The search for another Earth

In early December, the Kepler satellite, which has so far discovered over 1,200 planets , found a planet that could be like ours.

In early December, the Kepler satellite, which has so far discovered over 1,200 planets orbiting other stars, found a planet that could be like ours. It is just over twice the diameter, and is the right distance from its parent star to have a comfortable average temperature of about 22 degrees Celsius. Moreover, its parent star is very similar to our Sun, so it will be stable enough and sufficiently long-lived for life possibly to have developed and evolved on the planet. This planet has been designated Kepler 22b. At this point we don’t know much about its atmosphere or conditions on its surface, but additional observations are planned.  Kepler 22b lies about 600 light years away. Since a single light year is almost 10,000,000,000,000 km, we will not be in a position to visit for some time.

There are at least two reasons we are really interested in finding life beyond our planet. Firstly we would like to know that we on our little planet are not alone in this huge, complicated and scary universe. Secondly, the universe seems to be tailor-made to produce carbon-based life – like what we have here on Earth, so we would expect it to be present wherever conditions are suitable.

At the beginning of the universe, the main elements formed were hydrogen and helium. Stars formed from this material and produced energy by turning these into heavier elements, like carbon, nitrogen, oxygen, phosphorus, sulphur, and so on, just as stars continue to do right now, and when stars explode, they produce all the additional elements. These elements are ejected by the dying stars and enrich the great clouds between the stars, where they slowly react, making water, formaldehyde, ammonia, methane and many other chemicals that are involved in the chemistry of life here on Earth.  Laboratory experiments suggest that if these chemicals find their way to a newly-formed world where the conditions are suitable, lightning and other electrical activity drives them to form aminoacids, the building blocks of proteins and life as we know it. All this suggests carbon-based life might exist at many places in the universe, including perhaps Kepler 22b. Of course, these life-forms are unlikely to look anything like us.

At 12:20 a.m. EST on Dec. 22, which is 09:20 p.m. PST on the 21st, the Sun will reach the southernmost point in its yearly travels. This point, called the Winter Solstice, marks the time of year where we have the most hours of darkness. This occasion has been special for thousands of years. For example, about three thousand years ago, at this time of year, people in southwestern England would walk along the processional way to Stonehenge, seeing the great stones silhouetted against the blaze of the winter sunset – assuming it wasn’t grey and raining. Later, the celebration was re-dedicated to the most important date in the Christian Calendar. Then we modified the calendar and the celebration slipped to 25 December.

Since this is the last article before we celebrate Christmas, I want to wish you a Merry Christmas and to remind you to keep looking up.

Jupiter dominates the southern sky during the night. Mars rises around 11p.m., Saturn around 3a.m. Venus might be visible low in the southwest after sunset. Mercury lies low in the east before sunrise. The Moon will be new on the 24th.

Ken Tapping is an astronomer with the National Research Council’s Herzberg Institute of Astrophysics, and is based at the Dominion Radio Astrophysical Observatory, Penticton.