Thursday, March 28, 2013


Planetary systems without star could exist by trillions in our galaxy but we don't have enough evidence yet.

Everywhere in nature there are more small objects than big ones.
In our solar system we have one star, many planets and a lot more satellites than planets. There are more asteroids than satellites, more rocks than asteroids, and more grains of space dust than rocks.

For every star, there should be many objects that didn't get big enough to ignite and make a star, and most of them would have satellites.

The number of these systems is not probably enough to account for the total of the missed matter in our galaxy (dark matter), but at least a part of it, and let’s face it, it has to be enormous. If there are 200 billions stars in our galaxy, and let’s say 10 non solar systems for every solar system, it can be easily about 2 trillions. Some estimations raise this number a lot.

Rogue planets or planemos  is the term usually used for  planets escaped of his star, but also apply for the ones naturally born in the interstellar space by the same process of aggregation of matter that formed the stars.
Sub brown dwarfs is the name actually under consideration by the IAU (international astronomical union).
13 times the mass of Jupiter is needed to start the thermonuclear reactions that make a star, so, the  planets in these systems could be of any size below this limit.

Common sense not always apply in science, especially when we consider subjects like quantum mechanics or relativity, but in this case, in my opinion we should take a look at the whole picture and consider the possibility that they could exist in mind blowing numbers.

We have some evidence of their existence due to observation techniques based on  gravitational microlensing, but current estimations of their numbers are still imprecise and varies from 2 sub brown dwarfs per star in our galaxy to an enormous amount.

Could life exist in such places?
Why don't?, but life like the one we know would be very limited because of the lack of energy, nothing quite like what we have  on earth, but something like the oases around hydrothermal vents we know where life thrive on heat and chemicals without any need of sun light, could be a very common thing. link to A proposal for a habitable planet in interstellar space

There wouldn't be need for a strong magnetic field and an ozone layer as protection against lethal radiations from the star. Also climates would be so much stable .
The planets would not necessarily be frozen. With thermal energy coming from volcanic activity and gravitational stresses caused by  a close orbit around a gas giant, let's think of Io, we could find all kinds of temperature ranges. 

Evolution wouldn't have been so hampered by a so long period of rock bombardment like the one planets around a big star have to undergo.
One of this places formed at the same time that a bigger system  with star could have the orbits cleaned of collision objects 1000 millions years before and therefore events like the  Cambrian explosion of life on earth could happen a lot sooner.

Another consideration would be unknown types of life. We can imagine that in absence of an abundant energy source, life could find his way taking advantage of the still mysterious low energy nuclear reactions that we know happens in biological 
processes, or at least there is some literature and reports about it (link), but this is still somewhat scifi.

And besides, we could consider that some of the planets we will discover in  the future, and maybe some of the ones we already know could be captured planets not naturally born around a star. A  big part of the stars in our galaxy are binary stars, which mean two stars orbiting each other. many of them could be captured stars.The  number of captured planets should be a lot bigger than the number of captured stars.

Anyway, the tendency seems to point to a broader view of what a solar system is, and instead of the classical view of a star orbited by planets, more something like just objects orbiting each other no matter what they are, stars, planets, black holes or rocks.

Extrasolar art by masbt