Most stars have habitable planets.

According to the existing ideas about the structure of the world, a prerequisite for the origin and existence of life on a particular planet is the presence of liquid water on it.
Recent studies of the moons of Saturn and Jupiter offer hope that the Earth is not the only body in the Solar System where this key substance can exist in liquid form. So, recently, scientists reported the presence of a huge ocean under the surface of Ganymede. But the real seas, which are located on the surface, should be looked for exclusively in other planetary systems.
The first mention of the possible existence of planets in another star appeared in 1855. Unfortunately, it has not yet been possible to confirm that particular case. It was only at the end of the 20th century that science learned to reliably register such objects outside the Solar System, and the real breakthrough in the discovery of alien worlds occurred in recent years, when scientists and astronomy enthusiasts gained access to a huge array of data collected by the Kepler space telescope.
If five years ago the annual number of discovered exoplanets was in the tens, now the count has gone to hundreds, and in January 2015, it was announced the discovery of a total of 1000 exoplanets by Kepler alone.
Of course, not all detected objects automatically fall into the list of potential candidates for the search for extraterrestrial life. For the existence of surface oceans, the planet must at least be at a certain distance from its star, where the temperature regime does not turn the surface into a hot hell or an icy desert. (How this distance is determined, we have described in detail in this article.
A new study by scientists from Australia and Denmark shows that the chances of finding habitable worlds are even higher than previously thought. According to an article published in the Monthly Notices of the Royal Astronomical Society, most stars in the Milky Way have between one and three planets in the habitable zone. That is, the number of potentially habitable worlds is estimated not even in millions, but in billions.
The work of researchers from the Australian National University (ANU) and the Niels Bohr Institute at the University of Copenhagen (Niels Bohr Institutet) is based on the Titius-Bode rule. This empirical formula, proposed in 1766, roughly describes the distance between the planets of the Solar System and the Sun. Scientists have tested the operation of the law in 151 planetary systems, where with the help of “Kepler” it was possible to detect from three to six planets.
It turned out that the rule worked perfectly in 124 of them. In some cases, the ratio of the orbits of the discovered planets corresponded to the law even better than in our own system. In addition, using the formula and computer models based on it, the team was able to fill in the empty spaces by calculating the orbits of planets that had not yet been “seen”.
“Using the Titius-Bode law, we tried to predict where else in these systems there may be planets. At the same time, we only worked with confirmed planets, or objects that have a good chance of confirmation,” says Steffen Jacobsen, co — author of the study, in a press release from the University of Copenhagen.
In total, scientists predicted the existence of 228 planets. They have compiled a list of 77 planets that are highly likely to be found using the transit method. When using it, scientists register dips in the luminosity of the star at the time of the passage of the exoplanet on its face.
Of course, the planets located in the habitable zones of their stars were of the greatest interest to researchers. The analysis showed that there may be from one to three planets in the habitable region of each studied system.
“According to statistics and observations, it is likely that a large proportion of objects in the habitable zones of stars are rocky planets with a solid surface, where there may be water in a liquid state, and where life may exist,” explains Jacobsen.
This means that there may be billions of habitable exoplanets in our Milky Way galaxy alone. This means that the probability of the existence of extraterrestrial life is quite high. The authors urge other astronomers to use the new information to search for exoplanets near other stars.