Scientists hint at possible Earth-sized ‘Planet Y’ nearby

Is “Planet Y” Real? According to scientists, there may be an Earth-sized planet lurking in our solar system.

Long believed to be completely mapped, the Solar System may still contain uncharted worlds. Recent research suggests there may be an Earth-sized planet beyond Neptune, informally called “Planet Y.” The idea of hidden planets is not new. However, new detection methods and unusual orbital patterns in distant objects have renewed scientific interest.

Context: Enigmas of the Extrasolar System

The Kuiper Belt and Oort Cloud stretch well beyond Neptune, and there are eight known planets in our solar system. These regions contain dwarf planets such as Pluto, Eris, and Haumea, along with many smaller objects. Some of these objects follow unusual orbits. Over the past 20 years, astronomers have observed irregularities in trans-Neptunian object (TNO) trajectories. These anomalies may suggest gravitational influences from unseen celestial bodies.

The well-known Planet Nine theory, proposed by Batygin and Brown in 2016, suggests that TNO orbits are influenced by a massive ice-giant planet several times the mass of Earth. Researchers are now exploring Planet Y, a smaller alternative. This hypothetical planet may orbit closer than Planet Nine, yet still beyond Neptune. It is estimated to be about the size of Earth or slightly smaller.

Somewhere at the edge of the solar system, there might be a new world, dubbed Planet Y, similar to Earth in size. https://t.co/OXEj8qJw1G

— New Scientist (@newscientist) August 21, 2025

Planet Y: What Is It?

Planet Y may be similar to Earth in size and possibly composition to Planet Nine, which is much larger and farther from the Sun. Because of its distance from the Sun, its environment would be much more harsh, but its Earth-like size makes it an interesting place to study. According to observations, Planet Y may have an impact on the orbits of TNOs and other far-off objects, producing faint gravitational effects that allude to its presence.

Proof in Favour of Planet Y

Astronomers have cataloged numerous TNOs and centaurs with unusual orbits. These objects show tilts and clustering that do not match known planetary influences. Certain spacecraft and planetary motions also reveal minor gravitational anomalies. These irregularities might be explained by a hidden plane. These patterns support the idea that there might be more bodies like Planet Y, even though there are other possible explanations.

The Oort Cloud and Kuiper Belt‘s vast size and mostly uncharted territory make an undiscovered planet more statistically likely. Smaller planets might have escaped detection due to the current telescopes’ limited reach, opening the door for theories like Planet Y.

Ways to Find Planet Y

Planet Y is difficult to detect because of its distance and weak sunlight. Indirect methods are used by scientists:

Orbital Perturbations: Examining the effects of gravity on the orbits of known objects.

Infrared observations: employing telescopes such as NASA’s WISE to detect subtle heat emissions from far-off, frigid planets.

Sky Surveys: To identify moving objects, large-scale initiatives such as the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory continuously map the sky.

Gravitational Microlensing: Sometimes the gravity of a planet causes light from far-off stars to bend, indicating the planet’s existence.

BREAKING🚨: An Earth-sized "Planet Y" may exist beyond Neptune in our solar system, new data reveals pic.twitter.com/76T1s9Kueb

— All day Astronomy (@forallcurious) August 23, 2025

Planet Nine versus Planet Y

Planet Y is smaller, possibly between the sizes of Mercury and Earth. It is closer to the Sun than Planet Nine, which is a massive, distant world about ten times Earth’s mass. Researchers suggest that Planet Y’s gravity could explain the tilted orbits of some Kuiper Belt objects. These orbits appear roughly 15 degrees off the plane of the Solar System. Like the early evidence for Planet Nine, there is a 2–4% chance that this alignment is purely coincidental. Notably, the possibility of Planet Y and Planet Nine coexisting could change how we perceive the Solar System.

The Formation and Origin

It’s possible that planet Y did not form in its present orbit. According to astronomers, it might have been forced outward when the giant planets in the early, chaotic Solar System settled into stable orbits. Its present location might be a reflection of the early Solar System’s dynamic gravitational interactions.

The Rubin Observatory’s Function

With its LSST, the future Vera C. Rubin Observatory in Chile is expected to expand our knowledge of the Kuiper Belt. Planet Y might be directly detected if it is within the survey range of the observatory. Indirect hints to its existence will be provided by LSST’s useful information on orbital tilts and patterns of distant objects, even if it stays hidden.

On May 27, 2022, a rare phenomenon was captured when Venus disappeared behind the Moon

The video shows the bright planet. pic.twitter.com/ALBiua4326

— M.Y. (@yasar1998_m) August 18, 2025

Consequences of Finding Planet Y

The discovery of Planet Y would have significant cultural, philosophical, and scientific ramifications. It would cast doubt on current Solar System models, advance our understanding of planetary formation, and uncover possible planet-type diversity. Studying Planet Y may provide insight into its extreme planetary environments, magnetic fields, and ice compositions, despite its inhospitable nature.

The public would be captivated by the discovery as well, reiterating the enthusiasm surrounding the discovery of Neptune and Pluto in the past. It would emphasise that there are still mysteries in our cosmic neighbourhood and that observation and investigation are still essential to comprehending the cosmos.

Obstacles and Doubt

The level of scepticism is still high. Instead of direct observation, the evidence that is currently available is indirect and is based on orbital patterns. Biases in observations or the cumulative effects of smaller objects may be the cause of anomalies. Furthermore, it is very challenging to detect a faint, far-off planet. Before confirming any discovery, scientists stress patience, careful observation, and accurate modelling.

In conclusion

The idea that Planet Y, a planet the size of Earth, is hiding in the outer Solar System is intriguing and tenable. Even though the search is still speculative, it is continued by research, sophisticated telescopes, and international cooperation. Whether or not Planet Y exists, the investigation serves as a reminder to humanity that even in familiar cosmic surroundings, surprises can still be found by those who are curious and diligent.