Nasa has discovered 6,000 worlds beyond our Solar System

Nasa continues to find worlds that exist far beyond our Solar System. And now, the American space agency has confirmed the discovery of exoplanet number 6,000!

An exoplanet is a planet that orbits a star outside our Solar System. These planets are incredibly far away - some hundreds of light years from Earth - and scientists first started to discover them about 30 years ago.

The first exoplanet found around a star like our Sun was discovered in 1995. It's called 51 Pegasi b, and it's a giant gas planet, a bit like Jupiter in our own Solar System.

Since then, discoveries have been speeding up. Just three years ago, the total was 5,000 - since then another 1,000 exoplanets have been found.

In a video released to mark the moment, Nasa said: "We're entering the next great chapter of exploration - worlds beyond our imagination. To look for planets that could support life and to remind us the universe still holds worlds waiting to be found."

How do you spot a planet millions of light years away?

Experts are able to spot exoplanets when they pass in front of bright stars

Stars are millions of times brighter than the planets orbiting them. That bright light makes it almost impossible to see the much smaller, dimmer planet beside it - like trying to spot an insect next to a giant floodlight from thousands of miles away.

In fact, fewer than 100 exoplanets have ever been directly photographed.

Instead, one way scientists can spot a planet is the transit method, where they look for a star that dims slightly as a planet passes in front of it - like moving your hand across a torch beam.

Another method is gravitational microlensing, where a planet's gravity bends the light of a star, creating a tiny signal scientists can detect.

The Transiting Exoplanet Survey Satellite (TESS) is a Nasa space telescope that discovers exoplanets by monitoring the brightness of stars

It can take years to confirm a planet is real. That's why, while Nasa has 6,000 confirmed exoplanets, there are still over 8,000 more waiting to be checked.

With powerful telescopes like Kepler, TESS (Transiting Exoplanet Survey Satellite), and the upcoming Nancy Grace Roman Space Telescope, scientists hope to find even more, maybe even a planet just like our Earth.

And, with Nasa'a James Webb Space Telescope able to analyse the chemistry of exoplanet atmospheres, scientists can learn what kind of conditions might be found on the surface.

What are the 6,000 exoplanets like?

So far, scientists have found all kinds of exoplanets:

• 2,035 Neptune-like planets – similar in size to Neptune or Uranus in our Solar System.

• 1,984 gas giants – massive, stormy planets like Jupiter.

• 1,761 super-Earths – Named this, not because they are like Earth, but because they're bigger than our planet but smaller than Neptune.

• 700 rocky planets – made of solid rock like Earth or Mars.

• Seven unknown types – they're still a mystery.

In the video marking the 6,000th exoplanet discovery, Nasa says: "There's one we haven't found - a planet just like ours."

But, as Dawn Gelino, head of Nasa Exoplanet Exploration Program, explains: "Each of the different types of planets we discover gives us information about the conditions under which planets can form and, ultimately, how common planets like Earth might be, and where we should be looking for them."