If that could be used, I just wounder if China's Dark Matter Particle Explorer (DAMPE) could also be used.

dtilque
2016-Apr-08, 10:37 PM
This might be the most convincing case yet. Perturbation's in Cassini's orbit may prove Planet Nine's existence:


It should be noted that SciAm corrected that article. It's perturbations in Saturn's orbit, not Cassini's orbit, that's the evidence. This makes much more sense orbital-mechanics-wise. Planet Nine's gravitational influence on Cassini should be virtually unmeasurable.

New link (http://www.scientificamerican.com/article/mysterious-gravitational-tug-on-saturn-may-help-find-planet-nine/)

selvaarchi
2016-Apr-09, 09:21 AM
It should be noted that SciAm corrected that article. It's perturbations in Saturn's orbit, not Cassini's orbit, that's the evidence. This makes much more sense orbital-mechanics-wise. Planet Nine's gravitational influence on Cassini should be virtually unmeasurable.

You must be right as experts at NASA's Jet Propulsion Laboratory in Pasadena, California say, Cassini spacecraft is not experiencing unexplained deviations in its orbit around Saturn.

http://www.jpl.nasa.gov/news/news.php?release=2016-101&rn=news.xml&rst=6200


Several recent news stories have reported that a mysterious anomaly in Cassini's orbit could potentially be explained by the gravitational tug of a theorized massive new planet in our solar system, lurking far beyond the orbit of Neptune. While the proposed planet's existence may eventually be confirmed by other means, mission navigators have observed no unexplained deviations in the spacecraft's orbit since its arrival there in 2004.

"An undiscovered planet outside the orbit of Neptune, 10 times the mass of Earth, would affect the orbit of Saturn, not Cassini," said William Folkner, a planetary scientist at JPL. Folkner develops planetary orbit information used for NASA's high-precision spacecraft navigation. "This could produce a signature in the measurements of Cassini while in orbit about Saturn if the planet was close enough to the sun. But we do not see any unexplained signature above the level of the measurement noise in Cassini data taken from 2004 to 2016."

publiusr
2016-Apr-09, 06:14 PM
Where was Gna located again?
http://www.centauri-dreams.org/?p=34606

or is that closer, and in another region?

parallaxicality
2016-Apr-09, 08:08 PM
It was not "located" anywhere. Its distance could never be pinned down, so all they could say was that if it was bound to the Sun, it was about ~20 AU away and about ~450 km wide BUT... if it WASN'T bound to the Sun, and was a rogue planet, it could have been 4000 AU away and REALLY REALLY BIG. Given ALMA's tiny field of view, and the fact that they had no actual justification for the latter position other than, "Man, that'd be kewl, dudes", the former position seems more likely. Assuming, of course, that they ever find it again. Which they haven't.

bknight
2016-Apr-10, 12:07 AM
It should be noted that SciAm corrected that article. It's perturbations in Saturn's orbit, not Cassini's orbit, that's the evidence. This makes much more sense orbital-mechanics-wise. Planet Nine's gravitational influence on Cassini should be virtually unmeasurable.

New link (http://www.scientificamerican.com/article/mysterious-gravitational-tug-on-saturn-may-help-find-planet-nine/)

Yes I would think that Jupiter would have more influence on Cassini than a proposed planet only 10 times the mass of the Earth 600 au.

EDIT:
Along with Uranus 14 times mass of Earth and "only" 1.9 au from the Sun. Or for that matter Neptune 17 times the mass of Earth and "only" 3 au from the Sun. Seems to me these could have far more impact then a 10 times mass 600 au.

Don Alexander
2016-Apr-16, 11:33 AM
The point is that with Cassini orbiting Saturn, we can use it to pin down Saturn's orbit with extreme precision, in contrast to the other gas/ice giants.

publiusr
2016-Apr-16, 07:06 PM
if Saturn didn't have other objects--and Cassini was the only thing in orbit--that would have made things a bit less noisy.

casey10s
2016-Apr-18, 04:34 AM
I think you are a magnitude of 10 off on the au's. Uranus is 19 au and Neptune is little less than 30 au from the sun.

Yes I would think that Jupiter would have more influence on Cassini than a proposed planet only 10 times the mass of the Earth 600 au.

EDIT:
Along with Uranus 14 times mass of Earth and "only" 1.9 au from the Sun. Or for that matter Neptune 17 times the mass of Earth and "only" 3 au from the Sun. Seems to me these could have far more impact then a 10 times mass 600 au.

bknight
2016-Apr-18, 03:34 PM
I think you are a magnitude of 10 off on the au's. Uranus is 19 au and Neptune is little less than 30 au from the sun.
Yes, thanks for the correction. However, they would still have more gravitational effects on Cassini.

casey10s
2016-Apr-18, 11:42 PM
Yes, thanks for the correction. However, they would still have more gravitational effects on Cassini.

I agree with that.

crosscountry
2016-Apr-22, 04:15 PM
You must be right as experts at NASA's Jet Propulsion Laboratory in Pasadena, California say, Cassini spacecraft is not experiencing unexplained deviations in its orbit around Saturn.

http://www.jpl.nasa.gov/news/news.php?release=2016-101&rn=news.xml&rst=6200

As it turns out, the Cassini deviations that had previously been modeled are better suited to this topic. The authors of this paper are narrowing down where planet nine can be and learning about its size.
https://www.newscientist.com/article/2084924-we-are-closing-in-on-possible-whereabouts-of-planet-nine/

01101001
2016-Apr-22, 08:31 PM
Observational Constraints on Planet Nine: Cassini Range Observations (http://arxiv.org/abs/1604.03180), PDF there:


Thus,
we assume (1) that the Cassini range residuals are primarily
due to the unmodeled acceleration of the Saturn
system barycyenter, (2) that we can ignore the acceleration
of the geocenter due to Planet Nine , and (3)
that Cassini range residuals are well approximated by
the changes in the separation between the barycenter
the Saturn system and the geocenter.

Like, Planet Nine says: Come a little closer, Saturn. And Saturn says, OK, but I have to bring this annoying Cassini thing with me.

crosscountry
2016-Apr-22, 08:47 PM
Pretty encouraging that these new, independent results, appear to agree with the previous papers on the topic.

bknight
2016-Apr-22, 11:31 PM
Observational Constraints on Planet Nine: Cassini Range Observations (http://arxiv.org/abs/1604.03180), PDF there:



Like, Planet Nine says: Come a little closer, Saturn. And Saturn says, OK, but I have to bring this annoying Cassini thing with me.
Seems to me it would be Saturn says come a little closer Planet Nine.

01101001
2016-Apr-23, 12:07 AM
Seduction may be a two-way street, but we cannot yet see that part of the relationship.

crosscountry
2016-Apr-23, 03:03 PM
Humorous but only loosely related
https://www.youtube.com/watch?v=W7QZnwKqopo

Ken G
2016-Apr-24, 06:29 PM
You can count me a skeptic. It's a very different thing to say "a planet of such-and-such a mass and location could explain some minor deviation in Saturn's orbit that we were never bothered by before" than to say you have independent confirmation of the already highly indirect reasoning that leads to a suspicion of planet 9. It's all possible, but I'm a long way from seeing it as probable.

crosscountry
2016-Apr-25, 11:50 AM
To be fair, no one ever said, "some minor deviation in Saturn's orbit that we were never bothered by before." Engineers were bothered by it enough to develop models that took into account Cassini's constant acceleration that couldn't be explained with the known bodies in the solar system.

bknight
2016-Apr-25, 02:32 PM
To be fair, no one ever said, "some minor deviation in Saturn's orbit that we were never bothered by before." Engineers were bothered by it enough to develop models that took into account Cassini's constant acceleration that couldn't be explained with the known bodies in the solar system.

Could you provide a link concerning the "minor deviation in Saturn's orbit"? I have been unable to find such information.

crosscountry
2016-Apr-25, 03:45 PM
Could you provide a link concerning the "minor deviation in Saturn's orbit"? I have been unable to find such information.

01101001's link discusses it.


Observational Constraints on Planet Nine: Cassini Range Observations (http://arxiv.org/abs/1604.03180), PDF there:


There is also Fienga et al. (2016). I hope you can find that one.

bknight
2016-Apr-25, 07:01 PM
No where that I am able to see any minor deviations to Saturn's orbit in this link.
http://arxiv.org/abs/1604.03180

crosscountry
2016-Apr-26, 03:04 AM
You have to read the document attached to that link.

http://arxiv.org/pdf/1604.03180v1 (warning, link downloads a 1 Mb manuscript)

bknight
2016-Apr-26, 03:44 PM
You have to read the document attached to that link.

http://arxiv.org/pdf/1604.03180v1 (warning, link downloads a 1 Mb manuscript)
Thanks, by inspection I didn't realize the two links were documents.
From the report any deviations is based on deviations in Cassini's orbit. Since NASA has indicated there is no deviations in that orbit, then Saturn's deviations are called into question.

selvaarchi
2016-Apr-27, 09:50 AM
Why are we being boged down with Saturn's orbit instead of concentrating on the orbits of the minor planets/asteroid that seem to be influenced by something like planet 9?

Sent from my SM-G900F using Tapatalk

01101001
2016-Apr-27, 06:35 PM
From the report any deviations is based on deviations in Cassini's orbit. Since NASA has indicated there is no deviations in that orbit, then Saturn's deviations are called into question.

Yeah, NASA: no deviation in orbit of Cassini relative to Saturn barycenter. I'm not sure about the consequent deviations being called into question.

Maybe you agree with this extracted snippet posted prior and I'm reading wrong? Cassini's orbit is of no interest to them, except that it stays pretty constant. They are measuring Cassini's deviating distance to Earth as a proxy for Saturn's deviating distance to Earth, and its correlated deviation in Saturn's orbit, as an indicator that Saturn is influenced by an unaccounted-for large body -- possibly narrowing the search zone of the suspected Planet Nine.


Thus,
we assume (1) that the Cassini range residuals are primarily
due to the unmodeled acceleration of the Saturn
system barycyenter, (2) that we can ignore the acceleration
of the geocenter due to Planet Nine , and (3)
that Cassini range residuals are well approximated by
the changes in the separation between the barycenter
the Saturn system and the geocenter.

And maybe that answers selvaarchi as to why Saturn is of interest: because its behavior can be measured so accurately due to Cassini and the speed of light.

crosscountry
2016-Apr-27, 09:19 PM
Why are we being boged down with Saturn's orbit instead of concentrating on the orbits of the minor planets/asteroid that seem to be influenced by something like planet 9?

Sent from my SM-G900F using Tapatalk

There are two constraints. The first is interesting but only narrows down the possible location a small amount. The second constraint (from Cassini) narrows down the possible location in another way. The sets combine to leave only two plausible regions in the sky for the planet to be.

blueshift
2016-Apr-28, 02:20 AM
Why don't we name it "Uncle Pluto"?

Ken G
2016-Apr-30, 05:54 PM
To be fair, no one ever said, "some minor deviation in Saturn's orbit that we were never bothered by before." Engineers were bothered by it enough to develop models that took into account Cassini's constant acceleration that couldn't be explained with the known bodies in the solar system.Do you have a citation on that? If such a constant acceleration were already detected, I can tell you right now where to look for planet 9, with no further analysis: in the direction of this constant acceleration those engineers found. How is that two different possible directions, and why did it require any further analysis to unearth? Something just doesn't wash here.

StupendousMan
2016-May-01, 01:57 AM
I suggest that one reads these papers, both published in the past few months:

http://arxiv.org/abs/1602.06116
http://arxiv.org/abs/1603.09008

Ken G
2016-May-01, 02:02 PM
What I would like to point out about those two papers is the important difference between the following statements:
1) Because potentially random and/or systematic errors can be reduced by postulating the existence of Planet 9, that is evidence that Planet 9 actually exists.
2) If Planet 9 actually exists, we can narrow down where to look for it by expecting its presence to reduce the systematic errors in some dataset.

The difference between those two statements is that the first assumes the errors in some dataset are more likely to be explained by the attributes of Planet 9 rather than some other way, and the second uses the logic in the proper direction by saying that if we take it as given that the errors are to be explained by Planet 9, we can constrain its attributes. Neither of those papers analyze that difference at all, so they are on much firmer footing to use the second statement rather than the first. They seem to try to imply both statements at the same time, without recognizing the different burdens of proof implied. In particular, neither paper tests a prediction.

Let me give a very clear example of what I mean here. Let's say you go to some distant planet and flip a coin 100 times. You get 60 heads and 40 tails. If you already think that planet experiences some strange force that affects coin flips, you can use that data to argue that the way the force works is to encourage heads. But if you are highly skeptical that any such force exists, you would never be swayed by data that can only be described as a marginal detection. This is what is known as Bayesian statistical analysis-- you can only assess the significance of a dataset if you already have a prior expectation that you are using the data to address. When you have no information that establishes a prior expectation, it is skepticism, not acceptance, that should be the default stance. After all, we have lots of astronomers combing a vast array of different data looking for evidence for planet 9. It's not at all surprising a few marginal detections should crop up!

So what this means is, if you have two different datasets that constrain where planet 9 might be, and only their overlap produces strong constraints, all you have is a good reason to look somewhere-- you do not have a good reason to expect a detection by looking there. For that, what you need are two datasets that independently produce strong constraints, and those strong constraints agree. Until you have that, you do not have a good reason to expect success, but you do have the possibility of embarrassment if you overstate that expectation.

At the moment, we have this principle playing out in at least two discovery contexts: planet 9 and gamma ray bursts associated with the gravitational wave event. I'm not convinced by either of those until there is corroboration of two datasets that independently strongly constrain those events as being statistically significant. Indeed, I predict that at least one of them will go away in time-- and either be forgotten was ever claimed, or will end up causing some embarrassment to the scientific method. The scientific method is built to avoid false negatives by encouraging openmindedness, but it is also built to avoid false positives by requiring the testing of what Popper called "risky" predictions.

George
2016-May-03, 09:47 PM
Let me give a very clear example of what I mean here. Let's say you go to some distant planet and flip a coin 100 times. You get 60 heads and 40 tails. If you already think that planet experiences some strange force that affects coin flips, you can use that data to argue that the way the force works is to encourage heads. But if you are highly skeptical that any such force exists, you would never be swayed by data that can only be described as a marginal detection. This is what is known as Bayesian statistical analysis-- you can only assess the significance of a dataset if you already have a prior expectation that you are using the data to address. When you have no information that establishes a prior expectation, it is skepticism, not acceptance, that should be the default stance. After all, we have lots of astronomers combing a vast array of different data looking for evidence for planet 9. It's not at all surprising a few marginal detections should crop up! That is a nice, lucid statement that is very helpful.


At the moment, we have this principle playing out in at least two discovery contexts: planet 9 and gamma ray bursts associated with the gravitational wave event. I'm not convinced by either of those until there is corroboration of two datasets that independently strongly constrain those events as being statistically significant. Indeed, I predict that at least one of them will go away in time-- and either be forgotten was ever claimed, or will end up causing some embarrassment to the scientific method. The scientific method is built to avoid false negatives by encouraging openmindedness, but it is also built to avoid false positives by requiring the testing of what Popper called "risky" predictions. Nice also, but note that there is a slight difference between the two cases. In the planet 9 case, a gravitational anomaly, or perhaps grouping would be more apt, is not a new arena for science so what you say makes great sense. Black hole mergers, I feel save to assume, are something astronomers have little information to offer, so I would expect more creative thinking would be almost encouraged. [Hence, both lightning (GRB) and thunder (GW) might go together after all.] It's still subjective thinking -- until a real hypothesis or two take form -- but there seems to be a nuance difference between the two cases, both gravitational, oddly enough. :)

selvaarchi
2016-May-04, 02:08 AM
New research (https://www.cfa.harvard.edu/news/2016-11) after examining a number of scenarios, finds that most of them have low probabilities. But they do concede "The evidence points to Planet Nine existing, but we can't explain for certain how it was produced" .

bknight
2016-May-04, 12:27 PM
New research (https://www.cfa.harvard.edu/news/2016-11) after examining a number of scenarios, finds that most of them have low probabilities. But they do concede "The evidence points to Planet Nine existing, but we can't explain for certain how it was produced" .
Rather like I know right but I don't know why I'm right.

Fiery Phoenix
2016-May-04, 06:56 PM
I think at this point the planet is as good as confirmed. There's already been multiple independent publications with essentially the same conclusion. I have no idea how and when we're going to be able to directly observe it, but I suspect it's sooner than not.

parallaxicality
2016-May-04, 07:52 PM
Yeah well, I'm still at the "T. rex has feathers" stage; even if every individual scientist in the field says it's true, I won't believe it unless I see it with my own eyes.

Swift
2016-May-04, 09:08 PM
I think at this point the planet is as good as confirmed. There's already been multiple independent publications with essentially the same conclusion. I have no idea how and when we're going to be able to directly observe it, but I suspect it's sooner than not.
I am not a professional astronomer, but I think that is "a push". Until it is actually observed, even if only as a point of light, and with enough observations to roughly calculate an orbit, I don't think I would use any form of the word "confirmed".

Fiery Phoenix
2016-May-04, 10:02 PM
I am not a professional astronomer, but I think that is "a push". Until it is actually observed, even if only as a point of light, and with enough observations to roughly calculate an orbit, I don't think I would use any form of the word "confirmed".
Fair enough ;)

To me, it sounds like another Neptune situation. First an indirect indication of its existence, then a direct observation and therefore final confirmation. We appear to be past the former, but have not quite achieved the latter.

selvaarchi
2016-May-05, 05:50 AM
Could planet 9 have an effect on New Horizon's flight path as there was talk of Cassini being influenced by it?

parallaxicality
2016-May-05, 07:06 AM
Cassini is in orbit around a planet, which is in orbit around the Sun. It gets tugged by the same things every thirty or so years. New Horizons is on a linear trajectory out of the Solar System. It will never be tugged by anything not directly in front of it, which, given that it is currently 35 AU out, is unlikely ever to happen, at least by accident.

selvaarchi
2016-May-05, 08:46 AM
Cassini is in orbit around a planet, which is in orbit around the Sun. It gets tugged by the same things every thirty or so years. New Horizons is on a linear trajectory out of the Solar System. It will never be tugged by anything not directly in front of it, which, given that it is currently 35 AU out, is unlikely ever to happen, at least by accident.

With some luck if Planet 9 is somewhere in front of it (not necessary directly) will it show in the velocity of New Horizon. That is what I am looking for.

selvaarchi
2016-May-05, 10:44 AM
The problem here is aperature cost. Finding TNOs implies blind searches - even if you stay in the ecliptic, you have a complete band of sky to search. TNOs are almost always fainter than 20th magnitude. If you want to find any, you need to go wide, not deep, which implies quite dedicated telescopes, and such telescopes are small, and can't go deeper than 22nd, maybe 23rd magnitude. You are not going to get time at Big Glass with pencil-beam optics to just randomly stare somewhere multiple times in the hopes of finding something..

Just been going through the thread from the beginning and a light bulb clicked when I read statements as above and it might take at least 5 years to find it.

Around 2020 China will launch ‘China’s Hubble’ (http://gbtimes.com/china/chinas-space-station-2-arms-wings-and-chinese-hubble) with a field of view 300 times larger than Hubble. Just what we need to look for Planet 9 if it has not been spotted by then.

parallaxicality
2016-May-05, 11:33 AM
With some luck if Planet 9 is somewhere in front of it (not necessary directly) will it show in the velocity of New Horizon. That is what I am looking for.

The Hill sphere of an object the mass of Neptune with a semi-major axis of 700 AU and an eccentricity of 0.6 is 7.2 AU, or 0.16 percent the circumference of its orbit. So yeah, you'd need a lot of luck.

Hornblower
2016-May-05, 03:44 PM
Cassini is in orbit around a planet, which is in orbit around the Sun. It gets tugged by the same things every thirty or so years. New Horizons is on a linear trajectory out of the Solar System. It will never be tugged by anything not directly in front of it, which, given that it is currently 35 AU out, is unlikely ever to happen, at least by accident.
Are you asserting that a massive body off to one side rather than directly in front will not perturb its trajectory gravitationally? If so, why?

Demian
2016-May-05, 09:24 PM
We're finally getting close to the truth about how our universe works. They're never going to find "planet nine" because it's not a planet. It's a local black hole. The solar system is an x-ray binary system in orbit around a black hole. The crazy thing is that this "planet x," which is a black hole, is also the key to understanding dark energy. The cause of the universe's expansion is not a mysterious dark energy but space and time contracting all around us as we approach periapsis in an orbit that we've been around for millions of years. Check out a thread I started in 2012.

http://cosmoquest.org/forum/archive/index.php/t-140403.html

Demian
2016-May-05, 09:50 PM
If it's a black hole (since we have not been able to discover the little bugger) it could be a lot more massive than caltech's calculations, and of course, further away. Exciting stuff!

Swift
2016-May-06, 01:51 AM
We're finally getting close to the truth about how our universe works. They're never going to find "planet nine" because it's not a planet. It's a local black hole. The solar system is an x-ray binary system in orbit around a black hole. The crazy thing is that this "planet x," which is a black hole, is also the key to understanding dark energy. The cause of the universe's expansion is not a mysterious dark energy but space and time contracting all around us as we approach periapsis in an orbit that we've been around for millions of years. Check out a thread I started in 2012.

http://cosmoquest.org/forum/archive/index.php/t-140403.html
Demian,

Thanks for the link to your previous ATM thread - it demonstrates that you should already be familiar with our rules. Since you did not learn from your previous attempt to discuss your Against The Mainstream (ATM) ideas in Astronomy, this time you'll get an infraction. I suggest you stop posting your non-mainstream ideas outside of our ATM forum if you wish to keep posting here.

Fiery Phoenix
2016-May-06, 02:47 AM
Cassini is in orbit around a planet, which is in orbit around the Sun. It gets tugged by the same things every thirty or so years. New Horizons is on a linear trajectory out of the Solar System. It will never be tugged by anything not directly in front of it, which, given that it is currently 35 AU out, is unlikely ever to happen, at least by accident.
I think you might be making a false assumption here. It doesn't have to be directly in front of something to be gravitationally perturbed by it. There's always going to be 'tugs' regardless of Cassini's orbital position. The only difference is the extent to which those tugs affect Cassini.

Unless, of course, this isn't what you meant, in which case you can feel free to elaborate.

selvaarchi
2016-Jun-02, 11:38 AM
Latest news says Planet 9 was actually formed around another star - not our Sun - and it was 'captured' by our own Solar System during a close encounter some 4.5 billion years ago.

http://www.popsci.com/if-planet-nine-exists-it-might-be-stolen


This past January, "Pluto Killer" Mike Brown, who is also a professor of astronomy at the California Institute of Technology, found that there were a few things out in the Kuiper Belt being pushed around in unexpected ways -- it appeared that some force was "clearing the neighborhood." They reported that the chance this behavior happened randomly was only .007%, so something should be causing all the pushing, maybe a new planet.

Now if the planet does exist, it's really far away, like 75 times further than Pluto, and it would have to be huge, about ten times larger than Earth, which has had plenty of scientists asking where it could have come from. Mustill's group ran some numbers and found that the chances of such a big planet all the way out there being stolen from another solar system was about 50 percent. Those are pretty good odds. However, our solar system would still need to fly by another solar system dangling a planet like our hypothetical planet nine and the chance of that happening are closer to .1 to 2 percent, reported The New Scientist. Those aren't great odds, but it's still a crazy possibility.

We don't know for sure if there's even a new planet, though. While the probability that all those Kuiper Belt objects are moving randomly is just .007%, the odds that you will be struck by lightning in your lifetime are about .008%, according to the National Weather Service. Maybe we found an new planet, or maybe we're just living in a solar system that was struck by lightning. One scientist, Greg Laughlin, told the New Yorker that given Brown's ability and rigorous analysis, there's about a 68% chance that the planet exists, or 2 to 1 odds. Brown has since found more evidence, but has not published it yet.

Ken G
2016-Jun-03, 09:26 PM
The strange thing about all these probability arguments is that it is almost as if the scientists reporting them don't understand that probability estimates are always conditional on a set of constraints. So what is the probability that the constraints being used to assess the probabilities are correct? This is the difference between what we might call random and systematic uncertainties. One should not quote random uncertainties as a way of avoiding talking about systematic ones, that's why in science, we wait for confirmation. Why do we always hear about how Neptune was discovered, and leave out how Pluto was discovered? Neptune was discovered due to a small random uncertainty, Pluto was discovered because of a large systematic one.

StupendousMan
2016-Jun-03, 10:21 PM
Neptune was discovered due to a small random uncertainty, Pluto was discovered because of a large systematic one.

Could you please explain what you mean by this statement? I thought Neptune was discovered in large part due to a correct prediction of its location in the sky, while Pluto was discovered essentially by "accident" -- meaning "due to the careful and exhaustive search of the entire region of the ecliptic over a period of many years, with no help from theory."

It's not clear to me how the words you use can be applied to these two situations.

Ken G
2016-Jun-04, 01:56 AM
Could you please explain what you mean by this statement? I thought Neptune was discovered in large part due to a correct prediction of its location in the sky, while Pluto was discovered essentially by "accident" -- meaning "due to the careful and exhaustive search of the entire region of the ecliptic over a period of many years, with no help from theory."That sounds more like the way Uranus was found by Herschel. The story I was told was that Neptune was discovered because the orbit of Uranus had a tiny inconsistency that was nevertheless larger than the random uncertainty. Pluto was discovered because the orbit of Neptune contained a large systematic error in interpretation (by Percival Lowell). However, by accident as you say, there happened to be a tiny planet lurking in that systematic error. The accident was that Pluto happened to be in that random spot, not that everywhere was searched (Tombaugh was told where to look by his boss, Lowell). If that story is apocryphal, that would be interesting. My point was, it's not always easy to tell the difference between a random error and a systematic one-- until there is confirmation. If it turns out that all the data that leads to the prediction of a ninth planet was simply being interpreted incorrectly, and a different explanation proves to be the right one, then the whole incident will disappear in a poof. No one will care then what the probability estimates were-- as they would be based on incorrect assumptions.

No question, this is a very important issue, and we need to use good science and reach a solid conclusion. If planet 9 is really there, new studies show that its origin might be capture from a neighboring star system. That might also imply there are other captures, such that it could lead to a whole new model of star systems as a set of planets close to the star that formed with the system, and a set of more distant planets that are swapped around between systems.

parallaxicality
2016-Jun-04, 06:48 AM
Actually no; Tombaugh didn't limit his search to just the points Lowell had predicted (since Lowell had only predicted about 2 spots, it would have been a pretty monumental coincidence if he'd found Pluto in one of them). He searched the entire ecliptic until he found something that moved. Pluto was six degrees from one of Lowell's suggested locations, which was deemed close enough. That's still a pretty monumental coincidence (about 1 in 15, given two spots and 12 degrees each) but less than 1 in 180.

Ken G
2016-Jun-04, 09:01 AM
That's interesting. Still, the point remains that the reason he carried out that exhaustive search was because of a systematic error in the analysis of Neptune. No doubt Pluto would have been discovered eventually, but my only point here is that Lowell thought that based on a perceived deviation in Neptune's orbit, there needed to be a ninth planet, and he might have attributed various probabilities to that expectation. But it makes no difference what probability Lowell would have attributed to the existence of that planet, because it was all based in a systematically incorrect analysis.

What we see in the current planet 9 discussions is papers that make statements like, if the orbital anomalies are to be explained by a ninth planet, its attributes would be such-and-such, or like, the probability that the anomalies are purely random are such-and-such. What's missing from those statements? They are sweeping under the rug the possibility of other explanations. What are the probabilities associated with that? Very hard to say, because we only know how to assess random uncertainties, not systematic ones.

parallaxicality
2016-Jun-04, 11:20 AM
That's interesting. Still, the point remains that the reason he carried out that exhaustive search was because of a systematic error in the analysis of Neptune. No doubt Pluto would have been discovered eventually, but my only point here is that Lowell thought that based on a perceived deviation in Neptune's orbit, there needed to be a ninth planet, and he might have attributed various probabilities to that expectation. But it makes no difference what probability Lowell would have attributed to the existence of that planet, because it was all based in a systematically incorrect analysis.

What we see in the current planet 9 discussions is papers that make statements like, if the orbital anomalies are to be explained by a ninth planet, its attributes would be such-and-such, or like, the probability that the anomalies are purely random are such-and-such. What's missing from those statements? They are sweeping under the rug the possibility of other explanations. What are the probabilities associated with that? Very hard to say, because we only know how to assess random uncertainties, not systematic ones.

The Solar System has a long history of screwing us over with coincidences. From the moon being exactly the same angular diameter as the Sun (which led to any number of ancient myths about monsters swallowing the Sun) to Saturn "swallowing its children" through a telescope to Jupiter actually being the largest planet to Bode's law accurately predicting the positions of both Uranus and Ceres (and, weirdly, the position of Pluto too if Neptune is ignored), our understanding of the Solar System has been positively fuelled by coincidence. That's why I don't see any value in discussing these Planet Nine hypotheses until we actually find the thing: to use the vulgar Internet term, POIDH: pics, or it didn't happen.

publiusr
2016-Jun-04, 04:03 PM
POIDH: pics, or it didn't happen.

Speculation *may* lead to those pix. Recent talk has it that our Sun may have stolen Plan-9 (sorry...I had to)
https://www.sciencedaily.com/releases/2016/05/160531082201.htm

Maybe someone can see just what star passed us close the last time and work backward from that. 'Scholz's Star' say...
http://www.skyandtelescope.com/astronomy-news/stars-closest-flyby-sun/
http://www.universetoday.com/119038/a-star-passed-through-the-solar-system-just-70000-years-ago/

Another near pass for us? https://en.wikipedia.org/wiki/HIP_85605
"Until now, the top candidate for the closest flyby had been the so-called “rogue star” HIP 85605"
http://cosmoquest.org/forum/showthread.php?161285-Solar-close-encounters-and-the-Oort-Cloud

Something knocked over Uranus axis at some point in time....

Hornblower
2016-Jun-04, 06:41 PM
Snip from post 151:

Neptune was discovered due to a small random uncertainty, Pluto was discovered because of a large systematic one.
Snip from post 153:

The story I was told was that Neptune was discovered because the orbit of Uranus had a tiny inconsistency that was nevertheless larger than the random uncertainty. Pluto was discovered because the orbit of Neptune contained a large systematic error in interpretation (by Percival Lowell).
See the following Wiki article about Pluto:
https://en.wikipedia.org/wiki/Pluto

It appears that calculations by Lowell, Pickering, et. al. were thrown off by, among other things, an overestimate of Neptune's mass by about 0.5%. After Voyager 2 firmed up Neptune's mass in 1989, recalculation eliminated any anomalies that would require the sort of Planet X that was being sought by Lowell. Even before 1989, estimates of Pluto's mass from the motions of Uranus and Neptune had been greatly reduced. The Wiki article did not specifically say why, but I can imagine that improved positional measurements of those planets over longer arcs of their orbits must have helped over the 70 years since Lowell's death.

I am not surprised by difficulties in determining Neptune's mass before 1989. All we had to go on was Triton's orbital motion, and we would have needed to measure its angular separation from the planet with an uncertainty of something like a few hundredths of an arcsecond to get a good result. My educated guess is that it was not easy to do so.

Ken G
2016-Jun-04, 09:52 PM
It appears that calculations by Lowell, Pickering, et. al. were thrown off by, among other things, an overestimate of Neptune's mass by about 0.5%. After Voyager 2 firmed up Neptune's mass in 1989, recalculation eliminated any anomalies that would require the sort of Planet X that was being sought by Lowell.OK, so that's a classic example of a systematic uncertainty. They are always so much harder to account for, you really have to just wait for them to be firmed up.

StupendousMan
2016-Jun-04, 11:58 PM
All we had to go on was Triton's orbital motion, and we would have needed to measure its angular separation from the planet with an uncertainty of something like a few hundredths of an arcsecond to get a good result. My educated guess is that it was not easy to do so.

Hmmm. Presumably we'd use a variant of Kepler's Third Law to derive the mass of Neptune from motions of Triton, right? In that case, the mass of Neptune would depend on the separation between Neptune and Triton to the third power. If an observer's error in the separation was about 10%, then the error in the mass of Neptune would be about 30%. And an error of 1% in separation would correspond to an error of about 3% in mass. So an error of 0.5% in mass would correspond to an error of, let's see, 0.5% / 3 = 0.16% or so.

Now, the angular separation of Triton from Neptune, as seen from the Earth, varies from about 10 arcsec to about 17 arcsec. Let's use the smaller value. An error of 0.16% out of 10 arcseconds would be ... 0.016 arcseconds.

Just like Hornblower said.

selvaarchi
2016-Jun-05, 02:21 AM
The strange thing about all these probability arguments is that it is almost as if the scientists reporting them don't understand that probability estimates are always conditional on a set of constraints. So what is the probability that the constraints being used to assess the probabilities are correct? This is the difference between what we might call random and systematic uncertainties. One should not quote random uncertainties as a way of avoiding talking about systematic ones, that's why in science, we wait for confirmation. Why do we always hear about how Neptune was discovered, and leave out how Pluto was discovered? Neptune was discovered due to a small random uncertainty, Pluto was discovered because of a large systematic one.
What I am hoping for is that they do find Planet 9. This will open up new phase of exploration opportunities. Due to distance involved new ways of covering that distance will be explored. The next step before we look at travelling to the nearest star and a much more realistic goal.

Sent from my SM-G900F using Tapatalk

Ken G
2016-Jun-05, 05:58 AM
What I am hoping for is that they do find Planet 9. This will open up new phase of exploration opportunities. Due to distance involved new ways of covering that distance will be explored. The next step before we look at travelling to the nearest star and a much more realistic goal.I agree, it would be really amazing if the universe sent us an exoplanet we could travel to. It would really change our picture of star systems if their outer planets were merely "on loan."

George
2016-Jun-08, 03:40 PM
I agree, it would be really amazing if the universe sent us an exoplanet we could travel to. It would really change our picture of star systems if their outer planets were merely "on loan."
If they are friendly, if they want it back, if they can prove it was theirs, if it doesn't have oil, if we can get a slight annual storage fee, I say let them have it. If's can be fun, even systematical ones.

"If if and buts were candy and nuts, we'd all have a merry Christmas!" -- Dandy Don Meredith.

AFJ
2016-Jun-10, 10:31 AM
: pics, or it didn't happen.

It might already been imaged by one of the sky surveys, just not identified as such.

For people that are interested in actively participating in a search for P9 based on above assumption, here is a cool unofficial Zooniverse project. It is a 1-man project started a couple of months ago by 'Planetaryscience', and is bound to gear up this summer with more subject images from a smaller search area:

https://www.zooniverse.org/projects/planetaryscience/x-marks-the-spot

Enjoy!