In the past three decades, the field of extrasolar planet studies has advanced by leaps and bounds. To date, 4,903 extrasolar planets have been confirmed in 3,677 planetary systems, with another 8,414 candidates awaiting confirmation. The diverse nature of these planets, ranging from Super-Jupiters and Super-Earths to Mini-Neptunes and Water Worlds, has raised many questions about the nature of planet formation and evolution. A rather important question is the role and commonality of natural satellites, aka. “exomoons.”
Given the number of moons in the Solar System, it is entirely reasonable to assume that moons are ubiquitous in our galaxy. Unfortunately, despite thousands of know exoplanets, there are still no confirmed exomoons available for study. But thanks to Columbia University’s Professor David Kipping and an international team of astronomers, that may have changed. In a recent NASA-supported study, Kipping and his colleagues report on the possible discovery of an exomoon they found while examining data from the Kepler Space Telescope.
The research team included members from the NASA Exoplanet Science Institute (NExScI) at Caltech, the NASA Ames Research Center, the Kavli Institute for Astrophysics and Space Research at MIT, the Mani Bhaumik Institute for Theoretical Physics at UCLA, the Institute for Particle Physics & Astrophysics at the Swiss Federal Institute of Technology (ETH) Zurich, and the Institute of Astronomy and Astrophysics at the Academia Sinica in Taipei. The paper describing their research and findings recently appeared in the journal Nature Astronomy.
An artist’s illustration of NASA’s Kepler spacecraft. Credit: NASA/Kepler
Professor Kipping is well-known for his pioneering work in exoplanet studies. As the Cool Worlds Laboratory leader at Columbia University, he and his colleagues have spent years developing methods for the study and characterization of exoplanets. Kipping is also the principal investigator of the Hunt for Exomoons with Kepler (HEK), a campaign affiliated with the Harvard-Smithsonian Center of Astrophysics (CfA) that is dedicated to finding evidence of exomoons in Kepler mission data. As Kipping told Universe Today via email:
“Astronomers tend to come into two flavors, those who want to understand how the universe works and those who want to know if we’re alone or not. In both themes, exomoons hold much promise. Concerning the former, they will provide other examples of how moons manifest in the Universe beyond our cosmic shore. When we look at the Moon, for example, we wonder – was its formation (likely through a giant impact) a 1 in a trillion fluke, or are we looking at the inevitable outcome of planet formation?
“And on the latter, moons may be frequent abodes for life, a common trope in sci-fi of course. Since an overarching goal of NASA is to understand how common are Earth-like worlds, looking for moons is a necessary part of that – for all we know that they may, in fact, dominate the habitable real estate in the cosmos.”
The formation and evolution of Earth’s only natural satellite, the Moon, is closely linked to that of Earth itself. According to the Giant Impact Hypothesis, both formed after a Mars-sized object (Theia) collided with a primordial Earth roughly 4.5 billion years ago. Furthermore, some scientists speculate that this giant impact may be the reason why Earth is habitable today. Another theory has it that the Moon helps maintain the dynamo in Earth’s interior, which generates the magnetic field that shields us from radiation.
For these reasons, Kipping and his colleagues have studied exoplanet systems and worked towards creating means for detecting exomoons. One of the methods Kipping and his colleagues have devised to look for them is the Transit Timing Variations (TTV), where an exoplanet’s gravitational wobbles are interpreted as the influence of exomoons (similar to the Radial Velocity Method). Another method is to look for the transits of exomoons themselves, which is
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