Astronomers have announced the possible discovery of an exomoon, the second sighting to date. The scientists behind the new search say their analysis points to a “mini-moon” the size of the planet Neptune orbiting a planet similar in size to Jupiter.
Not long ago, scientists proudly announced for the first time that they had discovered a planet outside our solar system, the so-called exoplanets. This was followed by the search for planets that showed as many similarities as possible with the Earth. Since then, astronomers have gone one step further in their efforts to fathom the Universe. They do this by locating exomoons, natural satellites that orbit exoplanets.
“Objects that everyone suspected existed”
“These are objects that everyone suspected were there, but not much formal research was done until 2007,” Marialis Rosario-Franco, an astrophysicist at the National Radio Astronomy Observatory in New Mexico, told Space.com. “The science of exomanes is still at a fairly early stage and is therefore full of possibilities. It is something that we are only now suspecting that we can observe. We do not perceive these objects directly; we only perceive the disturbance caused by the presence of the objects in the normal signal of an exoplanet.”
To find an exoplanet, Kepler images of a star had to be scanned tirelessly until 2018. Scientists then look for a minute change in the brightness of the exoplanet. That indicates the passage of the planet between the star and the telescope. In the new study, the scientists examined 70 of these data sets, each representing a cold gas giant, like the massive planets in our own solar system. The researchers then used a series of models to see which Kepler observations matched what they would expect to see if such a planet had a moon.
Clues, but no conclusive evidence
Only three stars were selected. For one of the galaxies, the team realized that the signal could be caused by Kepler itself; for another galaxy, the signal could come from dark spots moving across the star’s surface. But for the latter candidate, a star known as Kepler 1708, none of their alternative explanations worked. The first exomoon had just been discovered in a galaxy called Kepler 1625.
The new study uses a similar technique, but is even more careful than the already rigorous process followed in the first study, Rosario-Franco said. According to Rosario-Franco, Kepler’s moon 1625 is “quite widely accepted by the astrophysical community”, although its existence has not yet been fully confirmed. In any case, this discovery gives us a glimpse of the variety of planetary ecosystems that can be found in our galaxy. That science allows us to better understand how moons form and evolve, both in our own solar system and much further away. There are probably many more surprises waiting for us.
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