The Kepler satellite discovers at a distant, exoplanets (planets not in our own Solar System) by observing if the light curve of a star shows a regular small dip in brightness, indicating a planet obscuring its light as it orbits its host. With this astronomers have found thousands of stars throughout Milky Way.

However, this data does not disclose anything about the habitability of all those untold planets.

Given the weakness of NASA’s Kepler satellite, designed to locate either stars or massive planets orbiting close to their host stars. That drops out the possibility of a number of smaller stars located within the sweet spot for habitability.

To calculate the probability of solar systems within the Milky Way that contain habitable exoplanets, a group of researchers from the Niels Bohr Institute at the University of Copenhagen have devised a method using 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.

The theory states that there is a ratio between the orbital periods of planets in a solar system.

It’s a bit technical, but the basic math behind the theory is that you can make an educated guess about the time it takes for other planets to orbit its host sun, if you have the time that some planets take to orbit their host in the solar system. 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, still the method is not perfect.

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.

Researchers used that method to calculate the potential planetary locations in 151 planetary systems – areas where Kepler has previously discovered between three and six planets.

Using the theory, the researchers then proposed that there were a total of 124 planets out of 151 planetary systems. It is not a bad average at all, 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.

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