This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side.
Caltech researchers have found evidence of a giant planet tracing a bizarre, highly elongated orbit in the distant solar system. The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of Earth and orbits about 20 times farther from the Sun on average than does Neptune which orbits the Sun at an average distance of 2.
In fact, it would take this new planet between 10, and 20, years to make just one full orbit around the Sun. Unlike the class of smaller objects now known as dwarf planets, Planet Nine gravitationally dominates its neighborhood of the solar system. To explain that similarity, they suggested the possible presence of a small planet.
Brown thought the planet solution was unlikely, but his interest was piqued. He took the problem down the hall to Batygin, and the two started what became a year-and-a-half-long collaboration to investigate the distant objects.
As an observer and a theorist, respectively, the researchers approached the work from very different perspectives -- Brown as someone who looks at the sky and tries to anchor everything in the context of what can be seen, and Batygin as someone who puts himself within the context of dynamics, considering how things might work from a physics standpoint.
That is particularly surprising because the outermost points of their orbits move around the solar system, and they travel at different rates. The odds of having that happen are something like 1 in , he says. But on top of that, the orbits of the six objects are also all tilted in the same way -- pointing about 30 degrees downward in the same direction relative to the plane of the eight known planets. The probability of that happening is about 0. The researchers quickly ruled this out when it turned out that such a scenario would require the Kuiper Belt to have about times the mass it has today.
That left them with the idea of a planet. Their first instinct was to run simulations involving a planet in a distant orbit that encircled the orbits of the six Kuiper Belt objects, acting like a giant lasso to wrangle them into their alignment.
Batygin says that almost works but does not provide the observed eccentricities precisely. But through a mechanism known as mean-motion resonance, the anti-aligned orbit of the ninth planet actually prevents the Kuiper Belt objects from colliding with it and keeps them aligned. As orbiting objects approach each other they exchange energy. So, for example, for every four orbits Planet Nine makes, a distant Kuiper Belt object might complete nine orbits.
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And as new and more powerful probes join our space exploration armada , even the immensity of space may no longer afford Planet X a hiding place. So, where is Planet X? The evidence remains circumstantial. The outer reaches of the solar system are a frontier that we are only just beginning to explore. We can, however, confidently pass on one piece of good news from Space.
A few years later, a self-described mystic claimed that this planet — which Sumerian astronomy experts never heard of — was headed for a collision with Earth. That was enough to launch a hundred tabloid stories about the Nibiru cataclysm.
But if Nibiru existed, says Space. The search for a Planet X is not new. In , the search led to the discovery of Pluto, which turned out to be much too small to cause the gravitational effects then attributed to Planet X. The search for new giant outer planets went on the back burner for a few decades.
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