How Many Stars Are There in the Milky Way? In the Universe?

Astronomers have discovered a technique to estimate the variety of stars within the universe.

Lookup on the sky on a transparent night time, and also you’ll see 1000's of stars – about 6,000 or so.

However that’s solely a tiny fraction of all the celebrities on the market. The remainder are too distant for us to see them.

The Solar is a star, the closest one to us – 93 million miles away.

The universe, galaxies, stars

But astronomers like me have found out how one can estimate the whole variety of stars within the universe, which is all the pieces that exists.

Scattered all through the universe are galaxies – clusters of stars, planets, fuel and mud bunched collectively.

Like individuals, galaxies are numerous. They arrive in numerous dimensions and shapes.

Artist’s idea of a face-on have a look at the Milky Approach. Word the spiral arms. Credit score: NASA/JPL-Caltech/R. Damage (SSC)

Earth is within the Milky Approach, a spiral galaxy; its stars cluster in spiral arms that swirl across the galaxy’s heart.

Different galaxies are elliptical – type of egg-shaped – and a few are irregular, with a wide range of shapes.

From Canyonlands Nationwide Park in Utah, a view of a small a part of the Milky Approach. Credit score: Nationwide Park Service/Emily Ogden

Counting the galaxies

Earlier than calculating the variety of stars within the universe, astronomers first need to estimate the variety of galaxies.

To do this, they take very detailed footage of small components of the sky and rely all of the galaxies they see in these footage.

That quantity is then multiplied by the variety of footage wanted to photograph the entire sky.

The reply: There are roughly 2,000,000,000,000 galaxies within the universe – that’s 2 trillion.

15,000 galaxies seem as small dots and blots on this NASA photograph of the nighttime sky. Every galaxy accommodates billions of stars. Credit score: NASA/ESA/P.Oesch/M.Montes

Counting the celebrities

Astronomers don’t know precisely what number of stars are in every of these 2 trillion galaxies. Most are so distant, there’s no technique to inform exactly.

However we will make guess on the variety of stars in our personal Milky Approach. These stars are numerous, too, and are available all kinds of sizes and colours.

Our Solar, a white star, is medium-size, medium-weight and medium-hot: 27 million levels Fahrenheit at its heart (15 million levels Celsius).

Larger, heavier and warmer stars are typically blue, like Vega within the constellation Lyra. Smaller, lighter and dimmer stars are often crimson, like Proxima Centauri. Apart from the Solar, it’s the closest star to us.

Artist’s idea of a crimson dwarf star with an exoplanet in orbit. About two-thirds of the celebrities within the Milky Approach are crimson dwarfs. Exoplanet is the identify for worlds exterior our photo voltaic system. Credit score: NASA/ESA/G. Bacon (STScI)

An unimaginable quantity

Crimson, white and blue stars give off completely different quantities of sunshine. By measuring that starlight – particularly, its coloration and brightness – astronomers can estimate what number of stars our galaxy holds.

With that technique, they found the Milky Approach has about 100 billion stars – 100,000,000,000.

Now the following step. Utilizing the Milky Approach as our mannequin, we will multiply the variety of stars in a typical galaxy (100 billion) by the variety of galaxies within the universe (2 trillion).

The reply is a fully astounding quantity. There are roughly 200 billion trillion stars within the universe. Or, to place it one other approach, 200 sextillion.

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

The quantity is so large, it’s exhausting to think about. However do that: It’s about 10 occasions the variety of cups of water in all of the oceans of Earth.

Take into consideration that the following time you’re wanting on the night time sky – after which marvel about what could be occurring on the trillions of worlds orbiting all these stars.

NASA video. Our Milky Approach galaxy: How large is house?

Written by Brian Jackson, Affiliate Professor of Astronomy, Boise State College.

This text was first printed in The Dialog.