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Exactly how many stars are in space? – MeeSong, Brookline, Massachusetts

Look up at the sky on a clear night, & you’ll see thousands of stars – about 6,000 or so.

But that’s only a tiny fraction of all the stars out there. The rest are too far away for us to lớn see them.


The Sun is a star, the closest one to lớn us – 93 million miles away. Roman Studio/Moment via Getty Images

The universe, galaxies, stars

Yet astronomers lượt thích me have figured out how khổng lồ estimate the total number of stars in the universe, which is everything that exists.

Scattered throughout the universe are galaxies – clusters of stars, planets, gas and dust bunched together.

Like people, galaxies are diverse. They come in different sizes & shapes.

Earth is in the Milky Way, a spiral galaxy; its stars cluster in spiral arms that swirl around the galaxy’s center.

Other galaxies are elliptical – kind of egg-shaped – và some are irregular, with a variety of shapes.


Artist’s concept of a face-on look at the Milky Way. lưu ý the spiral arms. NASA/JPL

From Canyonlands National Park in Utah, a view of a small part of the Milky Way. National Park Service/Emily Ogden

Counting the galaxies

Before calculating the number of stars in the universe, astronomers first have sầu to estimate the number of galaxies.

To vì that, they take very detailed pictures of small parts of the sky & count all the galaxies they see in those pictures.

That number is then multiplied by the number of pictures needed to lớn photograph the whole sky.

The answer: There are approximately 2,000,000,000,000 galaxies in the universe – that’s 2 trillion.


15,000 galaxies appear as small dots và blots in this NASA photograph of the nighttime sky. Each galaxy contains billions of stars. NASA/ESA/Phường.Oesch/M.Montes

Counting the stars

Astronomers don’t know exactly how many stars are in each of those 2 trillion galaxies. Most are so distant, there’s no way khổng lồ tell precisely.

But we can make a good guess at the number of stars in our own Milky Way. Those stars are diverse, too, & come in a wide variety of sizes và colors.

Our Sun, a white star, is medium-kích cỡ, medium-weight & medium-hot: 27 million degrees Fahrenheit at its center (15 million degrees Celsius).

Bigger, heavier & hotter stars tend khổng lồ be xanh, like Vega in the constellation Lyra. Smaller, lighter và dimmer stars are usually red, like Proxima Centauri. Except for the Sun, it’s the closest star to us.

Artist’s concept of a red dwarf star with an exoplanet in orbit. About two-thirds of the stars in the Milky Way are red dwarfs. Exoplanet is the name for worlds outside our solar system. NASA/ESA/G.Bacon/STScI

An incredible number

Red, White & blue stars give off different amounts of light. By measuring that starlight – specifically, its color & brightness – astronomers can estimate how many stars our galaxy holds.

With that method, they discovered the Milky Way has about 100 billion stars – 100,000,000,000.

Now the next step. Using the Milky Way as our mã sản phẩm, we can multiply the number of stars in a typical galaxy (100 billion) by the number of galaxies in the universe (2 trillion).

The answer is an absolutely astounding number. There are approximately 200 billion trillion stars in the universe. Or, khổng lồ put it another way, 200 sextillion.

That’s 200,000,000,000,000,000,000,000!

The number is so big, it’s hard khổng lồ imagine. But try this: It’s about 10 times the number of cups of water in all the oceans of Earth.

Think about that the next time you’re looking at the night sky – & then wonder about what might be happening on the trillions of worlds orbiting all those stars.

NASA đoạn phim. Our Milky Way galaxy: How big is space?

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