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"While the current wave of research is moving towards habitability and biosignatures, our signature is a signature of destruction," explained astrophysicist Apurva Oza at the Institute of Physics of the University of Bern on the detection of an "exo-moon" hidden in the WASP-49b exoplanet system, which seems to be an extreme version of the moon Io of Jupiter – the volcanic epicenter of our solar system. "Some of these worlds could be destroyed in the next few billion years because of extreme mass loss. The interesting part is that we can monitor these destructive processes in real time, like fireworks. "
"It would be a dangerous volcanic world with a molten lava surface, a lunar version of nearby super-lands like 55 Cancri-e," says Oza, an associate of NCCR PlanetS, "a place where Jedis will die, perilously . familiar to Anakin Skywalker. But the object described by Oza and his colleagues in their work seems to be even more exotic than the science fiction of Star Wars: the eventual exomoon would gravitate around a burning giant planet, which would run to turn around the host star. in less than three days – a scenario 550 light-years away from the unobtrusive constellation of Lepus, under the brilliant constellation of Orion.
Io's Surt Volcano
In February 2001, an eruption of the Surt volcano on the Io hemisphere facing Jupiter occurred with an estimated production of 78,000 gigawatts. For comparison, the 1992 Mount Etna eruption in Sicily was estimated at 12 gigawatts. During its heyday, observed in Hawaii by the WM Keck II telescope, its output almost matched the eruptive power of all active Io volcanoes combined.
Volcanic Epicenter of the Solar System – A New Hot Spot on Jupiter's Io, Monster Surt Volcano Site
There is today evidence that an active moon outside our solar system, an exo-Io, could be hidden in the WASP-49b exoplanet system.
Sodium gas as indirect evidence
The astronomers have not yet discovered a rocky moon beyond our solar system and it is on the basis of circumstantial evidence that the researchers in Berne conclude to the exo-Io: the sodium gas was detected at the WASP 49-b at an abnormally high altitude. "The sodium-free gas is so far away from the planet that it's unlikely that it's emitted solely by a global wind," says Oza. The observations of Jupiter and Io in our solar system, made by the international team, as well as mass loss calculations show that an exo-Io could be a very plausible source of sodium to WASP 49-b . "Sodium is where it should be," says the astrophysicist.
Tides keep the system stable
Already in 2006, Bob Johnson of the University of Virginia and the late Patrick Huggins of the University of New York in the United States had shown that a large amount of sodium in an exoplanet could indicate a moon or a ring of hidden material. Ten years ago, researchers in Virginia calculated that such a compact system of three bodies: a star, a giant planet close together and the moon, can be stable for billions of years. Apurva Oza was then a student in Virginia and after his doctorate on the atmospheres of moons in Paris, decided to resume the theoretical calculations of these researchers.
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"The huge tidal forces in such a system are the key to everything," says Oza. The energy released by the tides towards the planet and its moon keeps the orbit of the moon stable, warms it and makes it simultaneously volcanic. In their work, the researchers were able to show that a small rocky moon could reject more sodium and potassium in space by this extreme volcanism than a large gaseous planet, especially at high altitudes.
"Sodium and potassium lines are quantum treasures for us astronomers because they are extremely bright," says Oza, "the street lights that illuminate our streets with a yellow haze resemble the gas we detect. now in the spectrum of a dozen or so exoplanets. . "
"We need to find more clues"
The researchers compared their calculations with these observations and found five candidate systems in which a hidden exomoon can survive destructive thermal evaporation. For WASP 49-b, the observed data can be better explained by the existence of an exo-Io. However, there are other options. For example, the exoplanet could be surrounded by a ring of ionized gas or non-thermal processes.
"We have to find more clues," Oza admits. The researchers therefore rely on other observations with terrestrial and spatial instruments.
The Daily Galaxy via the University of Bern
Image credits: NASA / JPL
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