
Discovering Planet Nine - jwmerrill
http://www.newyorker.com/tech/elements/discovering-planet-nine
======
chrispeel
I would love an update on efforts to find planet 9, unfortunately this article
is from January 2016. See [1] for a Hacker News thread from Jan on Planet 9,
and [2] for a blog from Batygin and Brown.

[1]
[https://news.ycombinator.com/item?id=10939306https://news.yc...](https://news.ycombinator.com/item?id=10939306https://news.ycombinator.com/item?id=10939306)

[2] [http://www.findplanetnine.com/](http://www.findplanetnine.com/)

~~~
Isinlor
If you are interested in latest research about planet 9 you can subscribe to
[https://www.reddit.com/r/planet9](https://www.reddit.com/r/planet9) \- I'm
trying to keep this subreddit up to date as much as possible.

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taliesinb
The most interesting alternative to the Planet Nine hypothesis (and to my mind
a more attractive one) is that there is a self-organizing dynamical process
that applies to large ensembles of bodies in highly eccentric orbits that
causes their argument of perihelion to become correlated.

There is a great SETI talk by the astronomer Ann-Marie Madigan that explains
the idea, it should be easy to follow if you've ever taken a mechanics course:
[https://www.youtube.com/watch?v=YW0Zb5gY0HA](https://www.youtube.com/watch?v=YW0Zb5gY0HA)

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zipwitch
To quote Mike Brown (who has the best Twitter handle _ever_ ), "Weekly PSA:
no, in fact the earth is NOT going to be destroyed by [fill in crazy thing
seen on internet here] next week. Thanks for asking."
[https://twitter.com/plutokiller](https://twitter.com/plutokiller)

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tunnuz
I'm no expert (and have not read the full article, just about half of it), but
could an object like this affect Earth when it's orbit gets closer to the sun?
I mean anything, from causing movements in Earth's crust or below, influencing
tides, carrying massive pieces of rock in its trail etc.?

~~~
jschwartzi
If I remember correctly from the article, if this object were capable of
perturbing Earth in any significant way, then we would be under much greater
threat from Jupiter and Saturn, which are at least order of magnitude closer
to us at any given time. Gravitation is a very weak force, and it scales as
the inverse square of the distance between two objects. An order of magnitude
reduction in distance would multiply the force by roughly 100 times. Thus, we
would see these effects all the time as a result of our proximity to Jupiter
and Saturn.

So no, what you're suggesting is impossible.

~~~
cmurf
What was this nonsense I remember from gradeschool about planets aligning
having a gravitation effect on the sun such that it'd start spewing fireballs
at earth? Of course nothing happened. The amount of gravitational force from a
mountain as you drive by it has more of an effect than the planets. It's kinda
like, how does astrology affect us again? Can you be precise? I mean, other
than for entertainment as by its own standard it's a real thing.

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mrfusion
This could be awesome for a slingshot manuever on the way to alpha cent,
right.

Does anyone know how to calculate that?

~~~
InclinedPlane
It wouldn't, actually, because gravity assists only add as much as the body's
orbital velocity, which would be tiny for an object in such a distant orbit.

~~~
mrfusion
That doesn't sound right because it got the voyagers to leave the solar
system.

~~~
InclinedPlane
It is, that's how it works. Relative to the planet the incoming and leaving
speeds are the same, but during the flyby the trajectory relative to the
planet's orbital motion changes. So if you come in from the "side" of the
orbit and leave headed in the same direction as the orbit, you'll increase
your velocity relative to the Solar System by the speed of the planet. But
that's the most you can gain from that.

Jupiter is the best planet for orbital slingshots not because it's going the
fastest, it isn't, but because it's high gravity makes it easy to "bend" the
trajectories of spacecraft a lot, so you can gain a bigger percentage of the
orbital speed easier, which makes for a higher total speed.

Here's a table of orbital speeds:
[http://www.sjsu.edu/faculty/watkins/orbital.htm](http://www.sjsu.edu/faculty/watkins/orbital.htm)

Here's a graph of Voyager 2's speed throughout it's journey through the Solar
System:
[https://solarsystem.nasa.gov/basics/bsf16-22.gif](https://solarsystem.nasa.gov/basics/bsf16-22.gif)

And here's Voyager 2's trajectory:
[http://i.imgur.com/ctbjmMW.jpg](http://i.imgur.com/ctbjmMW.jpg)

Notice how extreme the changes in direction are for the passes by Jupiter and
Saturn, versus Uranus and Neptune. They are very sharp curves, that go from
nearly approaching the planets from the side to leaving nearly in the same
direction as the planets are moving. You can pick up at most 43% of Earth's
orbital speed from a single gravity assist at Jupiter, but that's still a
significant amount.

Additionally, as you can see from the second link, the farther out you are
from Earth (at least in the more inner parts of the Solar System) the more
bang for the buck you get from speed increases, because you're higher up out
of the depths of the gravity well.

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Cozumel
Pluto is planet nine.

This is 'planet ten', it's called 'Nibiru', and the Babylonians, Sumerians and
Akkadian among others have astronomical records of it over 3,600 years ago.

 _tin foil hat time_ I do wonder if that's why Pluto was demoted, so when the
'tenth' planet was found it'd actually be called the 'ninth' so nobody would
be as concerned about all the doomsday myths surrounding it.

~~~
dalke
[https://en.wikipedia.org/wiki/Nibiru_cataclysm#Scientific_re...](https://en.wikipedia.org/wiki/Nibiru_cataclysm#Scientific_rejection)

If Pluto is #9, what numbers are Ceres, Sedna, Eris, Haumea, and Makemake?
Ceres was considered a planet until the 1850s.

Astronomers think there are a few hundred more such dwarf planets, with 2007
OR10, Quaoar, Sedna, Orcus, (307261) 2002 MS4 and Salacia as likely
candidates.

Which numbers are those?

The hypothetical planet the New Yorker mentions has an orbital period between
twelve and twenty thousand years. Sitchin says the Babylonian religious texts
say the period is 3,600 years.

These are not the same planet.

~~~
Houshalter
I don't like the classification of dwarf planet. The classification should be
based on its size, shape, and make up. Instead they classified it based on the
number of objects in its orbit, which is so arbitrary and weird. If
hypothetically we cleared up the objects and dumped them in Earths orbit,
Pluto would suddenly become a planet and Earth would lose its classification.

Just bite the bullet and accept there are a lot of small planets in our solar
system, or classify them based on size.

~~~
dalke
The odd phrase "clearing the neighborhood around its orbit" exists because
people want to think of Ganymede (which is bigger than Mercury) as a moon, not
a planet, which your proposal would do.

If hypothetically we moved the Earth so it orbits Jupiter, then it would be a
moon, yes?

See also
[https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Dis...](https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Disagreement)
.

~~~
Houshalter
Yes I accept orbiting the sun and not another object, as a reasonable criteria
of a planet. That's included in the old definition. The new definition goes
well beyond that though. If there are asteroids and debris in it's orbit
around the sun, it no longer counts as a planet. It's really weird, and it's
only purpose is to exclude the newly discovered planets from that
classification.

~~~
dalke
Yes, it is weird, but I disagree with your interpretation.

You wrote: "If there are asteroids and debris in it's orbit around the sun, it
no longer counts as a planet." That Wikipedia link I pointed to says: "As to
the extent of orbit clearing required, Jean-Luc Margot emphasises "a planet
can never completely clear its orbital zone, because gravitational and
radiative forces continually perturb the orbits of asteroids and comets into
planet-crossing orbits" and states that the IAU did not intend the impossible
standard of impeccable orbit clearing.[2]

It further lists a few attempts to define things more rigorously.

You write: "it's only purpose is to exclude the newly discovered planets from
that classification". The same page also points out "In 2015, a proposal was
made to use the criterion in extending the definition to exoplanets". This is
from the same Margot, whose proposed criteria can "categorise a body based
only on its own mass, its semi-major axis, and its star's mass."

