---
title: 'Our Solar System Lost Two Planets!'
source: 'https://youtube.com/watch?v=XcHRXum97Tw'
video_id: 'XcHRXum97Tw'
date: 2026-08-04
duration_sec: 378
---

# Our Solar System Lost Two Planets!

> Source: [Our Solar System Lost Two Planets!](https://youtube.com/watch?v=XcHRXum97Tw)

## Summary

A recent study suggests that the early solar system may have had six giant planets instead of four, with two being ejected billions of years ago. The video explains the formation of the solar system, the evidence from Uranus's tilted axis and its moons, and the chaotic dynamics that likely led to the loss of these planets.

### Key Points

- **Lost Planets Discovery** [00:00] — A recent study suggests the solar system originally had six giant planets, not four, and two were lost billions of years ago.
- **Solar System Formation** [00:25] — The solar system formed from a collapsing cloud of gas and dust, with the Sun igniting at the center and planets forming from a surrounding disc.
- **Inner vs Outer Planets** [01:06] — Close to the Sun, only rock could clump, forming small rocky planets like Earth. Further out, ice allowed for more material, leading to gas giants like Jupiter and Saturn.
- **Simulation Requirement** [02:17] — Computer simulations of solar system formation require at least one or two extra giant planets to match observations, indicating the original system had more planets.
- **Uranus's Tilt as Evidence** [02:30] — Uranus's extreme axial tilt suggests it was hit by a massive object, providing a clue to past planetary chaos.
- **Moons Support the Theory** [02:55] — Uranus's moons, especially Miranda, have unusual features that fit the scenario of a collision and subsequent re-formation.
- **Chaotic Early System** [03:21] — The early solar system had six ice giants close together, leading to unstable orbits and chaos that ejected two planets.
- **Collision and Ejection** [03:45] — One of the wandering planets hit Uranus, tilting its axis, while the two extra planets were eventually ejected from the solar system.
- **Fate of Lost Planets** [04:09] — The ejected planets may still exist as rogue planets, wandering cold and dark between the stars.
- **Scientific Uncertainty** [04:22] — The evidence is indirect, making the reconstruction of past events difficult, but the physics-based approach is more tractable than other historical sciences.

### Conclusion

The solar system's history is more dynamic than textbooks suggest, with the loss of two giant planets explaining current observations. While the evidence is indirect, the study provides a coherent model for the solar system's evolution.

## Transcript

We may have lost two planets. And no, I don't  mean astrophysicists have another disagreement   about what we're allowed to call a planet. I mean  the result of a recent study which found that the  
solar system used to have six giant planets, not  four, but we lost two of them billions of years   ago. That's relatable. I mean, who hasn't lost  a planet or two? But seriously, what the hell  
happened there? I have a brief summary. The solar  system was not born as the neat diagram you find in   school books with the planets all in place. It  formed from a huge cloud of gas and dust. The  
cloud contracted under the pole of its own gravity  and began to spin. The center became so dense and   hot that nuclear fusion ignited it. That became  our Sun. The leftover material formed a flat   disc around the young Sun. Inside that disc,  tiny grains began to stick together and slowly  
built larger and larger objects which became  the planets and their moons. So far so clear.   The devil is in the details. And it's the details  that the authors of the new paper have now put  
together and compared with evidence. What we do  know is that in the early solar system, it was so   hot close to the Sun that only rock could clump  and form planets. That's why the inner planets,  
Mercury, Venus, Earth, and Mars are small and  rocky. Further out, it was cold enough for ice to   also clump. That gave the young planets out there  much more building material. Jupiter and Saturn  
grew quickly and became massive enough to pull in  huge amounts of gas. Uranus and Neptune also grew   large, but not large enough to collect as much gas  before the disc disappeared. These four planets  
are called 'gas giants', and they're fascinating. If  Jupiter were hollow, about 1,000 Earths could fit   inside. Saturn has such a low density that it'll  float in water if you could find a bathtub to fit  
it in. But here's the thing. If physicists try to  reproduce the formation of our solar system on a   computer, it doesn't work if there are only these  planets. The way that they do this is to start   with the initial distribution of matter and let  it form a solar system. Then they keep only cases  
which result in something that looks similar  to what we in fact observe. The thing is now   that to match our observations, they need at least  one but better two large extra planets otherwise,  
the solar system does not come out correctly.  The idea is not entirely new. The biggest hint   that something dramatic must have happened in the  young solar system is Uranus because its axis is  
tilted a lot to the side and is not aligned with  the overall axis of the solar system. This doesn't   naturally come about during the formation of the  solar system. It seems that something hit Uranus,
hard. The new paper now looked at Uranus's moons  and finds that these fit the picture as well. The   moons also orbit around the tilted axis. And these  moons, especially one by the name of Miranda,  
have more rise than one would expect. The  authors now say this all fits together like this:   The early solar system had not four, but  probably six of these ice giants. They were  
much closer together than the ice giants are  now. If these giant planets are close together,   this makes their orbits very unstable. Solar  systems are naturally chaotic and in a case like  
this, the chaos sets in very quickly. So, two of  the giant planets didn't stay on regular orbits,   but instead began to wander around and one of them  hit Uranus and tilted its axis. In the aftermath,  
Uranus's moons got shaken out of their orbit and  collided, which created multiple smaller moons,   which then put on extra ice. The two extra planets  eventually ended up on a path that took them out  
of the solar system entirely. This would have  happened billions of years ago, so they'd be far   away from us now. They may still exist somewhere,  but by now they'd be wandering between the stars,  
cold and dark, alone, and probably not subscribed  to my channel. I give this paper a 3 out of 10 on the bullshit meter. Not because of the  paper, but because of the general difficulty  
of the subject. We're trying to patch together  what happened in the distant past from what we   see today. So all the evidence we can ever have  is indirect. The problem is not so different from  
trying to understand the origin of life, but it's  more dominated by physics. So I think it's more   doable. I couldn't think of a closing joke, so I  asked Chad GPT. And here's what he came up with.  
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