The answer as to how many stars are in our Solar System is simple: just one!
Our Sun is a star, and it's located at the centre of our Solar System, with the planets orbiting around it.
The revelation that our Sun is a star may be a surprise to some people, but there's probably good reason for that.
The constant presence of the Sun in daytime and the nightly appearance of the stars is taken for granted by many of us.
This day-night cycle is so regular and constant that we perhaps don't think much about what's really going on above our heads.
One of the biggest misconceptions, for example, is that the Moon is a nighttime object, when in fact the Moon's appearance has nothing to do with nighttime, and the Moon is often visible during the day.
The way we perceive daytime and nighttime can lead to the idea that the Sun is visible during the day, and when the Sun sets, the stars come out.
But the truth is the stars are always there in the sky: we just can't see them when the Sun is out because the Sun's brightness washes them from our view.
When the side of Earth we're on rotates away from the Sun, nighttime falls and we're able to see those stars because they're not being washed out by sunlight.
Many stars and constellations are only visible at certain times of year (like Orion in winter, for example), while others - circumpolar constellations - are visible all year round.
This apparent movement and changing of the sky doesn't represent a changing Universe; rather a changing perspective as Earth rotates on its axis and orbits our host star, the Sun.
Sometimes the side of Earth we're on is facing the Sun, and we perceive 'daytime'; sometimes it's facing away from the Sun, and we perceive 'nighttime'.
Far from the Sun being something different from the stars, the Sun is a star, and it's the star around which Earth and the other planets in our Solar System revolve.
Our Sun is a star
Yes, our Sun is a star. It's a yellow dwarf star, a G-type Main Sequence star to be exact, and is about 4.6 billion years old.
The Sun is just like all those other stars you see in the night sky, but many of the stars in the night sky are much, much bigger and brighter than the Sun.
To state the obvious, it's just that the stars in the night sky are much further away.
Sirius, the brightest star in the sky, for example, is twice as big as our Sun.
Another famous star, the red giant Betelgeuse that forms the shoulder of Orion, is thought to be about 7,500 - 14,000 times the size of our Sun.
And star UY Scuti, generally regarded as the biggest star in the Universe that we know of, is so big that you could fit 5 billion Suns in it.
Just as those huge stars are so far away that they appear tiny, only visible under the darkness of night, the same is true of our Sun.
If you were an extra-terrestrial being living on another planet, our Sun would appear to you as another speck of starlight on an inky black canvas.
The Sun, a star, and the Solar System
The Sun is at the centre of our Solar System, which means that all the planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune – orbit it.
It is Earth's host star and bathes our planet in heat and light, providing energy for plants and animals to thrive.
The Sun and the presence of water are the main reasons life was able to develop and flourish on Earth.
Liquid water is essential for life as we know it, and if Earth orbited too close to the Sun, it would be a hellish nightmare, too hot for water to exist as a liquid on the surface.
If Earth orbited too far away, our planet would be an icy world like Uranus and Neptune.
Earth is orbiting at just the right distance - and has the right kind of atmosphere - for liquid water to pool on its surface, giving us oceans and lakes, rain and rivers, and the right balance of conditions for life to thrive.
So far, Earth is the only place that we know of to host life, and that's all thanks to our atmosphere, our Sun and our orbit.
Formation of our Solar System
If the Sun is a star, where did it come from?
About 4.6 billion years ago, a cosmic cloud of gas and dust – the ingredients out of which stars form –began to clump together, amassing more and more material until it eventually became so massive it collapsed under its own gravity.
This is the way, as astronomers understand it, that stars form, and our Sun was no different.
After its formation, the Sun was surrounded by a spinning disc of leftover dust and gas.
In time clumps of this material coalesced to form small pebbles, which amassed more and more material, grew bigger and bigger and formed larger bodies.
These grew even bigger and eventually became the planets and moons orbiting the Sun.
This is what we know today as our Solar System.
Our Sun accounts for 99.8% of the Solar System's total mass, so not much material was left over after its formation.
But there was enough to form the planets, including Earth, the small, blue, watery world that we call home.
The term 'Solar System' refers to our Sun and the planets in orbit around it, and that is why we can say there is only one star in our Solar System.
That star effectively is our Solar System.
And the Solar System is not the same as the Galaxy. Our Galaxy is known as the Milky Way and contains our Sun and about 100 billion other stars, the majority of which probably also have planets in orbit around them.
What's more, our Galaxy is just one of an estimated 200 billion galaxies in the Universe (and that's only the 'observable Universe').
Other Suns with planets
Our Solar System has a star – the Sun – at its centre. So it stands to reason that other stars might have planets orbiting them.
The idea of other planets orbiting distant stars is centuries-old, but it was only in the mid 1990s that the first was confirmed.
Planets orbiting stars beyond our Solar System are known as 'exoplanets', we've discovered thousands, and there are all manner of weird and wonderful exoplanets out there.
We now know that, on average, every star you can see in the night sky has at least one planet in orbit around it.
Perhaps astronomers on a distant world have discovered this fact too, and are looking at our Sun as you read this, wondering whether there's anyone else out there.
Some exoplanets are extremely hot and some are extremely cold, orbiting too close or too far from stars much bigger than our Sun.
But astronomers have also found Earth-like worlds that are orbiting at just the right distance from their stars and which could host liquid water.
Using powerful telescopes like the James Webb Space Telescope, astronomers have even been able to study the atmospheres of these exoplanets, and on some occasions have discovered signs of organic materials that are key to the development of life.
That doesn't mean astronomers have found definitive signs of life on exoplanets around distant stars, but it does show that planets beyond our Solar System may at least have the potential for life to take hold.
Solar Systems with two suns
Our Solar System has one star: the Sun.
But some stars are known to orbit another star, and we call these binary stars.
Binary stars are two stars in orbit around each other, and astronomers have even been able to find exoplanets orbiting binary systems.
This could mean, in effect, that any creatures living on planets orbiting binary stars might be treated to two suns in the sky at once.
Remember in Star Wars how Luke Skywalker's home planet, Tattooine, had two suns? What was once considered fantastical science fiction is now science fact.
So while our Solar System does indeed have just one star, other civilisations may be lucky enough to have two.
