A New World’s Extraordinary Orbit Points to Planet Nine | Hacker News Reader

A New World’s Extraordinary Orbit Points to Planet Nine

quantamagazine.org

149 pointsbcaulfield51 comments

It occurs to me that, in the early 21st century, astronomy has once again become the hot area in physics, whereas particle physics was for the last part of the 20th century. Not that it's necessarily a contest, but I read of a lot more exciting new discoveries from the physics of the very large, in recent years, than from the physics of the very small.

This is very directly a product of the rapid increase in astronomical equipment vs a collider situation that has been dominated by the LHC with no new construction beyond that to speak of. They are slowly upgrading the LHC but that's nothing compared to the rapid growth that ended with the massive political failure of the Superconducting Supercollider in the US.

I believe it's also about new computational techniques that allow more to be concluded from e.g. planet wobbles.

New computational techniques are also being developed for analysing collision data, CERN are not just sitting on their hands; However the new science there does not all sound as exciting as electroweak unification or the discovery of the antiproton at the Bevatron and so on. The LHC got one big win (the Higgs) and many smaller victories (copious quark gluon plasma production and a detector especially designed to study it, more charm production than we ever had before, I could go on for hours). However "more charmed mesons produced than before" doesn't ignite the layperson's imagination and capture their support like exoplanets or new bosons do.

It goes both ways (in astronomy and particle physics) but I think the difference is there's more bang for the computational buck in astronomy. It takes trillions of collisions to collect enough data to make a discovery about a single particle, for example.

Interestingly, one way that computational resources have recently had an impact is with the GAIA astrometry survey mission. There's a concept in optics of an image being "diffraction limited" meaning that there is a characteristic resolution limit for a particular wavelength of light and optical instrument size. Meaning that there isn't an advantage to having pixels that are smaller than that limit, since you'll just have a blurry blob that is smeared across multiple pixels anyway, you won't actually be able to increase the resolution of what you can see. However, this isn't entirely true. What actually happens is that the light from a point-like source is spread out over an area in a characteristic pattern called the "point spread function". If you were to resolve a distant star over multiple pixels (beyond the diffraction resolution limit) then if you were able to model the point spread function to fit the data for those pixels you could potentially locate the position of the star to a precision that was higher than the diffraction limits of your optical assembly. And this is precisely what GAIA does. It uses a telescope that is much smaller than the Hubble but it has an enormous (gigapixel) CCD imager which enables it to map the point spread functions for huge numbers of stars simultaneously. Before the advent of ubiquitous high performance computing this wouldn't have been possible.

Perhaps the astrophysicists are getting on the data bandwagon, going back through collected data and applying the latest techniques on them. Are there any papers on this not behind paywalls?

I think you're being downvoted, i would say mistakenly, because that's not the case. What's happening in astronomy is that huge amounts of new high-quality data are becoming available.

This particular bit of Planet Nine business fell out of the Dark Energy Survey [1]:

The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

Over five years (2013-2018), the DES collaboration is using 525 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth.

Other big surveys recently include Kepler, looking for exoplanets since 2009 and only now running out of fuel [2], and Gaia, which for the last five years has been mapping over a a billion (!) stars across the galaxy [3] [4].

And in a few years, we should get the James Webb telescope going up. Exciting times!

[1] https://www.darkenergysurvey.org/the-des-project/overview/

[2] https://www.nasa.gov/feature/ames/nasa-s-kepler-spacecraft-n...

[3] http://sci.esa.int/gaia/28890-objectives/

[4] https://gizmodo.com/tomorrows-star-map-release-could-revolut...

Astronomy has gotten much better at promoting itself than it did in the past. Hubble helped; painting up all those pale objects in gorgeous colors, for example. (For shame!)

Most advances in modern physics are about invisible objects. Most people? given a choice between seeing the fireworks, or seeing an equation explaining how they work?

Well even if they are, I consider it more than ethical to use sci-hub

A lot of that is due to massive increases in our capabilities in astronomy. The '90s saw the advent of proper space telescopes, a whole slew of new giant ground based telescopes, and instrumentation that had gotten better by leaps and bounds. That was followed by new kinds of instruments becoming more common (infrared and x-ray telescopes, dedicated planet hunting telescopes) along with a rolling wave of new discoveries in astronomy, cosmology, and astrophysics (measuring the age of the universe precisely, detecting the acceleration of the universe, nailing down the energy and matter composition of the universe, detecting exoplanets, detecting colliding black holes and then neutron stars, etc.)

Today the field is in a state where technology and expertise is at a mature enough level to where certain capabilities are increasing rapidly year over year which has meant that new questions and new fields of study keep piling up even as old questions get answered. This is definitely an exciting time to be alive if you care about this sort of stuff. When I was a kid the error margins on the age of the Universe were laughably large, now they are a fraction of a percent.

Absolutely. NASA's TESS telescope just completed its first lunar flyby this morning on its way to its final orbital path. ESA PLATO mission launches next year. As well as JWST. All with open calls for citizen scientists!

Mikulski Archive For Space Telescopes

https://archive.stsci.edu/tess/

A review on Asteroseismology

https://arxiv.org/pdf/1703.07604.pdf

Computation has had two effects in astronomy.

Unprecedented data-analysis capability, sure. The other affect that I have seen is how new telescopes can be built, literally out of digital electronics. Radio-telescope arrays, CCD sensors for radio, infrared, visible-wavelength astronomy.

Sure, particle physics sensor data is getting a similar boost there, but those instruments have to make things go boom.

At the current state of the art, maybe telescopes can scale up faster than particle accelerators?

where can I learn more about CCD sensors for radio astronomy?

Software is eating Astronomy.

When I was taking chemistry classes... a few decades ago, organic chemistry was "all the rage". This was with the professors at a highly regarded if smaller undergraduate chemistry program.

Inorganic chemistry, some of which actually interested me more, seemed to be considered at least by a fair fraction of them comparatively sterile and having a more constrained future, especially with respect to the budding careers of us future chemists. I don't think that was a complete nor monolithic opinion, but I do remember it being a significant one that was being actively impressed upon impressionable young students.

Then, while organic chemistry didn't exactly decline, the semi-conductor industry and related applications, as well as a big spate of other advanced materials engineering, all took off.

It gets pretty hard to predict what's going to be hot, in the future -- and when.

Work at being at least somewhat of a polyglot, and you get to enjoy it all!

Planet Nine

I enjoyed the recent Science Friday episode that featured two New Horizons mission scientists, who were quite critical of IAU's goofy decision to demote Pluto.

Link to the interview: https://www.sciencefriday.com/segments/chasing-pluto-as-long...

> ... IAU's goofy decision to demote Pluto

I see what you did there.

Ha! I won't blame anyone who doesn't believe me, but that was genuinely unintended. I had typed something more strident, but dialed it back without rereading the whole passage. "Goofy" is a versatile word.

It is Planet X not Planet IX and they want our women! Get your tropes right. :-)

Does anyone know off hand the limit for reflected light from the Sun in terms of detection? Assuming a rockie planet is 'cold' and has a diameter 'd', at what distance is its magnitude so low that it is only detectable by star occlusion rather than reflected sunlight.

Not an astronomer, but let's try going by Wikipedia: Neptune has apparent magnitude of about 8. If you displaced it to twice as far, it'd become 16 times as dim (twice the distance, squared). The scale of apparent magnitude is a factor of 2.512 per step, so that'd be a change of about 3, to magnitude 11. The biggest ground-based telescopes can go up to around 24-26, if you dedicate significant observing time. So (26-8)/3=6 doublings: they could detect Neptune at 64 times as far out as it is, if they knew where to look. That's ~1900 AU.

But of course Neptune is bigger and likely more reflective than the target. I guess you could expect a brightness about one more magnitude lower. A quick skim of https://arxiv.org/abs/1601.05438 (the paper proposing the new planet) is difficult for me, but one concrete number they mention as a possibility is 700 AU. So, apparently, that'd be within reach of a ground-based telescope but it'd have to be a darned big state-of-the-art one.

I get why Pluto had to be demoted to minor league status.

But they should at least have retired the number. Pluto will always be Planet Nine.

How did they detect 2015 BP519? On the diagram, it looks like the proposed Planet 9 is 10% farther than the detected object, but is 10x Earth size compared to the size of a Kupier belt object.

It seems like detecting the smaller inject would be the harder task yet Planet 9 remains undetected.

There is some degree of luck in these detections: we can watch large patches of the sky at low sensitivity or small patches of the sky at high sensitivity, but at high sensitivity we cannot watch the whole sky at once (rather, choosing small patches to study).

there's only one planet 9 but probably zillions of dwarf planets. there are enough of them that it's feasible that you can stumble across one through something closer to dumb luck

Imagine finding a penny on the sidewalk. Happens all the time right? Now imagine I asked you to go out and find a half-dollar on the sidewalk, but not just any one, a specific one. But don't worry, you don't have to look everywhere, it's almost certainly in one of the US states on the East Coast.

That's the difference here. We don't spend all our time scanning the entire sky down to the dimness level that Planet 9 could be spotted, we simply do not have the resources. Our telescopes give a soda straw view, so we miss a lot of what's going on, most of it in fact. If someone knew already where Planet 9 was in the sky we could point our telescopes there over a few days and confirm it. But we don't, we only know a general area in the sky that it could be, and actually detecting it will require dozens of observations from some of the largest telescopes on Earth.

On the other hand, we have detected lots of other objects in the Solar System that would be more difficult than Planet 9 to detect if we had to look for just them, but there are lots of those, and we find them easily by accident as we perform other observations or through surveys. Just as if we decided to go looking for lost change on sidewalks we could find a great many coins, but if we were tasked with finding a specific coin somewhere on the East Coast it would take a tremendous effort (or tremendous luck) to find it.

I'm pretty sure there is some reason I'm missing, but I really don't understand why its really difficult to find a planet in the Solar system (or at the edge) while we are hearing lot of news them finding exo/non-exo planets at the distant galaxies? Why are these planets so elusive to our so advanced eyes/lenses in our orbits?

I understand the reason is that we only detect distant planets indirectly, by looking at the behaviors of the stars they block. With planets in the outer solar system I guess they're too small (angle-wise) to be blocking anything we can easily examine.

That make sense, thanks

The reason that's difficult to do with planets in our own solar system is because we are also orbiting the same star. Detecting exo-planets transiting their host star is possible because we aren't orbiting that star. We could never observe this planet transiting the Sun because it never passes in between the Earth and the Sun. And if it did, we probably would be quite aware of it already.

It's hard to detect dark, cold things that are far away. Planet Nine is very cold, likely to be quite dark and also very far away (anywhere between 200 AU and 1200 AU depending on where it currently is in its orbit). Its estimated apparent magnitude is greater than 22.5. That means you'll need a large telescope (I guess around 5m), a dark sky and sensitive cameras to be able to see it.

Stars are neither dark nor cold, however brown dwarves that are pretty cold are much harder to detect.

If you look at the list¹ of the sixty nearest stars to our sun, you'll notice that many close brown dwarves have only been found fairly recently (e.g. Luhman 16a/b, 6.5ly away were found in 2013).

¹ https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brow...

Something I've never understood: Why is our known solar-system on a flat plane? Why don't the planets all have different orbital axis? Is there a body (or bodies) out there exerting a force on the planets to keep them all in the same plane?

It’s not perfectly flat, but somewhat close to it, because all of our solar system’s planets formed from the same accretion disk, during which time there was opportunity for exchange of angular momentum.

There is a brief explanation here:

http://curious.astro.cornell.edu/about-us/57-our-solar-syste...

Thx! Perfect succinct explanation, including 'so why is the disc of dust flat' question that immediately followed!

Nibiru exists! https://en.wikipedia.org/wiki/Nibiru_cataclysm

Nobody can convince me that Pluto is not planet 9.

Ceres was also reasonably considered a planet, until evidence was discovered that showed it was just one of many similar bodies.

Including Pluto in a classification with the 8 major planets, but not including Eris, is simply not a useful way to describe the bodies in the solar system.

Personally, I use the word “planet” for anything even vaguely planet-like, but there's no logical way to count “planets”, under any definition of the word, that leads to Pluto being the 9th.

The first four detected asteroids, in fact. They were all discovered in a 6 year period during the early 19th century. And all were labelled planets.

That's how things sat for years, decades even. And then in a span of 5 years in the late 1840s the next 6 asteroids were discovered. By the end of the 1850s they were up to 57 asteroids, in the 1860s they found more than 50 more, in the 1870s they found over a hundred more than that. It had become rapidly apparent that Ceres, Pallas, Juno, and Vesta weren't just little quirky oddball planets, they were merely members of a much larger population of other bodies (that would come to be known as asteroids) separate from the planets.

The situation is identical with Pluto, the only difference being that Pluto was alone in its new classification of "little quirky oddball planet" in the 20th century for about 80 years. But now it has become apparent that Pluto isn't a weird little planet, it's a member of a different family of objects (Trans-Neptunians, of which Triton was probably also a member before being captured by Neptune).

I was really hoping this was a reprint of an article from 1930 and not something written this week.

I have two young daughters. They like space as much as any not-yet-in-gradeschool kids might. We only buy planet books in our family that include Pluto as a planet.

>perhaps as large as a dwarf planet

Seriously? Dwarf planets aren't classified on size. I would expect Quanta to know better than to publish such rubbish.

One of the criteria is that it has sufficient mass to reach hydrostatic equilibrium.

I appreciate the "great theory predicts new data" proposition, but the chronology seems off.

In early 2016, two planetary scientists declared that a ghost planet is hiding in the depths of the solar system, well beyond the orbit of Pluto.... Batygin and Brown made a case for Planet Nine’s existence based on the peculiar orbits of a handful of distant worlds known as Kuiper belt objects.

Later in TFA we learn:

The Dark Energy Survey first detected evidence for the new object in late 2014. Gerdes and his colleagues have spent the years since then tracking its orbit and trying to understand its origins.

So the data were "new" in 2014. I suppose the various grad students and lab assistants on Gerdes's team could all sign affidavits to the effect that they didn't directly or indirectly inform these two famous researchers in their field of this data, despite the fact that they routinely attend the same conferences and otherwise correspond about these exact issues. Still, it seems a bit sneaky for TFA to raise this point and not attempt to fill in this significant hole in the narrative.

Having the data on a hard drive or tape somewhere is not the same as someone looking at it or recognizing it for what it is.

Heck, someone just looked at 20-year-old Voyager data to find evidence that it flew through plumes of water on Europa.

The mind can only boggle at the sheer magnitude of cosmological data floating around the world right now.

This is commonplace in astronomy, a lot of discoveries come about from analyzing old data. You are putting a bizarre tom clancy spin on this for no reason whatsoever.

IANAAstronomer, but Quanta seems to be written for the general public. I'm not saying that any of the researchers have done anything wrong, merely that TFA needs to do a little more work to support this prediction story.

You seem to have an enormously strong prior in favor of conspiratorial fraud by astronomers...

I could understand this response to my first post, since 'InclinedPlane had largely the same reaction. I had thought the post to which you've responded would have clarified the matter? Do you not believe me when I type "I'm not saying that any of the researchers have done anything wrong"?

Consider this as honest feedback on your writing: the way your first post is written heavily implies that something malicious and conspiratorial is going on, in such a way that is not defused by saying "I'm not saying something fishy is going on".

It happens in biology too, where scientists sometimes identify new species while examining old specimens that have been in museum collections for decades or longer.

I've had a book in my nightstand for at least 2 years and every once in a while I swear to myself "this month I'm gonna read it, this month..." then I fall asleep.

I better call my layer and get my story straight for when the thought police get here demanding answers.

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