Hundreds of years ago we finally put a pin on the existence of the eighth planet of
our solar system, Neptune. Remarkably the discovery was done way before we were able
to build our state-of-the-art telescopes, or send out the first satellite into space.
So with so much advancement made in the area of space exploration,
a lot of people believe that we’ve finally solidified our knowledge of the nature
and composition of everything within the limits of our solar system. But amazingly scientists
today are still taking steps to discover what lies beyond Neptune. And the truth is,
there are some mysterious objects beyond Neptune that have scientists struggling to understand.
Discovery of the 8 planets
When we think about the discovery of the planets we picture astronomers peaking
through their telescopes and identifying moving spheres out in the darkness of space.
But interestingly enough the first five planets, namely: Mercury, Venus, Mars, Jupiter and Saturn
were all already identified way back during the time of the ancient greeks. These brilliant Greeks
were able to pinpoint these planetary bodies from the multitude of stars in the background
because they noticed that unlike stars these heavenly objects moved as time progressed.
Thus they named these bodies planetes, which means wanderer. It was only a hundred years later
that the discovery of telescopes allowed early astronomers to view the very silhouette of these
planets. It was around this century that William Herschel, an English astronomer and musician, used
the telescope to discover the 7th planet – Uranus. The planet, due to its distance from the sun,
did not reflect much light, so it appeared dimmer compared to the first five planets.
William however took note that this particular object moved, which led him to believe that this
discovery of his was not a mere star but could in fact be a planet. After further investigation,
it was soon established that William’s discovery was not a star or a comet but a previously unknown
planet, thus solidifying the discovery of the seventh planet of our solar system.
As the discoverer of the 7th planet gained popularity so did his discovery. With the
sudden recognition of its existence, several astronomers decided to observe Uranus and its
orbital pathway. With continued observation, it was seen that Uranus’ orbit did not follow
Newton’s law of gravitation. There appeared to be discrepancies in its orbital pathway that
astronomers cannot account for. This led them to consider the possibility of a potential planetary
object that's ‘pulling’ Uranus out from its usual course. With a bit of mathematical equations
and confirmation via telescope, the 8th planet was discovered – Neptune.
At this point, astronomers have established that within our solar system, there exist
eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and finally Neptune,
which all revolve around a massive star, which is our Sun with the cosmic codename - Sol.
As you’ve seen, the farther a planet is from the sun, the harder it gets to discover it.
The five was already pinpointed earlier by the ancient Greeks,
Uranus was discovered as being a dim planetary body via the use of a telescope, and finally,
with the clue of Uranus’ orbital pathway as well as a few mathematical equations,
Neptune was finally discovered. Thus we are left with the remaining question of what’s
beyond Neptune? Is it possible that there exists a 9th planet that astronomers are yet to discover?
What lies beyond Neptune? As expected, scientists have shifted their
focus to the space that lies beyond the boundaries of Neptune. In the past decade alone, they were
able to identify hundreds of objects floating beyond the orbit of Neptune, some even having the
same size as the dwarf planet pluto. What they discovered is that, just like in the discovery
of Neptune, there appears to be discrepancies in the orbits of some of these objects. Reasonably,
these objects were expected to move around the gravitational pull of Neptune especially given
the eight planet’s considerable size. However, it doesn’t appear that way. Some of these objects
had orbits that swerved away from the sun or what scientists call orbital perturbations.
If it sounds familiar that’s because this was exactly the same scenario of how Neptune was
discovered. Remember that Uranus also had discrepancies in its orbital path
that cannot be accounted for leading to the consideration of the existence of an eight
planet which we now know as Neptune. So now scientists are hypothesizing that there might
be a 9th planet that’s large enough to cause such a gravitational pull on these objects.
Scientists have dubbed this planet as ‘Planet 9.’ Of course this is just a temporary name
since the honor of actually naming the planet goes to whoever discovers it first.
Planet 9 How can it be detected?
One thing we need to understand is that the closer a celestial body is to the Sun the easier it would
be for us to detect it. That’s because light from the sun is reflected by these planetary objects
from their surface and bounces back to us here on earth, allowing us to see them as specks of
light in the sky. That’s the reason why the first five planets were easily pinpointed. The farther
planets, just like Uranus and Neptune, appear significantly more dim and are harder to detect by
a telescope alone. According to the mathematical equations that take into account the reflection
of light and distance, it would appear that there is a logarithmic decrease in an object’s ability
to reflect light from the sun the farther it is. So if we can’t count on the reflective
ability of the planet due to its distance what then could we use? The answer? – Radiation!
It is known that objects in the Universe have the ability to emit different kinds of EM radiation
depending on its temperature. Anything from the Stars, to the Earth and even Spacetime itself has
the ability to emit a specific kind of radiation that can be detected by our technology today.
This is how scientists believe they’ll be able to detect Planet 9. Now despite this approach being
more reliable than reflected sunlight it still has its limits. Once again, the planet’s distance
from the Sun plays a role in the amount and type of radiation it can emit, because as we’ve said,
radiation emitted would depend on the temperature of that particular celestial object.
Given the hypothesized distance of Planet 9 from the Sun it is estimated that the planet
would be very cold, specifically reaching 37-48 Kelvin or -393 to -373 Fahrenheit.
This cold temperature already sets a limit to the kind of radiation the planet can emit.
Specifically, it would only be able to emit microwaves and radio waves.
Fortunately! We have a powerful Telescope that has the ability to observe these large wavelengths.
Say hello to the Atacama Cosmology Telescope, a powerful radio telescope that is situated at
an altitude of 17,000 feet on the volcano in the Atacama Desert in Chile. To make
up for the dim images obtained from such an overwhelming distance, scientists have
proposed to instead capture an enormous amount of photographs taken over the span of seven years.
The astronomers then hypothesized all the possible orbital pathways that planet 9 would make
based on computer simulations and clues set by the orbital perturbations by the
observed objects beyond Neptune’s orbit. For each of those orbits, the potential
location of Planet 9 is estimated. The sets of images are then ‘stacked’ on top of each other
in order to create a larger image in hopes that the elusive Planet would come into focus.
So far, scientists have been able to exclude a significant proportion of the findings as being
planet 9. That sounds a bit weird, but given the magnitude and the overwhelming challenges
of discovering the planet, the only approach to this is by the process of elimination. This
basically involves observing the total elements present in a picture and excluding those that
do not fall in line with the characteristics of the hypothesized Planet 9. The existence
of the hypothetical planet can only be done once there is 100% exclusion of all subjects.
As we speak, scientists are still striving to definitely prove the existence of Planet 9,
running countless simulations and processing several sets of images.
However, in the event that Planet 9 is proven to not exist then the possibility of something
else causing the gravitational pull is an exciting concept to think about. True enough,
space exploration still holds a lot of mysteries that are yet to be discovered.
Yet when they are discovered, you’ll be the first to know about it.
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