You might think we know Solar System pretty well, but there’s a lot more to our cosmic neighborhood than meets the eye (or telescope).
Most of the good stuff like planets, the moons and the asteroid belt, are clustered relatively closely toward the center of the solar system and are illuminated by solar radiation, making them easy to spot. But if you look towards the edge of the solar system, you will find a vast dark place where mysterious entities can easily hide. As a result, the researchers had a field day figuring out all the things that could be hiding there.
From a massive ninth planet and the second Kuiper belt to interstellar visitors and mini-black holes, here are eight hypothetical objects that could be lurking in the dark.
Related: 10 Out-of-This-World Solar System Discoveries in 2023
Planet Nine
The largest and most controversial object that could be lurking in our cosmic neighborhood is a hypothetical ninth planet located far beyond the other known worlds of the solar system, which researchers have creatively dubbed “planet nine.”
Scientists first proposed Planet Nine in 2016 to explain the eccentric orbits of several large objects in and around the Kuiper Belt — the massive ring of asteroids and other rocky objects that orbit the Sun beyond the orbit of Neptune. Some researchers believe that these objects are being gravitationally pulled by a massive unknown world beyond the Kuiper Belt. Despite the fact that even more of these objects have been found in recent years, the actual planet has so far eluded detection.
If it exists, Planet Nine is likely an ice gas giant about seven times the mass of Earth, which would make it the fifth largest planet in the Solar System. However, the planet could be extremely far away, perhaps orbiting our Sun once every 10,000 years, meaning it would be very faint and extremely difficult to detect.
Researchers have narrowed down the area where Planet Nine could be hiding, but are limited by the power of currently available telescopes. However, with new state-of-the-art telescopes coming online soon, it could be discovered within the next few years, experts recently told Live Science.
Baby black holes
Not everyone believes that Planet Nine is responsible for the orbital anomalies of Kuiper Belt objects. Other scientists believe that something equally elusive could be gravitationally tugging at these distant space rocks—a mini black hole.
Researchers say a moon- or planet-sized black hole could exerting the same gravitational force as the supposed planet nine. Black holes of this size are theoretically possible but have never been observed, making the idea somewhat controversial. To prove this theory, researchers would likely need to detect Hawking radiation coming from a black hole or watch something fall beyond the event horizon.
But even if the tiny black hole is not mistaken for Planet Nine, other scientists believe that there could be even smaller “primordial” black holes in the outer solar system, and that these supersmall singularities can cause some planets and moons to fluctuate.
Captured alien worlds
Some researchers believe that there could be more hidden worlds in the outer reaches of the solar system than Planet Nine.
But unlike Planet Nine, these hypothetical planets — known as rogue planets — may not be from our neck of the woods. Instead, they would be castaways from distant stars that may have been pulled in by the sun after eons drifting in interstellar space.
Scientists have he has already discovered hundreds of rogue planets approach via the Milky Way. However, in 2023, researchers suggested that the rogue planet may be lurking near the edge of the solar system, even further than Planet Nine. And if that wasn’t crazy enough, the 2024 paper also hinted at it there’s room for up to five Earth-sized rogue planets to the edge of our cosmic neighborhood.
The second Kuiper belt
The Kuiper belt could play a key role in uncovering hidden worlds in the solar system. But it may also be hiding a secret of its own – a twin.
In 2023, the researchers announced the potential discovery of a dozen new rock objects lurking beyond the Kuiper Belt. These massive space rocks, which are likely all asteroids, are located about 10 AU (10 times the distance between the Earth and the Sun) from most of the Kuiper Belt – suggesting they may belong to a second, smaller asteroid belt. .
However, other surveys have failed to identify any more of these objects outside the Kuiper Belt, abandoning the theory for now.
More dwarf planets
After full-fledged worlds and missing asteroid belts, the next largest objects that could be hiding under our noses are dwarf planets – large space rocks that are large enough to be gravitationally rounded like planets, but not large enough to to completely clear their orbital path of debris.
The Solar System harbors five known dwarf planets: Ceres, Haumea, Eris, Makemake, and a former planet Plutoaccording to NASA. Other candidates like Gonggong, Quaoar and Sit down they are not officially recognized as dwarf planets, but astronomers often refer to them as such.
All of these mini-worlds lie in or outside the Kuiper belt—except for Ceres, which is in the asteroid belt between Mars and Jupiter. But as we’ve already seen, there are plenty of places in the outer solar system for objects to hide. Some estimates suggest that there could be dozens or even up to a hundred dwarf planets still waiting to be discovered. International Astronomical Union.
Until recently, researchers believed that dwarf planets were mostly geologically dead, except for Pluto, which has an ice supervolcano. However, new data collected by the James Webb Space Telescope has revealed this Eris and Makemake may also be geologically activewhich increases the chances that they or other future dwarf planets could harbor alien life.
Volcanic comets
Far beyond the Kuiper Belt lies a huge reservoir comets known as the Oort Cloud, which extends to a distance of about 1000 AU from the Sun. A very small percentage of these icy objects are what researchers refer to as cryovolcanoes, or cold volcanoes, which shoot dust and frozen gas into space when they erupt.
Cryovolcanic comets only explode near the Sun when solar radiation causes intense pressure to build up in their outer envelopes or cores. sets off explosive blasts. However, most comets have highly elliptical orbits, meaning they spend most of their orbits floating around the outer solar system before entering the inner solar system every few decades or centuries. This makes it hard to tell which ones are cryovolcanic.
For example, Comet 12P/Pons-Brooks, also known as “Devil’s Comet”, when it made its closest approach to the Sun in approximately 71 years slingshot around our home star in April 2024. Since June 2023, when the comet began its dive bomb into the inner solar system, the comet has been eruption seen several times. But in the past 69 years, astronomers have not seen it explode even once.
As a result, astronomers suspect that many more cryovolcanic comets are hiding in plain sight in the Oort Cloud, and that we only identify them when they eventually approach the Sun.
Interstellar visitors
In addition to suspected dangerous planets, the Sun’s gravitational force is also capable of attracting other free-floating objects from interstellar space. Unlike hypothesized captured worlds, however, most of these objects likely pass through our cosmic neighborhood and never return.
Astronomers have already spotted two confirmed interstellar objects: “Oumuamua, an elongated object that made headlines in 2017 after some researchers mistakenly suggested it might be an alien probe; and Comet 2I/Borisov, which was spotted in 2019 as it traveled through the solar system. Other researchers suspect that a a small meteor that exploded above Earth in 2014 he was also an interstellar intruder.
Given the small number of confirmed sightings, you’d be forgiven for thinking that interstellar objects are rare. However, some researchers estimate that there are between 1,000 and 10,000 of these objects in the solar system at any one time, according to sister site Live Science. Space.com.
Some researchers have proposed the creation of a special “interstellar interceptor” spacecraft. which could be hidden in orbit around Earth so that scientists can quickly chase and study new objects as they are discovered. However, there are currently no official plans for such spacecraft.
Killer asteroids
The last objects on this list are the most dangerous. But fortunately, they are among the least likely to be found.
The inner solar system is filled potentially dangerous asteroids, which orbit the Sun close enough to Earth to be considered a threat to our planet (although most never reach us). These dangerous space rocks can range in size from “urban killers“which could destroy large population centers”planet killers“like that one wiped out the dinosaurs.
Similar massive rocks reside in the Kuiper Belt and beyond. Unlike comets, however, asteroids don’t usually migrate in and out of the inner solar system, meaning these rocks don’t pose much of a threat to us. But that doesn’t mean it’s impossible. If a massive asteroid ventured toward Earth, it might as well to be covered by the sun’s raysdepending on its position, which could give us very little warning before it crept up on us.
Scientists calculate that potentially dangerous asteroids they pose no threat to Earth for at least 1000 years. However, this calculation is based only on the space rocks we know about.