Race to discover Planet Nine using astronomy and new computational techniques | Hacker News Reader

Race to discover Planet Nine using astronomy and new computational techniques

spectrum.ieee.org

166 pointssohkamyung58 comments

Anyone interested in the search should follow Brown and Batygin's Planet Nine blog at http://www.findplanetnine.com/

New And Better Data Disfavors A Giant World Beyond Neptune

https://www.forbes.com/sites/startswithabang/2017/06/21/good...

As the months passed since it was first proposed by Konstantin Batygin and Mike Brown, they compiled additional evidence for it, and things were looking rosy. But a new study by Shankman et al. has turned the evidence on its head, disfavoring the planet's existence and uncovering a bias in the data itself.

https://arxiv.org/abs/1706.05348

"The clustered TNOs were detected across different and independent surveys, which has led to claims that the detections are therefore free of observational bias. This apparent clustering has led to the so-called "Planet 9" hypothesis that a super-Earth currently resides in the distant solar system and causes this clustering. The Outer Solar System Origins Survey (OSSOS) is a large program that ran on the Canada-France-Hawaii Telescope from 2013--2017, discovering more than 800 new TNOs. One of the primary design goals of OSSOS was the careful determination of observational biases that would manifest within the detected sample. We demonstrate the striking and non-intuitive biases that exist for the detection of TNOs with large semi-major axes. The eight large semi-major axis OSSOS detections are an independent dataset, of comparable size to the conglomerate samples used in previous studies. We conclude that the orbital distribution of the OSSOS sample is consistent with being detected from a uniform underlying angular distribution."

Yes, I've heard of that. Some follow-up articles I've read [1] [2] say that the evidence against (or for) Planet Nine is still inconclusive. But the question should be settled one way or another: Planet Nine will either be there or it won't.

[1] "Solar System survey casts doubt on mysterious 'Planet Nine'" [ https://www.nature.com/news/solar-system-survey-casts-doubt-... ]

[2] "Planet Nine Is Put on Trial in Absentia" [ https://www.quantamagazine.org/planet-nine-is-put-on-trial-i... ]

They thought that about dark matter.

The article accounts for this new data. You might want to see Batygin's post itself here: http://www.findplanetnine.com/2017/06/status-update-part-1.h...

Basically, yes, if you just look at bodies that OSSOS detected, it does not support the Planet Nine hypothesis. If however you consider both what OSSOS found and the already known TNOs, the new picture reinforces the Planet Nine hypothesis (with one outlier TNO that doesn't really fit, although it can apparently be made to).

And from Batygin and Brown's (font-mangled) website: "A recent paper[1] that Mike put together shows exactly the opposite to be true for the non-OSSOS dataset: observational bias cannot account for orbital clustering beyond 250AU."

I love this sort of debate.

[1] https://arxiv.org/pdf/1706.04175.pdf

A nice update in the search for Planet Nine that touches on a lot of new computational, survey-based, and modeling efforts to localize the planet. Great level of detail.

I hope I get to see some New Horizons-esque images of it by the time I'm old and grey.

Imagine its moons. Does it have rings? Does it have Trojans? Is it another line of defence, a remote cosmic vacuum cleaner, like Jupiter? Maybe Clarke's monolith lurks in its orbit.

I can't wait to find out.

Even more interesting, is this disturber of the cuiper belt, the responsible one for the exstinction events (dinosaurs) that happened to our little world.

This is awesome. Also I found a tiny nitpick

"But the early 1990s also brought a big breakthrough in an algorithm, known as symplectic integration, that reduced computational times by an order of magnitude."

then

"Because symplectic integrators don’t waste time rediscovering Kepler’s laws over and over, they run orbital simulations hundreds of times as fast as older methods do."

100 times as fast is two orders of magnitude.

Maybe,maybe not. Depends on what base you are measuring magnitude in.

In base 10, 100x is 2 orders of magnitude.

In base 2, the same speed up (written in binary: 1100100x) is between 6 and 7 orders of magnitude.

No one means any base other than base 10 when they use that phrase in casual speech (without previously saying so).

If "Planet Nine" doesn't exist, that will be fitting Karma for those who proposed it, since they developed the new definition of planet specifically to exclude Pluto and any other planets like Pluto.

(I disagree with that definition as it made no consultation with planetary scientists who actually study planets.)

I'm confused by your parenthetical, as the definition that excludes Pluto (and Eris) was arrived at by the International Astronomical Union (https://www.iau.org/).

IAU is made of astronomers (i.e. People who study stars and stuff), not so many planetary scientists (who specifically study planets).

I think it's fair to define planets based on an astronomical perspective; it's clear that Pluto, Eris and things like it, astronomically, belong to a different class than the other planets. Pluto is now classified as a dwarf planet. If we didn't "demote" it to a dwarf planet, then we would have to define a new term for the existing planets.

I don't follow. Planet Nine is not expected to be another dwarf planet like Pluto. There are a handful of other dwarf planets known already, some bigger than Pluto, and it's expected that there are hundreds more yet to be discovered.

Some may be bigger than Earth, yet still classed as dwarf planets. Therefore, I think the definition is BS as it has nothing to do with the planet itself (such as its geography, size, etc) but only the bodies around it.

You say "may be bigger than Earth", but I'm unaware of any dwarf planets that are bigger than Earth. Are there any? Assuming there are none, that's rather the point: bodies that large would tend to clear out their local zone.

I am intrigued by your conspiracy theory and would like to subscribe to your newsletter. Why did they want to "specifically exclude Pluto"?

Pluto is notoriously different from the other eight planets, as can be explained in very elementary terms [1]. So, not to open any wounds, but the question is inevitably raised as to whether it is the same kind of "thing" as the other planetary bodies.

[1]. https://airandspace.si.edu/stories/editorial/pluto%E2%80%99s...

The actual planet itself is very active geologically and has a whole system of moons. The only reason you'd say it's very unlike the other 8 is due to orbital dynamics, i.e. due to other bodies besides itself. This is a strongly anti-planetary-science bias, IMHO.

Sooo... mass and composition are irrelevant? Because Pluto (and its fellows, like Eris) are smaller than a half-dozen moons. Pluto has less than _five percent_ of the mass of the smallest planet, Mercury. It is also mostly _ice_ unlike the inner (rocky) planets and the gas giants.

And variety of solar-system bodies are geologically active, from the inner planets, through numerous moons, down to comets and asteroids, and probably many other Trans-Neptunian Objects like Pluto (many of which also have moons). Your proposed criteria fail to be useful.

Maybe I missed it in the article, but why would P9 be at a 30 degree angle from all the other planets. Are they saying that what we know of how solar systems collapses to the nearly the same plane is wrong?

That effect decreases further out in the gravity well.

It would have been knocked into an eccentric orbit early in the Solar System's formation (when we had a lot more planets).

It couldn't have formed that far out. We know Uranus and Neptune are too far away - they formed closer in than they are now, and interactions with Saturn and Jupiter pushed them out. In fact, there's evidence that they switched places (Neptune originally being closer). Planet Nine could have been thrown into an eccentric orbit during this time.

Here's a relevant wikipedia article: https://en.wikipedia.org/wiki/Nice_model

What do you define as a planet though? If you consider our sun a frame of reference, you might find that technically some far away objects bigger than the sun have complex periodical movements around the sun.

Are you suggesting that the galaxy revolves around the sun? Heresy!

I am going to become a flat-galaxier!

I'm pretty sure the definition would include having the sun as the major gravitational force acting on the object.

Well the definition that removed pluto from being a planet is this:

https://en.m.wikipedia.org/wiki/IAU_definition_of_planet

I think that's an interesting question, but the search being described is for a fairly specific kind of object with constrained parameters: https://en.wikipedia.org/wiki/Planet_Nine

definition of a planet as follows: a planet is what ever arbitrary metrics Brown can come up with that demotes Pluto and includes the other 8 (sort of) so that he can write papers / gain fame / etc. They didn't come up with criteria and found Pluto didn't fit, they kept coming up with criteria UNTIL Pluto didn't fit and the other planets did fit.

Brown has no army over me, and I don't buy into the academic nonsense. Pluto is a planet.

Another American that can't live if Pluto is a planet....

Can we name this one Pluto too, for old times' sake?

Pl2to

Plu2

"And we shall call it Pluto Too!"

"Pluto Two!? That's ridiculous!"

"Wait, is it two like the number two or too like also??"

---

I don't know how our story resolves, but that exchange popped in to my head.

Pluto To Who?

No Who's on first

I vote for either Yuggoth or Nibiru.

Nibiru is usually referred to as "Planet X". If it was called "Planet IX", it would be a better fit. :-)

IX would be a slightly ominous name to choose :) https://en.wikipedia.org/wiki/Ix_(Dune)

There's a remark in one of the books that the Ixians were completely unaware that their planet was named that because it was the ninth out from the Sun.

+1 for Yuggoth!!!

Of course, if we name it that, we have to go looking for Fungi out there! ;-P

or Urectum

I vote Goofy.

Noob question: Why isn't it passing in front of stars? Are we seeing a sequential dimming of occluded stars along the plane of the ecliptic?

The odds of catching an unknown planet dimming a star are (pardon the pun) astronomical.

Even the New Horizons team needed a lot of effort to catch their new target passing in front of a star [1]. Granted, Planet Nine is a bigger target, but the odds are still pretty low.

[1] "NASA’s New Horizons Team Strikes Gold in Argentina" https://www.nasa.gov/feature/nasa-s-new-horizons-team-strike...

My intuition suggests that a planet far out and small would be very difficult to detect by its occlusion.

This page calculates that Pluto for instance spans only 3 pixels at the Hubble space telescopes resolution: http://www.planetary.org/blogs/emily-lakdawalla/2013/0214101...

Indeed. The article says that the hypothetical planet would be 2 pixels.

The pixel size isn't what determines if occlusion happens.

The planet and the star can both be much smaller than a pixel, as long as the planet is big enough to cover the star.

If Hubble can barely see Pluto, how the heck did terrestrial telescopes find it in the first place?

Wasn't the presence of a Pluto-like body _known_ because the orbits of other planets didn't match expectations based on the gravitational pulls of all the other known bodies in our solar system?

Not exactly. It's true that Neptune was discovered that way and that people found Pluto while looking for a "Planet X" that would explain other gravitational discrepancies:

In the 1840s, Urbain Le Verrier used Newtonian mechanics to predict the position of the then-undiscovered planet Neptune after analyzing perturbations in the orbit of Uranus. Subsequent observations of Neptune in the late 19th century led astronomers to speculate that Uranus's orbit was being disturbed by another planet besides Neptune.[1]

However it turned out that Pluto was not Planet X after all. After all Neptune and Uranus are respectively about 7900 and 6700 times more massive than Pluto.

In 1978, the discovery of Pluto's moon Charon allowed the measurement of Pluto's mass for the first time: roughly 0.2% that of Earth, and far too small to account for the discrepancies in the orbit of Uranus. Subsequent searches for an alternative Planet X, notably by Robert Sutton Harrington, failed. In 1992, Myles Standish used data from Voyager 2's flyby of Neptune in 1989, which had revised the estimates of Neptune's mass downward by 0.5%—an amount comparable to the mass of Mars—to recalculate its gravitational effect on Uranus. With the new figures added in, the discrepancies, and with them the need for a Planet X, vanished. Today, the majority of scientists agree that Planet X, as Lowell defined it, does not exist. Lowell had made a prediction of Planet X's orbit and position in 1915 that was fairly close to Pluto's actual orbit and its position at that time; Ernest W. Brown concluded soon after Pluto's discovery that this was a coincidence, a view still held today.[2]

[1] https://en.wikipedia.org/wiki/Pluto#Discovery [2] https://en.wikipedia.org/wiki/Pluto#Planet_X_disproved

To see something that acts like a point of light, size doesn't matter at all. Glowing objects are visible even when their area is a small fraction of a pixel. But your chances of noticing occlusion are much lower.

p9 is not believed to be aligned with the ecliptic. The most recent article I've seen estimates it to be inclined around 30° relative

[1] https://www.theguardian.com/science/2016/oct/19/planet-nine-...

As other repliers have said, this sort of thing is very rare. Trans-Neptunian Objects are so far away that their visible size is absolutely tiny, so occulations are rare and last for maybe a second or so.

But! They do happen and are a great way to learn more about those objects as very briefly you can see something of them. The problem is that first you need to know the exact orbit, then you can predict occulations.

See https://en.m.wikipedia.org/wiki/(486958)_2014_MU69 for an example. It recently had some occulations that have helped better understand it.

If we pointed any of a handful of our most powerful telescopes at it we could image it directly. But how would we know it's planet nine versus something else? Some uncatalogued star or some undiscovered asteroid? We'd need to already know where it was supposed to be. Or, we'd need to have multiple images of the same section of the sky over a period of enough days to have the image of the planet move relative to the stars and be able to reveal itself as a distant planet.

The fact is, we simply do not image enough of the sky on a regular basis to have all this imagery just lying around. We do have some pretty good all sky surveys, but they don't use telescopes big enough to see something like planet nine. That's why it takes a dedicated effort to discover planet nine. It'll take imaging huge sections of the sky multiple times with enough delay between them to be able to see separation in the position of the object. Such large telescopes are very expensive and rare so their time is very valuable and in high demand.

Distant stellar transits will happen but we're not monitoring the entire sky 24/7 to the degree needed to spot all of them. If we were we'd be able to see the planet directly just as easily.

Our view of the sky is typically just a matter of seeing through little soda straws from one day to the next, so we miss a lot.

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