Far from home: In eternal darkness, an ejected planet could drift through the Milky Way. (c) Southwest Research Institute
Read aloud Numerous lonely, sunless planets stray around in the Milky Way. One of them could come from our solar system, believes US astronomer David Nesvorný. Simulation calculations by the researcher show that probably originally five giant planets belonged to the solar system. One of them, an ice planet the size of Uranus or Neptune, was hurled into space by Jupiter during a chaotic period 3.8 billion years ago. "We have all kinds of clues as to how the early evolution of the solar system has expired, " says Nesvorný. The craters on the moon, for example, suggest that a massive meteorite hailed in the inner solar system 3.8 billion years ago. And on the outer edge of the solar system there should actually be many more little ice worlds than you actually observe.

Hence, Nesvorný and other planetary researchers conclude a period of instability, about 700 million years after the solar system was created. During these chaos days, the giant planets shifted their orbits drastically and came several times dangerously close. On their migrations they threw most of the minor planets out of their orbit which were outside the planet's zone. One part flew into the inner solar system and crackled there as a meteorite hail on the rock planets and the moon. Many were also thrown out of the solar system.

Nesvorný now comes to the conclusion that a planet was one of the victims of the riots. His simulation calculations suggest that there were originally five large planets. For models that start with four giant planets, comes in the end almost never a realistic result. In almost all cases, Uranus or Neptune is thrown out of the solar system.

In models where there are initially five giant planets, however, the correct end configuration comes out much more often, reports the researchers. The lost world therefore had a similar mass as Uranus. Nesvorný thinks it is quite possible that the youth of the solar system actually played like in his simulation. "It has recently been discovered that there are numerous free-floating planets in interstellar space, " says the researcher. That shows that throwing planets out of their system is not unusual. display

It is unclear where she is the victim of the sibling riots today: During his encounter with Jupiter, the planet was probably accelerated to a speed of over 300, 000 kilometers per hour. In just under four billion years, he is likely to have moved significantly away from his old homeland.

David Nesvorný (Southwest Research Institute, Boulder, Colorado): Astrophysical Journal Letters, Vol. 742, L22 doi: 10.1088 / 2041-8205 / 742/2 / L22 © science.de - Ute Kehse

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