"Lonely" planets, flung from their solar system by gravitational effects, can be 50 percent more common than planets near stars.
Microlensing detects stray planets
Most planet search techniques, such as star eclipses and star oscillations, only find worlds close to stars. But with micro lenses - where a planet moves past a background star and the gravitational well temporarily acts as a magnifying glass - you can also find planets that are further away.
Takahiro Sumi of Osaka University in Japan and colleagues have observed 50 million stars in the Milky Way at least once every hour for about two years. They found 10 objects roughly the mass of Jupiter that did not appear to belong to a star.
Their technique cannot rule out the existence of invisible host stars (because the movements are not periodic), but the measurements suggest that the planets are at least as far from their star as Saturn is from the sun (ie ten times the distance from Earth to the sun). ). They argue that the scarcity of the planets depicted at wide divisions of their host stars suggests that about three-quarters of the 10 new objects are not bound to the stars.
Ten objects doesn't sound like many, but micro lens events are very rare, because the precise alignment of a background star, the planet's "lens" and the Earth is required and the universe is large. Extremely big. Based on this, the researchers calculated that the new observations imply that wandering planets are 50 percent more common than planets around host stars and nearly twice as common as stars in the Milky Way.
Not all astronomers agree with this high number, but it is certain that there are a significant number of wandering planets. That is a fascinating possibility roaming planets can harbor life under a thick insulating ice layer, where radioactive decay provides the energy. For a planet the size of Jupiter, the effective temperature would barely drop - Jupiter already emits nearly 2.5 times the heat the planet receives from the sun. A super-earth would also be able to sustain life through radioactive processes. It has previously been suggested that annihilation of dark matter in wandering planets in the center of the Milky Way, could keep it warm, but in the absence of empirical evidence, this hypothesis seems less popular.