How Many Suns Are in the Universe?

The object we refer to as the Sun burns brightly at the center of our Solar System. It is our one and only source of heat and light, and without it, the Earth would quickly freeze into a dark, inhospitable place. In this article, we take a look at how many suns are in the universe.

NASA Kepler mission has discovered a world where two suns set over the horizon instead of just one.
NASA Kepler mission has discovered a world where two suns set over the horizon instead of just one. (Image credit: NASA)

The Sun Explained

Our Sun is a star comprised primarily of hydrogen that it fuses into helium atoms. This process, known as nuclear fusion, emits both the heat and light that make their way to the Earth (and beyond). The Sun is massive compared to our planet, but it is actually quite average next to other stars.

The Sun's first three-dimensional image
The Sun’s first three-dimensional image. (Image credit: NASA)

There’s nothing about the Sun that really makes it stand out. It is a yellow dwarf star that averages a temperature of 5,700 Kelvin on its surface. This is nothing compared to stars that can reach in excess of 50,000 K.

It is also not particularly bright or large in diameter or mass. The largest star in the known universe, UY Scuti, has a diameter roughly 1,500 times our star. UY Scuti is also ten times more massive and glows 340,000 times brighter. Can you imagine if we had ended up with UY Scuti instead of our Sun?

While the Sun isn’t all that special in the grand scheme of things, it is our star. It’s the perfect size and has enough heat and light output to keep us alive.

There Is Only One Sun

The word “sun” is often used to describe many multitudes of stars in our galaxy and beyond, but doing so is a misnomer. The Sun is the name of our star, just as Sirius is the brightest star in Canis Major. When referring to these balls of gas outside of our Solar System, we should always use the term “star.”

This diagram illustrates the locations of the star systems closest to the sun
This diagram illustrates the locations of the star systems closest to the sun. (Image credit: NASA)

Classifying Other “Suns”

Some scientists have taken to calling other stars with planetary bodies orbiting them as suns to differentiate them from those without satellites. The Earth is the only home we’ve ever known, but having knowledge of what else is out there could save us some time down the road.

We are still very limited in our ability to view other solar systems in the Milky Way, let alone in galaxies beyond our own. The downside about hunting for other planets is that they give off no light of their own and are really only detectable when they block light from their star.

How Many “Suns” Are in the Milky Way?

Of the research conducted on our Milky Way galaxy so far, scientists have located just over 3,500 stars with planets circling around them. Each of these orbiting bodies are called “exoplanets,” which simply means they represent a planet that orbits a star outside our Solar System.

Proxima d, a planet candidate recently discovered orbiting the red dwarf star Proxima Centauri, is depicted in this artist's impression.
Proxima d, a planet candidate recently discovered orbiting the red dwarf star Proxima Centauri, is depicted in this artist’s impression. (Image credit: ESO/L. Calçada on Wikimedia Commons CC BY 4.0)

Interestingly, Proxima Centauri is the nearest star to our Sun and has two confirmed exoplanets. One of these two worlds may exist within the star’s hospitable zone and could even have an ocean of liquid water. Being a red dwarf star, Proxima Centauri has some flare activity that could have damaged the exoplanet’s atmosphere or the amount of water it has.

Even if this world is deemed suitable for human life with water and breathable air, it still begs the question of how to get there. Traveling at the speed of light, it would still take 4.2 years to make the trip.

Kepler-47 is a binary star system with three confirmed exoplanets orbiting the two stars. One star has 85% of the output of our Sun, while the other only provides 1% of the Sun’s light. This system has at least one star in its hospitable zone but exists over 3,000 light-years from us.

Although we’ve only scratched the surface of what’s out there, it’s estimated that there could be upwards of 6 billion Earth-like planets in the Milky Way. Add that to gas planets and other sized worlds, and there could easily be 100 billion exoplanets in our galaxy alone.

How Many “Suns” Are in the Universe?

Messier 51, the first three-galaxy object seen from UCL's Mill Hill observatory
Messier 51, the first three-galaxy object seen from UCL’s Mill Hill observatory. (Image credit: UCL Mathematical and Physical Sciences from London, UK on Wikimedia Commons CC BY 2.0)

Only recently, astronomers believe they’ve located the first exoplanet in the Whirlpool galaxy some 23 million light-years from our own. Such a finding was no surprise and is likely the first of very many. With an assumed 200 billion galaxies in existence, our Earth may be just one of over 20 sextillion planets.

What if Earth Had 2 Suns?

Life on Earth would look a lot different if we were part of a star system with two distinct suns. We’d certainly have a different understanding of day and night, and the sky would probably be much brighter (and perhaps hotter) during those long days.

Depending on what part of the binary system’s habitable zone we’d be located in, we might still enjoy a temperate climate with weather changes and seasons.
What if we could see two suns falling below Earth’s horizon instead of just one?

Final Thoughts

It’s amazing to consider the tiny part our Solar System plays in this cosmic game. Where our ancestors thought we were the center of the universe, we’ve now discovered that the Earth is one of likely billions of planets in the Milky Way alone.

If technology continues to improve, we may have a chance to reach another hospitable world before our Sun starts to die a few billion years from now. No matter where we end up, our star will always be the only one we can truly call the Sun.

About Noah Zelvis

Noah is a content writer who has had a love of all things astronomy for as long as he can remember.
When not reaching for the stars, you’ll likely find Noah traveling or running.