Final answer:
Based on estimations, if 50% of the Milky Way's 100 billion stars have planetary systems, and further probabilities are applied for habitable planets and intelligent life, there could be about 5,000 instances of intelligent life in our galaxy. The mass of interstellar matter contributes to potential for life by providing material for new stars and planets.
Step-by-step explanation:
Estimating Instances of Intelligent Life in the Milky Way
Astronomers have provided us with fascinating estimates about the composition and dynamics of the Milky Way Galaxy. Considering the vast number of about 100 billion stars in the galaxy, if we apply probabilistic estimations: 50% of stars could have planetary systems, 10% of those might host a rocky planet in the habitable zone, and further narrowing down with 10% in benign environments suitable for life.
If just 0.1% of these actually develop life and another 0.1% evolve to intelligent life forms, we are left with a possibility of about one instance of intelligent life for every 20 million stars. Given there are 100 billion stars, this rough calculation would result in about 5,000 potential instances of intelligent life within our Milky Way.
While this is a speculative figure, it gives us an idea of the potential for intelligent life in our own galactic neighborhood. Factors such as interstellar matter, which makes up about 15% of the mass of the stars in the galaxy, provide the raw material for new stars and potentially habitable planets. Additionally, the motion of stars orbiting around the massive black hole at the center of the Milky Way helps astronomers estimate the galaxy's mass and the presence of dark matter.