With four inner planets, four outer planets, and an asteroid belt cutting a path through
the middle, the layout of the solar system can feel remarkably neat. But it didn’t just
spring into life this way… and, billions of years ago, when the system was first forming,
the earliest planets were scattering through space. This period is much more difficult to map.
Thanks to new research, however, science may finally know what happened… and it could
have major implications toward their being another, hidden world out there, somewhere.
This is Unveiled, and today we’re answering the extraordinary question;
did scientists just prove there’s an undiscovered planet in the solar system?
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Moving out from the sun, we have Mercury, Venus, Earth, Mars, the Asteroid Belt, Jupiter,
Saturn, Uranus, and Neptune. It’s the last four of those we’re particularly interested in today,
birthed (as they were) more than four billion years ago,
out of an ancient disk of gas, dust, and debris around our star, the sun… which, in itself,
had also only just come into being. This was the beginning of all things for the solar system,
and a starting point from which it raced outwards. Now, Neptune, the furthest planet from the sun,
is on average 2.8 billion miles away from it. But it’s not as though the solar system ends at this
far off, icy, checkpoint world. The most famous object beyond Neptune is Pluto,
the one-time planet demoted to “dwarf” planet status in 2006 - it’s 3.6 billion miles away.
But, even then, we’re still a huge distance away from the edge of the solar system.
There’s the rest of the Kuiper Belt, the Scattered Disk, and the Oort Cloud to consider… spanning for
not just billions but trillions of miles out from the sun. It’s perhaps little wonder then
that there’s always been some suggestion that there could be more planets out there, traveling
around our star but completely out of sight. Part of the reason for theories toward a so-called
“planet nine” is that the very earliest days of the solar system are still quite unknown
to us. In general, we know that planets like Jupiter and Saturn formed and moved to their
current positions… but the process for moving them to those positions has been something of
a mystery. Why did they land precisely where they have done? Why are their orbits all different from
one another’s rather than alike, seeing as they will have seemingly shared a similar origin story?
However, a recent study may provide the answers. Published in late April 2022, in the journal
“Nature”, the multi-authored paper leads with the title; “Early Solar System instability triggered
by dispersal of the gaseous disk”. It lays out a new model for how the gas and ice giants may
have found their place in space, and the “gaseous disk” is key. The study refers to “an episode of
dynamical instability among the giant planets” in the early creation of the solar system’s
“orbital structure”… but it reiterates that the cause and timing of that instability is unknown.
By running countless simulations of that formative time, however, those behind the study appear to
have revealed what really happened. The destinies of Jupiter, Saturn, Uranus, and Neptune were
shaped when the gaseous disk “dispersed”; when it first thinned and spread out from the sun.
Imagine a newly ignited star, burning away its early life in the middle of a fog of dust.
That’s our sun around 4.5 billion years ago… and, gradually, it creates room for itself,
pushing the fog of dust further and further away from it. It’s as though the early planets,
busy forming within that dust, are then marked off, one by one, as the disk breaches wider and
wider distances. And so, their orbital paths and evolutionary routes are set into motion. They’re
still crucially and fundamentally reliant on the sun, of course, but it’s like they’ve flown the
nest - cosmologically speaking. We might still refer to this process as having “instability”,
because the planet’s final destinations are still difficult to determine… but the general
nature of the early solar system now suddenly seems a whole lot less chaotic. There really
is a neatness to how it unfolds, with the solar system systematically painted into life something
like clearing soap suds off a freshly cleaned window… or icing a cake from inside to out.
While this is all very controlled and satisfying, however, where does the “undiscovered planet” come
into it? There isn’t a focus on planet nine in the “Nature” article itself, but those behind
the study have since touched on the possible implications for it - including in a release
by Michigan State University, where one of the researchers - Seth Jacobson - is based. Broadly
speaking, as we know that there was instability during the early solar system, can we now say with
confidence that we know everything that was born out of that? Probably not. No matter which model
you follow for how the solar system ended up as it is right now, there’s always room for surprises
and unexpected developments in something so vast and enigmatic as an entire star system. Adding
just one extra planet into the mix might feel, if anything, like the least that could happen.
Among the simulations run for the study, there were variations tested with both four and five
planets at the start of it. And results showed that, actually, there wasn’t a great deal of
difference in what happened next. The solar system up until Neptune ended up looking much the same
with or without that extra world to contend with. And, in fact, it was found that having that
extra planet might even improve the chances that the four other planets should remain (as we know
they have). Clearly, as we don’t currently know of a fifth gas giant (and ninth solar system planet,
overall) the model has nothing to match its potential orbit to in the real world. But, while
estimates do vary, it’s thought that if it does exist, it could be orbiting as far out as fifty
billion miles from the sun. Neptune, remember, sits just three billion miles away, only.
It means that if planet nine is out there, it will have had a radically different lifetime
and journey to any of the other planets. Already there are vast, fundamental differences between,
say, Mercury and Uranus, or Earth and Saturn… but those worlds are tightly packed next-door
neighbours by comparison. Planet nine would be so far removed from the rest of
anything else in the solar system. A lonely but unique world that, really, it’s very
difficult to even imagine. As there are some theories that it could still exert a gravitational
influence over the rest of the planets from wherever it is that it’s hiding, it may be
that it’s truly massive… lurking on the edge, with the sun’s light serving as just the faintest,
tiniest sign that there’s more going on in the solar system’s center.
Would life be possible on such a world? It’s unlikely, based on what we currently search for
in potentially hospitable planets. Naturally, it’s a long, long way away from the “goldilocks zone”
for habitability… and most of everything about this place would likely be very un-Earth-like.
Could planet nine ever cause us a problem, then? There are theories toward that end, particularly
in relation to the supposedly foretold “Nibiru Cataclysm”… where it’s said that, one day,
an ancient planet could come crashing through the solar system, potentially striking and destroying
Earth as it goes. However, most scientists never seriously entertain that possibility,
and assure us that we can sleep soundly in the knowledge that we’re not about
to get blown out of the sky anytime soon. Nevertheless, most major scientific groups
do acknowledge at least the possibility of planet nine. NASA, for example,
draws on research published by a team at Caltech in 2015, involving mathematical models that also
seemingly show that an extra world is possible. NASA says that planet nine, if it does exist,
could have ten times the mass of Earth, and it could take up to 20,000 Earth years for it to
travel once around the sun - that’s how far out it could be. But the underlying reality is that
planet nine still hasn’t been directly observed. For now, we can say that studies like this most
recent analysis of “early solar system instability” provide tantalizing hints
of what’s potentially out there. We’re still waiting for definite evidence… but that’s why
scientists might have just proved that there’s an undiscovered planet in the solar system.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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