Whatever be the arguments about Pluto, it’s well known that the Solar System has four giant planets in orbit around the Sun – Jupiter, Saturn, Uranus, and Neptune. These are the four outermost planets, located beyond the asteroid belt, and all of them are comprised of gases rather than rock (unlike the four inner planets).
The last few weeks however, have brought out reports on a fifth gas giant that once used to orbit the Sun. According to one report, an argument for a fifth giant began to emerge when a researcher at the Southwest Research Institute in Colorado, USA began to study a portion of the Kuiper Belt (a belt of random stuff located beyond Pluto). He noticed that this portion (called the ‘kernel’) lay on the same plane as the planets orbiting the Sun and by building a simulation, he concluded that the kernel once used to orbit Neptune. He further argues that the kernel was separated from Neptune due to some kind of cosmic disturbance, most probably an encounter with another giant planet. This giant planet was subsequently ejected from the Solar System into interstellar space.
What’s remarkable is that at almost the same time, there was another study published by researchers at the University of Toronto on November 1st, that also looks into the possibility of a fifth giant planet. However, the researchers here argue that the fifth giant was ejected from the Solar System after a tussle with either Jupiter or Saturn – most probably Jupiter. They concluded this by studying the orbits of the planets’ satellites, noting that while orbits of Saturn’s satellites are probably not consistent with a fifth-giant scenario, Jupiter’s moons show greater likelihood of having experienced such an event. Thus, it’s quite likely that Jupiter had had an encounter with a giant planet in the past that had resulted in the latter being kicked out.
So, is there a clash here? One study claims an encounter with Neptune and another with Jupiter. I am just a layman, but the odds of a single giant coming into contact with two other planets while being thrown out of the system seem low. Another possibility is that there were two different giant planets, both kicked out, possibly at different stages of the Solar System’s evolution, but even this seems odd. On the other hand, what do I know? I am just a layman and all of these scenarios may be possible. There is something to be noted though – the University of Toronto study compares only Saturn and Jupiter, not Neptune. A comparison between Jupiter and Neptune for encounters with a giant planet (if it’s possible) may be interesting.
In all this though, I find the idea of a rogue planet fascinating. There’s a poetic feel about this story of giants clashing with each other in the depths of space with one being exiled forever from its home. There’s also something incredibly desolate and lonely about the idea of a planet wandering the darkness of interstellar space on its own. What’s most incredible however, is that all these things actually happen, as we speak and read and live and breathe, right above our heads, in millions of places in the universe. Most of the time we are barely aware of anything.