The Hunt for Planet 9 Just Got Serious

Added: 2026-05-12

[00:00:00]Somewhere beyond Pluto. Indications in the data that there may be something even further out.

[00:00:06]If I add up all the gravity that's affecting them, they should move this way, but they don't. They move another way.

[00:00:11]In one of the darkest regions of our solar system, something may be hiding.

[00:00:16]Not a tiny asteroid, not another icy rock, a planet.

[00:00:20]A ninth planet.

[00:00:21]>> Planet nine.

[00:00:22]>> Planet nine.

[00:00:23]>> Planet nine. A massive, frozen world so far from the sun that one orbit could take thousands of years. We have never seen it directly. [music] We do not know exactly where it is, but for years astronomers have noticed something strange. Some of the most distant objects in the solar system move as if something invisible is pulling on them.

[00:00:45]And [music] now, the hunt for planet nine may be entering its most serious phase yet. Because with new surveys, new data, and new distant [music] objects being discovered, we may finally be reaching the point where this mystery has to break one way or the other.

[00:01:00]Either planet nine is real or the solar system has been fooling us. The story [music] actually starts in the Kuiper Belt, that wide ring of frozen leftovers stretching [music] far past Neptune. Astronomers expected the orbits out there to be a chaotic mess, [music] random angles, random directions, scattered like a handful of marbles [music] dropped on a kitchen floor.

[00:01:23]But that is not what they found.

[00:01:25]Instead, [snorts] >> [music] >> a small group of these distant icy worlds, the most extreme ones, all seemed to lean the same way.

[00:01:34]Their long, stretched orbits point in roughly the same direction as if every single one of them is being tugged by the same invisible hand. Statistically, that should not happen, not by chance.

[00:01:47]Two Caltech astronomers, >> [music] >> Konstantin Batygin and Mike Brown, ran the math back in 2016 and came to a conclusion that surprised even them. The simplest explanation for this cosmic alignment is a real [music] physical planet, something around five to 10 times the mass of Earth, sitting impossibly far from the Sun and quietly steering everything around it like a shepherd in the dark. We can call this effect the phantom pull, an invisible gravitational fingerprint left on objects we can actually see. Sedna, the dwarf [music] planet in the Kuiper Belt, and other long-orbit objects seem to whisper the same thing. Something is out there. But here is where it gets weirder >> [music] >> and where most explanations fall apart.

[00:02:34]Picture this. If you shrink the entire solar system so that Earth orbits the Sun at a comfortable 5 ft, about the height of an average adult, then Neptune would be roughly 150 ft away, sitting outside the building. Planet Nine, on the other hand, would be more than 3,000 ft out, more than half a mile away. So far that the Sun from up there would look like just another bright star [music] in the sky.

[00:03:01]We are talking about something potentially 700 times farther from the Sun than Earth is. That is around 65 billion miles.

[00:03:09]A single orbit could take 10,000 years, maybe 20,000. Civilizations would rise and fall in the time it takes Planet Nine to circle the Sun just once, and it would do that completely indifferent to anything happening here on the third rock. Blinking past entire light houses of human history without ever knowing we existed. Now, the question you are probably thinking is, if astronomers know it might be there, why have we not found it yet? The honest answer is that finding it is brutally hard. At that distance, Planet Nine would reflect almost no sunlight. It would barely move across the sky.

[00:03:48]>> [music] >> From our point of view, it would drift so slowly that the difference between one year and the next is smaller than the width of a fingernail held at arms length. Imagine trying to spot a single dark coin moving across a football field at night while standing in Manhattan.

[00:04:05]That is roughly the level of difficulty.

[00:04:07]For nearly a decade, the search came up empty until 2025.

[00:04:12]A team led by Terry Long Fan [music] working with his advisor Tomotsugu Goto had a clever idea.

[00:04:19]>> [music] >> Instead of looking for visible light, look for heat. Even a freezing planet emits a faint glow in infrared. So, they pulled out two old infrared sky surveys taken 23 years apart. IRAS launched back in 1983 [music] and Akari launched in 2006.

[00:04:38]If Planet Nine was real, it should appear in slightly different spots between the two maps. A tiny, lonely shift across the dark. They started with around 2 million sources. They filtered.

[00:04:50]They cut. They cross-checked. And after every test, one stubborn pair of dots refused to go away. A faint object that appears in IRAS in 1983 and then, [music] 23 years later, shows up in Akari in a slightly different position. It had moved about 47 arc minutes across the sky, >> [music] >> roughly one and a half times the width of the full moon. Exactly the kind of motion you would expect from a Neptune-sized world sitting around 700 astronomical units away.

[00:05:23]For a moment, it looked like the search was [music] over.

[00:05:27]But actually, this is where it gets complicated and far more interesting.

[00:05:32]Because Mike Brown, the very astronomer who first proposed Planet Nine, looked at this candidate and said something nobody expected. He believes it is too far away. The orbit does not quite match the gravitational fingerprint we see in the Kuiper Belt. In his words, this object, if it is real, would not produce the effects we have actually been measuring for 10 years, which leads to a strange and almost funny possibility. We may have just stumbled across an entirely different unknown planet while looking for the unknown planet we already could not find. As Konstantin Batygin put it, if it is not Planet Nine, he would happily call it Planet 8.5. The solar system, it turns out, may be hiding more than one secret, and this [music] is where the hunt finally enters its most serious phase yet.

[00:06:24]On June 23rd, 2025, a brand new telescope on a mountaintop in Chile opened its eyes for the first time.

[00:06:33]The Vera C. Rubin Observatory carries the largest [music] digital camera ever built, 3.2 billion pixels. A single image covers an area of sky equal to 45 [music] full moons, and every few nights, for the next 10 years, it will scan the entire southern sky, quietly comparing every new image to the last one, looking for anything that moved.

[00:07:00]In just the first 10 hours of test observations, it found over 2,000 [music] brand new asteroids. Astronomers estimate that if Planet Nine exists, Rubin has somewhere between a 70 and 80% chance of finding it within the next few years. Three-quarters of the predicted hiding zones have already been ruled [music] out by other surveys. The walls are closing in. But even if Rubin does not see Planet Nine directly, >> [music] >> it will discover hundreds, maybe thousands, of new distant objects. Each one is another data point, another tiny finger pointing back toward whatever is out there. The phantom pull becomes harder and harder to ignore the more eyes we put on it.

[00:07:44]So, where does this leave us, cosmonauts?

[00:07:47]We have a candidate that may not even be the right planet. We have a telescope built almost perfectly to settle the question. And we have an entire region of our own solar system [music] that has been quietly behaving as if something massive is hiding inside it. In the next few years, one of two things will happen. We will finally see Planet Nine [music] with our own instruments and rewrite the textbooks for the first time since Neptune. Or Rubin will sweep the sky, find nothing, and force us to admit that the solar system has been fooling us [music] all along. That the phantom pull has some other explanation we have not even imagined yet.

[00:08:24]Either way, the silence ends soon. So, here is the real question. If Planet Nine turns out to be real, and there is a frozen world out there older than every human story ever told, what do you think we should name it?