The hunt for planets located outside of our own Solar System is not a new concept.Since 1995 scientists and astronomers have been aware of these distant worlds orbiting their host stars.The first exoplanet discovered was 51 Pegasi located in the constellation of Pegasus.To date over 3000 potential exoplanets have been discovered, however not all of these have been confirmed.With dedicated missions searching for these different new worlds we are learning now more than ever what lies out beyond our own planet Earth.
Looking in the direction of the constellation Cygnus the Swan and launched by NASA in 2009 is the Kepler Space Observatory.Many previous missions searching for exoplanets mainly detected large giant planets, like large hot Jupiters (it is easier to detect larger planets).However Kepler’s main objective is to search for much smaller planets located in a habitable zone which is not too close nor too far from their star; planets which may be just like our Earth.
Kepler uses a transit method to identify new planets using an instrument called a photometer.This devise records the brightness of thousands of stars in its field of view.This information is then transmitted to Earth and analysed.Scientists are looking for a dip in brightness in the data recorded.Periodic dips in brightness reveal that a planetary body is in orbit around that star.The Kepler spacecraft was originally planned to last just 3 years however with that time already elapsed and new exciting discoveries still being made this mission has now been extended until 2016.
Recently a new planetary system 1200 light years distant was discovered with two planets orbiting very close to each other around host star Kepler-36. This sub-giant star is similar in size to our Sun but is a few billion years older.At the closest approach these planets are a little more than a million miles apart, just four times the Earth-Moon separation, and are the closest planetary neighbours to have ever been discovered.
The smaller inner planet, Kepler-36b orbits this star every two weeks at a distance of just under 11 million miles and is a rocky planet around 1.5 times the size of the Earth.It may very well be an example of a chthonian planet. The larger planet, Kepler-36c is a gaseous planet 3.7 times the size of the Earth orbiting every 16 days at a distance of 12 million miles and is much like a hot Neptune. Both these planets are thought to be too close to their host star to be in a habitable zone (“habitable” for most of our readers that is, if you like bathing in molten sulphur you would find these planets’ climates just peachy) but are likely to have an active topography. The close proximity to each other suggests that both planets are likely to experience quite strong and significant tidal affects. This could cause the inner rocky planet to be quite volcanic and prone to earthquakes going up to 11 on the Richter Scale.
In our Solar System the inner planets are rocky and located closer to the Sun and the gas giant planets are located much further away.
The unusual position of Kepler-36b and Kepler- 36c poses the question of how these different worlds came to be so close to one another.Both planets are approximately only a third of the Mercury to Sun distance to their own star.Perhaps they were originally further apart and have come together over time or perhaps their composition has been altered due to the close proximity to their parent star.
Locating the presence of an exo-planet is completed by detecting periodic dimming in the stars brightness.However, more detailed information can be collected by scientists as they measure vibrations coming from Kepler-36.These oscillations help to determine the composition of this star as well as providing more precise details about the planetary couple.Kepler’s field of view encompasses 150,000 stars so it’s quite spectacular to know details facts about these alien worlds.If by some chance there was life on Kepler-36b they would have quite a spectacular sight in the evening sky.They would see planet c, purpler than our planet Neptune, 2.5 times the size of a full moon appear every 97 days when they are the closest to each other.
The Kepler spacecraft is currently giving us some new information on new worlds beyond our Solar System; yet despite the thousands of candidate systems discovered, few seem similar to the Earth and none have been found able to support life.However, as Kepler is only half way through its mission no doubt more of these strange findings will be discovered to give us a little more insight into the Universe around us.
(Article by Martina Redpath, Education Support Officer)