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Corresponding with the three-year anniversary of their announcement hypothesizing the existence of a ninth planet in the solar system, Caltech's Mike Brown and Konstantin Batygin are publishing a pair of papers analyzing the evidence for Planet Nine's existence.
The papers offer new details about the suspected nature and location of the planet, which has been the subject of an intense international search ever since Batygin and Brown's 2016 announcement.
The first, titled "Orbital Clustering in the Distant Solar System," was published in The Astronomical Journal on January 22. The Planet Nine hypothesis is founded on evidence suggesting that the clustering of objects in the Kuiper Belt, a field of icy bodies that lies beyond Neptune, is influenced by the gravitational tugs of an unseen planet. It has been an open question as to whether that clustering is indeed occurring, or whether it is an artifact resulting from bias in how and where Kuiper Belt objects are observed.
To assess whether observational bias is behind the apparent clustering, Brown and Batygin developed a method to quantify the amount of bias in each individual observation, then calculated the probability that the clustering is spurious. That probability, they found, is around one in 500.
[...] The second paper is titled "The Planet Nine Hypothesis," and is an invited review that will be published in the next issue of Physics Reports. The paper provides thousands of new computer models of the dynamical evolution of the distant solar system and offers updated insight into the nature of Planet Nine, including an estimate that it is smaller and closer to the sun than previously suspected. Based on the new models, Batygin and Brown -- together with Fred Adams and Juliette Becker (BS '14) of the University of Michigan -- concluded that Planet Nine has a mass of about five times that of the earth and has an orbital semimajor axis in the neighborhood of 400 astronomical units (AU), making it smaller and closer to the sun than previously suspected -- and potentially brighter. Each astronomical unit is equivalent to the distance between the center of Earth and the center of the sun, or about 149.6 million kilometers.
-- submitted from IRC
The planet nine hypothesis (DOI: 10.1016/j.physrep.2019.01.009) (DX)
Orbital Clustering in the Distant Solar System (DOI: 10.3847/1538-3881/aaf051) (DX)
Previously: CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
(Score: 3, Interesting) by takyon on Friday March 01 2019, @04:49PM (27 children)
If Planet Nine exists and these new estimated characteristics are closer to being true, it would mean that Planet Nine is easier to reach and less likely to be ejected by passing stars (see this recent paper [sciencedaily.com] about how an object currently over 700 AU from its star interacted with passing stars).
Then we have a lower mass assumption of 5 Earth masses, or somewhere between 5-10. This raises the possibility of the planet having a solid surface that could be landed on by rovers or humans, with a surface gravity around 1g or up. If it doesn't have a crushing Venus-like atmospheric pressure, then humans could live there, and possibly find life in a subsurface ocean. I guess the only downside would be that the planet would have a smaller Hill sphere from being closer to the Sun and less massive, so it would have less potential moons.
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(Score: 4, Insightful) by fyngyrz on Friday March 01 2019, @05:10PM (24 children)
FTFY
Planet nine is Pluto, and will always be Pluto, unless a new planet is discovered in a closer orbit.
The IAU's "point 3" [wikipedia.org] is the dumbest bloody thing ever put out by a modern (supposedly) scientific body. What if some asteroid or comet, or several, breaks up in Earth's orbit? Are we then no longer a planet because our orbit isn't clear? What about something that takes much longer to make an orbit (cough, Pluto)? Are they expecting clearance to be equally achievable / likely there? What about the moon? Our orbit hasn't been cleared of that. And artificial satellites — our orbit definitely isn't clear.
Somebody needs to smack those idiots repeatedly with a rolled-up newspaper. Otherwise, next meeting, they're likely to add point 4: "a planet must have a McDonalds."
Idiots.
--
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(Score: 2) by choose another one on Friday March 01 2019, @05:59PM (2 children)
> What if some asteroid or comet, or several, breaks up in Earth's orbit? Are we then no longer a planet because our orbit isn't clear?
Ahem already happened - see Cruthine, asteroid, "co-oribital". With Earth.
(Score: 2) by fyngyrz on Friday March 01 2019, @06:52PM (1 child)
Well, there you go. According to the loonies at the IAU, Earth's not a planet. 😊
And besides that — what about two [rule 1,2] compliant objects in the same orbit on opposite sides of their star? Ones like Earth, or Venus? They're not planets either? Sheesh.
--
A sheep, a drum, and a snake fall off a cliff.
BA-DUM-TSS
(Score: 2) by All Your Lawn Are Belong To Us on Friday March 01 2019, @07:14PM
Except that just because something is co-orbital has no final say in regards to being clear of the neighborhood. By that category all the L4/L5's of Jupiter and Saturn mean they're not planets either. For Earth, 2002_AA29 would be a better choice than Cruithne in terms of co-orbital similarity.
But that doesn't mean one jumps for joy. Oddly I don't find a mass for Cruithne listed anywhere handy. But Cruithne is about 5 km diameter per Wikipedia. Exactly how is that supposed to challenge Earth's gravitational dominance - the real distinguishment to say a planet hasn't cleared its orbit? Doesn't matter if it smacks Earth and ends all life as we know it, either - what does that do to Earth's orbit? Answer: nothing.
Paging Rick Sanchez for orbital mechanics consult....
This sig for rent.
(Score: 3, Interesting) by bob_super on Friday March 01 2019, @06:05PM
We have already found a planet nearer: Ceres. And a few distant ones, making this unknown giant at least number 14...
The stupidest part about that dumb decision, is that it could not have happened today.
Pluto used to be less than a dozen pixels on a Hubble picture, and people already got pissed at the declassification.
Try to imagine the uproar, if they were to try to do that after the New Horizon pictures came in, with the Heart, the mountains, the atmosphere...
(Score: 4, Insightful) by Thexalon on Friday March 01 2019, @06:51PM
I understand exactly what they were trying to get at with that third point: Planets are supposed to be big rocks or balls of gas. Ceres, Pluto, Eris, etc aren't really all that big - the largest of them that we know about is about 1/20th the size of Mercury, which is the smallest object everyone agrees is a planet. The fact that they're all that small, and there's that much other stuff near them, suggests that it's a different phenomenon from the other 8 objects that everyone agrees is a planet.
Also, by any reasonable standard, Eris would have more claim to "planet" status than Pluto does.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 4, Insightful) by urza9814 on Friday March 01 2019, @07:08PM (12 children)
Define "Planet", and explain how that definition fits Pluto without including something like Ceres.
Once upon a time the solar system was known to have 23 planets. Refining the definition isn't exactly unprecedented. That's how science works -- we learn new things and we update our understanding accordingly. Deal with it.
Hell, you can even still call Pluto a planet if you want, it is a Dwarf Planet after all. But it still isn't number nine.
(Score: 2) by tangomargarine on Friday March 01 2019, @08:02PM (1 child)
Sure, but I'm not really sure why people seem to think we *need* a smaller number of planets. That 10 or 11 or whatever is just "too many."
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 2) by urza9814 on Friday March 01 2019, @08:17PM
Yeah, that's fine. I know people who claim Pluto is a planet because it's a "Dwarf Planet", which is a perfectly legitimate stance as far as I'm concerned as long as you include all such bodies. There's just no justifiable argument by which Pluto would be number 9. But if you want to call it number 24 or whatever the number would be, that's fine by me.
(Score: 3, Informative) by Arik on Friday March 01 2019, @08:55PM (7 children)
Why can't it include Ceres?
The classical definition of a planet is 'a moving star' - an object in the night sky which moves independently and at a speed which allows movement to be detected in a single night - as opposed to the 'fixed stars' - the objects in the night sky which move together, and whose movement occurs on an annual cycle which can only be detected after observing for some time and comparing positions across at least a portion of the year.
Now as time went on we realized that the reason the planets move is because they're much closer - they're actually other spheres in orbit around the same sun here. And the so without that original definition really being changed (it still fit and worked) the additional layer of meaning or understanding became added to the word - that they are local objects orbiting our star, rather than other stars. But operationally, they're still the stars that move (quickly.) Also the moon, at this time, started to be less likely to show up in lists of "planets" but that was neither immediate nor complete. The moon still makes the list in some contexts today, though it's no longer considered astronomically correct.
The next time that definition was altered was, coincidentally, not so very long after the discovery of Ceres. Ceres was initially considered a planet (though commonly with the adjective 'minor' which is still how it's referred to today,) however this usage fell out of favor as dozens of similar objects were quickly discovered in approximately the same orbit. This made it look more like a fragment of a planet, whether one that formed and then was somehow destroyed, or one that never managed to form. However you explain it, the counting of Ceres as a planet was quickly replaced with the note of the asteroid belt as a sort of planetary vicar.
And of course in sketching that out I've just about made the case for rejecting Pluto. There are certainly similarities. When Ceres was discovered it immediately became the smallest known planet - if you really considered it a planet. The same could be said for Pluto. Both are much smaller than Mercury, the smallest of the classical planets. And both could be said to occupy roughly the same orbit as a number of smaller objects. So by analogy to Ceres, you can argue that Pluto is better considered part of the Kuiper disk than a planet on its own. Especially after the discovery of Eris, of course.
But Pluto is still an order of magnitude larger than Ceres (in fact it's larger than the entire belt would be if you stuffed them all together.) The other asteroids seem to be pretty consistent with Ceres in composition and orbit, while most of the Kuiper objects are just iceballs and the orbits vary wildly. Also very few people ever really considered Ceres to be anything other than a 'minor planet' to begin with.
I think a decent argument can be made for the reclassification, but the way that it was supposedly done - one ambitious astronomer with a talent for politics lobbied until he got a professional organization to proclaim it as a new fact for the unwashed masses to quickly memorize and swear allegiance to - was so completely wrong that it will probably take another generation before the change actually occurs. Language policing provokes backlash.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Saturday March 02 2019, @12:38AM (5 children)
Because then Pluto would be Planet Ten (or more), refuting fyngyrz's claim.
(Score: 2) by fyngyrz on Saturday March 02 2019, @01:19AM (4 children)
No, it doesn't:
Carry on. 😊
--
Government: Designed to provide you with "service" and...
...the Media: Designed to provide you with Vaseline.
(Score: 0) by Anonymous Coward on Saturday March 02 2019, @01:52AM (3 children)
In what sense is Ceres, discovered 129 years prior to Pluto, a "new planet"?
(Score: 2) by fyngyrz on Saturday March 02 2019, @04:24PM (2 children)
In what sense is this relevant to anything? If an object is found to meet the criteria as a planet, it's a planet. Not the IAU's criteria, of course, because those people have clearly failed to define a useful, consistent metric.
Once an object is found to be a planet, it's planet number [whatever] as counted outwards by the majority of its orbit. Planets in orbits further out then become planet number [whatever+1].
How hard is this to understand?
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I have neither the time or the crayons to explain.
(Score: 0) by Anonymous Coward on Saturday March 02 2019, @04:31PM (1 child)
Why ask us how it's relevant? You're the one who said it, you should know.
(Score: 2) by fyngyrz on Saturday March 02 2019, @05:30PM
Okay. I see where you're going.
When a planet is newly found to meet the criteria, then...
Get it now? That's how I was using the term. Seemed blindingly obvious to me, but I guess that's because I already understood what I meant. Sorry.
--
The actor who played captain Kirk on TOS has
shut down his new line of ladies lingerie.
Apparently "Shatner Panties" wasn't the
best choice for a name.
(Score: 4, Informative) by bzipitidoo on Saturday March 02 2019, @05:43AM
What definitions are the most useful? The distinctions between planet, dwarf planet, moon, and asteroid are to a large degree circumstantial and artificial.
Yes, I agree that from a standpoint of impartial objectivity, the timing of the most recent redefinition of planet was very poor. New Horizons was on the way to give us our first close view of Pluto. They could have and should have waited for that information. Clearly, other considerations were in play. Perhaps they wanted to generate publicity, and one of the best ways to do that is whip up some drama. The media would have loved it even more if the astronomers had gotten into a fist fight during their meeting. Another likely motive was to poke at the US. And what better way than to demote the only planet discovered by an American? Even better that it was done when an American probe was en route for the only look we are likely to have for decades. That appearance of petty spite was unworthy of scientists.
Another factor that causes controversy is the highly questionable criteria they adopted. People have somewhat gleefully pointed out serious problems, presenting situations in which the new definition does not work well. For instance, a body could change status between planet and moon once each orbit. Pluto and Charon are really a double planet, as their barycenter is in space, not within Pluto, yet everyone calls Charon a moon of Pluto. If Charon was in a highly elliptic orbit, the barycenter would move in and out of Pluto as Charon approached and then receded from perigee with Pluto. Even our own moon will eventually change status into a planet, when it has receded far enough to move the barycenter outside Earth. One of the big problems with gravitational dominance is that the further a body is from the star it orbits, the more massive it has to be to qualify as a planet.
(Score: 2) by fyngyrz on Saturday March 02 2019, @01:10AM (1 child)
Why bother? Why not just include Ceres? And Eris, and Makemake, and Haumea?
Why try to change the understanding of what a planet is for absolutely no good reason?
And good grief, just look at it! [futurecdn.net]
Define planet? I think I can do that pretty easily:
Admittedly that may not be a perfect set of criteria, but I submit that it is at least close. Much closer than the IAU's recent profound lapse of judgement.
We've had a solid understanding of these general ideas for a very long time, and recasting that understanding for absolutely no good cause at all is no more than an exercise in absurdity.
Pluto is a planet, and I'm pretty sure it will always be a planet, despite this unfortunate incident of IAU shills finding nothing more productive to do with their time.
--
Diapers and Politicians should be changed often.
Both for the same reason.
(Score: 2) by dry on Saturday March 02 2019, @07:12AM
Pluto was always questionable as a planet. It's small, has a weird orbit and it seems that the only reason it was pushed to be a planet was some emotional Americans.
Anyways if you're going to insist it is a planet, it wouldn't be number nine, as we might as well reinstate Ceres and perhaps Vesta as planets.
(Score: 2) by All Your Lawn Are Belong To Us on Friday March 01 2019, @07:16PM (3 children)
Forgot to ask if it exists, when are we going there?
This sig for rent.
(Score: 3, Informative) by bzipitidoo on Friday March 01 2019, @07:51PM
Not for a couple of decades. I would love to have a New Horizons 2 ready to launch the moment Planet 9 is found. But there are a lot of problem to overcome first. NASA is definitely not going to build a probe before we've even found the planet, for the simple reason that it might not exist. The next problem is that Planet 9 is never closer than about 250 AU. That's roughly 6 times further than Pluto. New Horizons would need something like at least 50 years to reach the planet. That's pushing the longevity of current technology. So we would probably rather send a smaller faster probe.
(Score: 3, Informative) by takyon on Friday March 01 2019, @07:55PM
https://soylentnews.org/~takyon/journal/2331 [soylentnews.org]
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(Score: 2) by All Your Lawn Are Belong To Us on Friday March 01 2019, @09:19PM
Shucks, was hoping somebody would get it..... We are going to Planet Ten Real Soon! [youtube.com]
This sig for rent.
(Score: 2) by Gaaark on Friday March 01 2019, @10:39PM
" "a planet must have a McDonalds.""
Surprised that's not happened yet....EVERYWHERE!
"Welcome to McDonalds on Mars: can i get you some shite food?"
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Friday March 01 2019, @11:10PM
Following your own link gets me here:
Emphasis mine.
So to disqualify earth it would have to be a HUGE comet.
(Score: 2) by dry on Saturday March 02 2019, @07:08AM (1 child)
Raises the question of whether an ice world, which this probably would be, can be landed on. Imagine landing a craft on frozen nitrogen, oxygen etc, it would have a tendency to sink.
(Score: 2) by takyon on Saturday March 02 2019, @03:25PM
I suspect it would be a solvable challenge, vs. the potentially impossible challenge of "landing" on Jupiter, Saturn, Uranus, or Neptune.
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