our crowded galaxy
February 16, 2009 Leave a comment
via the BBC on February 15, 2009:
There could be one hundred billion Earth-like planets in our galaxy, a US conference has heard. Dr Alan Boss of the Carnegie Institution of Science said many of these worlds could be inhabited by simple lifeforms.
… based on the limited numbers of planets found so far, Dr Boss has estimated that each Sun-like star has on average one “Earth-like” planet. This simple calculation means there would be huge numbers capable of supporting life.
… Recent work at Edinburgh University tried to quantify how many intelligent civilisations might be out there. The research suggested there could be thousands of them.
actually, tens of thousands:
“It’s a process of quantifying our ignorance,” said Duncan Forgan, the University of Edinburgh researcher who carried out the work.
In his new approach, Mr Forgan simulated a galaxy much like our own, allowing it to develop solar systems based on what is now known from the existence of so-called exoplanets in our galactic neighbourhood.
These simulated alien worlds were then subjected to a number of different scenarios.
The first assumed that it is difficult for life to be formed but easy for it to evolve, and suggested there were 361 intelligent civilisations in the galaxy.
A second scenario assumed life was easily formed but struggled to develop intelligence. Under these conditions, 31,513 other forms of life were estimated to exist.
The final scenario examined the possibility that life could be passed from one planet to another during asteroid collisions – a popular theory for how life arose here on Earth.
That approach gave a result of some 37,964 intelligent civilisations in existence.