New evidence found for the existence of the Ninth planet

Astronomers presented compelling arguments in favor of a hypothetical celestial body beyond Neptune's orbit

On July 16, 2025, an international group of astronomers from the California Institute of Technology (Caltech) and the Maunakea Observatory in Hawaii presented new data strengthening the hypothesis about the existence of the so-called Planet Nine - a massive object presumably located on the outskirts of the Solar System.

What is Planet Nine?

By Planet Nine, scientists mean a hypothetical celestial body whose mass is estimated to be 5-10 times greater than Earth's, and whose orbit lies 10-20 times farther from the Sun than Pluto's orbit. The assumption about its existence was first proposed by astronomers Konstantin Batygin and Michael Brown in 2016 based on the analysis of anomalies in the movement of trans-Neptunian objects (TNOs).

New data and methods

In the new scientific paper published on July 15, 2025, in The Astronomical Journal, researchers presented the results of detailed analysis of the orbits of more than 20 TNOs located at distances of over 250 astronomical units (AU) from the Sun. These bodies demonstrate unexplainable synchronization in orbital parameters, which, according to scientists, most likely indicates the influence of a massive and yet undiscovered object.

For data collection, the capabilities of the Subaru telescope, located at the summit of Mauna Kea, were used, as well as archival images obtained from the Pan-STARRS survey. Additionally, computational simulations were applied, modeling the influence of the hypothetical planet on the dynamics of distant bodies over millions of years.

What astronomers are saying

Professor Konstantin Batygin noted:

"We are not claiming that we have found Planet Nine, but the probability that the detected anomalies are caused by a random distribution of objects is now less than 0.4%. This is a serious reason to continue the search."

His colleague Michael Brown added that new observations allow narrowing down the presumed search area:

"We assume that the planet is located in a sector of the celestial sphere distant from the center of the Milky Way, which makes its visual detection difficult, but not impossible."

What's next?

Astronomers plan to continue observations in 2025-2026, using the new Large Synoptic Survey Telescope (LSST) in Chile, which is scheduled to launch at the end of this year. Its high sensitivity and frequency of surveys will significantly increase the chances of directly detecting Planet Nine or its indirect trace.

If the existence of the planet is confirmed, it will be the most significant discovery in the Solar System in recent decades, comparable in importance to the discovery of Pluto in 1930 and its subsequent reclassification as a dwarf planet in 2006.

Context:
The current classification of Solar System planets includes eight official planets. Planet Nine, if it exists, could explain a number of anomalies in the distribution of TNOs and shed light on the formation processes of the outer Solar System.