Saturn is now the planet with the highest number of moons in the solar system. Recently, astronomers discovered 62 new moons orbiting Saturn, which brings the total number of moons the gas giant has to 145. Thus, Saturn has got its 'moon crown' back from Jupiter, which has 95 moons as of February 25, 2023.
The team, whose work resulted in the discovery of Saturn catapulting back into the first place of the 'moon race', was led by Dr Edward Ashton, a postdoctoral fellow at Taiwan's Academia Sinica Institute of Astronomy and Astrophysics.
New milestones for Saturn
The different milestones which the ringed planet has achieved after the discovery of the new moons include overtaking Jupiter to become the planet with the most known moons in the solar system, and becoming the first planet to have more than 100 discovered moons in total.
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How the new Saturnian moons were discovered
The sensitivity of telescopes, astronomical instruments and spacecraft have increased over the years, as a result of which astronomers are to observe the surroundings of Saturn with great clarity. According to a statement released by the University of British Columbia, the team used a technique called 'shift and stack' to find fainter and smaller moons around Saturn. Astronomers have used this technique to search for moons around Uranus and Neptune in the past, but never for Saturn.
As part of the technique, researchers shift a set of sequential images at the rate that the moon is moving across the sky. This causes the moon's signal to be enhanced when all the data is combined. As a result, the moons that were too faint to be seen in individual images become visible in the 'stacked' image.
Between 2019 and 2021, the researchers used data obtained by the Canada-France-Hawaii Telescope (CFHT) on top of Mauna Kea, Hawaii. They detected moons of Saturn down to about 2.5 kilometres in diameter by shifting and stacking many sequential images taken during three hours.
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Why is it important to track an object for several years to confirm that it is a moon?
According to the statement, the original discovery search was done in 2019. At that time, Ashton and Matthew Beaudoin, one of the researchers involved in the study, were students at the University of British Columbia. They uncovered the moons using the CFHT. However, an astronomer cannot say for sure that an object found close to Saturn will be a moon. The object could also be an asteroid. Therefore, it is important to track the object for several years before being absolutely sure that it is orbiting the planet.
Over two years, the team matched objects detected on different nights, and tracked a total of 63 objects. They confirmed all these objects as new moons. The team announced the discovery of one of the new moons, designated S/2019 S 1, in 2021. The remaining 62 new moons were announced over the last couple of weeks.
Some of the orbits found by the researchers had been identified in the past, but were not tracked enough for long to establish their orbits around Saturn.
Quoting Ashton, the statement said tracking these moons makes him recall playing the kid's game Dot-to-Dot, because they have to connect the various appearances of these moons in their data with a viable orbit.
The new Saturnian moons are irregular moons. What does this mean?
All the new moons belong to a class called irregular moons, which are characterised by their large, elliptical and inclined orbits compared to regular moons. After the discovery of these new moons, the number of irregular moons orbiting Saturn has more than doubled to 121. Previously, the gas giant was known to have 58 irregular moons.
What are the three different groups of irregular moons?
Depending on the tilt in their orbits, the irregular moons tend to clump together. Three such groups are present in the saturnian system, whose names are drawn from different mythologies. These groups are: the Inuit group, the Gallic group, and the Norse group.
Three newly discovered moons belong to the Inuit group. They have very small orbits tilted similarly to that of the previously known larger irregular moons Kiviuq and Ijiraq. The Norse group has the highest number of newly discovered moons.
Why are certain moons present in groups?
The moons present together in a group are believed to be the result of one or more collisions on the originally captured moons.
A large number of small Saturnian moons are on retrograde orbits, which means they spin or rotate in a direction opposite to that of their host planet, Saturn. According to the researchers, these moons are the result of a relatively recent disruption of a moderately sized irregular moon. In other words, in the last 100 million years, which is relatively recent in astronomical terms, a moderately sized irregular moon was subject to collision, and broke into many fragments, each of which became a new moon belonging to the Norse group.