The historic discovery was made by new scientific analysis of data obtained by the Kepler space telescope, which is scouring the galaxy for planets like Earth.
Paul Hertz, Astrophysics Division director at NASA Headquarters in Washington, said: “We have found for the first time an eigth planet in a distant planetary system in the Kepler 90 system – this ties Kepler 90 with own solar system for having the most known planets.
“Kepler 90 is the first star to host as many planets as our own.”
The new planet – Kepler 90i – is a small rocky planet, but very close to the sun which is hotter than ours, and is 2,500 light years from Earth.
It would be scorching hot and unable to hold life itself, although some planets in the system may be able to.
But, it means that NASA now believes most stars in space are likely to have a series of planets orbiting, boosting the chances of there being more like Earth with the conditions for life to evolve.