Roughly how many stars shine in our own galaxy, the Milky Way?
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Answer
About 200 billion stars
Nobody can count them directly. Astronomers weigh the galaxy from the way it rotates, then divide by the mass of a typical star, which is why estimates range from 100 to 400 billion.
How to estimate it
Treat the galaxy as a disc 100,000 light-years across and 1,000 thick: 3.14 × 50,000² × 1,000 is about 8 trillion cubic light-years. Near the Sun, stars sit 4 to 5 light-years apart, so each claims about 100 cubic light-years. 8 trillion / 100 = 80 billion, and the crowded centre pushes the total higher. Astronomers' estimates centre on roughly 200 billion stars.
Source: NASA; ESA
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