Scientists may have found a fiery exomoon that's like a volcanic planet from 'Star Wars' - CNN

Scientists may have found a fiery exomoon that's like a volcanic planet from 'Star Wars'

By Ashley Strickland, CNN

Updated 1807 GMT (0207 HKT) September 5, 2019

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.
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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.
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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.
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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.
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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.
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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.
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TOI 700 d is the first potentially habitable Earth-size planet spotted by NASA's planet-hunting TESS mission.
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TOI 700 d is the first potentially habitable Earth-size planet spotted by NASA's planet-hunting TESS mission.
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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.
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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.
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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.
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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.
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The discovery of a second exomoon candidate hints at the possibility that exomoons may be as common as exoplanets.
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The discovery of a second exomoon candidate hints at the possibility that exomoons may be as common as exoplanets.
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This artist's impression shows the football-shaped planet WASP-103b (left) closely orbiting its host star.
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This artist's impression shows the football-shaped planet WASP-103b (left) closely orbiting its host star.
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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.
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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.
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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.
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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.
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This artist's illustration shows the night-side view of the exoplanet WASP-76b, where iron rains down from the sky.
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This artist's illustration shows the night-side view of the exoplanet WASP-76b, where iron rains down from the sky.
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Astronomers have identified a new class of habitable planets, which they call Hycean planets. These are hot, ocean-covered planets with hydrogen-rich atmospheres.
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Astronomers have identified a new class of habitable planets, which they call Hycean planets. These are hot, ocean-covered planets with hydrogen-rich atmospheres.
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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.
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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.
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In this artist's illustration, two gaseous exoplanets can be seen orbiting the bright sun-like star HD 152843.
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In this artist's illustration, two gaseous exoplanets can be seen orbiting the bright sun-like star HD 152843.
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An artist's rendering of TOI-1231 b, a Neptune-like planet about 90 light years away from Earth.
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An artist's rendering of TOI-1231 b, a Neptune-like planet about 90 light years away from Earth.
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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.
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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.
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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.
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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.
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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.
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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.
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This artist's illustration shows the view from the furthest planet in the TOI-178 system.
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This artist's illustration shows the view from the furthest planet in the TOI-178 system.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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This is an artist's impression of the multiplanetary system of newly discovered super-Earths orbiting a nearby red dwarf star called Gliese 887.
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This is an artist's impression of the multiplanetary system of newly discovered super-Earths orbiting a nearby red dwarf star called Gliese 887.
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The newly discovered exoplanet AU Mic b is about the size of Neptune.
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The newly discovered exoplanet AU Mic b is about the size of Neptune.
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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.
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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.
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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.
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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.
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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.
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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.
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planet LP 791-18 d01 exoplanet GJ 486 bNASA TOI 700 e planet02 expolanets gallery 0105exoplanets 2022 wasp 121b01 proxima d exoplanetkepler 1708b exomoonWASP-103b exoplanet01 b centauri planetary system02 White Dwarf System01 exoplanets WASP 76bexoplanets Hycean01 exoplanets 0804exoplanet planet hunters TESS discoveryexoplanet toi 1231b02 proxima flareexoplanet GJ 1132 01 exoplanets TRAPPIST six exoplanets rendering01 super earth TOI-561Exoplanet HD 106906bmicrolensing free floating planetWASP-189b exoplanetswhite dwarf exoplanet01 carbon exoplanets diamondsRESTRICTED 01 exoplanets galleryexoplanets hot jupiterexoplanets red dwarf Gliese 887RESTRICTED 01 exoplanets gallery01 new exoplanet 0824white dwarf artist renderingKepler-88 exoplanets

(CNN)Although thousands of exoplanets have been discovered outside our solar system since the 1990s, astronomers are still hunting for something that remains elusive there: exomoons.

Over the last year, a few researchers have suggested potential evidence for locating these small moons around exoplanets, but nothing has been confirmed.
Now, researchers believe they have found possible indications of an exomoon orbiting a giant, scorching exoplanet in the Lepus constellation, 550 light-years from Earth. And it's comparable to Mustafar, a small volcanic planet sandwiched between two gas giants where Anakin Skywalker undergoes his dark, painful transition into Darth Vader in "Star Wars: Episode III -- Revenge of the Sith."
    Wandering moons called 'ploonets' could be the culprits behind astronomical mysteries
    Wandering moons called 'ploonets' could be the culprits behind astronomical mysteries
    "It would be a dangerous volcanic world with a molten surface of lava, a place where Jedis go to die, perilously familiar to Anakin Skywalker," said Apurva Oza, study author and postdoctoral fellow at the Physics Institute of the University of Bern.
      The WASP 49-b exoplanet system includes a gas giant that completes one orbit around its star every three days. The planet was discovered orbiting the WASP 49 star in 2012 via the transit method, which is when an exoplanet passes in front of its star, causing detectable dips in starlight.
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      Astronomers believe they found evidence for a moon due to the presence of sodium gas where they didn't expect to find it. The researchers published their findings this week in The Astrophysical Journal.
      "The neutral sodium gas is so far away from the planet that it is unlikely to be emitted solely by a planetary wind," Oza said.
        Exoplanet has a 'glowing water vapor' atmosphere
        Exoplanet has a 'glowing water vapor' atmosphere
        To understand why sodium gas is a key indicator, the astronomers looked at Jupiter's volcanic moon Io. Io is the most volcanically active body in our solar system, according to NASA. Volcanoes on Io belch out sodium gas, which is then pulled around Jupiter in a cloud, according to previous research.
        When applying the Jupiter and Io model to the Wasp 49-b system, "the sodium is right where it should be," Oza said. But their discovery implies that the exomoon is actually losing mass through the emission of sodium gas at high altitude.
        First suspected 'exomoon' discovered 8,000 light-years away
        First suspected 'exomoon' discovered 8,000 light-years away
        Researchers, including the University of Virginia's Bob Johnson in the current study, have previously demonstrated that large quantities of sodium present at exoplanets could suggest the presence of rings or even hidden bodies like moons.
        If the sodium detected in the exoplanet system doesn't lead to the discovery of a moon, it could mean that a ring of gas surrounds the planet.
        This exoplanet is inflated like a balloon
        This exoplanet is inflated like a balloon
        "Sodium and potassium lines are quantum treasures to us astronomers because they are extremely bright," Oza said. "The vintage street lamps that light up our streets with yellow haze is akin to the gas we are now detecting in the spectra of a dozen exoplanets."
        And a system including a star closely orbited by a giant planet with its own moon can actually exist stably for billions of years.
        "The enormous tidal forces in such a system are the key to everything," Oza said. Tides create stability for the moon's orbit, which also help to heat it and keep it volcanically active.
          The researchers also found other potential star systems where moons could be hiding from our view, but they need to find more clues.
          "While the current wave of research is going towards habitability and biosignatures, our signature is a signature of destruction," Oza said. "The exciting part is that we can monitor these destructive processes in real time, like fireworks."