How many stars are there in the Milky Way?

How many stars are there in the Milky Way?

Have you ever wondered how many stars are in the Milky Way? If you look up at the sky on a dark night and away from light pollution, you might see as many as four thousand stars. However, the number of stars that make up our galaxy is much larger, easily reaching a few hundred billion.

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It is extremely difficult to determine the exact number of stars in our galaxy. It is that, in addition to not being possible to count each one of them individually, many of them cannot be observed due to the structure of the Milky Way.

The center of the Milky Way is made up of stars, gas and dust — not to mention Sagittarius A*, our galaxy’s supermassive black hole. The matter there is so densely packed that not even the most powerful telescopes can see what’s in the region.

Therefore, astronomers have developed some techniques to arrive at estimates and thus try to approximate the total number of stars in the Milky Way.

After all, how many stars are there in the Milky Way?

The short answer is “no one knows for sure”. It may sound frustrating, but so far, it has only been possible to arrive at estimates that, as the name implies, do not exactly represent the number of stars in the Milky Way, but come close.

Therefore, the number of stars varies. Some astronomers suggest the existence of around 100 billion of them, while others propose something closer to 300 billion stars. It is worth remembering that these numbers apply only to the Milky Way, and do not represent estimates for other galaxies.

The European Space Agency’s Gaia mission has been studying the number of stars in the night sky for nearly a decade. She has already mapped the position of 1.7 billion stars, and the data obtained suggest that there are between 100 and 400 billion of them.

How to know how many stars are in the Milky Way?

Astronomers have developed some techniques to try to answer this question. One involves analyzing the color and brightness of stars in our galaxy: the biggest, most massive stars, like Vega, tend to be bluish, and the smallest, darkest ones, reddish.

As white, blue and red stars emit different amounts of light, it is possible to measure this light and arrive at estimates of the amount of them there is.

Another way is to measure the mass of the Milky Way through rotation and the spectrum of emitted light. As most of the mass is formed by dark matter, that which does not emit light and which makes up most of the matter in the universe, it is still necessary to determine how much of the total mass comes, alone, from the stars.

Typically, 90% of the galactic mass obtained from the rotation curve comes from dark matter. Much of the remainder is made up of gas and dust, and only 3% is made up of stars — but since we are dealing with estimates, this number may vary.