There are at least 300 million potentially habitable planets in our galaxy, NASA finds

Jessie Yeung
By Jessie Yeung, CNN
Published 11:57 PM EST, Thu November 5, 2020
This artist's impression shows the football-shaped planet WASP-103b (left) closely orbiting its host star.
This artist's impression shows the football-shaped planet WASP-103b (left) closely orbiting its host star.
European Space Agency
This image shows double-star system b Centauri and its giant planet b Centauri b. The star pair is the bright object at top left. The planet is visible as a bright dot in the lower right. The other bright dot (top right) is a background star.
This image shows double-star system b Centauri and its giant planet b Centauri b. The star pair is the bright object at top left. The planet is visible as a bright dot in the lower right. The other bright dot (top right) is a background star.
Janson et al./ESO
This artist's rendering shows a Jupiter-like planet orbiting a dead white dwarf star 6,500 light-years away from Earth. The planet survived the violent phases of stellar evolution leading to the star's death.
This artist's rendering shows a Jupiter-like planet orbiting a dead white dwarf star 6,500 light-years away from Earth. The planet survived the violent phases of stellar evolution leading to the star's death.
Adam Makarenko/W. M. Keck Observatory
This artist's illustration shows the night-side view of the exoplanet WASP-76b, where iron rains down from the sky.
This artist's illustration shows the night-side view of the exoplanet WASP-76b, where iron rains down from the sky.
M. Kornmesser/ESO
Astronomers have identified a new class of habitable planets, which they call Hycean planets. These are hot, ocean-covered planets with hydrogen-rich atmospheres.
Astronomers have identified a new class of habitable planets, which they call Hycean planets. These are hot, ocean-covered planets with hydrogen-rich atmospheres.
Amanda Smith/University of Cambridge
This artist's illustration shows L 98-59b, one of the planets in a planetary system 35 light-years away from Earth. This planet has half the mass of Venus.
This artist's illustration shows L 98-59b, one of the planets in a planetary system 35 light-years away from Earth. This planet has half the mass of Venus.
M. Kornmesser/ESO
In this artist's illustration, two gaseous exoplanets can be seen orbiting the bright sun-like star HD 152843.
In this artist's illustration, two gaseous exoplanets can be seen orbiting the bright sun-like star HD 152843.
Scott Wiessinger/NASA
An artist's rendering of TOI-1231 b, a Neptune-like planet about 90 light years away from Earth.
An artist's rendering of TOI-1231 b, a Neptune-like planet about 90 light years away from Earth.
JPL-Caltech/NASA
This artist's conception depicts a violent flare erupting on the star Proxima Centauri as seen from the viewpoint of a planet orbiting the star called Proxima Centauri b.
This artist's conception depicts a violent flare erupting on the star Proxima Centauri as seen from the viewpoint of a planet orbiting the star called Proxima Centauri b.
From NRAO/S. Dagnello
After losing its gaseous envelope, the Earth-size core of an exoplanet formed a second atmosphere. It's a toxic blend of hydrogen, methane, and hydrogen cyanide that is likely fueled by volcanic activity occurring beneath a thin crust, leading to its cracked appearance.
After losing its gaseous envelope, the Earth-size core of an exoplanet formed a second atmosphere. It's a toxic blend of hydrogen, methane, and hydrogen cyanide that is likely fueled by volcanic activity occurring beneath a thin crust, leading to its cracked appearance.
NASA/ESA/R. Hurt
This illustration shows the metaphorical measuring of the density of each of the seven planets in the nearby TRAPPIST-1 system. New measurements have revealed the most precise densities yet for these planets and they're very similar -- which means they also likely have similar compositions.
This illustration shows the metaphorical measuring of the density of each of the seven planets in the nearby TRAPPIST-1 system. New measurements have revealed the most precise densities yet for these planets and they're very similar -- which means they also likely have similar compositions.
NASA/JPL-Caltech
This artist's illustration shows the view from the furthest planet in the TOI-178 system.
This artist's illustration shows the view from the furthest planet in the TOI-178 system.
L. Calçada/ESO
This artist's illustration shows TOI-561b, one of the oldest and most metal-poor planetary systems discovered yet in the Milky Way galaxy. Astronomers found a super-Earth and two other planets orbiting the star.
This artist's illustration shows TOI-561b, one of the oldest and most metal-poor planetary systems discovered yet in the Milky Way galaxy. Astronomers found a super-Earth and two other planets orbiting the star.
W. M. Keck Observatory/Adam Makarenko
This massive and distant exoplanet, called HD106906 b, has an elongated and angled orbit that causes it to take 15,000 Earth years to complete one lap around its twin stars.
This massive and distant exoplanet, called HD106906 b, has an elongated and angled orbit that causes it to take 15,000 Earth years to complete one lap around its twin stars.
ESA/Hubble/M. Kornmesser
This is an artist's impression of a free-floating rogue planet being detected in our Milky Way galaxy using a technique called microlensing. Microlensing occurs when an object in space can warp space-time.
This is an artist's impression of a free-floating rogue planet being detected in our Milky Way galaxy using a technique called microlensing. Microlensing occurs when an object in space can warp space-time.
Jan Skowron/Astronomical Observatory, University of Warsaw
This is an artist's impression of exoplanet WASP-189 b orbiting its host star. The star appears to glow blue because it's more than 2,000 degrees hotter than our sun. The planet, which is slightly larger than Jupiter, has a tilted orbit around the star's poles rather than its equator.
This is an artist's impression of exoplanet WASP-189 b orbiting its host star. The star appears to glow blue because it's more than 2,000 degrees hotter than our sun. The planet, which is slightly larger than Jupiter, has a tilted orbit around the star's poles rather than its equator.
ESA
For the first time, an exoplanet has been found orbiting a dead star known as a white dwarf. In this artist's illustration, the Jupiter-sized planet WD 1856 b orbits the white dwarf every day and a half.
For the first time, an exoplanet has been found orbiting a dead star known as a white dwarf. In this artist's illustration, the Jupiter-sized planet WD 1856 b orbits the white dwarf every day and a half.
NASA's Goddard Space Flight Ce
This illustration shows a carbon-rich planet with diamond and silica as ts main minerals. Water can convert a carbon-rich planet into one that's made of diamonds. In the interior, the main minerals would be diamond and silica (a layer with crystals in the illustration). The core (dark blue) might be made of an iron-carbon alloy.
This illustration shows a carbon-rich planet with diamond and silica as ts main minerals. Water can convert a carbon-rich planet into one that's made of diamonds. In the interior, the main minerals would be diamond and silica (a layer with crystals in the illustration). The core (dark blue) might be made of an iron-carbon alloy.
Shim/ASU/Vecteezy
This image shows a young sun-like star being orbited by two gas giant exoplanets. It was taken by the SPHERE instrument on European Southern Observatory's Very Large Telescope. The star can be seen in the top left corner, and the planets are the two bright dots.
This image shows a young sun-like star being orbited by two gas giant exoplanets. It was taken by the SPHERE instrument on European Southern Observatory's Very Large Telescope. The star can be seen in the top left corner, and the planets are the two bright dots.
European Southern Observatory/Bohn et al.
This artist's impression shows a Neptune-sized planet in the Neptunian Desert. It is extremely rare to find an object of this size and density so close to its star.
This artist's impression shows a Neptune-sized planet in the Neptunian Desert. It is extremely rare to find an object of this size and density so close to its star.
Mark Garlick/University of Warwick
This is an artist's impression of the multiplanetary system of newly discovered super-Earths orbiting a nearby red dwarf star called Gliese 887.
This is an artist's impression of the multiplanetary system of newly discovered super-Earths orbiting a nearby red dwarf star called Gliese 887.
Mark Garlick
The newly discovered exoplanet AU Mic b is about the size of Neptune.
The newly discovered exoplanet AU Mic b is about the size of Neptune.
NASA's Goddard Space Flight Center/Chris Smith (USRA)
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. Proxima b is a little more massive than the Earth.
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. Proxima b is a little more massive than the Earth.
European Southern Observatory/M. Kornmesser
This is an artist's illustration of an exoplanet's atmosphere with a white dwarf star visible on the horizon. The starlight of a white dwarf filtered through the atmosphere of an exoplanet that's orbiting it could reveal if the planet has biosignatures.
This is an artist's illustration of an exoplanet's atmosphere with a white dwarf star visible on the horizon. The starlight of a white dwarf filtered through the atmosphere of an exoplanet that's orbiting it could reveal if the planet has biosignatures.
Jack Madden/Carl Sagan Institute/Cornell University
This is an artist's illustration of the Kepler-88 planetary system, where one giant exoplanet and two smaller planets orbit the Kepler-88 star. The system is more than 1,200 light-years away.
This is an artist's illustration of the Kepler-88 planetary system, where one giant exoplanet and two smaller planets orbit the Kepler-88 star. The system is more than 1,200 light-years away.
Adam Makarenko/W. M. Keck Observatory
This is an illustration of newly discovered exoplanet Kepler-1649c orbiting around its host red dwarf star.
This is an illustration of newly discovered exoplanet Kepler-1649c orbiting around its host red dwarf star.
NASA/Ames Research Center/Daniel Rutter
This is an artist's concept of a ringed planet passing in front of its host star. It shows how "puffy" a ringed planet may look to us from afar.
This is an artist's concept of a ringed planet passing in front of its host star. It shows how "puffy" a ringed planet may look to us from afar.
Robin Dienel/Carnegie Institution for Science
The sizes of the 17 new planet candidates, seen here in orange, are compared to colorized representations of Mars, Earth and Neptune. The green planet is KIC-7340288 b, a rocky planet in the habitable zone of its star.
The sizes of the 17 new planet candidates, seen here in orange, are compared to colorized representations of Mars, Earth and Neptune. The green planet is KIC-7340288 b, a rocky planet in the habitable zone of its star.
Michelle Kunimoto
Artist's impression of K2-18b. CREDIT Amanda Smith
Artist's impression of K2-18b. CREDIT Amanda Smith
courtesy Amanda Smith
This is an artist's illustration a massive planet orbiting a cool, young star. In the case of the newly discovered system, the planet is 10 times more massive than Jupiter, and the orbit of the planet is nearly 600 times that of Earth around the sun.
This is an artist's illustration a massive planet orbiting a cool, young star. In the case of the newly discovered system, the planet is 10 times more massive than Jupiter, and the orbit of the planet is nearly 600 times that of Earth around the sun.
NASA/JPL-Caltech/R. Hurt
Welcome to the KELT-9 system. The host star is a hot, rapidly rotating A-type star that is about 2.5 times more massive and almost twice as hot as our sun. The hot star blasts its nearby planet KELT-9b with massive amounts of radiation, leading to a daylight temperature of 7800 degrees Fahrenheit, hotter that most stars and only 2000 degrees cooler than the sun.
Welcome to the KELT-9 system. The host star is a hot, rapidly rotating A-type star that is about 2.5 times more massive and almost twice as hot as our sun. The hot star blasts its nearby planet KELT-9b with massive amounts of radiation, leading to a daylight temperature of 7800 degrees Fahrenheit, hotter that most stars and only 2000 degrees cooler than the sun.
R. Hurt (IPAC)/NASA/JPL-Caltech
This is an artist's rendering of the Proxima Centauri planetary system. The newly discovered super-Earth exoplanet Proxima c, on the right, has an orbit of about 5.2 Earth years around its host star. The system also comprises the smaller Proxima b, on the left, discovered in 2016. Illustration by Lorenzo Santinelli.
This is an artist's rendering of the Proxima Centauri planetary system. The newly discovered super-Earth exoplanet Proxima c, on the right, has an orbit of about 5.2 Earth years around its host star. The system also comprises the smaller Proxima b, on the left, discovered in 2016. Illustration by Lorenzo Santinelli.
Lorenzo Santinelli
This is an artist's concept of GJ180d, the nearest temperate super-Earth to us with the potential to support life.
This is an artist's concept of GJ180d, the nearest temperate super-Earth to us with the potential to support life.
Robin Dienel/Courtesy of the Carnegie Institution for Science
An illustration of WASP-12b as it spirals in a death dance towards its star. The planet will meet its end in three million years.
An illustration of WASP-12b as it spirals in a death dance towards its star. The planet will meet its end in three million years.
NASA/JPL-Caltech
TOI 700 d is the first potentially habitable Earth-size planet spotted by NASA's planet-hunting TESS mission.
TOI 700 d is the first potentially habitable Earth-size planet spotted by NASA's planet-hunting TESS mission.
NASA's Goddard Space Flight Center
TOI 1338 b is silhouetted by its two host stars, making it the first such discovery for the TESS mission. TESS only detects transits from the larger star
TOI 1338 b is silhouetted by its two host stars, making it the first such discovery for the TESS mission. TESS only detects transits from the larger star
NASA's Goddard Space Flight Center/Chris Smith
This artist's illustration shows a wet exoplanet with an oxygen atmosphere. The red sphere is the M-dwarf star the exoplanet orbits.
This artist's illustration shows a wet exoplanet with an oxygen atmosphere. The red sphere is the M-dwarf star the exoplanet orbits.
Friedlander-Griswold/GSFC/NASA
This artist's illustration shows a dry exoplanet with an oxygen atmosphere. The red sphere is the M-dwarf star the exoplanet orbits.
This artist's illustration shows a dry exoplanet with an oxygen atmosphere. The red sphere is the M-dwarf star the exoplanet orbits.
Friedlander-Griswold/GSFC/NASA
This artist's illustration of the Kepler 51 system shows newly discovered super-puff exoplanets, which are also called "cotton candy" exoplanets because they're so lightweight.
This artist's illustration of the Kepler 51 system shows newly discovered super-puff exoplanets, which are also called "cotton candy" exoplanets because they're so lightweight.
NASA/ESA/STSci
This artist's concept illustration shows an exoplanet with two moons orbiting within the habitable zone of a red dwarf star.
This artist's concept illustration shows an exoplanet with two moons orbiting within the habitable zone of a red dwarf star.
NASA/Harvard-Smithsonian Center for Astrophysics/D. Aguilar
This is an artist's illustration of two exoplanets colliding in a binary star system.
This is an artist's illustration of two exoplanets colliding in a binary star system.
Lynette Cook/SOFIA/NASA
This is an artist's illustration of a Neptune-type exoplanet in the icy outer reaches of its star system. It could look something like a large, newly discovered gas giant that takes about 20 years to orbit a star 11 light years away from Earth.
This is an artist's illustration of a Neptune-type exoplanet in the icy outer reaches of its star system. It could look something like a large, newly discovered gas giant that takes about 20 years to orbit a star 11 light years away from Earth.
Francis Reddy/NASA's Goddard Space Flight Center
This image shows a comparison of red dwarf star GJ 3512 to our solar system, as well as other nearby red-dwarf planetary systems.
This image shows a comparison of red dwarf star GJ 3512 to our solar system, as well as other nearby red-dwarf planetary systems.
Guillem Anglada-Escude/IEEC/SpaceEngine.org
This artist's illustration showcases exoplanet K2-18b orbiting its host star. It's currently the only super-Earth exoplanet that has water vapor in its atmosphere and could be within the right temperature to support life.
This artist's illustration showcases exoplanet K2-18b orbiting its host star. It's currently the only super-Earth exoplanet that has water vapor in its atmosphere and could be within the right temperature to support life.
ESA/Hubble/M. Kornmesser
This is an illustration of an exomoon losing mass as it's being pulled around the gas giant it orbits.
This is an illustration of an exomoon losing mass as it's being pulled around the gas giant it orbits.
Thibaut Roger/University of Bern
An illustration shows what the orbit of exoplanet HR 5183 b would look like if it was dropped down in our solar system. It would likely swing from the asteroid belt to out past Neptune, the eighth planet in our solar system.
An illustration shows what the orbit of exoplanet HR 5183 b would look like if it was dropped down in our solar system. It would likely swing from the asteroid belt to out past Neptune, the eighth planet in our solar system.
Adam Makarenko/W. M. Keck Observatory
At least two giant planets, aged 20 million years at most, orbit the Beta Pictoris star. A disk of dust and gas surrounding the star can be seen in the background.
At least two giant planets, aged 20 million years at most, orbit the Beta Pictoris star. A disk of dust and gas surrounding the star can be seen in the background.
P Rubini/AM Lagrange
This is an artist's interpretation of what super-Earth GJ 357 d might look like. It lies within the habitable zone of its star which is 31 light-years from Earth.
This is an artist's interpretation of what super-Earth GJ 357 d might look like. It lies within the habitable zone of its star which is 31 light-years from Earth.
NASA's Goddard Space Flight Center/Chris Smith
An artist's impression of a circumplanetary disk around PDS 70 c, a gas giant exoplanet in a star system 370 light-years away.
An artist's impression of a circumplanetary disk around PDS 70 c, a gas giant exoplanet in a star system 370 light-years away.
NRAO/AUI/NSF, S. Dagnello
This artist's illustration shows two gas giant exoplanets orbiting the young star PDS 70. These planets are still growing by gathering material from a surrounding disk. In the process, they have gravitationally carved out a large gap in the disk.
This artist's illustration shows two gas giant exoplanets orbiting the young star PDS 70. These planets are still growing by gathering material from a surrounding disk. In the process, they have gravitationally carved out a large gap in the disk.
J. Olmsted (STScI)
An artist's illustration of HD 21749c, the first Earth-size planet found by TESS, as well as its sibling, HD 21749b, a warm mini-Neptune.
An artist's illustration of HD 21749c, the first Earth-size planet found by TESS, as well as its sibling, HD 21749b, a warm mini-Neptune.
Robin Dienel/Carnegie Institution for Science
A "hot Saturn" passes in front of its host star in this illustration. Astronomers who study stars used "starquakes" to characterize the star, which provided critical information about the planet.
A "hot Saturn" passes in front of its host star in this illustration. Astronomers who study stars used "starquakes" to characterize the star, which provided critical information about the planet.
Gabriel Perez Diaz/Instituto de Astrofísica de Canarias
Artist's concept of TESS against background of stars & orbiting planets in the Milky Way. Credit: ESA, M. Kornmesser (ESO), Aaron E. Lepsch (ADNET Systems Inc.), Britt Griswold (Maslow Media Group), NASA's Goddard Space Flight Center & Cornell University
Artist's concept of TESS against background of stars & orbiting planets in the Milky Way. Credit: ESA, M. Kornmesser (ESO), Aaron E. Lepsch (ADNET Systems Inc.), Britt Griswold (Maslow Media Group), NASA's Goddard Space Flight Center & Cornell University
NASA's Goddard Space Flight Center/Cornell University
A super-telescope made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterizing many of the exoplanets known today.
A super-telescope made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterizing many of the exoplanets known today.
ESO
This image shows an artist's impression of the surface of Barnard's star b, a cold Super-Earth discovered orbiting Barnard's star 6 light-years away.
This image shows an artist's impression of the surface of Barnard's star b, a cold Super-Earth discovered orbiting Barnard's star 6 light-years away.
ESO/M. Kornmesser
This artist's illustration shows newly discovered exoplanet K2-288Bb, 226 light-years away and half the size of Neptune. It orbits the fainter member of a pair of cool M-type stars every 31.3 days.
This artist's illustration shows newly discovered exoplanet K2-288Bb, 226 light-years away and half the size of Neptune. It orbits the fainter member of a pair of cool M-type stars every 31.3 days.
Francis Reddy/Goddard Space Flight Center/NASA
This is an artist's impression of the exoplanet HAT-P-11b. The planet has an extended helium atmosphere that's being blown away by the star, an orange dwarf star smaller but more active than our sun.
This is an artist's impression of the exoplanet HAT-P-11b. The planet has an extended helium atmosphere that's being blown away by the star, an orange dwarf star smaller but more active than our sun.
Courtesy of Denis Bajram
An artist's illustration of what the super-Earth found around the orange-hued star HD 26965 (also known as 40 Eridani A) might look like. The recently discovered exoplanet is being compared to the fictional planet of Vulcan because Star Trek creator Gene Roddenberry said the star was the ideal candidate to host Vulcan, Mr. Spock's home world.
An artist's illustration of what the super-Earth found around the orange-hued star HD 26965 (also known as 40 Eridani A) might look like. The recently discovered exoplanet is being compared to the fictional planet of Vulcan because Star Trek creator Gene Roddenberry said the star was the ideal candidate to host Vulcan, Mr. Spock's home world.
University of Florida/Don Davis
The TRAPPIST-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it.
The TRAPPIST-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it.
NASA/JPL-Caltech
For the first time, eight planets have been found orbiting another star, tying with our solar system for the most known planets around a single star. The Kepler-90 system is in the constellation Draco, more than 2,500 light-years from Earth.
For the first time, eight planets have been found orbiting another star, tying with our solar system for the most known planets around a single star. The Kepler-90 system is in the constellation Draco, more than 2,500 light-years from Earth.
NASA/Ames Research Center/Wendy Stenzel
This artist's illustration shows exoplanet Ross 128 b, with its red dwarf host star in the background. The planet is only 11 light-years from our solar system. It is now the second-closest temperate planet to be detected, after Proxima b.
This artist's illustration shows exoplanet Ross 128 b, with its red dwarf host star in the background. The planet is only 11 light-years from our solar system. It is now the second-closest temperate planet to be detected, after Proxima b.
M. Kornmesser/Southern Observatory
WASP-121b, 880 light-years away, is considered a hot Jupiter-like planet. It has a greater mass and radius than Jupiter, making it "puffier." If WASP-121b were any closer to its host star, it would be ripped apart by the star's gravity.
WASP-121b, 880 light-years away, is considered a hot Jupiter-like planet. It has a greater mass and radius than Jupiter, making it "puffier." If WASP-121b were any closer to its host star, it would be ripped apart by the star's gravity.
Engine House VFX/Bristol Science Centre/University of Exeter
NASA's Kepler space telescope team has identified 219 more planet candidates, 10 of which are near-Earth size and in the habitable zone of their stars.
NASA's Kepler space telescope team has identified 219 more planet candidates, 10 of which are near-Earth size and in the habitable zone of their stars.
NASA/JPL-Caltech
This artist's concept shows OGLE-2016-BLG-1195Lb, a planet orbiting an incredibly faint star 13,000 light-years away from us. It is an "iceball" planet with temperatures reaching minus-400 degrees Fahrenheit.
This artist's concept shows OGLE-2016-BLG-1195Lb, a planet orbiting an incredibly faint star 13,000 light-years away from us. It is an "iceball" planet with temperatures reaching minus-400 degrees Fahrenheit.
NASA/JPL-Caltech
LHS 1140b is located in the liquid water habitable zone surrounding its host star, a small, faint red star named LHS 1140. The planet weighs about 6.6 times the mass of Earth and is shown passing in front of LHS 1140. Depicted in blue is the atmosphere the planet may have retained.
LHS 1140b is located in the liquid water habitable zone surrounding its host star, a small, faint red star named LHS 1140. The planet weighs about 6.6 times the mass of Earth and is shown passing in front of LHS 1140. Depicted in blue is the atmosphere the planet may have retained.
M. Weiss/European Southern Observatory/CfA
An artist's concept image of the surface of the exoplanet TRAPPIST-1f. Of the seven exoplanets discovered orbiting the ultracool dwarf star TRAPPIST-1, this one may be the most suitable for life. It is similar in size to Earth, is a little cooler than Earth's temperature and is in the habitable zone of the star, meaning liquid water (and even oceans) could be on the surface. The proximity of the star gives the sky a salmon hue, and the other planets are so close that they appear in the sky, much like our own moon.
An artist's concept image of the surface of the exoplanet TRAPPIST-1f. Of the seven exoplanets discovered orbiting the ultracool dwarf star TRAPPIST-1, this one may be the most suitable for life. It is similar in size to Earth, is a little cooler than Earth's temperature and is in the habitable zone of the star, meaning liquid water (and even oceans) could be on the surface. The proximity of the star gives the sky a salmon hue, and the other planets are so close that they appear in the sky, much like our own moon.
NASA/JPL-Caltech
Artist's conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.
Artist's conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed.
Courtesy Robin Dienel
This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.
This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.
European Southern Observatory/ESO/M. Kornmesser
An artist's rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.
An artist's rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres.
From NASA
Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.
Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets.
NASA/JPL-Caltech
This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.
This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date.
European Southern Observatory/ESO/L. Calçada
An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.
An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone.
Lynette Cook
HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.
HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event.
NASA/JPL-Caltech/R. Hurt (SSC-Caltech)
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.
Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth.
NASA/Kepler Mission/Dana Berry
This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker's home planet Tatooine in "Star Wars."
This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker's home planet Tatooine in "Star Wars."
NASA/JPL's Planetquest/Caltech
Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.
Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra.
Harvard-Smithsonian, Center for Astrophysics/D. A. Aguilar
Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.
Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus.
Michael Bachofner
This artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun's closest stellar neighbors are red dwarfs.
This artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun's closest stellar neighbors are red dwarfs.
D. Aguilar/Harvard-Smithsonian Center for Astrophysics
Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet's surface.
Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet's surface.
NASA/JPL-Caltech/T. Pyle
Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.
Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus.
NASA Ames/JPL-Caltech/T. Pyle
The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.
The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days.
Tiago Campante/Peter Devine
This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old -- 1.5 billion years older than our sun.
This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old -- 1.5 billion years older than our sun.
NASA/Ames/JPL-Caltech/T. Pyle
Weird and wonderful planets beyond our solar system
CNN  — 

Our galaxy is filled with potentially habitable planets – at least 300 million of them, according to NASA.

The US space agency’s Kepler Space Telescope spent nine years on a planet-hunting mission, successfully identifying thousands of exoplanets in our galaxy before running out of fuel in 2018. But the original mission’s core question remained: how many of these planets are habitable?

Scientists around the world pored over Kepler’s data for years – and they think they’ve found the answer. According to research released in The Astronomical Journal, there are roughly 300 million potentially habitable worlds in our galaxy, meaning rocky planets capable of supporting liquid water on their surface.

An artist's concept showing NASA's Kepler Space Telescope on its K2 mission.
An artist's concept showing NASA's Kepler Space Telescope on its K2 mission.
NASA

That figure is a rough estimate on the conservative side, and “there could be many more,” said NASA in a news release. Some of these planets could be close enough to be considered “interstellar neighbors” – the closest is around 20 light-years away.

“Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable,” said NASA researcher and lead author Steve Bryson in the release.

“Though this result is far from a final value, and water on a planet’s surface is only one of many factors to support life, it’s extremely exciting that we calculated these worlds are this common with such high confidence and precision.”

The study was a global collaboration between NASA scientists who worked on the Kepler mission, and researchers from international agencies ranging from Brazil to Denmark.

How they did it

There are about 100 to 400 billion stars in our Milky Way galaxy, according to NASA estimates. Every star in the sky probably hosts at least one planet – meaning there are likely trillions of planets out there, of which we have only discovered and confirmed a few thousand.

A lot of factors that influence whether a planet can support life, including its atmosphere and chemical composition. But to narrow down the trillions, the researchers in this study focused on a few basic requirements.

An artist's conception shows a hypothetical planet with two moons orbiting within the habitable zone of a red dwarf star. Credit: NASA/Harvard-Smithsonian Center for Astrophysics/D. Aguilar
An artist's conception shows a hypothetical planet with two moons orbiting within the habitable zone of a red dwarf star. Credit: NASA/Harvard-Smithsonian Center for Astrophysics/D. Aguilar
NASA/Harvard-Smithsonian Center for Astrophysics/D. Aguilar

What makes a planet potentially habitable

They looked for stars similar to our own Sun in age and temperature, so it wouldn’t be too hot or active. They also looked for exoplanets with a similar radius to Earth, and singled out those that were likely to be rocky.

They also took into consideration each planet’s distance from its star – too close and the heat could vaporize any water, too far and any water could freeze.

A habitable planet needs to be in the “just right” zone, or the so-called Goldilocks zone, to support liquid water on its surface.

Previous estimates of the number of habitable planets did not reflect how a star’s temperature and energy could be absorbed by its planets, said the NASA release. But this time, scientists were able to factor temperature into their analysis, thanks to additional data gathered by the European Space Agency’s Gaia mission, which is charting a three-dimensional map of our galaxy.

“We always knew defining habitability simply in terms of a planet’s physical distance from a star, so that it’s not too hot or cold, left us making a lot of assumptions,” said NASA scientist and study author Ravi Kopparapu in the release.

An illustration of Kepler-1649c orbiting around its host red dwarf star. This newly discovered exoplanet is in its star's habitable zone and is the closest to Earth in size and temperature found yet in Kepler's data. Credits: NASA/Ames Research Center/Daniel Rutter
An illustration of Kepler-1649c orbiting around its host red dwarf star. This newly discovered exoplanet is in its star's habitable zone and is the closest to Earth in size and temperature found yet in Kepler's data. Credits: NASA/Ames Research Center/Daniel Rutter
NASA/Ames Research Center/Daniel Rutter

New potentially habitable exoplanet is similar in size and temperature to Earth

“Gaia’s data on stars allowed us to look at these planets and their stars in an entirely new way.”

After calculating these factors, researchers used a conservative estimate that 7% of Sun-like stars could host habitable worlds. But the rate could be as high as 75%, scientists said.

NASA said it and other space agencies will continue to refine the estimate in future research, which will help shape plans for the next stages of exoplanet discoveries and telescopes. Currently, NASA’s TESS mission is the latest planet-hunter seeking out exoplanets.