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To evaluate whether an exoplanet (a planet orbiting a star other than our Sun) is capable of supporting life, scientists take into account various factors. The primary factor is the exoplanet’s semimajor axis, which represents the average distance from the planet to its star, and its relationship to the star’s habitable zone.
The habitable zone refers to the region around a star where conditions are just right for a planet like Earth to potentially have liquid water on its surface. Without the presence of water, life as we understand it cannot exist.
Scientists also examine other important factors. For example, the exoplanet should be rocky in nature rather than gaseous. Its radius and mass should fall within a specific range: 0.5 to 1.5 times Earth’s radius, and 0.1 to 5.0 times Earth’s mass.
The exoplanets featured in this list were chosen from the catalog of potentially habitable exoplanets curated by the Planetary Habitability Laboratory at the University of Puerto Rico.
10. Tau Ceti E
Tau Ceti is a star situated approximately 12 light-years from Earth in the constellation Cetus. Despite the distance, it is close enough to be visible to the naked eye. The star’s magnesium-to-silicon ratio is 1.78, which is around 70 percent higher than that of our Sun.
Tau Ceti e is a planetary candidate within this star system, which means it hasn’t been confirmed as a planet yet. Discovered in 2012, it completes a year in 168.1 Earth days.
Tau Ceti e orbits near the inner boundary of the habitable zone, raising the possibility that liquid water might exist on the planet’s surface. The planet’s average global temperature is estimated to be around 70 degrees Celsius (158 °F), which contrasts with Earth’s average of 15 degrees Celsius (58 °F).
This extremely high temperature makes it unlikely for humans to live on Tau Ceti e. However, it may still support life forms in the early stages of evolution.
The planet’s radius ranges from 1.1 to 2.0 times that of Earth. With a mass equal to or greater than 4.3 times Earth’s mass, Tau Ceti e lies on the outer edges of a potentially habitable zone for life in its early developmental stages.
As space travel advances, Tau Ceti e could potentially support more advanced life forms, including humans.
9. Kepler 438b
Kepler 438, the star at the center of this planetary system, lies about 473 light-years away from Earth in the Lyra constellation. At roughly 4.4 billion years old, this red dwarf star has a fainter light, which brings the habitable zone closer to the star compared to a brighter star.
Kepler 438b, a planet just 12 percent larger than Earth, has a mass ranging from 0.6 to 4.0 times that of Earth. It is likely a rocky planet and orbits within the habitable zone of its star, making liquid water possible.
With a radius 1.1 times that of Earth, Kepler 438b’s characteristics make it potentially capable of supporting recognizable life. However, its average temperature of 3 degrees Celsius (37 °F) may pose a challenge for humans.
Humans might adapt to survive at such temperatures, though it would be quite challenging. This exoplanet is more likely to support the early phases of life rather than human colonization at this time.
8. GJ 667C E
GJ 667C, a red dwarf star located 22 light-years away from Earth in the Scorpius constellation, is part of a triple-star system with two orange dwarfs orbiting each other.
The red dwarf orbits both orange dwarfs, and all three stars are estimated to be between 2 and 10 billion years old. They would be visible from a planet orbiting the red dwarf.
GJ 667C e, which is still awaiting confirmation of its planetary status, has a year length of 62 Earth days and a radius ranging from 1.0 to 1.8 times that of Earth. While its radius is at the upper limit for a habitable planet, its mass, likely greater than 2.7 times Earth’s, seems favorable for habitability.
This potential exoplanet resides comfortably within the habitable zone, where the presence of liquid water is possible. However, GJ 667C e is likely tidally locked, which would result in one side being hot and the other cold, as the same side of the exoplanet continuously faces its star.
While this condition might limit the habitable area of the exoplanet, it doesn’t change the possibility that it could support human life.
7. Kepler 186f
Kepler 186, located 561 light-years from Earth in the Cygnus constellation, is a red dwarf that is cooler and less massive than our Sun. This causes the habitable zone to be much closer to Kepler 186 than it would be around a brighter star.
On Kepler 186f, one year lasts around 130 Earth days. This exoplanet, which is situated in its star’s habitable zone, is similar in size to Earth. While the mass of Kepler 186f remains unknown, its radius is only 1.1 times that of Earth.
Kepler 186f orbits in the outer zone of its star's habitable region, resulting in an average surface temperature of just 0 degrees Celsius (32 °F). It is right on the boundary of being suitable for human habitation unless it has a dense atmosphere rich in carbon dioxide.
6. Kepler 62f
Kepler 62, a star in the Lyra constellation, is located around 1,200 light-years from Earth. Its mass and radius are approximately 0.69 and 0.63 times that of the Sun, respectively.
Kepler 62f, an exoplanet discovered in 2013, has a year that spans approximately 268 Earth days. Its mass is compared to that of Jupiter, which has a mass about 318 times that of Earth.
In comparison, the mass of Kepler 62f is roughly 0.11 times that of Jupiter. The exoplanet’s radius is about 1.4 times that of Earth. Positioned within its star’s habitable zone, Kepler 62f could potentially have liquid water on its surface.
Kepler 62f experiences a surface temperature of -30 degrees Celsius (-22 °F), placing it on the colder side of habitability. However, all of these conditions make it a promising candidate for human colonization.
5. Kapteyn B
Kapteyn, a red dwarf situated 13 light-years away in the constellation Pictor, has a mass and radius approximately 0.28 and 0.29 times those of our Sun. This star is estimated to be around eight billion years old.
Named after Jacobus Kapteyn, the Dutch astronomer who identified it at the close of the 19th century, Kapteyn is the fastest moving star in the sky and is visible to amateur astronomers.
Kapteyn b, pending confirmation as a planet, orbits in just 48 Earth days. While its radius is unknown, it has five times the mass of Earth and may possess surface water. The available data suggests this exoplanet and its star could potentially support human life.
4. Wolf 1061c
Wolf 1061, a red dwarf star, resides 14 light-years away from Earth in the constellation Ophiuchus. It ranks as the 35th-closest star to our planet. With only 0.25 times the mass of our Sun, the star’s dim light brings the habitable zone closer than it would be with a brighter star.
Exoplanet Wolf 1061c may be rocky and is situated within the zone where liquid water could exist. The planet’s gravity is approximately 1.8 times that of Earth. Tidally locked, Wolf 1061c’s two sides experience extreme conditions—one side faces perpetual heat, while the other is in constant cold.
These drastic temperature differences make survival on either hemisphere unlikely, though life might be possible along the boundary between the hot and cold zones, though it would be far from ideal.
3. GJ 667C C
Exoplanet GJ 667C c also orbits the star GJ 667C. Its year lasts about 28 Earth days, but intriguingly, one full day on GJ 667C c is equal to 56.2 Earth days. The planet’s mass is around 0.01 times that of Jupiter. It remains unclear whether the surface is rocky or gaseous.
Nevertheless, GJ 667C c resides within the zone where liquid water is likely to exist, enhancing the chances of it having a rocky surface. This suggests that, in the future, this exoplanet may be capable of supporting human life.
As demonstrated, numerous exoplanets could potentially accommodate human colonies in the future, assuming we overcome the challenge of interstellar travel.
2. Kepler 442b
The star Kepler 442 is estimated to be approximately three billion years old. Its mass and radius are roughly 0.61 and 0.60 times that of our Sun, respectively. Located 1,100 light-years away from Earth in the constellation Lyra, Kepler 442 is a noteworthy star.
Kepler 442b, discovered in 2015 via telescopic observation, was identified when the planet's shadow interfered with the light emitted by its orange dwarf host star. The planet's year is approximately 112 Earth days.
Kepler 442b has a radius of 1.34 times that of Earth. It is likely rocky and resides at a distance from its star where liquid water could potentially exist on its surface. As of February 2016, Kepler 442b is considered one of the most Earth-like exoplanets discovered.
These factors together suggest a high likelihood that Kepler 442b may one day be capable of supporting human life.
1. GJ 667C F
We have previously mentioned the star GJ 667C, as GJ 667C e and GJ 667C f, both of which are awaiting confirmation as planets, belong to the same star system. Let’s revisit the details to refresh our understanding.
GJ 667C is a red dwarf located 22 light-years away from Earth in the Scorpius constellation. It is part of a triple-star system where two orange dwarfs orbit each other, and GJ 667C orbits both stars. These stars are estimated to be between 2–10 billion years old. If a planet orbited GJ 667C, all three stars would be visible from its surface.
Now, let's focus on the exoplanet GJ 667C f. Discovered in 2013, it lies 24 light-years from Earth. GJ 667C f has a year lasting 39 Earth days and a mass that is at most 2.7 times that of Earth. Its radius is 1.5 times Earth's.
These characteristics make GJ 667C f a strong candidate for being a potentially habitable exoplanet.
