Researchers announced 62 new moons of Saturn

The work of an international team of astronomers resulted in the announcement of 62 new moons for Saturn, propelling it to first place in the “moon race” around the giant planets in our solar system.

The team is led by Edward Ashton (currently a postdoctoral fellow at Academia Sinica Taiwan’s Institute for Astronomy and Astrophysics) and includes Professor Brett Gladman (UBC Department of Physics and Astronomy), Mike Alexandersen (Harvard-Smithsonian Center for Astrophysics) and Jean-Marc Petit (Observatoire de Besancon ) and Matthew Bowdoin (University of British Columbia).

Over the past two decades, Saturn’s surroundings have been scanned again and again for moons of increasing sensitivity. In this latest study, Dr. Ashton’s team used a technique known as “shift and jam” in order to find fainter (and therefore smaller) Saturn’s moons. This method was used for moon He searches around Neptune and Uranus, but never Saturn.

Changing a set of sequential images at the rate the moon is moving across the sky improves the moon’s signal when all the data is combined, allowing moons too faint to be seen in individual images to become visible in the “stack” image. The team used data taken with the Canada-France Telescope -Hawaii (CFHT) atop Mauna Kea, Hawaii between 2019 and 2021. By swapping and stacking several sequential images taken over 3-hour time periods, they were able to detect moons of Saturn up to about 2.5 kilometers in diameter.

The search for the original discovery was made in 2019 when Ashton and Baudouin were students at the University of British Columbia, uncovering moons in Precision research on CFHT deep imaging acquired in that year. But just finding an object close to Saturn in the sky is not enough to say with certainty that it is a moon; It could in principle be an asteroid that happened to pass very close to the planet (although this is unlikely).

To be absolutely sure, an object would have to be tracked for several years before one could prove that it orbited the planet for sure. After painstakingly matching objects detected on different nights over the course of two years, the team was able to track down 63 objects, thus confirming them as new moons. one of the new moons, Designated S/2019 S1, it was announced again in 2021, with the remainder announced within the last two weeks. Some of the team’s associated orbits were determined by previous observations many years ago that briefly glimpsed some of these moons (but were not tracked long enough to determine their orbit around Saturn).

“Tracking these moons makes me remember playing the children’s game Dot-to-Dot, because we have to correlate the different shapes of these moons in our data with a viable orbit,” Edward Ashton explains, “but with about 100 different games on the same page and not knowing which point belongs to any puzzle.

All new moons fall into the category of irregular moons, which were initially thought to have been captured by their host planet long ago. Irregular moons are distinguished by their large, elliptical orbits compared to regular moons. The number of known irregular moons of Saturn has more than doubled to 121, with 58 previously known before the search began.

Including the 24 regular moons, there are now a total of 145 known moons (by the International Astronomical Union) orbiting Saturn. New discoveries have led to many milestones for the ringed planet. Not only has Saturn reclaimed its crown for having the most famous moons (it surpasses Jupiter with 95 known moons), but it’s also the first planet to have more than 100 moons discovered in total.

Irregular moons tend to cluster together in orbital groups based on the inclination of their orbits. In the Saturnian system, there are 3 such groups drawn from different mythologies: there is the Inuit group, the Gallic group, and the more populous Norse group. For example, three new discoveries in the Inuit group: S/2019 S1, S/2020 S1, and S/2005 S4 have very small orbits that are tilted similarly to the larger irregular orbits of Kiviuq and Ijiraq previously known. All new moons fall into one of the three known groups, with the Norse group again being the most populous of the new moons. The clusters are thought to be the result of collisions, with the current moons in a cluster the remnants of one or more collisions on the moons that were originally captured.

Thus, a better understanding of the orbital distribution provides insight into the collision history of Saturn’s irregular moon system. Based on their previous studies of these moons, this team has suggested that the large number of small moons in retrograde orbits is the result of a relatively recent perturbation (in astronomical terms, it was in the past 100 million years) of an irregular, medium-sized moon. which is now divided into many parts which are cataloged in the Norse group.

As Professor Gladman explains, “As one pushes the limits of modern telescopes, we find increasing evidence that a medium-sized, retrograde-orbiting moon of Saturn was shattered 100 million years ago.”