Using the Kepler satellite, astronomers have found thousands of stars strewn throughout the Milky Way, many of which are surrounded by a number of exoplanets (planets not in our own Solar System) at various distances from their host star. This data, however, does not tell us anything about the habitability of all those untold planets. However, a group of researchers at the Niels Bohr Institute at the University of Copenhagen have devised a method to calculate the probability of solar systems within the Milky Way that contain habitable exoplanets.
Part of the trick lies in a weakness with NASA’s Kepler satellite, designed to locate either stars or massive planets orbiting close to their host stars. That leaves out the possibility of a number of smaller stars located within the sweet spot for habitability.
For the moment, this leaves astronomers falling back on the power of mathematics, relying on a two hundred and fifty year old method called the Titius-Bode law. It was named after the mathematicians, Johann Elert Bode and Johann Daniel Titius, and was used to correctly predict the orbit of both Uranus and the moon Ceres.
It’s a bit technical, but the basic math behind the theory is that if you know the time it takes for some of the planets in a solar system to orbit their host sun, you can make an educated guess about the time it takes for other planets. It’s even possible to predict “missing” planets, those that would fill out the equation. The theory works because every planet in a solar system has an orbit that is a certain ratio to the planet preceding or succeeding it in orbit.
While neat, the method is not perfect.
Researchers used it to calculate the potential planetary locations in 151 planetary systems – areas where Kepler has previously discovered between three and six planets. According to Steffen Kjær Jacobsen, a Ph.D student at the university, the Titius-Bode law fit with the position of the planets in 124 of the planetary systems.
124 out of 151 is not a bad average, and it will give those using Kepler a set of data which has a greater chance to find inhabitable exoplanets. The team has provided an even smaller number of stars in which they believe the probability of locating a habitable planet is significantly greater.
The information will be used to spur further research and to focus more of our attention on the Milky Way and habitable exoplanets. You can get the full text from the Royal Astronomical Society.
