MIT study on exoplanet orbits may narrow parameters in search for life
A team of researchersfrom MIT and Aarhus University, Denmark, have discovered thatEarth-sized exoplanets orbit their parent stars in the same way thatour planet orbits our own Sun – maintaining a roughly equidistantcircular orbit. The discovery further narrows the characteristics ofworlds that could potentially play host to extraterrestrial life.
Astronomers have longwondered whether the highly-structured orbital trend displayed in oursolar system was simply the norm, or the result of an amazingcoincidence. A new study that examined the orbits of 74 exoplanetsorbiting 28 distant stars appears to put the question to rest.
The team created modelorbits for the exoplanets by observing the characteristics ofspecially selected parent stars with predetermined characteristics.By having a knowledge of the mass and radius of a host star, theresearchers could extrapolate the speed at which a potentialEarth-like planet would travel around it, assuming that its orbit wascircular.
The team then usedNASA's Kepler space telescope to determine the actual orbital periodsof the exoplanets. Subsequent observations found that all 74 of theexoplanets matched up well with the predicted models, meaning thatthe orbits were essentially circular. This orbital pattern representsa marked contrast to that of giant exoplanets, which are prone tohighly eccentric orbits that often bring them into extremely closeproximity with their parent stars.
The discovery will likely have far-reaching implications on thesearch for extraterrestrial life. There is now solid evidence thatEarth-sized planets hold a stable orbit around their parent star, andthis means that the conditions on those planets will be more or lesssteady over time. In contrast, larger exoplanets with more eccentricorbits will have wildly varying planetside conditions, thanks totheir varying proximity to their host stars.
However, whilst the results of the study were overwhelmingly positivein their support of Earth-sized planets undertaking circular orbits,it must be noted that 72 stars represents a tiny focus group in thecontext of the countless planetary systems in our galaxy. Furthersampling will be necessary if astronomers are to determine whetherthe properties of our solar system are indeed the galactic norm.