Astronomers find fastest known star in the galaxy

Did you know that when you look at the stars in the night sky, you are only seeing a tiny percentage of the known stars in the galaxy?

Humans can only see around 4,500 stars with the naked eye, but there are somewhere between 100 and 400 BILLION stars in the Milky Way - which is the home galaxy of Earth and our solar system.

Well, astronomers have now spotted one of those stars that can only be seen with special high-tech telescopes travelling around a giant black hole at an incredible speed.

The star - called S301 - is travelling at around 25,000 kilometres every second. That's around 100,000 times faster than a commercial aeroplane.

And the astronomers are hoping that the speedy star can tell us a LOT about our universe.

Read on to find out why...

The star, S301, is orbiting (travelling around) , a supermassive black hole, called Sagittarius A*, which is located at the centre of our galaxy.

Scientists say it gets closer to a black hole than any other known star.

Black holes are places in space where gravity is so strong that even light cannot escape. But don't worry, S301 isn't expected to fall in.

Even though it gets very close, it is predicted to continue racing around the black hole on the same path.

But scientists from the Max Planck Institute for Extra-terrestrial Physics (MPE) in Germany are especially excited because the star could help them learn more about how black holes work.

One big mystery is whether this black hole, Sagittarius A*, is spinning.

Astronomers have long suspected this is how black holes behave, but have not been able to prove it conclusively.

If they can measure its spin, they may be able to unlock many more secrets of the universe, including the evolution of the Milky Way.

Previously it had been thought that it would require measuring the motion of many different stars for several decades to estimate the spin of Sagittarius A*.

However, the scientists were able to trace S301's orbit back to 2017 and, by tracking it through its next closest passage in 2031, hope to have enough data.

"With this star we hope to measure, within the next 10 years, the spin of the black hole," said Felix Mang, a PhD student at the Max Planck Institute.

This is complicated, so to understand this, we need you to use your imagination a bit... ready? Okay!

If you were to put a heavy bowling ball on a circular trampoline, it would create a large dip in the middle.

Now, if you took a marble and sent it rolling around the trampoline, eventually, gravity would send it towards the dip and the bowling ball.

But, if the marble is travelling fast enough, it won't fall into the dip the bowling ball is creating. It will stay on track.

You with us so far?

In this example, the bowling ball is the black hole, the marble is the speedy star travelling around the black hole and the trampoline is the 'fabric' of space, bending around the hugely heavy object.

Now, imagine the bowling ball is spinning around and around and the fabric of the trampoline is being twisted on itself. This is how scientists say they understand black holes work.

The way they are hoping to prove this is by keeping a close watch on S301 and following its path around Sagittarius A*.

If the star changes how far away it is between now and when it is next closest to the black hole, they will be able to say whether it is spinning or not.