While it was once believed that planets were relatively rare, discoveries over the past few decades have shown that planets are actually quite common in our galaxy. However, it is currently unknown whether all stars have planets orbiting them, as our knowledge is limited by our observational capabilities.
Based on data from various surveys and observations, including the Kepler mission and other exoplanet surveys, it is estimated that a large majority of stars in the Milky Way galaxy could have planets orbiting them. These surveys have found thousands of confirmed exoplanets and have identified many more candidate planets.
When it comes to the question of how many of these planets might have life, it is still a topic of active research and speculation. The search for extraterrestrial life is a complex and ongoing endeavor, and at present, we do not have definitive evidence of life beyond Earth.
While we have discovered a wide range of exoplanets, from rocky terrestrial worlds to gas giants, determining whether any of them harbor life requires more detailed study. Factors such as a planet's distance from its star, its composition, the presence of water, and the conditions necessary for life as we know it (liquid water, suitable temperatures, and chemical building blocks) are all important considerations.
To date, our search for extraterrestrial life has primarily focused on identifying potentially habitable planets within the "habitable zone" of their star, where conditions may be favorable for liquid water to exist. The discovery of such planets is an important step, but it does not guarantee the presence of life.
In the coming years and with advancing technology, new telescopes and missions are planned, such as the James Webb Space Telescope, which will provide more detailed observations of exoplanets and their atmospheres. These advancements may bring us closer to determining the prevalence of life in the universe, but at present, we are still in the early stages of understanding the potential for life beyond Earth.