Armchair Explorers: How members of the public are taking an active role in the search for other worlds
Stars are easy to see – just go out at night and look up at the sky. But distant planets? That’s a bit more difficult. Helen Klus, in her shortlisted entry for the 2011 Wellcome Trust Science Writing Prize, explains how scientists and the public are working to discover new worlds.
The desire to explore our surroundings is part of human nature. It led our ancestors to leave Africa tens of thousands of years ago, walking across continents and traversing unmapped seas on simple rafts. It drove Christopher Columbus during the European Renaissance and eventually put twelve people on the Moon.
With the Earth now mapped and human exploration of the rest of the Solar System still many years away, we may feel that there is nothing left to discover. We will never get to experience what it felt like for those early explorers upon encountering an unimagined animal, mountain range or waterfall.
But all that is changing. This year we discovered that there are a multitude of worlds left to explore, each with new lands, resources and possibly even life. In February, NASA Space Scientist William Borucki stated that there could be at least fifty billion planets in our galaxy alone – with at least five hundred million that may be capable of supporting life1. We have only located a small proportion so far but these include a planet that may have mountains made of diamond, a planet that may be covered by a single giant ocean and a planet covered in ‘hot’ ice.
Scientists have been discovering extrasolar planets, ‘exoplanets’ for short, for almost two decades. Now, thanks to the launch of NASA’s Kepler spacecraft, members of the public can contribute to the exploration of the universe from their own home. Earlier this year, NASA announced the discovery of over a thousand new planetary candidates, over sixty of which were identified by amateurs.
Kepler detects planets by looking for the dip in brightness that occurs when a planet orbits in front of its star. By studying patterns in the starlight scientists can work out the size of a planet, its temperature and what it is made of. If the planet has an atmosphere then it is often possible to determine its composition. 2014 will see the launch of the James Webb Space Telescope – the Hubble telescope’s replacement – that may allow us to directly detect oceans2.
In order to contain an ocean of liquid water a planet must be within the ‘habitable zone’ of its star. This means it must not be so close that all the water boils, but not be so far away that it freezes. Over fifty of Kepler’s planetary candidates are located in this zone and five are close to the size of the Earth. Scientists hope that planets so similar to Earth may contain life.
Once these planets have been confirmed scientists will want to look at the composition of their atmospheres. If large amounts of methane and oxygen are found then this would suggest that something is continually producing these gases, like plants do for oxygen on Earth. In the next few decades, more precise observations could reveal the presence of chlorophyll, the pigment that gives plants their green colour, on the surface of a planet. Intelligent life might be spotted by the presence of artificial compounds like CFCs.
If we do find signs of life on another planet the next step will be exploration with robotic probes and attempted communication – sending them a message at the speed of light. Two messages have already been sent to the star system thought most likely to contain life. The first was composed of over five hundred pictures and messages submitted to the social networking site Bebo. The second contained over twenty five thousand messages written by members of the public. Both signals are due to arrive in the next twenty years.
More opportunities to send such messages are bound to occur as new planets are confirmed to be habitable. Until then, you have the chance to discover a world yourself by visiting planethunters.org, a ‘citizen science’ project that allows members of the public to search data from the Kepler spacecraft to identify potential exoplanets.
This is an edited version of Helen’s original essay. Views expressed are the author’s own.
Over the coming months, we’ll be publishing the shortlisted essays in this year’s inaugural competition.
1. Borucki announced this during the American Association for the Advancement of Science annual conference in Washington on the 19th February 2011 – http://aaas.confex.com/aaas/2011/webprogram/Session2404.html
2. Robinson, T.D., Meadows, V. S., Crisp, D., 2010, ‘Detecting Oceans on Extrasolar Planets Using the Glint Effect’, The Astrophysical Journal, 721 – http://arxiv.org/abs/1008.3864