The Earth is special to us – it’s our home. But is it really special as a planet? Every star we can see in the night sky is likely to be orbited by planets. There are probably a thousand billion planets in our galaxy alone.
In about twenty years, more than 3700 “exoplanets” have been discovered in distant solar systems. There are planets completing a revolution around their mother star in less than one day, as well as planets orbiting two or even three stars or moving on trajectories so eccentric as to resemble comets. Some of them are freezing cold, some are so hot that their surface is molten. But beyond that our knowledge falters: What are they made of? How did they form? What’s the weather like there? Are they habitable?
Fortunately, even a tiny amount of light can hold a huge amount of information. In recent years, we have pioneered techniques to extract information about exoplanets from starlight filtered through their atmospheres as they pass in front of their star or go behind it. Molecules in the atmosphere absorb light leaving a unique pattern of lines – a bit like a barcode. By recording these barcodes, we can work out which gases are present, what is the atmospheric temperature, if there are clouds.
These measurements are easier to be done from space, outside the Earth’s atmosphere. In the next decade, new space missions (JWST, ARIEL, Twinkle) will unveil the nature of hundreds of worlds, light-years away from us.
Giovanna Tinetti is Professor of Astrophysics at University College London where she coordinates a research team on extrasolar planets.
Select appointments and achievements include Principal Investigator of the European Research Council-funded program “Exo-Lights”, co-editor of planetary journal ICARUS and Institute of Physics Moseley medal 2011 for pioneering the use of IR transmission spectroscopy for molecular detection in exoplanet atmospheres. She is the Principal Investigator of ARIEL, the European Space Agency’s next medium-class (M4) science mission candidate; co-founder and co-director of Blue Skies Space Ltd, which aims at creating new opportunities for science space satellites.
Awarded a PhD in Theoretical Physics from the University of Turin in Italy, Giovanna has continued her academic career as NASA Astrobiology Institute/NRC fellow at Caltech/JPL and then as European Space Agency external fellow in Paris, before moving to London in 2007 as Royal Society URF.