Beyond Earth’s blue skies stretches a universe full of possibilities, including countless stars with planets that might support life. While Earth is the only known host of life, astronomers have identified several exoplanets that could potentially support it.
“An exoplanet is a planet that orbits a star other than our Sun,” explains Michelle Hill, an Earth and planetary science researcher at the University of California, Riverside.
One crucial factor in determining a planet’s potential for life is its location within the “habitable zone,” or “Goldilocks zone,” of its star. This region is where conditions are just right for life as we know it, allowing liquid water to exist on a planet’s surface – not too hot and not too cold.
Here are six of the most promising exoplanets that could potentially support life.
1. Proxima Centauri b
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system.
ESO/M. Kornmesser (Credit: NASA)
Distance: 4.24 light-years away
Proxima Centauri b, the closest known exoplanet to our solar system, orbits in the habitable zone of the red dwarf star, Proxima Centauri. It has a mass of 1.27 Earths, making it a super-Earth, a type of exoplanet with a mass larger than Earth’s but significantly less than that of gas giants like Neptune or Jupiter. Proxima Centauri b takes 11.2 days to complete one orbit around its sun.
Researchers believe Proxima Centauri b might have a rocky surface, suggesting this exoplanet could have the right conditions to support liquid water. Despite this potential, Proxima Centauri b faces extreme ultraviolet radiation from its star, which can strip away its atmosphere and complicate its habitability.
2. TRAPPIST-1e
This still from a video shows illustrations of the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 40 light-years away, based on data current as of February 2018. Each planet is shown in sequence, starting with the innermost TRAPPIST-1b and ending with the outermost TRAPPIST-1h. The video presents the planets’ relative sizes as well as the relative scale of the central star as seen from each planet. The art highlights possibilities for how the surfaces of these intriguing worlds might look based on their newly calculated properties. The seven planets of TRAPPIST-1 are all Earth-sized and terrestrial. TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its planets orbit very close to it. In the background, slightly distorted versions our familiar constellations, including Orion and Taurus, are shown as they would appear from the location of TRAPPIST-1 (backdrop image courtesy California Academy of Sciences/Dan Tell). An animation is available at https://photojournal.jpl.nasa.gov/catalog/PIA22098 (Credit: NASA)
Distance: 39 light-years away
TRAPPIST-1e is one of seven rocky exoplanets orbiting the cool dwarf star TRAPPIST-1. This super-Earth exoplanet, discovered in 2017, has a mass of approximately 0.69 Earths and takes 6.1 days to complete one orbit around its star. Its size and density suggest a rocky composition similar to Earth, raising the potential for it to support liquid water.
Despite its close proximity to its star, TRAPPIST-1e could maintain a stable climate due to the star’s low-energy output. Some studies even suggest TRAPPIST-1e might hold more water than Earth’s oceans, making it an intriguing target for future research.
3. Kepler-186f
The artist’s concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone—a range of distance from a star where liquid water might pool on the planet’s surface. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zones of other stars and signals a significant st (Image credit: NASA Ames/JPL-Caltech/T. Pyle)
Distance: 500 light-years away
Kepler-186f was the first Earth-sized planet discovered in the habitable zone of another star. It receives about one-third of the sunlight Earth does, suggesting it could have temperatures conducive to liquid water. Orbiting a red dwarf star, which typically has a longer lifespan than larger stars like our Sun, Kepler-186f might benefit from stable conditions for billions of years, giving life more time to potentially develop. Kepler-186f is likely rocky, enhancing its potential for habitability.
4. LHS 1140 b
This artist’s impression shows the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth and may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Using ESO’s HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers discovered this super-Earth orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth and has likely retained most of its atmosphere. (Credit: ESO/spaceengine.org)
Distance: 40 light-years away
LHS 1140 b, another super-Earth, is in the habitable zone of its star. It has a mass of about 5.6 times that of Earth, suggesting a rocky composition. This planet is believed to have a thick atmosphere, which is crucial as it can help retain heat, maintain stable surface temperatures, and protect potential liquid water from evaporating into space.
LHS 1140 b orbits a relatively quiet red dwarf star, reducing the risk of harmful stellar flares. Recent studies suggest it could be an ocean world with significant water content, increasing its potential habitability.
5. K2-18b
This artist’s impression shows the planet K2-18b, its host star and an accompanying planet in this system. ESA/Hubble, M. Kornmesser. (Credit: NASA)
Distance: 124 light-years away
K2-18b has captured the attention of researchers when they detected water vapor in its atmosphere. Discovered in 2015, this exoplanet orbits within the habitable zone of its star. With a mass approximately 8.6 times that of Earth, K2-18b likely has a thick, hydrogen-rich atmosphere, which could help retain heat and maintain stable conditions conducive to life.
Recent studies also suggest the presence of carbon-bearing molecules like methane and carbon dioxide, supporting the hypothesis of a water ocean beneath this thick atmosphere.
6. Gliese 12 b
Illustration of Earth compared to various models of Gliese 12 b (Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC))
Distance: 40 light-years away
Gliese 12 b orbits a cool, red dwarf star and takes 12.8 days to complete an orbit. The planet, about the size of Venus, might have temperatures around 107 degrees Fahrenheit, making it potentially temperate enough to support life.
Scientists are eager to study its atmosphere, which could provide insights into how planets close to their stars retain or lose their atmospheres. The discovery of this “exo-Venus” may also help scientists understand the habitability of planets orbiting cool stars in our Milky Way galaxy.
“Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy,” says Shishir Dholakia, an astrophysicist at the University of Southern Queensland, in a statement to the Royal Astronomical Society following the discovery of Gliese 12 b.
These six exoplanets are among the most promising candidates for hosting extraterrestrial life. As technology advances and we explore these distant worlds in greater detail, the possibility of finding life beyond Earth becomes more tangible.
Read More: Earth-Sized Exoplanet Found 55 Million Light-years Away From Our Planet
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