Scientists have been searching for moons around planets outside our solar system, known as exomoons, for a long time. However, a new study has questioned the validity of previous discoveries of giant exomoons orbiting two distant exoplanets, Kepler-1625b and Kepler-1708b.
The original claims
The original claims of exomoons were based on observations from NASA’s Kepler space telescope and the Hubble Space Telescope, which detected what appeared to be signs of giant moons. These moons, if they existed, would have been extraordinary in size — dwarfing all known moons in our solar system. The initial discovery of potential moons around these exoplanets was heralded as a monumental find, suggesting that our solar system’s commonality of planets with natural satellites might extend across the cosmos .
The new study
However, the new study, published in Nature Astronomy, suggests that “planet-only” interpretations of the data are more likely, upending the notion that two of the over 5300 known exoplanets had moons. Scientists from the Max Planck Institute for Solar System Research (MPS) and the Sonnenberg Observatory have used a newly developed computer algorithm called Pandora to analyze the same data sets and found no conclusive evidence of exomoons, instead offering alternative explanations for the observed light patterns .
Dr. Rene Heller, the lead author of the study, expressed disappointment in the results, stating, “We would have liked to confirm the discovery of exomoons around Kepler-1625b and Kepler-1708b, but unfortunately, our analyses show otherwise.” The study also highlighted the susceptibility of exomoon search algorithms to false positives, with an estimated 11 percent chance of mistakenly identifying a moon when only a planet is present.
The challenges and implications
The study’s findings point to the complexity of detecting such distant objects, which are often much smaller than their host planets and obscured by various interstellar factors. Astronomers always knew spotting moons around planets outside the solar system would be no mean feat — but a debate currently raging in planetary science circles shows just how tough detecting these so-called exomoons is going to be.
Looking ahead, the researchers predict that any exomoons detectable with current technology would be atypical when compared to those in our solar system. They would need to be exceptionally large and in wide orbits around their planets, making the first alien moon a rare and remarkable sight.
The search for exomoons is not only motivated by curiosity, but also by the potential implications for planetary formation and habitability. Exomoons could provide clues about how planets and their satellites form in different environments, as well as offer additional possibilities for hosting life beyond Earth.
Despite the setback, scientists are not giving up on finding exomoons. They hope that future missions and instruments, such as NASA’s James Webb Space Telescope and ESA’s PLATO mission, will be able to detect smaller and more common exomoons around other stars.