The search for extraterrestrial life has been one of the most enduring preoccupations of humanity. From ancient Greek philosophers to Mayan mythologies, since history began there is a record of fascination with the idea that life could exist somewhere other than on earth. Even today, science fiction blockbusters, literature and obscure conspiracy theories continue to captivate popular imagination. But as our obsession for alien life continues, scientists are converging efforts and technology to bring us a step closer to better understand what might be awaiting us out in the vastness of space.
Despite the groundbreaking scientific discoveries of the 16th and 17th centuries – Copernicus’s heliocentric model of the universe and the invention of the telescope by Galileo – as well as the more recent development of listening stations that monitor space for non-human communication, modern astronomers haven’t made any major breakthroughs when it comes to finding extraterrestrial life.
Now, however, we could be closer than ever before to discovering that we are not alone in the world. Earlier this year, on the 28th April, astrophysicist Dr John Southworth and his team at Keele University detected the first atmosphere around an Earth-like planet, on an exoplanet known as GJ 1132b, 39 light years away.
The discovery of exoplanets, planets outside our solar system, are seen as a prerequisite for the discovery of extraterrestrial life and yet, as Dr Southworth tells me, they have been notoriously difficult to locate in the past. “Finding these planets used to be difficult as they are often small, dim and too far away to be directly imaged by telescopes,” he says on the phone from his laboratory in Keele. “Lacking the necessary technology, astronomers had to try and detect their effects on their host star. This is how in 1995, Michel Mayor and Didier Queloz discovered the first exoplanet, 51 Pegasi B.”
Since then, technology has progressed and improvements have been made in spectrometers, the instruments that separate starlight into its component colours for analysis – essential for detecting exoplanets. In 2009, NASA set up the Kepler Mission to survey the Milky Way galaxy and find earth-size planets in or near the habitable zone of their stars where liquid water might exist on the surface of the planet. Since the discovery of Kepler 10b in 2011, it has now been estimated that there are around a trillion of such planets outside of our solar system.
“It’s what we call the ‘Drake Equation,’” explains Dr Southworth. “Though it’s not really that mathematical. You try to work out how many stars there are in our galaxy, and then you try to work out how many planets there are around all of these stars. Then you try to figure out which fraction of these planets might have the right size, mass and temperatures to support life and then how many of them do support life. A lot of this is extremely uncertain but we reckon that there are around 7 million planets in our galaxy alone which may have life. We just can’t see it yet.”
Armed with patience and a telescope of the European Southern Observatory in Chile, Dr Southworth and his team spent a year studying the exoplanet. Last April their efforts paid off when they finally discovered evidence of an atmosphere – a first in the astronomy field and one that could have huge implications for the discovery of extraterrestrial life.
“From our data, we can conclude that the atmosphere is probably composed of gaseous water or methane, or a mixture of those two things,” Dr Southworth tells me. “But for this case in particular, the surface temperature is around 370°C – too hot for life. On earth, the hottest temperature at which life can survive is around 120°C. However we have proven that a planet can have an atmosphere for billions of years. Therefore other planets in our universe are capable of supporting atmospheres and, if they are cooler, they could also be capable of supporting ‘human’ life.”
Interestingly, as we speak Dr Southworth makes clear that it is the discovery of a civilisation, not the existence of life that is what would be most exciting. As he points out, “life on earth, in the form of microbes, have been around on earth for 4 billion years, but civilisation as we know it is only a few thousand years old.”
In his quest to find extraterrestrial life, Dr Southworth will be applying the process that led to the detection of GJ 113B to other planets who present similar characteristics to earth. “The most interesting set of planets ever has only been discovered a few months ago. These seven planets around the star called TRAPPIST-1 are very close in to a cold star, so at least one of them might have the right temperature to support life. Finding atmosphere on that planet would mean that we can show that there is an atmosphere on a planet with the right temperature; that would be a huge step forward.”
Dr Southworth and his team’s discovery certainly opens a window for new investigation methods. His research and work by other astrophysicists from all over the world have already brought us a step closer to finding extraterrestrial life and now we are waiting for what’s next.