How Many Suns Are There?

Have you ever wondered how many Suns are there? Technically, there is only one Sun, and it’s the name we gave our solar system’s only star. Find Earth’s Sun in the finger of a spiral arm of the Milky Way galaxy called the Orion Spur. And even though there’s only one Sun, the spiral galaxy contains many giant stars illuminating the interstellar gas and dust building blocks.

But you might still be wondering how many other Sun-sized stars are there. So we’re jumping right in to learn just how many Suns there are.

How Many Suns Are There?

Earth’s Sun is a yellow dwarf star, about 4.5 billion years old. It’s a giant gas ball made of hydrogen and helium that sits at our solar system’s center.

Even though the Sun is approximately 93 million miles (150 million kilometers) away, its energy is Earth’s life force. And without it, life on our home planet couldn’t exist as we know it. Ours would be a frozen, likely uninhabitable world.

The Sun is our solar system’s most prominent object, with a diameter of about 865,000 miles (1.4 million kilometers). In addition, it has an enormous gravity that holds our entire system together. It keeps the planets and even celestial dust in their correct orbits around itself.

But even though the Sun is central to our survival and our solar system’s stability, it’s not a particularly remarkable star. Instead, it is average in size, temperature, and brightness. And there are much larger stars than the Sun.

There Is Only One Sun

Let’s delve into more information about Earth’s one and only Sun. While there are many Sun-sized stars throughout the universe, none of them are quite as remarkable as our central star.

Incredible Facts About The Sun

Here are some incredible facts about Earth’s one and only Sun.

• The Sun shines as a yellow dwarf star with average surface (or photosphere) temperatures of about 10,000 °F (5,500 °C.)
• And if you don’t think that sounds very hot, consider that the Sun’s core reaches 27 million °F (15 million °C.)
• But wait, there’s more! The Sun’s corona or outer atmosphere gets hotter further away from the surface. And it reaches a whopping 3.5 million °F (2 million °C). Now that’s scorching hot!
• Although the Sun is enormous compared to the planets in our solar system, it is actually an average-sized star. In fact, UY Scuti, the most giant star in the universe, is about 1,500 times the Sun’s diameter, with ten times more density and 340,000 times more brightness.
• The Sun is averaged sized, but it still dwarfs Earth. As a result, you could fit 1.3 million Earth-sized planets within the Sun’s volume. And you’d need more than 330,000 Earths to equal the Sun’s mass.
• The Sun’s closest stellar neighbors are a triple star system, Alpha Centauri. But they aren’t even very close. For example, Proxima Centauri is a red dwarf star, 4.24 light-years from the Sun. And the other two sunlike stars in the system, Alpha Centauri A and B, reside 4.37 light-years distant. And if you recall that light travels about 6 trillion miles (9.5 trillion kilometers) in one year, you’ll realize that the closest star to the Sun is still an enormous distance away. (See NASA’s neighborhood chart below.)
• While the Sun doesn’t technically have years, it does orbit the Milky Way’s center. And everything in our solar system goes along with it, whipping along at 450,000 miles per hour (720,000 kilometers per hour.) But even at this average velocity, the Sun still takes 230 million years to make a complete trip around the galaxy.
• The Sun does rotate on its axis while it orbits the Milky Way. But since it isn’t solid, different regions rotate at different speeds. For example, one rotation at the Sun’s poles takes 36 Earth days. But that shortens to only 25 Earth days at the Sun’s equator.

How Did The Sun Get Its Name?

The Sun gets its name from the Latin word “sol.” It also becomes the main adjective or root word for Sun-related items, like solar, solstice, and parasol. By the same token, Helios was ancient Greek’s sun god. And he also loans his name to Sun-related words.

For instance, the heliosphere is the solar system’s region of space where solar wind significantly influences its surroundings. Scientists believe each star creates a similar bubble around itself, a heliosphere. However, at the edges of these bubbles, stars emit electromagnetic radiation, gasses, and dust particles that continually feed the interstellar medium.

So if Helios was the sun god, why isn’t the Sun named directly after him? That would be the work of the Romans and their vast empire. They worshipped several sun gods but replaced the Greek word Helios with the Latin word Sol. Ancient Rome’s most potent sun god was Sol Invictus, or Unconquered Sun.

How Many Suns Are There In The Universe?

Some scientists refer to stars with planets orbiting as suns, but it is more a means to differentiate them from stars without planets and satellites easily. However, even with the continually impressive technology and telescopes, researchers are limited in finding other “solar systems” within the Milky Way, much less in galaxies further out.

And finding how many suns are there in the universe is a little easier than searching for new planets since they don’t emit light. But it is still a difficult task.

The observable universe is the portion we can see from where we live on Earth. And it is about 93 billion light-years across but continuously expands. So there are regions of space beyond our visible reach.

Now here’s the fun part!

• Scientists believe there are likely one to two trillion galaxies within the observable universe.
• Based on the Milky Way, there are probably 100 billion stars per galaxy.
• So there are likely 100 to 200 sextillion stars in the observable universe.

That is a staggering amount of stars. But let’s do a little more math.

• Scientists also believe about 75% of stars are small red dwarfs, which are not comparable to the Sun’s size and mass.
• Eliminating the red dwarfs still leave us with 25 to 50 sextillion sunlike stars in the observable universe.

But just when you think there’s an answer, it gets even crazier because researchers now think that even small red dwarfs can have planet-sized objects as natural satellites.

Check out this artist’s concept drawing of CHRX 73, the red dwarf star in the upper left. It shows the companion CHRX 73 B in the lower right. Now this companion is one of the smallest found around a typical star (beyond the Sun), and it weighs in at 12 times Jupiter’s mass.

CHRX 73 B is small enough that it could be a planet, but it’s also large enough to qualify as a failed star, a brown dwarf. The Hubble Space Telescope discovered this small star and its companion in 2006. And the objects are a reminder that not all astronomers agree on whether satellites orbiting other stars are planets, brown dwarfs, or other celestial entities.

But they do know and agree that this object orbits its star about 200 times farther than Earth orbits the Sun. And CHRX 73 is only a two million-year-old star with only about a third of the Sun’s mass. Both lie approximately 500 light-years from our home planet in the Milky Way’s star-forming region, the Chamaeleon I.

How Many Suns Are There: Spectral Type

A huge determiner of whether or not a star is “sunlike” comes from its spectral type classification. It’s a way to classify stars by their temperatures. Each star’s radius, mass, and luminosity are linked closely. So larger, hotter stars don’t live as long as shorter, cooler stars.

The seven main classifications of stars follow.

• O
• B
• A
• F
• G (The Sun)
• K
• M

Stars’ spectral types influence their lifespans. For example, O and B-type stars are short-lived. O-types live about 10 million years, while Bs live for about 100 million years. But they are a drop in the bucket of time compared to other star lifespans. Like the Sun’s G-type, medium stars live about ten billion years. The Sun has reached almost half its expected lifecycle.

The minor stars are K and M-types. Ks live about 50 billion years, and Ms have a life expectancy of 100 billion to trillions of years.

A star’s spectral type affects its color. The hottest stars burn blue and blue-white, while smaller and cooler stars burn red. If you think of it in relation to cooking on a gas-burning stove top, blue flames are hotter than red flames. And stars follow that same heat pattern.

In addition to color and temperature, a star’s spectral type also defines its size. M-type stars are the tiniest stars in the universe, while O-types are colossal in size. Smaller sizes have dwarf classifications, and the more prominent stars have giant, supergiant, and hypergiant statuses.

So to answer the question of how many Suns are there, you need to understand how stars are classified by their spectral types. And if you realize that at least 75% and possibly up to 90% of all stars are M-types, then you’ll see that fewer sunlike stars exist in comparison.

How Many Solar Systems Are In The Galaxy?

Those last numbers are almost impossible to wrap your head around. So let’s take it back down to the Milky Way Galaxy. The red dwarf CHRX 73 isn’t the only star with a natural satellite in our galaxy.

Just like there is only one Sun, there is also only one solar system. But how many suns are there in the galaxy? Scientists believe more than 3,200 other sun-like stars exist with exoplanets orbiting them.

Exoplanet simply refers to any planet outside our own solar system. And these bodies are complicated to find, even though scientists think most stars probably have one or more exoplanets in their orbits.

While ours is the only solar system, the Milky Way has 4,207 other planetary systems. So let’s explore a few of the 5,407 confirmed exoplanet discoveries. But keep in mind there are still 9,719 exoplanet candidates awaiting confirmation, and the numbers often change as scientists continue making and confirming exoplanet discoveries.

Kepler-16

Binary star Kepler-16 has K-type and M-type components that orbit one another once every 41 days. Both are about two billion years old, compared to the Sun’s 4.6 billion years. In addition, both stars are significantly smaller than the Sun, with much lower luminosities.

Exoplanet Kepler-16b orbits both stars, so you’d get pretty amazing double sunsets. It was the first Kepler telescope discovery of a planet orbiting two stars in a “circumbinary” orbit. This gas giant is about three-quarters the size of Jupiter and only a third of its mass, discovered in 2011.

Even though it has two stars, both are much cooler than the Sun, so there is likely not enough energy for the formation of life. In addition, the exoplanet is outside both stars’ habitable zones, so liquid water could not exist.

Kepler 51

This sunlike star is young, only about 500 million years old. Three puffy planets orbit it. Kepler-51 b, c, and d are Jupiter-sized exoplanets with small masses, a few times that of Earth. So because of Hubble data, scientists equate them to having lighter styrofoam densities rather than rocky compositions in comparison to their large sizes. Interestingly, the exoplanets’ hydrogen and helium atmospheres are leaking into space, leading researchers to believe that much smaller planets could be left behind.

The artist’s rendition below takes color liberty with the exoplanets when comparing their sizes to planets in our solar system. Since scientists have no direct imaging, the colors are arbitrary.

Stars With Planetary Systems: The Potential For Habitable Life

There are some sunlike stars and even smaller red dwarfs that have exoplanets within their habitable zones. So the potential for life outside of Earth does exist. Let’s explore a few of these planetary systems.

What Is The Habitable Zone?

First things first, in order to understand if a star has an exoplanet in the habitable zone, it helps to know what exactly that means.

Habitable Zone: Also known as a Goldilocks zone. The distance from a star to the point in space where orbiting planets could have liquid water.

That means planetary conditions need to be just right. Not too cold or too hot to sustain life. All stars have a habitable zone, but where it lies depends on the star’s brightness and size.

When astronomers search for potentially habitable planetary systems, they start with worlds similar to Earth. And while they’ve found many Earth-size rocky planets, most of them orbit red dwarf stars. Scientists think terrestrial worlds similar in size to our own that widely orbit sunlike stars are more likely to have the potential for life. However, finding them is difficult.

But here’s why a sunlike star is essential in the search for life forms. While on the hunt for habitable exoplanets, it’s all about the planetary system’s dominant force: the star.

Hotter sunlike stars have a much wider habitable zone than smaller and dimmer red dwarfs. Unfortunately, red dwarfs, which are the most common star type in our galaxy, have much narrower Goldilocks zones. 

And because they don’t emit as much energy as giant hot stars, the exoplanet is closer and gets exposed to extreme X-ray levels. In addition, the ultraviolet radiation in a tight habitable zone can be more intense than the UV rays Earth gets from the Sun, hundreds of thousands of times more intense.

So there are more red dwarfs with exoplanets in the habitable zone, but that zone is questionable because of the X-ray and UV damage the closer proximity cause. And that’s why astronomers hope to find Earth-size rocky planets with sunlike stars for the best chance of life potential.

Proxima Centauri

Part of the Sun’s closest neighbors, Alpha Centauri, Proxima Centauri is the third and faintest star. This red dwarf (M-type) star has a mass of only one-eighth of the Sun’s mass with a diameter of about one-seventh of the Sun.

Proxima Centauri has at least three exoplanets, the nearest ones to the Sun.

• Proxima Centauri b, discovered in 2016, has a mass of 1.07 the Earth’s. It orbits within the star’s habitable zone.
• Proxima Centauri c, discovered in 2019, is the first directly imaged exoplanet.
• Proxima Centauri d, discovered in 2019 and confirmed in 2022, is a tiny exoplanet. It is one of the lightest exoplanets detected at only about one-fourth of Earth’s mass.

Liquid water could potentially exist on Proxima Centauri b, but it regularly gets bombarded with stellar winds up to 2,000 times what we experience on Earth. In addition, the exoplanet is likely tidally locked to its star, so if life could exist, it would probably be in the Twilight zones. These are the regions between the perpetual day and night sides, where the temperatures are less extreme.

Tau Ceti

This single star in the Cetus constellation is spectrally similar to the Sun. Tau Ceti has almost 80% of the Sun’s mass and is nearly 12 light-years away. It is the closest single G-type star. Researchers find more than ten times the amount of dust surrounding this star than is present in our solar system. So the four confirmed super-Earth exoplanets face many more impact events than Earth.

However, even with the potential for impacts, two of these exoplanets potentially lie in Tau Ceti’s habitable zone. Although in addition to impacts, the exoplanets receive almost twice as much starlight as Earth receives from the Sun.

Tau Ceti has many sunlike characteristics, and it remains stable. So despite the stellar heat and impact event hurdles, the star’s planetary system remains a target in the Search for extraterrestrial intelligence, SETI.

In addition, four more unconfirmed planets also orbit the sunlike star, one of which is a Jovian-like exoplanet. So the potential for some type of life in Tau Ceti’s planetary system still deserves exploration.

The artist’s impression below shows how planetary systems form from massive collisions of rocky objects. NASA’s Spitzer Space Telescope used infrared vision to see the dust generated from the crashes. So collisions can still occur even after a star has full-sized, young planets.

TRAPPIST-1

The TRAPPIST-1 star is the most studied star and planetary system outside our solar system, lying about 40 light-years away. And its seven rocky exoplanets have the most potential for finding habitable life conditions. So in answering the question, how many Suns are there, you have to take TRAPPIST-1 into consideration.

TRAPPIST-1 is a small star with a mass of 0.09 times the Sun’s mass. It is an ultracool red dwarf (M-dwarf) with a relatively low temperature of only 2,566 kelvin.

The planetary system’s first James Webb Space Telescope data was released in March 2023, with future data expected. It showed that the innermost planet, which is about the size of Earth and its density, has little to no atmosphere.

TRAPPIST-1 b has a dayside temperature of around 450 degrees Fahrenheit (232 degrees Celsius.) While it is too close to its star to be in the habitable zone, observations help provide information about the sibling planets in the TRAPPIST planetary system. It also helps scientists better understand M-dwarf systems.

There are ten times more M-dwarf stars in the galaxy as there are sunlike stars, with double the likelihood of rocky planets of the sunlike stars. But since these red dwarfs are young, they’re very active. And that means they are very bright, giving off X-rays that can obliterate an exoplanet’s atmosphere.

One of the most exciting details to emerge from Webb’s measuring of TRAPPIST-1 b’s temperature is the use of the telescope’s Mid-Infrared Instrument (MIRI.) It used the exoplanet’s thermal emission, meaning the heat energy as expressed by infrared light.

And MIRI technology means Webb can characterize temperate, approximately-Earth-sized exoplanets, opening a world of exploration.

Sagittarius Galaxy: The Forming of New Milky Way Stars

Stars are born in regions rich in cosmic dust clouds and gasses. But you might wonder how these stellar nursery regions form and if they impact how many Suns are there. Even as we noted above, rocky bodies might crash into one another to create the building blocks for newer planetary systems, so it appears can galaxies.

A team of scientists on the European Space Agency’s (ESA) Gaia project published a report in 2020 regarding Gaia’s evidence of the smaller Sagittarius galaxy impacting the Milky Way. When these collisions occurred, new star-forming regions developed as cosmic dust and gas clouds from Sagittarius remained behind in the larger galaxy.

Researchers say Sagittarius fell into the Milky Way on three (possibly four) different occasions. And the first time it happened corresponds with the timing around the Sun’s birth. So, while they can’t explicitly say that the Sun would not exist without the intergalactic collision, there is strong evidence leading that way.

ESA Video of Sagittarius and the Milky Way

Or here’s the main page to get the video.

Scientists believe Sagittarius colliding with the Milky Way helped form the Sun and our solar system. They say it is like the smaller galaxy fell in, disrupted the Milky Way’s equilibrium, and caused the still dust and gas to slide around like ripples on water.

And in that way, Sagittarius helped build up the Milky Way, creating a high density of dust and gas in some areas that would then trigger new star formations. Gaia project researchers believe an essential part of the Milky Way’s stellar mass formed due to Sagittarius interactions. So our Sun may not have existed without the smaller galaxy’s influence.

Join The Search: How Many Suns Are There? Cool Neighbors

NASA researchers are currently looking for citizen scientists to help discover brown dwarfs, the Sun’s celestial neighbors! These objects have masses between stars and giant Jupiter sizes. But they have much lower temperatures than the Sun, so they got the nickname Cool Neighbors.

You can help answer scientists’ questions about whether the found celestial object is an exoplanet or a brown dwarf. And who knows? Maybe you’ll get to choose the name of one of them!

Use your phone or computer to help examine NASA’s Wide-field Infrared Survey Explorer (WISE) telescope’s new data. And who knows? Maybe you’ll discover the Sun’s next cool neighbor!

Wrap-Up: How Many Suns Are There?

We’ve explored planetary systems around sunlike stars and even smaller stars. And we’ve looked at some numbers around the potential for how many suns are there. The opportunities for thousands of planetary systems exist. And ground-based telescopes combined with the astonishing technologies of the Webb scope and Gaia mission will indeed expose more sunlike stars and their orbiting planets.