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<\/p>\nAstronomers have found evidence for a volcanic moon orbiting an exoplanet 635 light-years from Earth. No moons have been confirmed to orbit planets outside our solar system, but a sodium cloud hints at the existence of one around exoplanet WASP-49 b.<\/p>\n
Moons orbiting planets outside our solar system \u2014 also known as exomoons \u2014 are hard to detect, as they are too small and too dim to be picked up by telescopes. Astronomers have found multiple candidates for exoplanets with moons, but none have been confirmed.<\/p>\n
However, volcanically active exomoons could be detected through the material they spew into space. A similar phenomenon occurs in our solar system, as volcanic activity on Jupiter\u2019s moon Io creates gigantic clouds of volcanic gasses around the planet. These clouds are many times the size of Jupiter, up to 1,000 times the planet\u2019s radius. A similar cloud has now been detected around WASP-49 b.<\/p>\n<\/p>\n
\u201cThe evidence is very compelling that something other than the planet and star are [sic] producing this cloud,\u201d said co-author Rosaly Lopes of NASA\u2019s Jet Propulsion Laboratory (JPL). \u201cDetecting an exomoon would be quite extraordinary, and because of Io, we know that a volcanic exomoon is possible.\u201d<\/p>\n
WASP-49 b is a planet with roughly the mass of Saturn, orbiting a Sun-like star. At only 10 percent of the distance between the Sun and Mercury, this planet completes a revolution in only 2.8 days. The sodium cloud around this exoplanet was first found in 2017.<\/p>\n
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Io surrounded by a cloud of volcanic gas. A plume of gas from the volcano Prometheus reflects sunlight. This image was captured by NASA\u2019s Galileo spacecraft using clear, green, and yellow filters. (Credit: NASA\/JPL)<\/p>\n
Astronomers study exoplanets like WASP-49 b by measuring their effect on the light emitted by their host stars. When the exoplanet transits its star, which means it passes between its star and Earth, it slightly changes the star\u2019s light signal. Studying how the starlight is absorbed by whatever passes in front of the star, helps scientists learn more about exoplanets or their potential moons.<\/p>\n
For this study, the team used data from the European Southern Observatory\u2019s (ESO) Very Large Telescope (VLT) in northern Chile. VLT observed the transiting exoplanet on Dec. 16, 2020, using its Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) instrument. The astronomers also reanalyzed the observations from the 2017 study, which observed WASP-49 b for three days in late 2015 and early 2016 using ESO\u2019s 3.6 m telescope.<\/p>\n
Aerospace industry analysis (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n The team found that the sodium cloud was located well within the zone around the exoplanet where moons can physically exist. That zone is defined by the planet\u2019s Hill sphere, within which a moon\u2019s orbit can be stable in the long term, and the Roche limit, wherein moons break up under immense tidal forces.<\/p>\n Moreover, the sodium cloud also seemed to move faster than WASP-49 b. The astronomers measured the cloud\u2019s Doppler shift, which is a change in the light signals\u2019 frequency resulting from the object moving toward or away from its observer. Using this method, they found that the cloud was moving in a way that had never been observed at exoplanets but was similar to the movement of Io\u2019s sodium cloud around Jupiter.<\/p>\n \u201cWe think this is a really critical piece of evidence,\u201d said study lead Apurva Oza of the California Institute of Technology (Caltech). \u201cThe cloud is moving in the opposite direction that physics tells us it should be going if it were part of the planet\u2019s atmosphere.\u201d<\/p>\n<\/p>\n