Science Facts

Which Planets Can Support Life? – Top 20 Exoplanets

Exoplanets

Which planets might support life? The first step to find life in our galaxy is locating exoplanets that orbit other stars. But once we find them, how can we tell if they can support life? The Trappist one system has seven earth-sized planets, with three of them in the habitable zone. The Hubble Space Telescope can tell whether these planets have hydrogen-rich atmospheres like icy gaseous Neptune or atmospheres more like rocky earth. To measure the planet’s composition and atmosphere, we need to use a technique called spectroscopy.

Astronomers use spectroscopy to sort light into its very specific components. The different chemicals and dust particles give off different telltale fingerprints. The Webb telescope has four spectrographs which will be trained on a few lucky exoplanets. Scientists will learn about the atmospheres of these planets by seeing their fingerprints as a shadow against their bright host star, in a similar way to the transit technique. Life changed the atmosphere of the earth over time, increasing the oxygen and decreasing the methane. By taking a virtual sample of the atmosphere of these exoplanets, we can look for evidence of carbon dioxide, water vapor, and methane.

What are exoplanets?

An exoplanet is a planet outside the solar system orbiting another star. They’re also called extrasolar planets, and thousands of possible exoplanets have been found using ground-based and space-based telescopes. There are different types of exoplanets: The gas and ice giants. These exoplanets are similar to Jupiter, Saturn, Uranus, and Neptune. Around two-thirds of exoplanets that have been discovered are either gas or ice giants.

  • Hot Jupiters, which are planets similar to the mass of Jupiter but orbiting their parent star.
  • Super Earths’ rocky planets with up to 10 times the mass of Earth.
  • Culture planets orbit pulsars and future stars.
  • Custodian planets were once gas giants whose atmosphere has been roasted away because they moved too close to their parent star and EXO Earth.

Planets with similar mass composition radius and atmosphere tumors orbit the habitable zone of their parent star. The habitable zone ranges from a star where liquid water can exist on a planet’s surface. This range depends on the size of the temperature of the star. The Trappist one planetary system comprises seven planets, of which five are similar to the size of the earth and two are between the size of Mars and Earth. Three of the planet’s orbit within the habitable zone.

Which planets can support life? ( Top 20 habitable planets)

Scientists are focusing on dwarf stars. They’re smaller and less luminous than the sun, but their lifespan can be between 20 and 70 billion years. This will give living organisms enough time to develop and evolve. Climactic conditions on super habitable planets will also be different.

The average temperature should be 8 degrees Fahrenheit higher than on earth. And there should be more water in the form of clouds, liquid, and humidity. These conditions are the most favorable for biodiversity. So the whole planet would be looking like tropical forests on earth. All 24 planets for better than earth are more than 100 light-years away from earth.

Now let’s take a look at the potentially inhabited exoplanets.

1. Kepler 186f

Kepler 186f was discovered on April 17, 2014, by NASA’s Kepler spacecraft. It is in the Cygnus constellation and is approximately 582 light-years away from Earth. With a radius similar to Earth’s, this exoplanet is one of five planets that orbit the red dwarf star. However, unlike the other planets in its system Kepler-186 B, C, D, and E. Kepler 186f resides at the right distance from its Sun to maintain a temperature above zero degrees Celsius. It means that it could have water and could therefore support life.

Kepler 186f
Kepler 186f
  • One day on planet Kepler 186f could be the equivalent of weeks months on earth. However, it has some striking similarities to earth due to its small axial tilt.
  • It has seasons just like Earth, and its seasons and climate are similar to Earth’s. So it was called one of the best planets for life in 2015.
  • The gravity on Kepler 186f could be very similar to Earth’s.

Kepler 186f rotates much more slowly than Earth, so its day could be weeks or months long. It may be tidally locked, which means one side of the planet always faces its star, and the other is in constant darkness. There is some possibility that it has an atmosphere that can help keep the water in liquid form. That’s why scientists have described Kepler 186f as a cousin to earth.

2. Gliese 581g

This controversial planet is known as Zarmina. However, its official name is Gliese 581g. This planet lives in the Libra constellation along with five other planets. Gliese 581g is the third planet from its host red dwarf star Gliese 581. It is relatively close to Earth at only 20.42 light-years away. In 2010 it was announced as the first potentially habitable planet.

Gliese 581g
Gliese 581g
  • This planet has a similar mass and gravity to Earth’s and is located right in the middle of its system’s habitable zone.
  • It also receives similar levels of sunshine as Earth.
  • This planet is tidally locked with the Sun.
  • If a strong atmosphere exists on the planet, it could circulate the heat from the sunny side over to the dark side, making it much more habitable.
  • It is possible for water to exist there with at least one ocean.
  • It is 1.5 times the size of Earth, having temperatures between negative 35 and 10 degrees Fahrenheit due to the weaker energy output from its small Sun.

Some scientists believe that Gliese 581g has a 100% chance of supporting life. However, not all scientists agree. It has been surrounded with controversy since its discovery. The planet has not yet been confirmed by the European Southern Observatory or the high accuracy radial searcher.

3. HD 85512 b

HD 85512b sits in the inner edge of its systems habitable zone and is classified as a rocky earth-sized exoplanet. It is 36.2 light-years away from Earth. In 2011 it was called a very promising candidate for supporting life. Its Sun is an orange dwarf star with about two-thirds the mass of Earth’s Sun. The planet is 3.6 times the size of Earth and was discovered by scientists from the University of Geneva. Also, it was discovered using High Accuracy Radial Velocity Planet Searcher ( HARPS ) for short.

HD 85512 b
HD 85512 b
  • Its orbit is 54 Earth days, and the temperature could be around 24.5 degrees Celsius.
  • It’s the star, though. A k-type star may give off too much radiation evaporating the surface water on the planet.

Whether or not this planet has life is dependent on whether or not this planet has clouds. It would need 50% cloud coverage. And scientists believe that if the planet has enough cloud cover, some of the radiation could be mitigated. The planet could have water and therefore could have life.

4. Gliese 667 Cc

Gliese 667 Cc was an exciting discovery and called the most earth-like object known outside our solar system. It is found in a system that has three stars, but Lisa 667 Cc orbits a red dwarf star called Lisa’s 667c. According to mass, it is likely a rocky planet like Earth but is much closer to its star than Earth. However, Gliese is 667 cc’s Sun is much cooler than earth’s Sun. Although it is much closer to its host star, it is the right distance from its star to support life.

Gliese 667 Cc
Gliese 667 Cc
  • Its orbit is 28 days meaning that a year on Gliese 667 Cc is 28 Earth days long.
  • With an average temperature of 30 degrees Celsius Gliese 667cc could support water.
  • Gliese receives the 90% of the light of Earth. One side is completely shrouded in eternal darkness while the other is continuously facing the red dwarf.

Interestingly Gliese is 667 Cc is so close to its Sun. Its Sun would appear 3 times larger in the sky than earth’s Sun. But at only 22 light-years away, any life on Gliese 667 Cc could see our Sun in the sky as a star. It’s believed that there is a probable chance to get an area of suitable temperature between these hemispheres that will support human life.

5. HD 40307 g

HD 40307 g was discovered on October 28, 2012, by a team of astronomers from both the universities of Hertfordshire & Godding ham. It is classified as a super-earth, and it sits in the southern constellation of the picture.

HD 40307 g
HD 40307 g
  • HD 40307 g is the sixth and furthest planet from its host sun, HD 403o7.
  • It is only 55.8 million miles from its host star, but its host star is considerably cooler than Earth’s, emitting 75% less energy.

In fact, the other five planets in HD 40307 g system are so close to their Sun that all five of them are closer than mercury is to earth’s Sun. However, its Sun is so much cooler than Earth’s. Also, HD 403o7 g is the right distance from its Sun to support life. More research on this earth-like planet is needed, but HD 403o7g has many similarities to earth. It is not tidally locked to rotate on an axis like Earth, meaning it has days and nights.

6. Tau Ceti F

Tau Ceti F is a recent discovery found in 2017. It is only 12 light-years away. In fact, its host star Tau Ceti is visible to the naked eye from Earth. It sits in the centas constellation, and its host star is the closest solitary G Class star found to date. This planet is similar in size and brightness to Earth’s star. Although there are four planets in its system, Tau Ceti F is the strongest candidate for life because of its distance from its star.

Tau Ceti F
Tau Ceti F
  • Its orbit is also similar to Earth’s at one point seven earth years.

Although promising, Tau Ceti F has one major obstacle when it comes to its possibility of supporting life. Its star Tau Ceti has a debris disc. This circumstellar disk made up of dust and debris orbits the star. Because of this, Tau Ceti F would likely experience many major impact events, including asteroids, meteorites, and comets. These impact events could impact the probability of life on this planet.

7. Kepler 442 b

Kepler 442 b orbits its host star kepler 442. It is about 12006 light-years away from Earth. It is classified as an earth-sized exoplanet, and it is a third larger than Earth. NASA’s Kepler mission first identified this planet. And its Sun, although similar to Earth’s, is smaller and cooler than Earth’s. Its orbit is 112 Earth days, but Kepler 442 B sits in a very habitable zone.

Kepler 442 b
Kepler 442 b

An article published in the Astrophysical Journal called the comparative habitability of transiting exoplanets called Kepler 440 more habitable than Earth. Although not enough is known yet about this planet, it ranks higher on the habitability scale than on earth. There is a very strong possibility that Kepler 442 B supports life.

8. Ross 128 b

Ross 128 b was found on November 17th by Xavier. The planet was discovered by radial velocity, and Ross 128 B is the second-closest known exoplanet at only 11 light-years away. Sitting in the Virgo constellation, the discovery of Ross 128 b was both intriguing and exciting to astrobiologists. And Ross 128 B has been called the most Earth-like planet ever found.

Ross 128 b
Ross 128 b
  • Ross 128 b likely receives 38% more sunlight than Earth. It is also likely rocky like earth and probably maintains a temperature of 21 degrees Celsius.

This makes it an excellent candidate for life as the probability of water on this planet is very high. Furthermore, Ross 128 B’s son is a quiet old red dwarf star that is stable and has limited solar activity. The only drawback is that Ross 128 B sits on the hot side of its habitable zone, which means that water may evaporate quicker on Ross 128 B than it does on earth.

9. Kepler-22b

Kepler-22b has so many similarities to earth that it has been called one of the best planets for another earth. In fact, Kepler 22b is the first habitable planet that the Kepler space telescope found. Kepler 22b sits in what is known as the Goldilocks zone of its system. It means that it is the perfect distance away from its host Sun. With a temperature of 22 degrees Celsius, the planet is not too hot, so water won’t evaporate and not too cold so that water won’t freeze.

Kepler 22b
Kepler 22b
  • Kepler 22b is double the size of Earth, but it has a rocky core like Earth. And potentially a very large ocean that could support life.

Furthermore, its Sun Kepler-22 is a G Star Class Sun similar to earth. And its orbit is also similar to Earth’s at 290 days. Kepler 22b is 600 light-years away and is in the Cygnus constellation. If something happens to the earth, this water-rich planet is the place where we will probably move to because it’s a prime contender for the next homeworld. When we arrived there in the future, there is a high possibility that many possible alien lives will encounter us. That may have evolved in the outer liquid layer.

10. Teegarden B

It’s an exoplanet that orbits a red dwarf star about 12 light-years away from the solar system. Typically red dwarfs can emit flares that blow away the atmosphere of the planets in their orbit. But this host star is calm and relatively passive. Teegarden B has almost the same mass as the earth. It makes a complete circle around its star in about five days. A year on Teegarden B is less than a week on earth.

Teegarden B
Teegarden B

Astronomers say this planet has the greatest similarity to earth out of any planet ever discovered. Despite not being in the solar system, the planet resembles planets that are in our solar system. The planet is only slightly heavier than Earth, and it’s located in a habitable zone where water can be present in liquid form. The reason why this planet is named Teegarden B is that it’s nearby to the Teegarden star. This star was discovered back in 2003, but the discovery of this exoplanet is recent.

  • The planet has a radius that is earth-like and an earth-like composition that being an iron core and a rocky crust. And it also has an ocean of water on its surface.
  • It has a surface temperature environment of zero to 50 degrees Celsius, similar to earth. That’s only slightly hotter than Earth, and the most normal temperature on this planet is 28 degrees centigrade.

Teegarden B’s star named Teegarden is ten times lighter than Sun, and it’s classified as an old red dwarf. These smallest stars are roughly 8 billion years old and are very difficult to research as it’s quite far away. But Teegarden B was given an earth similarity index score of 0.9 v. To put that into perspective, one is earth, so on this scale, it only points five different from Earth.

11. Kepler-1638b

The furthest potential inhabited planet is Kepler 1638b. It’s in the constellation Cygnus, about 3 000 light-years away from earth. It belongs to the super-earth class is twice as wide and four times as heavy as earth.

Kepler-1638b
Kepler-1638b

The gravity on it will feel much stronger. Even a normal jump will be much harder for you than on earth. Although if this planet is inhabited, local life is used to such conditions.

12. LHS 1140 B

This planet is very rocky and solid. Although its size is only 40 percent larger than the earth, it’s seven times as massive. It has a strong gravity of 3.25 G. On this planet, you’d barely be able to stand on your feet because of its large mass.

LHS 1140 B
LHS 1140 B
  • It’s about 15% of the Sun’s mass, and as a red dwarf, any object orbiting around it.
  • It is probably in a tidal lock.

This planet has a thicker atmosphere, and because of the greenhouse effect, its temperature can be above 19 degrees Fahrenheit. It rotates around its star quite quickly, and it makes a full circle in just 24 days.

13. Trappist-1

It is an ultracold dwarf, a small planet that orbits in its habitable zone. It’s three times lighter than the earth. Its temperature is similar to earth’s, but the gravity is half as weak.

Trappist-1
Trappist-1
  • It is a red dwarf star just a bit under 40 light-years away from earth.
  • It burns very coolly, with a surface temperature of only about 2,500 Kelvin, or less than half as hot as our sun.

Trappist-1 is barely bigger than the planet Jupiter, although much more massive since Jupiter is predominately made of gas. It is almost identical to earth in mass though just slightly larger and orbits less than two million kilometers from its star.

14. Kepler-452 B

Kepler-452b was first discovered in July 2015, which is an exoplanet and also known as super-earth. Moreover, it is around five times the mass of Earth. It completes a full orbit in 385 days. Due to its large size, it also has twice the earth’s gravity and receives more sun energy making it hotter. Still, it’s a good candidate for hosting life if we’re ever able to reach Kepler 452b.

Kepler-452 B
Kepler-452 B
  • The host star is only 11 percent older than the sun and is almost 2 billion years older. The exoplanet itself is 6.5 billion years old compared to 4.5 billion of earth.

Unfortunately, the planet is 45,000 light-years away. If we travel in a spaceship at a speed of 37,000 miles per hour, then 26 million years is needed to get there. Then cryogenic preservation and age-reversing agents will be mandatory requirements for this journey. Although four or five be mirrors earth, it is highly susceptible to the greenhouse effect. So it could become a giant ball of hot death by the time we arrive there.

15. Proxima Centauri B

Proxima Centauri B is the nearest Earth-like planet discovered to date. Its home constellation Centaurus is only 4.2 light-years away from Earth. The planet was found by Doppel spectroscopy. Its star Proxima Centauri is an M-type red dwarf star and is the closest star to our solar system. It is an m-type star, and it likely experiences many flares, although the planet could support life. It would also likely experience a lot of intense solar winds and radiation.

Proxima Centauri B
Proxima Centauri B

The biggest hurdle to the possibility of life on this planet is its star’s instability. Furthermore, M Stars start very hotly. A lot of water would have evaporated in the early years of this planet’s existence. However, it is possible that Proxima Centauri B started with a lot more water than earth did. Therefore still has water. Although Proxima Centauri is the closest star after the sun, we can’t see it with a naked eye because it’s too dim.

16. Kepler-438 b

Kepler 438B was first discovered in 2015 and located 470 light-years away from earth. Kepler 438B was deemed one of the most Earth-like planets ever discovered due to its Earth’s similarity index or ESI, which is 88% similar to earth. Hence that makes a suitable candidate for the potential of life. Kepler-438 b is just 12% larger and receives 40% more light compared to the earth.

Kepler-438 b
Kepler-438 b

But still, it’s missing some necessary qualities for habitation, such as it doesn’t have a proper atmosphere and the planets nearby star emits flares 10 times more powerful than our Sun. This planet might be the second option if it has a magnetic field like earth.

17. Kepler-62f

This planet is also known as super-earth and was discovered in April 2013. Kepler-62f is situated in the habitable zone of a seven billion-year-old star. It has Earth’s similarity index of 0.67 and is 1.4 times Earth’s slightly smaller and cooler than Sun. Unfortunately, this rocky planet is an earth-like Waterworld that contains oceans are at least ice. In either case, this planet is an excellent candidate for alien life and feasible for hosting human life.

Kepler-62f
Kepler-62f
  • It takes 267 days to complete a full orbit around its Sun and receives 41% of the sunlight compared to earth.

However, the planet might be tidally locked in orbit, which means one side facing the hot Sun while the other will be in complete darkness. So humans can only survive at the border between light and dark areas where the temperature is suitable to support life.

18. Kepler-62e

It’s 1.6 times larger than Earth, has a rocky surface with a high probability of water, and maybe covered with oceans. The distance from earth is one year is 122 days long and 1,200 light-years. All planets in this list are larger than Earth. That’s why they are called super-Earths which means they are larger than our planet.

Kepler-62e
Kepler-62e

It would have similar characteristics that an exoplanet has: Cloudy sky warm and humid everywhere other than the polar caps. Its stellar flux is 20% more than earth enough to trigger a runaway greenhouse effect, decreasing the chance of habitability.

19. Kepler 69c

Kepler 69c is an exoplanet found orbiting in the Kepler 69 system, located around 2400 light-years from Earth. The planet is most likely rocky and is referred to as super-earth because its mass and dammit earth are way bigger. The discovery of the planet was announced on the 13th of April 2013.

Kepler 69c
Kepler 69c

NASA’s Kepler observed over 50 thousand stars that included Kepler 69, and this was made between May 2009 and March 2012. It was observed that Kepler 69c orbit its star every 242 days. And the conclusion which they could have only been responsible by a planetary body. There have been different thoughts on whether the planet is a super-earth, this habitable, or super Venus.

  • The surface temperature is around 275 degrees and is over 6 times the mass of the earth and close to twice the earth’s radius.

When the planet was discovered, scientists considered the likelihood of water or even an ocean being on the planet. This is because the planet orbited a habitable zone where liquid water could form. However, further investigation showed the planet should be categorized under the Venus category. The host star has around 80 percent of our sun’s luminosity. Considering the distance of Kepler 69 c to its stars 64% compared to the Earth’s distance to the Sun.

Researchers for the planet is too close to harbor life in it. Even if it could, the planet would be located at the edge of a habitable zone. A runaway greenhouse effect on the planet’s surface from a high Estela flux would cause the oceans to boil. The surface temperature would rise to over 227 degrees because vapor would have submerged the atmosphere, which is part of the important component that makes up greenhouse gases.

20. Mars

Humans have limited time and limited technology to find a suitable home planet far away from us. It makes sense to look next door. Mars could be the next permanent home for us. And we may be able to see it happen in our lifetime. Definitely, this red planet could be a great candidate for life with its ancient water-rich soil, sufficient amount of sunlight, and a similar day length. That is only 40 minutes longer than Earth.

Mars
Mars
  • Mars gravity is 38% weaker than the earth but still within the acceptable range for survival.

There are high chances to successfully tear for Mars because of its thin atmosphere that already protects the planet from the sun’s radiation could hold oxygen and become breathable. SpaceX is currently training astronaut settlers to colonize Mars, with the first group blasting off in 2031. We could see homes on Mars very soon.

How can we live on other planets?

Scientists have recently found, are in the habitable zone of their host stars and theory. We can colonize them and make them suitable for human life in the future. Modern rockets can fly at five times the speed of sound. It will take us more than one hundred thousand years to get to Proxima Centauri, even at such speeds.

We need to develop something faster to travel to a new home on one of these exoplanets. Perhaps scientists already have the answer: warp drive. This is a piece of technology that will allow us to manipulate space and time. It creates a kind of a bubble in which the normal laws of motion don’t work. So the spacecraft will be able to exceed the speed of light significantly. Humanity already has such technology, although just in theory yet.

Since no object with mass can travel at the speed of light, we need to do one trick. The spacecraft has to move by compressing the space in front of it and expanding it behind it. Thus not only the ship is moving but also the space-time inside this warp drive bubble. And the maximum speed can be 10 times that of light. But to warp space-time, the ship must be incredibly large. To power, it will need the amount of energy close to what the whole planet of Jupiter generates.

Still, recent Nasa’s jet propulsion lab calculations showed that the ring around the ship should create the so-called warp field. It shouldn’t be perfectly round as it was thought before. It can be more donut-shaped. This will greatly simplify the design and construction and make it possible to test this technology on a spacecraft the size of a Voyager 1 pro. Though it still seems impossible, scientists are already saying that there is hope and don’t know what technology will be used.

In 2069 NASA plans to launch its first interstellar mission to explore potentially habitable planets outside the solar system. Various rumors say that the speed of light can be achieved with laser technology. If the probe is very small, it can be launched to the alpha Centauri star at almost the speed of light. There are also two other alternatives to power spaceships. These are nuclear energy and energy from matter and anti-matter collisions. These technologies are still a mystery to humanity, though.


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Sources:

“The Habitable Exoplanets Catalog”. Planetary Habitability Laboratory. University of Puerto Rico at Arecibo.
Khodachenko M, “What makes a planet habitable?”
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