
A New World’s Extraordinary Orbit Points to Planet Nine - bcaulfield
https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/
======
rossdavidh
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.

~~~
ralphc
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?

~~~
twic
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/](https://www.darkenergysurvey.org/the-des-project/overview/)

[2] [https://www.nasa.gov/feature/ames/nasa-s-kepler-
spacecraft-n...](https://www.nasa.gov/feature/ames/nasa-s-kepler-spacecraft-
nearing-the-end-as-fuel-runs-low)

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

[4] [https://gizmodo.com/tomorrows-star-map-release-could-
revolut...](https://gizmodo.com/tomorrows-star-map-release-could-
revolutionize-our-unde-1825503300)

~~~
8bitsrule
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?

------
jessaustin
_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.

~~~
yongjik
> ... IAU's _goofy_ decision to demote Pluto

I see what you did there.

~~~
jessaustin
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.

------
ChuckMcM
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.

~~~
abecedarius
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](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.

------
BurningFrog
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.

------
everdev
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.

~~~
InclinedPlane
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.

------
sv12l
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?

~~~
mehrdadn
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.

~~~
nkrisc
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.

------
Jaruzel
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?

~~~
archevel
There is a brief explanation here:

[http://curious.astro.cornell.edu/about-us/57-our-solar-
syste...](http://curious.astro.cornell.edu/about-us/57-our-solar-
system/planets-and-dwarf-planets/orbits/242-why-do-all-the-planets-orbit-in-
the-same-plane-intermediate)

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

------
dalore
Nibiru exists!
[https://en.wikipedia.org/wiki/Nibiru_cataclysm](https://en.wikipedia.org/wiki/Nibiru_cataclysm)

------
masterleep
Nobody can convince me that Pluto is not planet 9.

~~~
gregknicholson
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.

~~~
InclinedPlane
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).

------
coldacid
>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.

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

------
jessaustin
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.

~~~
InclinedPlane
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.

~~~
jessaustin
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.

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

~~~
jessaustin
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"?

~~~
canjobear
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".

