SCIENTISTS have discovered 24 potentially "superhabitable" planets with conditions that may be better for life than Earth.
The mysterious worlds are older, larger, warmer and possibly wetter than our planet, making them prime targets for future alien-hunting missions.
Researchers at Washington State University (WSU) outlined their stunning find in a scientific paper published Monday.
The planets are 100 light-years from Earth, making them too distant to visit, but possible to study with future advanced space telescopes.
Probes like the European Space Agency's ARIEL mission, due for launch in 2028, are specially designed to seek signs of life on faraway worlds.
"With the next space telescopes coming up, we will get more information, so it is important to select some targets," WSU scientist Professor Dirk Schulze-Makuch said.
"We have to focus on certain planets that have the most promising conditions for complex life.
"However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours."
The team created a "superhabitability criteria", which they lined up against 4,500 known exoplanets – planets outside the Solar System.
Habitability wasn't defined as definite signs of life, but as hosting conditions that make them ripe for its growth.
The criteria included being up to 10 per cent larger than Earth, with a surface temperature 5C (9F) above that of our own planet and an age of between 5 billion and 8 billions years old (Earth is 4.5 billion years old).
What is an exoplanet?
Here’s what you need to know…
- An exoplanet is a planet that is located outside of our Solar System and one that is orbiting its own star, as Earth orbits the Sun
- They are very hard to see with telescopes because they are often hidden by the brightness of their star
- Nasa sent the Kepler space telescope into orbit with the purpose of finding Earth-sized exoplanets that might support life
- More than 4,000 exoplanets have been discovered so far and more missions to find even more exoplanets are planned
- A good way to spot an exoplanet is to look for "wobbly" stars because a disruption to starlight can indicate that a planet is orbiting it and blocking its light intermittently
- Expoplanets are very common in the universe and the more we find that look like Earth, the closer we get to knowing whether Earth is the only life-bearing planet
Worlds also had to exist in their star's habitable zone – defined as the area in which a planet could support water at its surface – and orbit a star that is cooler than our Sun, meaning it has a longer lifespan.
In total, 24 potentially "superhabitable" planets were found that may have conditions better for supporting life than Earth.
None of the planets conclusively met all five of the criteria laid out by scientists, but one met four of them.
Researchers stressed that the results do not mean the 24 worlds definitely host life.
"Habitability does not mean these planets definitely have life, merely the conditions that would be conducive to life," WSU said in a press release.
The distant rocks could become key targets for planet-scanning space telescopes of the future.
More than 4,500 exoplanets have been detected by scientists but we don’t know much about them.
The next generation of space probes, including ARIEL mission and Nasa's James Webb telescope, will be able to observe atmospheres in more detail.
ARIEL aims to observe 1,000 planets in detail to give us a more accurate picture of potential alien worlds.
By observing a huge number of planets, scientists hope to reveal secrets about their chemistry, formation and evolution.
The research was published in the journal Astrobiology.
In other news, water was found on a habitable "super-Earth" last month ins a breakthrough in the search for alien life.
China's giant alien-hunting telescope has received 'mysterious signals' from outer space.
And, Nasa has released a stunning image showing the remnants of a massive ancient supernova.
Do you think alien life is out there in the universe? Let us know in the comments!
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