Editorial note: Japanese astronomers have proposed the existence of an “Earth-like” planet within the
Kuiper Belt, closer to our solar system than the elusive Planet Nine. The researchers, Patryk Sofia
Lykawka and Takashi Ito, suggest this potential Kuiper Belt planet (KBP) could be up to 500 astronomical
units from the sun, closer than Planet Nine. While the KBP could be three times the mass of Earth, it
likely has frigid temperatures unsuitable for life. The Kuiper Belt, home to many icy objects, offers clues
about the early solar system and potential undiscovered planets. This proposal adds intrigue to our
exploration of the outer solar system, though more research is needed to confirm its existence. – by
Talukder Tetulia, Washington DC
Scientists: “Earth-like planet” is hiding in our
own solar system
Story by Chrissy Sexton
Japanese astronomers have proposed that an “Earth-like” planet exists much closer to home than the
infamous Planet Nine. The research is published in The Astronomical .
For years, the astronomy community has speculated about a ninth planet in our solar system, commonly
referred to as Planet Nine.
Kuiper Belt planet
However, researchers from Japan now suggest that there might be another planet, closer than Planet
Nine, hiding in the Kuiper Belt, a doughnut-shaped ring of objects just beyond Neptune’s orbit.
The study was conducted by Patryk Sofia Lykawka of Kindai University in Osaka, Japan, and Takashi Ito of
the National Astronomical Observatory of Japan in Tokyo.
“We predict the existence of an Earth-like planet,” the researchers wrote. “It is plausible that a
primordial planetary body could survive in the distant Kuiper Belt as a Kuiper Belt planet (KBP), as many
such bodies existed in the early solar system.”
The scientists believe that this KBP is up to 500 astronomical units (AU) from the sun. This is 500 times
the distance between Earth and the sun, and closer than Planet Nine.
Icy objects
According to the experts, the KBP could be up to three times as massive as Earth. However, the
temperatures are likely too cold to sustain life as we know it.
The Kuiper Belt is known to contain millions of icy objects, referred to as trans-Neptunian objects
(TNOs), because they are located beyond Neptune.
Astronomers believe that TNOs are remnants from the formation of the solar system. They are
composed of mixtures of rock, amorphous carbon, and volatile ices such as water and methane.
“The orbits of trans-Neptunian objects (TNOs) can indicate the existence of an undiscovered planet in
the outer solar system,” the researchers noted. “These rock and ice bodies are the remnants of planet
formation in the outer solar system.”f
Gravitational pull
The research team observed that something larger nearby gravitationally influences some of these
objects, giving them “peculiar orbits”.
Additionally, the belt has a significant population of high-inclination objects, those with a high tilt as
they orbit around the sun. Computer simulations suggested that the hypothetical KBP could be
responsible for these effects.
“We determined that an Earth-like planet located on a distant and inclined orbit can explain three
fundamental properties of the distant Kuiper Belt,” the researchers wrote.
Location and span
The Kuiper Belt starts at approximately 30 astronomical units (AU) from the Sun and extends outward to
about 50 AU. To put this into perspective, one astronomical unit is the average distance between Earth
and the Sun. Thus, the Kuiper Belt starts where Neptune orbits and stretches out into deeper space.
“[These are] a prominent population of TNOs with orbits beyond Neptune’s gravitational influence, a
significant population of high-inclination objects, and the existence of some extreme objects with
peculiar orbits.”
The researchers clarify that they predict, rather than confirm, the existence of the KBP, and more
research is needed.
Planet Nine
They also emphasized that their proposed planet is different from the already-hypothesized Planet Nine,
which is much more massive and thought to be located on a more distant orbit.
Planet Nine was first theorized by experts from Caltech in 2014 when they noticed that the orbits of the
most distant TNOs were being perturbed or disrupted.
Astronomers still claim that this can be explained by the gravitational pull of a ninth planet in our solar
system that orbits 20 times farther from our sun than Neptune. However, to date, astronomers only
have circumstantial evidence for the existence of Planet Nine. Some aren’t convinced it exists at all.
Outer reaches of the solar system
If it does exist, Planet Nine is believed to be in the outer reaches of our solar system, beyond the Kuiper
Belt, rather than within it.
A separate team of researchers suggested in 2020 that Planet Nine could have formed in the inner solar
system at its genesis and was then kicked out by interactions with Jupiter.
Another study published earlier this year suggested that Planet Nine could be surrounded by 20 hot
moons, which might help experts locate it.
The new proposal by the Japanese researchers adds another layer of intrigue in the quest to fully
understand the outer reaches of our solar system. While the existence of the KBP is yet to be confirmed,
its prediction brings us one step closer to unveiling the mysteries of the cosmos.
More about the Kuiper Belt
Beyond the orbit of Neptune lies a region of space teeming with icy objects, dwarf planets, and
mysteries waiting to be unraveled. It is called the Kuiper Belt. Acting as a cosmic frontier, this region
holds clues to our solar system’s early days and the processes that shaped it.
Planet Nine
They also emphasized that their proposed planet is different from the already-hypothesized Planet Nine,
which is much more massive and thought to be located on a more distant orbit.
Planet Nine was first theorized by experts from Caltech in 2014 when they noticed that the orbits of the
most distant TNOs were being perturbed or disrupted.
Astronomers still claim that this can be explained by the gravitational pull of a ninth planet in our solar
system that orbits 20 times farther from our sun than Neptune. However, to date, astronomers only
have circumstantial evidence for the existence of Planet Nine. Some aren’t convinced it exists at all.
Outer reaches of the solar system
If it does exist, Planet Nine is believed to be in the outer reaches of our solar system, beyond the Kuiper
Belt, rather than within it.
A separate team of researchers suggested in 2020 that Planet Nine could have formed in the inner solar
system at its genesis and was then kicked out by interactions with Jupiter.
Another study published earlier this year suggested that Planet Nine could be surrounded by 20 hot
moons, which might help experts locate it.
The new proposal by the Japanese researchers adds another layer of intrigue in the quest to fully
understand the outer reaches of our solar system. While the existence of the KBP is yet to be confirmed,
its prediction brings us one step closer to unveiling the mysteries of the cosmos.
More about the Kuiper Belt
Beyond the orbit of Neptune lies a region of space teeming with icy objects, dwarf planets, and
mysteries waiting to be unraveled. It is called the Kuiper Belt. Acting as a cosmic frontier, this region
holds clues to our solar system’s early days and the processes that shaped it.
Location and span
The Kuiper Belt starts at approximately 30 astronomical units (AU) from the Sun and extends outward to
about 50 AU. To put this into perspective, one astronomical unit is the average distance between Earth
and the Sun. Thus, the Kuiper Belt starts where Neptune orbits and stretches out into deeper space.
Composition and inhabitants
Composed mainly of frozen volatiles like water, methane, and ammonia, the Kuiper Belt contains a vast
number of icy bodies. These remnants from the solar system’s formation vary in size from tiny particles
to dwarf planets.
Pluto, once regarded as the ninth planet, is the most famous of these Kuiper Belt Objects (KBOs). But
other significant bodies, such as Haumea, Makemake, and Eris, also call this region home.
Formation and importance
Scientists believe the Kuiper Belt formed around the same time as the solar system, about 4.6 billion
years ago. Gravitational interactions with giant planets, like Jupiter and Neptune, scattered many of
these icy objects into the belt.
Studying the Kuiper Belt offers us a unique window into these primordial times. The composition and
behavior of its objects can provide insights into the solar system’s early conditions and the processes
that led to planet formation.
Exploration and discoveries
Humanity’s interest in the Kuiper Belt intensified when the New Horizons mission flew past Pluto in
- The spacecraft sent back unprecedented images and data. This historic encounter showed us a
diverse landscape of mountains, valleys, and plains on Pluto, reshaping our understanding of KBOs.
New Horizons continued its journey, visiting the object Arrokoth in 2019, further expanding our
knowledge of these distant icy worlds.
The future of exploration
The Kuiper Belt remains a region of significant interest for future space missions. As technology
advances, we can anticipate more spacecraft venturing into this icy realm. These journeys will unveil
further mysteries of our solar system’s outer limits.
In summary, the Kuiper Belt stands as a testament to the vastness and complexity of our solar system.
Its icy inhabitants, both large and small, offer us invaluable insights into the past and beckon explorers
to uncover their secrets. As we continue to gaze outward, the Kuiper Belt will undoubtedly remain a
focal point in our quest to understand the cosmos.
More about Neptune
Neptune, the eighth planet from the Sun, reigns as one of the solar system’s most enigmatic worlds.
Possessing deep blue hues and tumultuous atmospheres, this gas giant beckons scientists and space
enthusiasts alike to delve into its mysteries.
Discovery and position
Astronomers Johann Galle and Urbain Le Verrier jointly discovered Neptune in 1846. Their achievement
stands out because they based the discovery on mathematical predictions rather than direct
observations. Located about 30 astronomical units (AU) from the Sun, Neptune orbits our star once
every 165 Earth years.
Physical characteristics
With a diameter of about 49,244 kilometers, Neptune holds the title of the fourth-largest planet in our
solar system. Its striking blue color arises from the absorption and reflection of sunlight by its
atmosphere.
This is particularly due to the presence of methane. But beneath its gaseous exterior, Neptune hides a
potential water-rich interior with a solid core.
Atmospheric activity
Neptune boasts some of the most violent weather in the solar system. Its winds, among the fastest
detected on any planet, can whip around at speeds exceeding 2,100 kilometers per hour.
The planet also showcases massive storms. The most famous is the “Great Dark Spot.” It rivalled the size
of Earth when the Voyager 2 spacecraft first observed it in 1989.
Moons and rings
Neptune commands a system of 14 known moons, with Triton being the largest and most intriguing.
Triton orbits Neptune in the opposite direction of the planet’s rotation. This suggests that Neptune
might have captured it from the Kuiper Belt.
Furthermore, this ice-covered moon spews nitrogen geysers from its polar regions. Neptune also
possesses a faint system of rings. They are composed primarily of ice particles and dust grains, which
astronomers believe might be relatively young and short-lived.
Exploration and the future
Voyager 2 remains the only spacecraft to visit Neptune, conducting a flyby in 1989. The data and images
it sent back revolutionized our understanding of this distant blue world.
However, with advancing technology and growing interest, future missions to Neptune might not be far
off. These missions could provide deeper insights into the planet’s atmosphere, internal structure, and
its intriguing moon, Triton.
In summary Neptune stands as a testament to the diversity and wonder of our solar system. Its deep
blue visage, turbulent atmosphere, and mysterious moons offer a plethora of opportunities for
exploration and discovery. As our understanding of the universe expands, Neptune will surely remain a
focal point in the quest for knowledge.
