The outer solar system has always been this mysterious place about which up until little
was known until relatively recently.
I remember pondering what mysteries might lie out there as a teenaged amateur astronomer
decades ago as Voyager II gave us our first look at Neptune concluding its grand tour
of the outer planets.
But what was there beyond Neptune?
Back then, little was known for sure about the transneptunian regions of the solar system
other than lots of ice out there and that's where comets originated.
But there were also murmurs of other things.
At the time there was a hypothesized second star in the solar system, termed Nemesis,
that might have been throwing comets into the inner solar system periodically causing
mass extinctions on earth.
Mysterious as it was, the trans-Neptunian region of the solar system posed a threat
to our planet.
Today, Nemesis has been ruled out, though the comets are still very much there.
But the mysteries of the far outer solar system have only deepened in the intervening years.
It turns out that thousands of small worlds orbit the sun beyond Neptune, and most no
doubt are yet to be discovered.
But the behavior of some of these little ice worlds may reveal the existence of something
more.
There may be proper, full-fledged planets out there too, and one may not even be native
to this solar system.
The first suspected planet is a new comer.
In a recent paper by Kat Volk and Renu Malhotra of the University of Arizona, link to all
papers mentioned in this video in the description below, they detail that most of the outer
Kuiper Belt objects known so far have an odd tilt to their orbital angles that would be
consistent with the presence of a Mars sized planet tugging on them.
If present, this planet is expected to be orbiting about 60 AU from the sun.
Little else is known about this potential planet, if it even exists.
If it does and another explanation for the tilting isn't found, perhaps this planet might
be a kind of super pluto, a world of ice and rock.
We shall have to wait and see.
Unfortunately it may be extraordinarily hard to pinpoint and verify that Planet 10 is actually
there, at least for now.
It has been suggested that one reason we may not have noticed this planet visually is that
it might sit against the backdrop of the Milky Way and seeing a tiny, very dim pin-point
moving object against that swath of stars would be difficult.
But that's soon to change.
The upcoming Large Synoptic Survey Telescope, or LSST, is set for first science light in
2021 and full operations in 2022.
This telescope has a very wide field of view and is designed to take full, all available
sky pictures once every few days as an ongoing sky survey.
This will make it uniquely suited to catch the movement of such a planet, and indeed
is expected to discover tens of thousands of more Kuiper Belt objects.
As an aside, I'm particularly looking forward to this telescope perhaps even as much as
I'm looking forward to the James Webb space telescope.
The reason is that much of astronomy is done in a focused manner, you look at an object
and study it.
But when you look at many objects at once, such as with the Kepler spacecraft, that's
where the serendipitous odd discoveries like Tabby's Star are made.
The LSST is particularly suited for these kinds of unexpected discoveries.
The second planet to discuss is planet nine.
I made a video nine months ago detailing this story, so won't repeat all of that content
here, but that story continues.
There is mounting indirect evidence of the existence of this planet.
A growing tally of trans-neptunian objects show odd orbits that are difficult to explain.
In addition to that other objects, such as Sedna, seem to have been detached from the
Kuiper belt through gravitational interaction with something big.
There are several theories to explain that, including the solar system having passed near
to a star in the past.
But the best explanation, at least right now, is that there is a planet in a highly elliptical
orbit of the sun extremely far out, as far as 1200 AU, though due to the elliptical orbit
it may come as close as 200 AU during part of its orbit, which is believed would have
a period of between 10 and 20 thousand years.
There are some hypotheses that offer alternate ways for the odd warping of the orbits of
the objects, but there's more indirect evidence for Planet Nine.
There is somewhat of a mystery regarding the solar system that another planet might finally
explain.
The sun's axis is tilted from the orbital plane of the larger planets of the solar system
and there has been no ready explanation for how that happened.
Planet Nine may help clear that up.
Also, the Cassini spacecraft found that something may be perturbing Saturn, which again would
point to another planet tugging on it, in fact this led to a likelihood that Planet
Nine is currently located somewhere near the constellation Cetus and that's where astronomer's
should be looking.
But this Saturnian perturbation is disputed, it may not exist at all, but in a paper by
Matthew Holman and Matthew Payne they found that Pluto too may be affected gravitationally
by Planet Nine.
More, Erez Michaely and Avi Loeb have suggested that Planet Nine might also be affecting the
Oort cloud.
If it exists, this planet would have to be big to have the apparent effects that it does,
but not huge.
The presence of anything as big as, say Jupiter, is ruled out.
But one the size of Neptune is not.
Something that size would definitely be defined as a proper major planet because it would
have the mass to have cleared out its neighborhood since its formation.
It could be another ice giant like Uranus or Neptune, or it might be a super earth,
or even the core of a giant planet that was ejected from the solar system early on, preventing
it from becoming another Jupiter or Saturn.
But I think the most interesting possibility is that planet nine, if it exists at all,
could have been captured by the sun from a passing solar system, or early on from one
the stars the sun formed with.
An interesting thought indeed, though it would likely be made of similar stuff to our own
planets.
There are active searches for Planet Nine going on right now, and if it's really there
it could be found any day now, but once again the LSST when it goes live is likely to find
Planet Nine, or disprove its existence.
And, for all we know, there may be even more large transneptunian planets lurking in the
outer reaches of the Solar System.
And it may well be that the old notions of Nemesis knocking comets into the inner solar
system might be replaced with questions of whether it's really due to the activities
of Planet Nine or another object.
And we may need to reclassify our gas and ice giants not as the outer planets, but the
middle ones.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently eyeing the outer
solar system suspiciously, it's hiding something and be sure to check out my books at your
favorite online book dealer and subscribe to my channel for regular, in-depth explorations
into the interesting, weird and unknown aspects of this amazing universe in which we live.