Lonely planets – the English ‘rogue planets’ seem even more interesting – they have yet to reveal many of their secrets. Their origin, for example. It is possible that some of the individual planets formed from a clump of gas and dust, and that there simply wasn’t enough material available to form a star. But it is also very likely that it originated in a galaxy, only after it was pushed away from a massive planet by the force of gravity.
It is also not clear whether life can exist. You might not think so, without the heat energy from the sun. But there is one conceivable scenario that could make life possible: geothermal action – heat from the planet’s interior – and a dense atmosphere could combine to create an energy cycle for life to thrive there. Using a liquid metal core, a solitary planet could have a magnetic field that could shield life from cosmic rays.
What we do know is how lonely planets are detected: using microlensing, a type of gravitational lensing. The space around us seems to stretch in a straight line. But objects of mass exert gravity, and when they are large enough, the space near that object is visibly skewed. This means that a beam of light that simply travels forward appears to the observer as being deflected toward such a heavy object. This effect is very strong for black holes. Albert Einstein predicted this as early as 1912, but the effect was not first noticed until 1979.
You can think of a micro lens as an effect on a small scale. You see this, for example, when a lonely planet moves in front of another body. This provides science with a good way to detect objects that are faint or no radiation at all.
Countless solitary planets
Recent Japanese research has revealed ten solitary planets. This may sound a little, but the Japanese have only discovered a small part of the universe. Estimates range from one planet per four stars to as many as 100,000 lone planets per star. Thus, even by the most conservative estimates, our Milky Way galaxy is teeming with lonely planets.