An artists's conception shows planet LP 791-18d. The volcanically active planet, which is a similar size to Earth, was discovered by NASA's Spitzer Space Telescope.
An artists's conception shows planet LP 791-18d. The volcanically active planet, which is a similar size to Earth, was discovered by NASA's Spitzer Space Telescope.
Chris Smith (KRBwyle)/NASA's Goddard Space Flight Center
This artist's illustration depicts the rocky exoplanet GJ 486 b, which orbits a red dwarf star located 26 light-years away from Earth. Astronomers have detected hints of water vapor in the system, but they can't be sure if it signifies a planetary atmosphere or if it's part of the star.
This artist's illustration depicts the rocky exoplanet GJ 486 b, which orbits a red dwarf star located 26 light-years away from Earth. Astronomers have detected hints of water vapor in the system, but they can't be sure if it signifies a planetary atmosphere or if it's part of the star.
NASA, ESA, CSA, Joseph Olmsted (STScI)
This illustration shows an Earth-size exoplanet called TOI 700 e, discovered orbiting the small, cool M dwarf star TOI 700, which is located 100 light-years away. Its other Earth-size sibling, TOI 700 d, can be seen in the distance.
This illustration shows an Earth-size exoplanet called TOI 700 e, discovered orbiting the small, cool M dwarf star TOI 700, which is located 100 light-years away. Its other Earth-size sibling, TOI 700 d, can be seen in the distance.
NASA/JPL-Caltech/Robert Hurt
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
Artist's impression of the exoplanet WASP-121 b. It belongs to the class of hot Jupiters. Due to its proximity to the central star, the planet's rotation is tidally locked to its orbit around it. As a result, one of WASP-121 b's hemispheres always faces the star, heating it to temperatures of up to 3000 degrees Celsius. The night side is always oriented towards cold space, which is why it is 1500 degrees Celsius cooler there.
Artist's impression of the exoplanet WASP-121 b. It belongs to the class of hot Jupiters. Due to its proximity to the central star, the planet's rotation is tidally locked to its orbit around it. As a result, one of WASP-121 b's hemispheres always faces the star, heating it to temperatures of up to 3000 degrees Celsius. The night side is always oriented towards cold space, which is why it is 1500 degrees Celsius cooler there.
Patricia Klein/MPIA
This artist's impression shows a close-up view of Proxima d, a planet candidate recently found orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The planet is believed to be rocky and to have a mass about a quarter that of Earth. Two other planets known to orbit Proxima Centauri are visible in the image too: Proxima b, a planet with about the same mass as Earth that orbits the star every 11 days and is within the habitable zone, and candidate Proxima c, which is on a longer five-year orbit around the star.
This artist's impression shows a close-up view of Proxima d, a planet candidate recently found orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The planet is believed to be rocky and to have a mass about a quarter that of Earth. Two other planets known to orbit Proxima Centauri are visible in the image too: Proxima b, a planet with about the same mass as Earth that orbits the star every 11 days and is within the habitable zone, and candidate Proxima c, which is on a longer five-year orbit around the star.
ESO/L. Calçada
The discovery of a second exomoon candidate hints at the possibility that exomoons may be as common as exoplanets.
The discovery of a second exomoon candidate hints at the possibility that exomoons may be as common as exoplanets.
Helena Valenzuela Widerström
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
Weird and wonderful planets beyond our solar system

Story highlights

Scientists had assumed that unstable gravity would fling out any planet

Each season on HD 131399Ab lasts longer than a human lifetime

CNN  — 

Astronomers have discovered a planet with three suns, where an observer would experience either constant daylight or triple sunrises and sunsets depending on the seasons, which last longer than a human lifetime.

The planet, HD 131399Ab, is the first discovered in a stable orbit in a triple-star system; previously, it had been assumed that the unstable gravity would result in any planet being quickly flung out.

An artistic impression of the planet Kepler-1647b. The planet 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. The planet 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

Related article NASA's Kepler discovers 'Tatooine' planet orbiting two suns

“If the planet was further away from the most massive star in the system, it would be kicked out of the system,” Daniel Apai of the University of Arizona said in a statement.

“Our computer simulations have shown that this type of orbit can be stable, but if you change things around just a little bit, it can become unstable very quickly.”

Kevin Wagner, who discovered the planet and led follow-up observations, said that “for about half of the planet’s orbit, which lasts 550 Earth years, three stars are visible in the sky.”

“It is not clear how this planet ended up on its wide orbit in this extreme system, and we can’t say yet what this means for our broader understanding of the types of planetary systems, but it shows that there is more variety out there than many would have deemed possible.”

planet discovery wolf 1061c beichman cnni nr intv_00002326.jpg
planet discovery wolf 1061c beichman cnni nr intv_00002326.jpg
University of New South Wales
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The planet – reminiscent of Luke Skywalker’s twin-starred homeworld of Tatooine in “Star Wars” – is located in the Centaurus constellation, about 320 light-years from Earth.

It was found using the SPHERE instrument on the European Southern Observatory’s Very Large Telescope, which is sensitive to infrared light, allowing it to detect the heat signatures of young planets.

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    About 16 million years old, HD 131399Ab is one of the youngest exoplanets discovered to date, the observatory said in a statement.

    By comparison, Earth is about 4.5 billion years old.

    With an average temperature of about 580 degrees Celsius (1,076 degrees Fahrenheit) and an estimated mass of four Jupiters, it is also one of the coldest and smallest directly imaged exoplanets.

    “HD 131399Ab is one of the few exoplanets that have been directly imaged, and it’s the first one in such an interesting dynamical configuration,” Apai said.