Astronomers have tantalizing new clues in the hunt for the elusive (hypothetical) “Planet Nine”! By sifting through old data from the 80s and 2000s, they found a potential object that moves very slowly, far, far beyond Neptune and Pluto. We’re talking a celestial body so massive its gravitational pull is rearranging the orbits of its tiny, icy neighbors, the extreme trans-Neptunian objects (ETNOs). The unseen force moving these ETNOs would need to be a full sized planet. Possibly a mini-Neptune.

The possibility of another planet in our system was first suggested by a Caltech team, Michael Brown and Konstantin Batygin, who in 2016 suggested an unseen giant was making ETNOs have very odd orbits Like moving backward from the other asteroids. A cosmic clue pointing to a new gravitational source. But despite our best observations, there was and is no direct observation of a solar planet. Not yet.

So, what kind of beast are we chasing? Imagine a world 5 to 10 times more massive than Earth, chilling out at 400 to 800 astronomical units from our Sun. That’s over 100 billion miles from Earth, only a fraction of lightyear, but dozens of times farther than the known 8 planets. Its orbit wouldn’t be a neat circle either; it would need to be a stretched-out oval that would take a mind-boggling 5,000 to 10,000 years to complete just one lonely spin around our Sun. The weird orbits of those ETNOs are the only facts we had for years, hinting at the gravitational influence of a big object.

This method can work, it’s how Neptune and Pluto were discovered, astronomers noticing strange orbits of other solar system objects. Then detailed surveys with powerful telescopes looking for a slow moving planet in that direction. That will be a real test of new technology.

Planet Nine, if it exists, barely reflects any sunlight way out there, making it incredibly faint – like trying to see a firefly in a stadium at midnight. And to make things even trickier, the galactic plane, our Milky Way’s disc of stars and cosmic dust, often obscures our view of distant objects. So infrared space telescopes are the best tool for finding anything in the distant solar system. They can see through the clouds. JWST is the modern version, but there were others.

In April 2025, a team led by Terry Long Phan decided to dig through the archives of space telescope data, sifting through old infrared data from the Infrared Astronomical Satellite (IRAS) and the AKARI mission. Their goal was to find faint, slow-moving heat signatures that could reveal the presence of a distant world. Studying thousands of images taken 23 years apart. Could a slow orbit across the stars be hiding in the old data?

They found thirteen pairs of objects showing the kind of movement and faint glow expected from a planet deep in the distant solar system. One stood out by appearing to move slowly, what you’d expect from a planet orbiting the Sun at 500 AU. Could this be Planet 9?

Before we can know the answer, we need a confirmed observation of a new object. Even the co-father of the modern Planet Nine hypothesis, Mike Brown, raised questions about the legacy study. This promising candidate seems to have an orbital tilt of around 120 degrees – way off from the predicted 15 to 20 degrees. Is this yet another object? Only more stargazing will tell.

Another discovery using legacy data was published in May, using data from the Dark Energy Survey in Cerro Tololo, Chile, and one of the telescopes on Mauna Kea, Hawaii. It’s another dwarf planet, like Pluto, called 2017 OF. That’s just a temporary name until it’s confirmed! It has a very strange orbit that goes extremely far and close to the sun, and could explain the observations made by Phan et al. This object takes 25,000 years to orbit the Sun!

A new technology is about to appear, one that can take movies of deep space. This may be what scientists need to get a true picture of these objects in motion. The Vera C. Rubin Observatory is a state-of-the-art sky-scanning giant high in the Chilean mountains, gearing up to begin its operations Summer 2025. This observatory is poised to revolutionize our search for everything from planets to dark energy, conducting a deep and wide survey of the entire Southern Hemisphere sky. Its powerful camera might just be able to spot the faint glimmer of Planet Nine and track its movement across time, finally delivering the definitive proof we’ve been waiting for. First images will be this Monday, June 23rd 2025.

So, while the 2025 discovery by Phan and his team offers a glimpse of a possible Planet Nine, the cosmic jury is still out. This intriguing object needs more scrutiny, more data, more late nights guiding huge telescopes. The Vera C. Rubin Observatory promises to be a game-changer in many ways, potentially unveiling the secrets of our solar system’s distant frontier and finally answering the question: is Planet Nine real?