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.
NASA*Ames Research Center*Wendy Stenzel
NASA Announcement: the Kepler Telescope has gazed at more than 150,000 stars.
For life to form, it is believed that a planet must be rocky, and at the right distance from its star to be not too hot or cold, so it can hold liquid water and an atmosphere.
A team of NASA scientists who have scoured the universe looking for planets that could potentially hold alien life today made the historic announcement in a briefing at 6pm British time.
It was to unveil the latest findings of the Kepler space telescope mission.
Kepler 90i orbits its home star every 14 days and is about 30 percent bigger than Earth.
The planets in the Kepler 90 system orbit much closer to their host star than Earth is to the sun.
Andrew Vanderburg, astronomer and NASA Sagan Postdoctoral Fellow at The University of Texas, Austin, said: “The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer.
“Kepler 90i is about 2,500 light years away in the northern sky.
We are probably not alone.
“It is the smallest of a bunch of probably rocky planets, not with thick atomosheres like the gas giants further out.
“But, I would not like to visit, it would have a surface temperature of about 800 degrees fahrenheit, the surface would be scorching hot.
“Kepler 90 is the first exoplanet system like ours with eight planets, but I think it won’t be the last.
“Our solar system is not sole record holder for solar systems with the most planets and we have just scratched the surface. There might be more out there that make our eight look small.”
Kepler-90i wasn’t the only new planet foujnd by the machine learning system.
In the separare Kepler-80 solar system, thought to have five planets, was a sixth.
The Earth-sized Kepler-80g, and four of its neighboring planets form what is called a resonant chain – where planets are locked by their mutual gravity in a rhythmic orbital dance.
The result is an extremely stable system, similar to the seven planets in the TRAPPIST-1 system, previously thought to be the next biggest solar system.
Previous Kepler announcements have included the discovery of several earth-like rocky planets that were at the right distance from their star to potentially house alien life.
The team has been searching for such planets since 2009, finding around 30 Earth-sized planets orbiting within the ‘habitable zones’ of their stars and another 20 ‘possibles’.
The space agency teamed up with Google to use artificial intelligence to search for exoplanets, which could support extraterrestrial organisms.
NASA says the new discovery has been made by researchers using machine learning from Google, which is an approach to artificial intelligence, and demonstrates new ways of analysing Kepler data.
The Kepler telescope recently found ten more planets outside our solar system which could be the size and temperature to support life.
A Nasa researcher hinted that aliens could be out there somewhere.
Kepler scientist Mario Perez said: “We are probably not alone.”
A NASA spokesman said: “When Kepler launched in March 2009, scientists didn’t know how common planets were beyond our solar system.
“Thanks to Kepler’s treasure trove of discoveries, astronomers now believe there may be at least one planet orbiting every star in the sky.”
Kepler completed its prime mission in 2012 and went on to collect data for an additional year in an extended mission.
In 2014, the spacecraft began a new extended mission called K2, which continues the search for planets outside our solar system, known as exoplanets, while introducing new research opportunities to study young stars, supernovae and other cosmic phenomena.
NASA
A NASA CGI impression of 452-b.
In May 2016 NASA scientists revealed they have found 1,284 using Kepler new planets that could house alien life.
The US space agency announced the discovery of the new “exoplanets” which are considered as similar to Earth due to their distance from the star they orbit.
Timothy Morton, associate research scholar at Princeton University in New Jersey, said at the time: “We have discovered 1,284 new planets – the most explanets ever announced at one time.”
It more than doubled the previous amount of exoplanets found by the Kepler Telescope, taking the total number to 2,325.
It comes after NASA said they also believe every star in space has at least one planet orbiting it, further increasing the chance of life evolving somewhere.
Paul Hertz, Astrophysics Division director at NASA Headquarters in Washington, said then: “When launched we did not know if exoplanets or rocky exoplanets were rare and we now know they are extremely common and most stars have at least one planet orbiting.”
NASA
This NASA CGI image shows how the surface of 452-b may appear.
Among the 2016 discoveries were also a further 100 grade A rocky exoplanets which are the most likely for life to begin just like Earth.
And of those 24 were found to be of a similar size to Earth and distance from their stars in the so-called Goldilocks habitable zone, making them the most likelyy candidates for life.
Combined with 12 already found by Kepler researchers, there were then 36 of the Earth-like planets and a further 12 possible ones awaiting verification.
One of the more notable exoplanet found came in July 2015 with the discovery of what NASA described as “Earth’s bigger older cousin”, called Kepler-452b, and later dubbed Earth 2.
Kepler project scientists used the telescope to track down the Earth-like planet, but estimated 452-b is 60 per cent bigger and probably weighs five times as much as our own planet.
The five times bigger mass would make Kepler 452-b’s gravitational pull at least twice as strong as on Earth – something humans would find very difficult to deal with, as possible space explorers would feel twice as heavy.
According to NASA scientists who unveiled the discovery of the planet, if humans ever reached Kepler 452-b we would eventually evolve into much stockier beings because of its gravitational force.