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My very educated mother just showed us nine planets.
This phrase was one of the mnemonics designed to help me in my youth to remember the names of the planets in our solar system.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
It's a little outdated, as in 2006, Pluto lost its status as the ninth planet,
meaning my very educated mother could no longer show us nine planets, only eight.
But what if I was to tell you that there might exist another planet,
an object five times the size of Earth,
that is floating out in the furthest reaches of our solar system?
Perhaps my mother knows what she's talking about after all.
I'm Alex McColgan and you're listening to the Astrum podcast.
Have you ever looked up in the night sky and just must be able to be able to
marveled at the boundlessness and the beauty of what you saw there.
Space is incredible. It's so vast. It's daunting.
And yet, it's so filled with dazzling sights.
Throughout history, great men and women have attempted to explore what exists in our universe.
And on this podcast, I hope to share with you a little of the wonder of what they found
and how they found it.
If you've come here from our YouTube channel, it's great to see you again.
These episodes cover some of the same topics you might find over there, except remade,
into a relaxed, audio-friendly format.
Perfect for you to listen to on the go, or perhaps when you're settling down with a nice,
warm drink for a relaxing night in.
For those of you who don't know my YouTube channel, maybe after this, go check it out.
There you'll find visual versions of these episodes.
of the wonders of space have to be seen to be believed. But wherever you're from, welcome. I really
hope that I can convey to you just how amazing space is. Today's episode will be a dive into
the elusive, enigmatic Planet X. I hope you enjoy. So how do we go about discovering new planets
in the first place? Discovering planets can be a tricky business. If you were to go outside at
night and look up at the night sky, you might get an immediate sense as to why. Can you spot a planet?
The answer is likely yes, and I'm not just talking about the Earth beneath you, which is admittedly
a very easy planet to spot. There are five different planets visible to us on Earth with just
our naked eye. Mercury, Venus, Mars, Jupiter and Saturn. However, they look incredible.
incredibly similar to the stars around it. All are simply sparkling dots in our night sky.
The first challenge for mapping out the heavens for any would-be astronomers is identifying which
of all these objects is actually a planet in disguise. So it's incredibly impressive that early
human astronomers were able to figure out which was which more than four millennia ago,
using nothing more than careful observation. By watching this,
the night sky every night and making intricately detailed star maps, Babylonian astronomers
were able to chart the motions of these celestial bodies and identify which were orbiting
around our solar system and which remained roughly in place. Stars, being so far away,
would not appear to move, unlike the planets which were much closer. Not a bad piece of deduction.
This observational method was able to identify the first six planets in the solar system,
everything from Mercury to Saturn. However, it fell short of identifying planets past that.
The more distant a planet became, the harder it was to spot with the naked eye.
The next planet, Uranus, was almost too far away to sea. As such, its discovery had to wait
until the invention of the telescope in the early 1600s. Even after that, it took until
1781 before Uranus was officially discovered. And when it happened, it was quite by accident.
Astronomer Sir William Herschel was in his garden in England one evening and was searching for
comets using a homemade 6.2 inch telescope. He just stumbled upon Uranus by chance. He initially thought
it was a comet, although over time he and other scientists realized that it must have been a planet
from signs like its lack of a tale. They named it Uranus after the father of Saturn, who in Roman
mythology was also the father of Zeus or Jupiter, thus keeping up with the naming convention.
Once they knew where Uranus was, astronomers realized that they'd actually seen it before.
In star charts dating as far back as 128 BC, there were possible references to it,
it, although all these identified it as a star rather than a planet. It took a telescope
to zoom in enough on Uranus to be able to tell the difference, and officially get it recognized
as to what it was. Interestingly, here the trend changes. It was not only with a telescope
that the final planet Neptune was discovered, but with maths. After a few decades of observing
Uranus and plotting out its orbit, a man named Alexis Boulevard published an astronomical
table detailing the orbit of Uranus, basing his calculations on Newtonian physics.
However, there was a problem. As astronomers watched Uranus, they realized that it failed to follow
the path Boulevard had predicted. They spent some time working out why this might be. Maybe they
had made some errors in their observations. Maybe Newtonian physics. Maybe Newtonian physics,
physics was not correct. It wasn't until 1845 that a French mathematician, Erban Le Verrier,
properly explained the solution. There had to be another planet influencing Uranus.
Uranus's orbit was being perturbed by something. This perturbanes could be exactly and precisely
predicted mathematically if there was another planet pulling on it, altering its orbit slightly.
So detailed were Laverier's calculations that they even told astronomers exactly where this extra
planet needed to be for all of this to work. Astronomer Johann Godfrey Gale looked there,
and sure enough, to within a degree of Laverier's calculations, he found Neptune. Just like with Uranus,
it quickly turned out that Neptune was not a completely new discovery. Once they knew where it was
and where it orbited, astronomers could look back through their records and were able to find
other references to it. Although it could not be seen by the naked eye, Galileo managed to spot it
with his telescope back in 1612. He even recorded it on a second occasion, and noted it had
strangely moved between the two times of recording. Although, apparently, he did not appreciate
what this meant. In the end, Galileo and others who saw it believed it was simply another star.
Only Ghalai knew that what he was seeing was a planet, and so was credited with the discovery of Neptune.
Neptune's discovery was significant, as it marked a fierce time a planet had been located in our solar system
through mathematical prediction, rather than through observation.
It wouldn't be too long before astronomers try to do this same thing again.
Which brings us to Planet 9. Let's jump forward to 1903.
At that time, Percival Lowell published a book where he believed that the existence of
Neptune did not sufficiently explain irregularities astronomers were observing in Uranus and
other celestial bodies in our solar system. Lowell became convinced that there had to be
another planet out there, something large enough to affect the other planet's gravities,
which he called Planet X. Searching for Planet X became a lifelong passion of his. He poured
years of his life into the search, and even after his death, encouraged others to keep looking
for it by donating $1 million in funding towards it. His efforts managed to prompt the later discovery
of Pluto in 1930, although this small dwarf planet was ruled out from being planet X because it was
too small. To this day, after 100 years, planet X or planet 9 still has not been officially discovered.
So why do we think it is there at all?
Well, just as it was before Neptune,
not all the objects in the solar system are orbiting as we would expect.
This was emphasised in 2016
by astronomers Mike Brown and Constantine Batigen,
who were studying Kuiper Belt objects.
The Kuiper Belt is a region of space out beyond Neptune,
covering from 30 to 55 astronomical units from the sun.
Brown and Batigen noted that 14 of these Kuiper Belt objects were clumping in an unusual
way at a particular point in their orbit around the Sun.
They argued that this was evidence that something was bringing them together, attracting
them and pulling them into the orbits that we see.
Brown and Batigen continue to claim this theory to this day and are continuing their search
for the planet they believe must be there.
there. According to them, Planet X exists to a 99.6% certainty. If their claim is true,
planet X is large. With a mass at least five times that of Earth, planet X will most likely
orbit between 300 and 520 astronomical units out from the sun. For a point of reference,
this is extremely far out. Neptune orbits 30 astronomical units from the sun.
the Sun, one astronomical unit being the distance from the Sun to the Earth.
This means that while it takes Neptune 165 years to complete one orbit, it could take the supposed
planet X around 10,000 years to complete just a single orbit. From Planet X, the Sun would appear
about as bright as the Moon, making it a cold and dark place even during its daytime.
There is some debate about whether Planet X would have formed
formed within our solar system, or whether it was captured in the sun's gravitational pull
from a passing star. Or perhaps it was a rogue planet just drifting through space. However,
not all astronomers are convinced that Planet X exists. In 2020, there were two astronomical surveys
that identified objects in the Khyber Belt, the outer solar system's origin survey and the
dark energy survey. Between them, they identified.
over 1,000 Khyberbelt objects in this space, but did not observe any bunching or strange
perturbances in their orbits. This has led astronomers to attribute other factors as the explanation
for Brown and Bathegan's observations. Perhaps the 14 bunched objects were just observation bias.
After all, these objects are very difficult to spot. Perhaps their bunching looks like that
because of insufficient data.
Or perhaps the bunching is real,
but there are other explanations
such as gravitational occultation.
From when Neptune passed through that area
early in the solar system's history.
Most pressingly of all is the pertinent question,
if Planet X is there, why haven't we seen it?
Thanks to modern computers and telescopes,
it is easy to check the areas
where Planet X is supposed to reside.
We have photographed vast swaths of the night sky already in minute detail,
and although La Veria's calculations allowed Neptune to be found after just an hour's searching,
no such outcome has happened from Brown and Bathegan's.
They have searched through existing astronomical data,
and have already examined over half of the possible locations of Planet X.
No planet was found in any of these places.
Even I myself have participated in a citizen science project on Zuniverse
where you can search Gaia data for Planet 9.
And while this citizen science project has accidentally discovered a whole host of nearby
brown dwarfs and stars, planet 9 still eludes us.
This does not completely rule out Planet X's existence though.
There are still a few explanations for why this planet remains elusive.
With an orbital period of 10,000 years,
it is possible that the planet just happens to be hiding
in a particular portion of its orbit
where it is difficult to spot.
For instance, next to a cluster of stars
that obscure it with their brightness.
Or at its abelian,
the furthest point in its orbital arc from the sun,
where it would be too dim for all but the largest of telescopes to see.
Or the possibility always exists that we have spotted it.
Just like with Uranus and Neptune, perhaps a photograph of Planet 9 already exists, but has
simply been misidentified as a star.
With so many billions of stars to keep track of, and again with Planet X's 10,000 year orbit
time, it would be forgivable if it took a few years to notice that one star was not in
exactly the same place it had been when it was last photographed.
And so, the search goes on through at least two methods.
Those searching for Planet X have enlisted the help of the Subaru Telescope, a device
powerful enough to scour even the hypothetical furthest reaches of Planet X's orbit.
If it is out there, by 2027, it will likely have been spotted.
Meanwhile, as of this recording, astronomers like Brown and Bathigin continue to run searches
of the existing data, hoping to spot the one dim dot amid billions that you have to see.
is ever so slightly out of place. It's tedious work. However, it's intriguing. With the last few
planetary discoveries, amateur astronomers were instrumental in finding the planets in our solar
system. Whether or not they recognized it, both Uranus and Neptune were discovered by people
just pointing their telescopes at the sky one night. Of course, the 9th planet might not be there at all,
be so far away that you would need a powerful telescope like Subaru to see it. But maybe not.
Whether it's by scouring the data or by doing a little amateur astronomy, perhaps it won't
be Brown or Bathegan who discovered the real 9th planet in our solar system. Perhaps it will be
us. Well, that's all we have time for today. I hope you've enjoyed listening to this podcast
on the search for Planet 9. If you like what you've heard,
Please feel free to follow us for more podcasts on other fascinating space topics.
But for now, I'm Alex McColgan, and this has been Astrum.
All the best, and see you next time.