Astronomy Practice Exam

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Approximately how many stars are in the Milky Way galaxy?

About 100 million
About 400 billion
About 1 trillion
About 1 billion

The correct answer is: About 400 billion

The Milky Way galaxy is estimated to contain about 400 billion stars. This approximation is based on various observational methods including star counts in different regions of the galaxy, measurements of light from distant stars, and gravitational dynamics. The methods used to estimate the number of stars take into account the large volume of space the Milky Way occupies and the distribution of stars throughout the galaxy, with denser star concentrations towards the center. Estimates have varied over time, but advancements in technology and observational techniques have refined the number to around 400 billion. This foundational understanding of the number of stars in our galaxy is critical in astrophysics as it impacts studies related to stellar formation, the evolution of galaxies, and the broader structure of the universe.