A few weeks ago we hosted an online astronomy event aimed at children. As part of this, we also ran a “draw your own alien” competition. Congratulations to our 3 winners Nathan, Tom and Dila (Figure 1).
We had lots of creative entries to our competition. This motivated us to dedicate this months blog to one of the most puzzling astrophysical mysteries: “are we really unique and alone in this Universe? If not, why have we never made communication with an alien lifeform?”
Many scientists worldwide also wonder about this and try to answer that exact question. In 1961, Frank Drake derived the “Drake Equation” used to estimate the number of extraterrestrial lifeforms living in our own galaxy that could potentially communicate with us in one way or another (Figure 2).
In recent years, scientists have been able to constrain the formation rate of stars in our galaxy (R*), and are advancing in understanding how many of those stars have planetary systems (fp), and even the fraction of planets that could harbor life (ne). Even if these parameters are well-known, there is huge uncertainty in knowing how likely it is for life to form on these habitable planets (fe), how likely such a life is to evolve into an intelligent civilization with technology capable of communicating with us (fi, fc), and how long such a civilization exists (L).
Given some estimates for these highly uncertain values, it appears that the odds of intelligent life existing in the Milky Way are pretty decent. Yet we have no evidence that any extraterrestrial lifeform has ever visited Earth, or attempted to communicate with us. This is known as the Fermi paradox. Potentially, by discovering life within our own Solar System, this could better constrain some of these unknown parameters and give us a better idea of how likely it is that there is other intelligent life out there.
Scientists are continuously searching for signals from other planetary systems that could be messages from another lifeform, but with no luck to date. Over a decade ago, fast radio bursts were discovered, coming from deep space. It was hypothesised that these could be signals coming from alien spacecrafts travelling between solar systems, but with more recent results, this seems unlikely. The nature of fast radio bursts is still a mystery to this day, however. Scientists have also sent radio messages containing basic information about Earth to nearby star clusters, but to date there has been no convincing communication between us and an alien lifeform.